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Objective: To get a better understanding of inflammatory pathways active in the osteoarthritic (OA) joint, we characterized and compared inflammatory cells in the synovium and the infrapatellar fat pad (IFP) of patients with knee OA., Methods: Infiltrating immune cells were characterized by flow cytometry in 76 patients with knee OA (mean age 63.3, 52% women, median body mass index 28.9) from whom synovial tissue (n = 40) and IFP (n = 68) samples were obtained. Pain was assessed by the visual analog scale (VAS; 0-100 mm). Spearman rank correlations and linear regression analyses adjusted for sex and age were performed., Results: Macrophages and T cells, followed by mast cells, were the most predominant immune cells in the synovium and IFP, and were equally abundant in these tissues. Macrophages and T cells secreted mostly proinflammatory cytokines even without additional stimulation, indicating their activated state. Accordingly, most CD4+ T cells had a memory phenotype and contained a significant population of cells expressing activation markers (CD25+, CD69+). Interestingly, the percent of CD69+ T cells was higher in synovial than IFP CD4+ T cells. Preliminary analyses indicated that the number of synovial CD4+ T cells were associated with VAS pain (β 0.51, 95% CI 0.09-1.02, p = 0.02)., Conclusion: Our data suggest that the immune cell composition of the synovium and the IFP is similar, and includes activated cells that could contribute to inflammation through secretion of proinflammatory cytokines. Moreover, preliminary analyses indicate that synovial CD4+ T cells might associate with pain in patients with endstage OA of the knee.

Objective: To investigate the relationship between plasma and synovial fluid (SF) metabolite concentrations in patients with osteoarthritis (OA)., Methods: Blood plasma and SF samples were collected from patients with primary knee OA undergoing total knee arthroplasty. Metabolic profiling was performed by electrospray ionization tandem mass spectrometry using the AbsoluteIDQ kit. The profiling yielded 168 metabolite concentrations. Correlation analysis between SF and plasma metabolite concentrations was done on absolute concentrations as well as metabolite concentration ratios using Spearman's rank correlation (ρ) method., Results: A total of 69 patients with knee OA were included, 30 men and 39 women, with an average age of 66 ± 8 years. For the absolute metabolite concentrations, the average ρ was 0.23 ± 0.13. Only 8 out of 168 metabolite concentrations had a ρ ≥ 0.45, with a p value ≤ 2.98 × 10(-4), statistically significant after correcting multiple testing with the Bonferroni method. For the metabolite ratios (n = 28,056), the average ρ was 0.29 ± 0.20. There were 4018 metabolite ratios with a ρ ≥ 0.52 and a p value ≤ 1.78 × 10(-6), significant after correcting multiple testing. Sex-separate analyses found no difference in ρ between men and women. Similarly, there was no difference in ρ between people younger and older than 65 years., Conclusion: Correlation between blood plasma and SF metabolite concentrations are modest. Metabolite ratios, which are considered proxies for enzymatic reaction rates and have higher correlations, should be considered when using blood plasma as a surrogate of SF in OA biomarker identification.

Objective: To investigate the expression of peroxisome proliferator-activated receptors (PPAR) α, β, and γ, and hematopoietic and lipocalin-type prostaglandin D synthase (H- and L-PGDS) over the course of osteoarthritis (OA) in the spontaneous Hartley guinea pig and the anterior cruciate ligament transection dog models., Methods: Guinea pigs were sacrificed at 2 (control group), 4, 8, and 12 months of age (n = 5 per group). Non-operated (control) and operated dogs were sacrificed at 4, 8, and 12 weeks postsurgery. Cartilage was evaluated histologically using the Osteoarthritis Research Society International (OARSI) guidelines. The expression of PPAR-α, β, γ, and H- and L-PGDS was evaluated by real-time PCR and immunohistochemistry. The nonparametric Spearman test was used for correlation analysis., Results: PPAR-α, β, and γ were detected in medial tibial plateau from control animals in both the spontaneous and surgical models. Levels of PPAR-α and β did not change over the course of OA, whereas PPAR-γ levels decreased during progression of disease. We also observed that the expression of H-PGDS remained unchanged, whereas L-PGDS increased over the course of OA. PPAR-γ levels correlated negatively, whereas L-PGDS levels correlated positively, with the histological score of OA., Conclusion: The level of PPAR-γ decreased, whereas level of L-PGDS increased during the progression of OA. These data suggest that reduced expression of PPAR-γ may contribute to the pathogenesis of OA, whereas enhanced expression of L-PGDS may be part of a reparative process.

Objective: Citrullination, a reaction converting arginine residue into citrulline residue, is essential for autoimmunity of rheumatoid arthritis (RA). We conducted 2-dimensional Western blot analyses (2-D WB) to screen for novel citrullinated proteins in synovial tissues from patients with RA., Methods: Total proteins were extracted from the synovial membranes of patients with RA (n = 10) and pooled. Four identical 2-D electrophoresis (2-DE) gels were prepared, and 2 gels were transblotted to polyvinylidene fluoride membranes that were separately probed with sera from patients with RA (n = 10) or an anticitrulline antibody. The protein profiles of the 2-DE gels were compared with the hybridization results on a global level. The immunoreactive protein spots were collected from the 2-DE gels and identified using mass spectrometry. Proteins that were detected by both RA sera and anticitrulline antibody were considered citrullinated proteins. The result was confirmed through routine WB, immunoprecipitation, and ELISA. Autoantibodies against these potential antigens were also examined in the blood of patients with RA by ELISA., Results: RA sera and the anticitrulline antibody on 2-D WB detected α-1-antitrypsin (A1AT), dynein heavy-chain 3, fibrinogen β chain, keratin type II cuticular Hb4 (KRT84), lumican, tubulin β-chain (TUBB), and vimentin. A1AT, KRT84, and TUBB had high expression in the synovial membranes (n = 5) of patients with RA and A1AT and KRT84 had high expression in RA synovial fluids (n = 40). A1AT, KRT84, and TUBB immunoprecipitated from synovial tissues showed citrullination. A high level of autoantibodies against KRT84 was detected in the blood of patients with RA (n = 92) compared to that of healthy controls (n = 92)., Conclusion: Our study identified some new citrullinated proteins in RA synovial tissues using 2-D WB.

Objective: Hemarthrosis triggers hemophilic arthropathy, involving the target joints. The histopathogenesis of blood-induced joint damage remains unclear. The triad of receptor activator of nuclear factor-κB (RANK), RANK ligand (RANKL), and osteoprotegerin (OPG; RANK-RANKL-OPG) controls bone turnover. Our aim was to evaluate RANK-RANKL-OPG expression in the synovium of hemophilic patients with severe arthropathy., Methods: Synovial biopsies were obtained from 18 patients with hemophilic arthropathy and 16 with osteoarthritis (OA) who were undergoing total knee replacement and synovectomy. The severity of hemophilic arthropathy was evaluated according to ultrasonography score, the World Federation of Hemophilia (WFH) orthopedic joint scale, and the radiographic Pettersson score. RANK-RANKL-OPG expression was examined by immunohistochemistry and Western blotting. Serum levels of soluble RANKL (sRANKL) and OPG from an extended group of 67 patients with hemophilic arthropathy and 30 healthy controls were measured by ELISA., Results: The mean ultrasonography, WFH orthopedic joint scale, and Pettersson scores in patients with hemophilic arthropathy indicated severe arthropathy. A decreased expression of OPG was found in hemophilic arthropathy synovium compared with patients with OA. RANK and RANKL immunopositivity was strong in the lining and sublining layers in hemophilic arthropathy synovial tissue. Western blotting confirmed the immunohistological findings. Serum levels of sRANKL and OPG in patients with hemophilia were lower than in healthy controls., Conclusion: In hemophilic arthropathy, the synovium highly expressed RANK and RANKL, whereas OPG immunopositivity decreased, suggesting an osteoclastic activation. Low tissue expression of OPG paralleled the serum levels of this protein and the severity of hemophilic arthropathy assessed by ultrasonography, Pettersson, and WFH orthopedic joint scale scores.

Objective: Our study uses the entire proteomes of serum and synovial fluid (SF) to characterize the avenues of microvascular egress of plasma proteins, and quantifies that traffic in normal and diseased human knees., Methods: Paired aliquots of serum and SF were collected from 17 knees of 11 subjects who died without evident joint disease and 16 patients with clinical effusions, fractionated by gel filtration chromatography and analyzed as continuous plots of the SF/serum concentration ratio versus molecular radius from 1 to 12 nanometers (nm). Curve-stripping methodology, a 3-pore model, and known protein kinetics were then applied to estimate the dimensions of and the net outflow through fenestral, "small," and "large" apertures in the microvascular endothelium., Results: The 3-pore model correlated highly with the observed data (r = 0.992 in normal and 0.980 in arthritis), yielding the following mean values: for the fenestra, the normal radius (nm) was 1.75 and the effused 3.5, and the normal flow (μl/min) was 1.74 and the arthritic 22.0; for the small pore, the normal radius was 8.6 and the effused 8.5, and the normal flow was 1.5 and the arthritic flow 9.1; for the large pore, the normal radius was 40 and the effused 36, and the normal flow was 0.24 and the arthritic flow 15.5., Conclusion: These findings provide the first functional definition of synovial, endothelial fenestrae; reveal that the "increased vascular permeability" of inflammation is not limited to interendothelial gaps; present evidence suggesting that glycocalyceal damage and aquaporin upregulation may affect permeability in arthritic synovium; and define a straightforward methodology for interpretation of biomarker concentrations in arthritic SF.

Objective: To examine differences in genes involved in fat metabolism, energy homeostasis, adipogenesis, and inflammation between endstage and early-stage knee osteoarthritis (OA) infrapatellar fat pads (IFP)., Methods: Twenty-nine endstage and 5 early-stage primary OA IFP were harvested at knee surgery. Total RNA was extracted, labeled, and hybridized to whole-genome expression arrays. Unsupervised analysis of all samples using principal components analysis or 2-way hierarchical clustering showed groupings based on tissue source and disease. Statistical testing identified sets of genes that displayed differences between the 2 fat types. Western blot analysis was performed for protein expression of an identified gene of interest., Results: The 29 IFP demonstrated an elevation in the expression of adipokines such as adiponectin and leptin. A statistically significant increased expression was seen for genes of adipogenesis, such as peroxisome proliferator-activated receptor-γ (PPAR-γ), diacylglycerol acyltransferase 2 (DGAT2), cluster of differentiation (CD36), and thyroid hormone responsive spot (THRSP) in the severe OA fat pads as compared to the controls. A subset of 5 patients in the endstage OA group were consistently similar in gene expression to early OA tissue. Protein expression of PPAR-γ2 was 5.4-fold and PPAR-γ1 was 1.4-fold greater in endstage versus early OA tissue., Conclusion: Endstage OA fat pads demonstrated a significant upregulation of genes for fat metabolism and energy homeostasis and a mixed result for inflammatory cytokines.

Objective: Evidence indicates that proteinase-activated receptor (PAR)-2 participates in the degradative processes of human osteoarthritis (OA). We evaluated the in vivo effect of PAR-2 on articular lesions in a PAR-2-knockout (KO) mouse model of OA., Methods: OA was surgically induced by destabilization of the medial meniscus of the right knee in C57Bl/6 wild-type (WT) and PAR-2 KO mice. Knee swelling was measured throughout the duration of the study (8 weeks postsurgery) and histologic evaluation of cartilage was done to assess structure, cellularity, matrix staining, and remodeling in the deep zone. Morphometric analysis of subchondral bone was also performed., Results: Data showed significant knee swelling in the operated WT mice immediately following surgery, which increased with time (8 weeks post-surgery). Knee swelling was significantly lower (p ≤ 0.0001) in PAR-2 KO mice than in WT mice at both 4 and 8 weeks postsurgery. Cartilage damage was found in both operated WT and PAR-2 KO mice; however, lesions were significantly less severe (global score; p ≤ 0.05) in the PAR-2 KO mice at 4 weeks postsurgery. Operated WT mice showed reduced subchondral bone surface and trabecular thickness with significance reached at 4 weeks (p ≤ 0.03 and p ≤ 0.05, respectively), while PAR-2 KO mice demonstrated a gradual increase in subchondral bone surface with significance reached at 8 weeks (p ≤ 0.007)., Conclusion: We demonstrated the in vivo implication of PAR-2 in the development of experimental OA, thus confirming its involvement in OA joint structural changes and reinforcing the therapeutic potential of a PAR-2 antagonist for treatment of OA.

Objective: Delayed gadolinium-enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC) is used to assess cartilage glycosaminoglycan distribution. Our aim was to determine the relationships between self-reported pain and disability, clinical variables, and serum leptin, and dGEMRIC indices in obese subjects with and without clinical knee osteoarthritis (OA)., Methods: Seventy-seven subjects were recruited from laparoscopic adjustable gastric banding or exercise and diet-weight loss programs. The dGEMRIC index was assessed on MRI according to established protocol. Regression analysis adjusted for age, sex, body mass index (BMI), and presence of clinical knee OA., Results: Mean age and BMI were 51 +/- 12.7 years and 39.6 +/- 6.2 kg/m(2). Twenty-three subjects (30%) had clinical knee OA (American College of Rheumatology criteria). The medial and lateral dGEMRIC indices were 538 +/- 80 ms and 539 +/- 86 ms. Age correlated negatively with medial (r = -0.40, p < 0.001) and lateral (r = -0.29, p = 0.012) dGEMRIC index. Subjects with clinical knee OA had significantly lower medial dGEMRIC index; however, no association was found for BMI. Varus alignment correlated with lower medial dGEMRIC index (r = -0.43, p < 0.006), while quadriceps strength correlated positively with lateral dGEMRIC index (r = 0.32, p = 0.008). There was also a negative correlation between serum leptin and lateral dGEMRIC index in women (r = -0.39, p = 0.035), with a trend in men (r = -0.52, p = 0.08). There were weak associations with physical disability, as self-reported on the WOMAC questionnaire., Conclusion: In obese subjects, knee dGEMRIC index was associated with age, clinical knee OA, abnormal tibiofemoral alignment, and quadriceps strength. Longitudinal studies are required to assess the potential for improvement in dGEMRIC index with interventions such as strength training.

Objective: Using a rabbit model of inflammatory arthritis, to determine the influence of early disease on expression of specific genes and investigate the influence of intraarticular (IA) and intramuscular (IM) corticosteroids on the regulation of these genes in connective tissues of the rabbit knee., Methods: Skeletally mature rabbits underwent induction of antigen-induced arthritis or remained untreated as control animals. Four days after disease induction, at an early stage of the disease, animals underwent either IA or IM treatment with glucocorticoids (GC) (5 mg/knee and 10 mg/kg methylprednisolone acetate, respectively). Twenty-four hours following treatment, synovium, menisci, and cartilage of the knee were collected and analyzed for changes in mRNA levels using reverse transcription-polymerase chain reaction for a number of relevant genes: collagen I, collagen II, biglycan, decorin, matrix metalloproteinases-3 and -13 (MMP-3 and MMP-13), cyclooxygenases-1 and -2 (COX-1 and COX-2), tumor necrosis factor-alpha (TNF-alpha), interleukin 1beta (IL-1beta), inducible nitric oxide synthase (iNOS), hyaluronan synthase-2 (HAS-2), and the housekeeping gene beta-actin., Results: Early inflammatory arthritis led to an overall upregulation of most genes assessed, but a downregulation of some genes (iNOS, HAS-2, COX-1) in some tissues. While genes such as collagen II, MMP-3, and MMP-13 were uniformly downregulated by GC treatment in both normal and arthritic tissues, other genes such as collagen I, biglycan, and decorin differed in their pattern of response depending on the tissue examined, the route of drug administration, and whether normal or arthritic tissue was studied., Conclusion: Early mRNA changes in RA-like disease led to alterations in all tissues examined. The changes were uniquely altered by GC treatment. Route of GC administration influenced outcome.

Objective: To determine the possible role of the plasminogen activator (PA)/plasmin system in gouty arthritis., Methods: We compared the antigenic values of urokinase-type PA (uPA), soluble uPA receptor (suPAR), and PA inhibitor type-1 (PAI-1) and the levels of matrix metalloproteinase-2 (MMP-2) and MMP-9 in 63 synovial fluid (SF) samples from knee joints of 38 patients with gouty arthritis and 20 SF samples from knee joints of 20 patients with osteoarthritis (OA)., Results: The increases of uPA, suPAR, and PAI-1 antigenic values in SF were associated with increased levels of latent MMP-9 (pro-MMP-9) (p < 0.001, p < 0.001, p < 0.001, respectively) in gouty arthritis, whereas a correlation was not observed between uPA, suPAR, and PAI-1 antigenic values and MMP-2 levels. Increased uPA, suPAR, and PAI-1 antigenic values in gouty arthritis SF were also correlated to each other (p < 0.001, p < 0.001, p < 0.001). In gouty arthritis SF, no significant relations were observed between uPA and suPAR antigenic values and leukocyte, neutrophil, or monocyte counts, while increased values of PAI-1 corresponded closely with increased leukocyte and neutrophil counts (p = 0.005, p = 0.004). Significantly higher values of the uPA, suPAR, and PAI-1 (p < 0.001, p < 0.001, p = 0.012) appeared in SF of gouty arthritis than in SF from patients with OA., Conclusion: These results show a correlation of the PA/plasmin system and MMP-9 in SF from patients with gouty arthritis, resulting in increased PA catalytic activity and contributing to inflammation in gouty arthritis.

Knee locking is a highly incapacitating condition attributable to mechanical or functional factors. Pain, mostly of capsuloligamentous or intraosseous origin, is the cause of functional locking. Meniscal injuries are the most frequent arthroscopic finding in the locked knee, due to mechanical factors. We describe a patient experiencing locking during extension whose history and examination suggested a tear of the anterior horn of the lateral meniscus of the right knee; a diagnostic/therapeutic arthroscopy revealed an intraarticular gouty tophus growing from the anterior horn of the lateral meniscus.

Objective: To determine the relationship between biochemical bone markers and knee cartilage volume and cartilage loss over 2 years; and to investigate whether bone markers are useful to predict the cartilage loss in healthy men., Methods: Forty healthy Caucasian men (mean age 52.3 yrs) with no symptoms of osteoarthritis (OA) were recruited. Each subject had magnetic resonance imaging (MRI) performed on his dominant knee at baseline and 2 years later. Serum level of osteocalcin (OC), urinary levels of pyridinoline (PYD) and deoxypyridinoline (DPD), and total body bone mineral content (BMC) were measured at baseline. Tibial plateau bone size was measured at baseline. Tibial cartilage volume was measured at baseline and at followup, by means of image processing., Results: Twenty-eight men (70%) completed the longitudinal MRI component of the study. At baseline, no significant associations were observed between values of serum OC or urine PYD and DPD and tibial cartilage volume. Higher baseline serum OC level tended to be associated with a decreased rate of cartilage loss (p = 0.06); no significant association was shown between baseline urine PYD and DPD and tibial cartilage loss, after adjusting for age, body mass index, total body BMC, and tibial plateau bone size., Conclusion: Higher baseline serum OC level tended to be associated with a decreased rate of cartilage loss, suggesting that increased bone formation may protect against tibial cartilage loss over 2 years. Studies are needed to determine the role of bone metabolism in the pathogenesis of knee OA.

Objective: Osteoarthritis (OA) is a painful degenerative joint disease. To assess joint nociceptor activation indirectly, we used a novel in vitro knee joint preparation and determined the release of calcitonin gene-related peptide (CGRP) and prostaglandin E2 (PGE2) in osteoarthritic mice., Methods: We studied STR/1N mice, which spontaneously develop OA, along with CD-1 mice as controls and C57/Bl6 mice with unilateral collagenase-induced OA and C57/Bl6 control mice. The release of CGRP and PGE2 from tibial and femoral joint preparations was determined separately in vitro with enzyme immunoassays; we investigated both basal release and release induced by stimulation with capsaicin (CAP, 1 microM) or bradykinin (BK, 10 microM)., Results: Basal PGE2 release from femoral and tibial preparations increased by 79% and 97%, respectively, in STR/1N mice between 6 and 18 weeks of age when they developed OA, while age-matched CD-1 mice exhibited only a weak increase (23%). BK-evoked PGE2 release was significantly higher in 18-week-old STR/1N mice (931 +/- 98 pg/ml and 759 +/- 82 pg/ml from femoral and tibial preparations, respectively) than in age-matched CD-1 controls (236 +/- 38 pg/ml and 246 +/- 34 pg/ml). CAP stimulation induced a significant CGRP release, which, however, did not correlate with the temporal development of OA in STR/1N mice. Tibial but not femoral joint preparations from mice with collagenase-induced OA exhibited a significantly enhanced release upon BK stimulation compared to sham controls, while CAP-induced CGRP release did not reveal such difference., Conclusion: Basal and evoked PGE2 release from knee joint preparations rose while osteoarthritic alterations developed, whereas CGRP release remained unaltered. The increased PGE2 release may contribute to enhanced nociceptor sensitivity underlying chronic OA pain.

Pigmented villonodular synovitis (PVNS) is a rare, benign, proliferative disease of the synovial membrane of joints, tendon sheaths, and bursas. Joint aspiration typically yields hemorrhagic or xanthochromic/serosanguinous (brown, murky) fluid. We describe a case of PVNS that presented as an acute, painless, nontraumatic right knee effusion with clear synovial fluid on arthrocentesis. Initial magnetic resonance imaging of the knee revealed no evidence for hemosiderin. A diagnostic arthroscopy and surgical arthrotomy revealed a unique case of PVNS evolving from local to diffuse involvement of the synovium.

Objective: To elucidate the mechanisms of calcium pyrophosphate dihydrate crystal deposition disease (CPPDCD) in the meniscus, synovium, labrum, tendon, ligament, and soft tissue, we studied the expression of cartilage intermediate layer protein (CILP)., Methods: Histological sections and clinical data from 33 patients who fulfilled the criteria of Ryan and McCarty for CPPD were reviewed. Formalin fixed and paraffin embedded tissue sections of 33 patients with CPPDCD were stained with hematoxylin and eosin (H&E) and alizarin red S. Immunostaining was performed using affinity purified polyclonal antibody to synthetic peptide corresponding to the N-terminal sequence of the 61 kDa domain of porcine CILP., Results: The age of patients ranged from 49 to 89 years (median 73). The knee was the commonest site. Radiologically, almost all lesions exhibited fine, radiopaque, linear deposits in the meniscus, articular cartilage, and synovium or joint capsule. Histopathologically, all cases showed deposits of birefringent monoclinic or triclinic crystals, which were visualized by polarized light microscopy with a red analyzer filter. In alizarin red S staining, more numerous crystals were observed than in H&E staining. Crystal deposition was usually associated with adjacent variable amounts of hypertrophic and/or metaplastic chondrocytes in each type of tissue. Variable intensity of CILP immunostaining was found in deposits of each lesion. Hypertrophic/metaplastic chondrocytes in and around CPPD deposits were also positive for CILP. Small cartilaginous islands remote from the CPPD deposits exhibited a weak positivity for CILP. In addition, weakly positive chondrocytes were noted in a transitional zone between cartilaginous islands with and without the deposits. In addition to cytoplasmic immunoreactivity, immunostaining for CILP was observed in the pericellular fibrous matrix., Conclusion: Hypertrophic or metaplastic chondrocytes characteristic of CPPDCD may be directly involved in the formation of CPPD crystals. Our study suggests that increased CILP expression was closely associated with CPPDCD, and might play a role in promoting CPPD crystal formation.

Objective: Studies have suggested that polymorphisms or mutations either in the COL2A1 or VDR gene. both on chromosome 12q, are associated with the occurrence of osteoarthritis (OA). We examined linkage and association between the VDR/COL2A1 locus and hand/knee OA in the Framingham Osteoarthritis Study (FOS)., Methods: Hand and knee joints were characterized radiographically in the FOS. An overall score for OA using the standard Kellgren and Lawrence grading scheme was determined, as well as scores for individual features of OA including osteophytes and joint space narrowing. For linkage studies, polymorphic microsatellite markers near the VDR-COL2AI genes on chromosome 12 were tested in a collection of 296 of the largest Framingham Heart Study families and the results analyzed using variance component linkage (SOLAR). For association studies, we characterized the allele status of a subset of subjects at the BsmI site of the VDR gene., Results: Overall, we found no linkage or association between OA and the COL2A1/VDR locus for either knee or hand OA, nor did we find an association or linkage between COL2AI or VDR with any individual radiographic features of OA., Conclusion: Despite studies suggesting associations of OA with both COL2A1 and VDR loci, our results suggest that mutations at the COL2A1/VDR locus do not play an important role as a cause of common OA in the population at large.

Objective: To investigate the expression of CD44 and its role in experimental chronic arthritis in rabbits., Methods: Rabbits were immunized with Escherichia coli 0:14 for short (4 mo) and long (8-10 mo) periods. Immunohistochemical staining was performed on knees, using anti-CD44 antibodies., Results: Lymphocyte infiltration in the synovium was found in 30.0% of rabbits after short term immunization, and the rate increased to 58.3% after longterm immunization. CD44 was present in synovial lining cells in 30.0% of rabbits after short term immunization, and it increased significantly (p < 0.05) after longterm immunization (66.7%). CD44 was also observed in lymphocytes in knee synovium after longterm immunization (25.0%)., Conclusion: CD44 in lining cells might play a role in promoting chronic arthritis in rabbits immunized with E. coli.

Objective: To determine if lowering of serum uric acid (SUA) concentrations below 6 mg/dl or longer duration of lowered SUA will result in depletion of urate crystals from the knee joints and prevent further attacks of gout., Methods: A prospective study was initiated 10 years ago at Philadelphia VA Medical Center to attempt to maintain SUA levels of patients with crystal proven gout at < 6.0 mg/dl. We recalled all 57 patients who were available during 1999. Patients were divided into 2 groups: Group A, with SUA still > 6 mg/dl, and Group B, with SUA < or = 6 mg/dl. A knee joint aspirate was requested from all asymptomatic Group B patients and many in Group A. Aspirates were examined by polarized light microscopy for identification of crystals., Results: There were no differences between the groups in age, sex, duration of gout, or serum creatinine. Group A (n = 38) had a mean of 6 attacks of gout for the recent year, those with tophi having the most frequent attacks. Among the 16 patients in this group who agreed to knee aspiration, monosodium urate (MSU) crystals were found in 14, although they were asymptomatic at the time. Nineteen patients (Group B) were able to maintain serum urate levels < or = 6 mg/dl for > 12 months. Nearly half of them had no attack of gout for 2 or more years, with a mean of 1 attack in the last year for the whole group. Three patients in whom tophi were found did not have major flares of gout within the past year. Knee joint aspiration was done on 16 asymptomatic patients. Seven (44%) still had MSU crystals present in their knees. Patients in this group who were taking prophylactic colchicine did not differ with respect to the character of synovial fluid from those who had discontinued it for up to several years, although the frequency of attacks was less in those who continued colchicine., Conclusion: A majority of patients were able to deplete urate crystal stores in their knee joint fluids when their SUA levels were kept to < or = 6 mg/dl for several years. The mechanisms for persistence in some patients, and whether such crystals have clinical implications, are not known. Patients with chronic gout need serum urate concentrations to be kept low to prevent further attacks.

Objective: To measure intracellular and tissue pH in periarticular soft tissue during different phases of antigen induced arthritis in the rat., Methods: pH was calculated using the following values: (1) the distribution of [14C]-dimethyl-oxazolidinedione; (2) the total tissue water and the extracellular space water volume, which was measured as [14C]-sucrose distribution in nephrectomized rats. Experiments were performed during both maximal inflammation (Day 3) and the restorative phase (Day 14)., Results: In all animals both tissue (pHt) and intracellular (pHi) pH were lower in arthritic joints than in the contralateral control. Mean pHt in control joints was 7.37+/-0.03. In arthritic rats it was 7.30+/-0.05 on Day 3 after challenge and 7.27+/-0.03 on Day 14. The pHi ranges were 6.86-7.81 for controls, 6.65-7.28 for arthritis Day 3, and 5.66-6.91 for arthritis Day 14., Conclusion: In this model there is a reduction in pH in the periarticular tissue of arthritic joints. The magnitude is, however, relatively small and the pannus tissue is not uniquely acidic in comparison with other compartments. There does not seem to be a correlation between pH and changes in metabolic balance, pannus formation, or healing.

Objective: To investigate osteoarthritic cartilage in comparison to normal cartilage in humans for the presence of the most relevant cytokines/growth factors known to be important for degradation and formation of new cartilage., Methods: Cartilage from knee or hip joints was obtained from 10 patients with osteoarthritis (OA) and from 7 age matched control patients with intact cartilage. Additionally, normal cartilage from 2 young patients (12 and 17 years old) was obtained after knee traumas. Immunohistological staining of cartilage sections was performed using antibodies for the following cytokines/growth factors: tumor necrosis factor alpha (TNF-alpha), interleukin 1alpha (IL-1alpha), IL-1beta, interferon-gamma, IL-6, IL-4, IL-10, transforming growth factor beta1 (TGF-beta1), insulin-like growth factor I (IGF-I), IGF-II, platelet derived growth factor AA (PDGF-AA), and PDGF-BB., Results: Immunohistochemical stainings were positive for all cytokines in OA cartilage, while only a faint or no staining was found in healthy cartilage. Activated chondrocytes expressing most of the cytokines were located in the middle and partly in the lower layer of cartilage, with the exception of IGF-I, which was expressed exclusively in the upper cartilage layer close to the surface. More chondrocytes stained positive for TNF-alpha than for IL-1, and expression of the degrading cytokine TNF-alpha was inversely correlated to the expression of the regulatory cytokines IL-4, IL-10, and TGF-beta., Conclusion: The most relevant cytokines known to be involved in cartilage metabolism are produced by chondrocytes themselves. They are upregulated in OA cartilage, suggesting that they serve some regulatory function and could be a target for future treatment.

Objective: To assess the variability of synovial histology, immunohistology, and cytokine mRNA expression at different sites within the knee joints of subjects with rheumatoid arthritis receiving slow acting antirheumatic drugs. The effects of intraarticular bupivacaine and adrenaline, and a comparison of synovial fluid cell and synovial membrane cytokine expression, were also investigated., Methods: Arthroscopically directed synovial biopsies were taken at 3 or 4 predetermined sites from the knee joints of 11 patients. Histology for synovial lining layer, sublining cellularity and vascularity, and immunohistology for T cells, T cell subsets, and macrophages were assessed. Messenger RNA expression of interleukins 1beta, 2, 4, 6, 8, 10, granulocyte-monocyte colony stimulating factor, tumor necrosis factor-alpha, and interferon-gamma was detected using the reverse transcription/polymerase chain reaction technique., Results: Synovial histology, immunohistology, and cytokine mRNA expression did not vary significantly. CD8 cell immunohistology was variable. Intraarticular bupivacaine and adrenaline did not change synovial characteristics. Synovial fluid cell and membrane cytokine expression did not match in 35% of comparisons., Conclusion: Biopsies from the suprapatellar pouch, medial gutter, and cartilage-pannus junction will provide a representative sample of synovial membrane pathology in patients with rheumatoid arthritis.

Objective: To test the hypothesis that bone mineral density (BMD) in periarticular subchondral regions of the knee joint is abnormal in patients with osteoarthritis (OA)., Methods: Sixty-two knees from patients with relatively mild OA (primarily radiographic grades 0, 1, 2) of the knee were compared with 62 knees from normal subjects matched for age, sex, race, and body side (right or left). BMD of the lumbar spine, distal femoral shaft, and several periarticular subchondral regions of the knee were determined by dual energy x-ray absorptiometry (DXA). To facilitate increased accuracy of BMD values, lateral DXA of the knees was also performed and used to provide a third dimension to the usual two-dimensional anterior-posterior g/cm2, producing measurements as g/cm3. Subchondral bone regions included both superficial and deep regions of the medial femoral, medial tibial, and lateral tibial compartments., Results: BMD (g/cm3) was lower than normal in 6 subchondral bone regions of the knees (n=43) of white female patients with OA (average decrease -13.3%), significant in all 6 subchondral regions (p=0.001 to p=0.047). Two-dimensional BMD (g/cm2) was lower than normal in 6 subchondral regions of the knees (n=43) of white female patients with OA (average decrease -7.3%), significant in only 2 of 6 subchondral regions (p=0.011 to p=0.014). BMD (g/cm3) was lower than normal in 6 subchondral regions of the knees (n=19) of African American female patients with OA (average decrease -9.1%), significant in only one of the 6 subchondral regions (p=0.016). There was no significant difference in spinal BMD (L1-L4) or femoral shaft BMD between normal and OA for either racial group. About 13% of the OA patients had osteoporosis at the spine., Conclusion: A significant decrease in periarticular subchondral BMD is present in female patients with relatively mild OA of the knee whether or not they had osteoporosis based on a spine BMD measurement.

Objective: To clarify in vivo applicability of adenovirus mediated gene delivery to examine a gene therapy for human joint diseases., Methods: We directly injected vectors harbouring beta-galactosidase gene and transforming growth factor (TGF)-beta1 gene into the joints of Hartley guinea pigs. Expressions of delivered LacZ were examined by 5-bromo-4-chloro-3-indolyl-beta-D-galactoside staining and reverse transcription-polymerase chain reaction. The levels of TGF-beta1 that were delivered to the joint and then transferred to the joint fluid were assessed by ELISA., Results: LacZ expression was observed in almost all synovial tissue samples and in chondrocytes on the surface of degenerated cartilage. In the other organs, expression of delivered genes was not observed. For 2 weeks following gene delivery TGF-beta1 levels in joint fluid were significantly higher than the levels in the controls for 2 weeks., Conclusion: Direct gene delivery into the joint cavity is feasible with the in vivo gene delivery method using adenovirus vector and would be clinically applicable.

Objective: To develop methods to quantify intraarticular connective tissue proliferation after immobility and to report results in an animal model of joint contracture., Methods: Six rats had their right knee joints immobilized with an internal fixator for 3 weeks. The joints were harvested and sectioned. We measured the length of synovial intima and the subintimal area with image analysis software. Proliferating synoviocytes were identified by immunohistochemistry using the "proliferating cell nuclear antigen" antibody and were counted under optical microscopy on whole joint sections. Two outcomes were analyzed: the subintimal area and a synoviocyte proliferation index (number of proliferating synoviocytes/synovial intima length). Both were obtained for posterior and anterior aspects of the knee., Results: Intra and interobserver reliabilities over 87% were found with these measurement techniques. Subintimal area means were not statistically different between immobilized and contralateral knees. In all subjects, the synoviocyte proliferation index (SPI) posteriorly was higher in immobilized than in contralateral knees (p<0.05), due to an increase in proliferating cells (p<0.05) rather than a change in synovial intima length (p>0.05). The SPI anteriorly was comparable in immobilized and contralateral knees (p>0.05)., Conclusion: We developed methods to measure intraarticular connective tissue proliferation in a contracture model in vivo. Proliferative changes in the posterior aspect of the knee suggest local mediation of connective tissue proliferation in the contracture process. These methods and preliminary results will benefit investigators assessing interventions in similar models.

Objective: To investigate whether macroscopically fibrillated human articular knee cartilage observed at autopsy can be considered an early, preclinical phase of osteoarthritis (OA)., Methods: Histological and biochemical characteristics of 3 types of articular knee cartilage were compared: macroscopically degenerated knee cartilage obtained at autopsy (6 donors) from donors without clinical history of OA, normal healthy knee cartilage obtained at autopsy (6 donors), and OA cartilage obtained during joint replacement surgery from patients (n = 6) with clinically defined OA of the knee. From the same donors synovial tissue and synovial fluid were obtained and analyzed for features of inflammation., Results: Histological changes of OA were comparable for degenerated and OA cartilage and significantly different from normal cartilage. Content and synthesis of proteoglycans showed intermediate levels for degenerated tissue compared to normal and OA cartilage. Analysis of synovial tissue revealed a low, mild, and moderate degree of inflammation for joints with normal, degenerated, and OA cartilage, respectively. The same sequence was found for metalloproteinase activity in synovial fluid., Conclusion: In general, all changes observed in OA joints were, to a lesser extent, observed in the joints with degenerated cartilage and were significantly different from joints with normal cartilage. We conclude that cartilage degeneration observed at autopsy can be considered a preclinical phase of OA, suitable for studying the process of cartilage degeneration in OA.

Objective: To establish the presence of inflammation in and cytokine production by synovial membranes from patients with various stages of early osteoarthritis (OA), with knee pain, normal knee radiographs, and arthroscopic evidence of chondral damage., Methods: Synovial membrane samples were obtained from the knees of 63 patients at the time of arthroscopy for unexplained knee pain or at the time of joint replacement surgery. Evaluations of synovial membrane variables including thickness of lining layer, vascularity, and inflammatory cell infiltrate were by a blinded observer. In a subset of 20 patients, production of interleukin 1 alpha (IL-1 alpha), interleukin 1 beta (IL-1 beta), tumor necrosis factor alpha (TNF-alpha), and IL-1 receptor antagonist (IL-1ra) at the mRNA and protein levels was determined using in situ hybridization with biotin labeled ribo-probes and immunohistochemistry., Results: There was evidence of thickening of the lining layer, increased vascularity, and inflammatory cell infiltration in synovial membranes from patients with all grades of OA, with the most marked changes seen in synovial tissue from patients with advanced grades of OA. Similarly, production of IL-1 alpha, IL-1 beta, and TNF-alpha was present in synovial membranes from all patients with OA, irrespective of the degree of articular cartilage damage. There was a trend to decreased levels of IL-1ra in synovial membranes from patients with OA that did not attain statistical significance. Similarly, there was a decrease in the ratio of IL-1ra to IL-1 alpha and beta with increasing grades of OA., Conclusion: Chronic inflammatory changes with production of proinflammatory cytokines are a feature of synovial membranes from patients with early OA, with the most severe changes seen in patients at the time of joint replacement surgery resembling those seen in rheumatoid arthritis. This low grade synovitis results in the production of cytokines that may contribute to the pathogenesis of OA.

Objective: The use of nonsteroidal antiinflammatory drug (NSAID) therapy in osteoarthritis (OA) is controversial because of suggestions that pure analgesics can be as effective as NSAID for pain relief. In addition, there is incomplete information whether antiinflammatory effects have any longterm benefit in OA. NSAID have been known to affect synovial fluid (SF) prostaglandins in rheumatoid arthritis. We describe the first examination of the effect of an NSAID, etodolac, on SF prostaglandins, cytokines, and cells in OA., Methods: Joint fluids were studied before and 2 weeks after initiation of therapy with etodolac 400 mg tid. Leukocyte counts, prostaglandin, interleukin 6, and tumor necrosis factor were measured., Results: Pretreatment features of SF did not predict clinical response. We found no change in the relatively low leukocyte counts. However, SF prostaglandin levels and interleukin 6 levels were significantly decreased and tumor necrosis factor alpha levels were increased after therapy with NSAID., Conclusion: This NSAID had potentially important local effects that could be either beneficial or deleterious. Further studies on effects of this and other NSAID on a broader variety of SF and synovial cytokines may help predict longterm effects of NSAID on progression of OA.

Objective: The magnitude of articular cartilage destruction or repair in osteoarthritic (OA) joints has been deduced in some studies from the synovial fluid (SF) concentration of proteins derived from the extracellular matrix of the cartilage, without regard to the low grade synovitis that is often present in this disease. We examined the clearance kinetics of albumin, as a surrogate for cartilage derived proteins, from OA and control joints in an established canine model., Methods: Twelve weeks after the left anterior cruciate ligament of 6 normal dogs was transected, 131I albumin (RISA) was injected into the contralateral (control) knee. Surface radioactivity was monitored for 7 h, and SF was then aspirated to determine the SF RISA concentration and leukocyte count, and calculate the volume of distribution (VD) and clearance of RISA. One week later, RISA was injected into the cruciate deficient knee and these measurements were repeated, then the intensity of synovial inflammation and severity of cartilage changes of OA in both knees were assessed., Results: Synovitis and articular cartilage ulceration were seen only in the cruciate-deficient OA knee, in which the mean SF leukocyte count (1570/mm3), thickness of the synovial intima (mean = 30 microns), and severity of synovial mononuclear cell infiltration (mean = 13,500 cells/mm2) significantly exceeded those in the contralateral knee (850/mm3, 13 microns, 1400 cells/mm2; p < or = 0.01 in each case). In each dog, RISA VD in the OA knee was higher than in the contralateral knee (mean = 9.2 +/- 3.6 and 3.7 +/- 0.9 ml, respectively; p = 0.008) and RISA clearance rate in the OA knee exceeded that in the contralateral knee (3.8 +/- 1.5 and 1.4 +/- 0.3 microliters/min, respectively; p = 0.009)., Conclusion: Accelerated clearance of protein from the OA joint with low grade synovitis could significantly affect the SF concentration of cartilage derived proteins. Therefore, inferences about the effect of a therapeutic agent on cartilage metabolism based upon changes in the concentration of a protein in serial samples of OA SF may be misleading unless protein clearance kinetics have been determined.

Objective: To determine whether bilateral arthroscopic anterior cruciate ligament (ACL) transection creates symmetrical osteoarthritis (OA) in canine knees., Methods: Six dogs underwent bilateral arthroscopic ACL transections. The animals were sacrificed at intervals ranging from 2 to 12 months post ACL transection. Both knees in each animal were assessed for gross pathology, histology, and biochemistry., Results: The limited invasiveness of arthroscopic ACL transection allowed bilateral ACL transections to be performed with minimal animal morbidity. Gross pathological, histological, and biochemical assessments of bilaterally ACL transected canine knees consistently confirmed the induction of OA changes in both knees. Of note, there was no significant difference in the degree of articular cartilage degeneration created in each pair of knees., Conclusion: Bilateral ACL transection induces symmetrical canine knee OA. This approach provides a potent model for investigating fundamental OA mechanisms and therapeutic approaches, since one knee can be experimentally manipulated while the other knee is used as a control. This allows each animal to be its own internal control, avoiding the interanimal variability associated with the unilateral canine OA model.

Objective: The synovial fluid (SF) concentration of proteins (or fragments thereof) derived from the articular cartilage may reflect the processes of cartilage breakdown or repair within an arthritic joint and, hence, serve as a marker of these processes. Because changes in the clearance kinetics of marker molecules in SF would invalidate the assumption that their concentration in SF is directly proportional to turnover of the cartilage matrix, we investigated whether reduction in the concentration and/or molecular size of hyaluronan (HA) in joint effusions affects clearance of albumin from the canine knee., Methods: The volume of distribution and clearance kinetics of radioiodinated serum albumin (RISA) were determined in normal dogs after injection of the knee with HA preparations whose concentration (3.0-0.03 mg/ml) and average molecular weight (0.2-6.1 x 10(6) Da) resembled those seen in synovial effusions, and which increased by roughly 270% the volume of fluid in the joint space., Results: In knees injected with a physiologic concentration (3.0 mg/ml) of high molecular weight HA, the RISA distribution volume (2.8 ml) and clearance rate (1.7 microliters/min) slightly exceeded those in knees in which the SF HA concentration was reduced 55-62% by injection of 0.3-0.03 mg/ml HA, but not those in knees in which the average molecular weight of the SF HA was reduced 84% by injection of exogenous HA with a molecular weight of 2.4 x 10(5) Da., Conclusion: Our data suggest that SF HA is a relatively minor determinant of the kinetics of RISA clearance from the joint, and the changes in HA content seen in joint effusions are unlikely to confound interpretation of the concentration of marker molecules in SF.

Objective: We studied whether inhibition of proteoglycan synthesis on different locations occurs according to a regular stimulus unrelated pattern or whether the response of cartilage is stimulus dependent., Methods: Proteoglycan synthesis in murine knee joint cartilage was measured after in vitro and in vivo exposure to 3 metabolic stimuli, iodoacetate, papain and interleukin 1 alpha (IL-1 alpha). Knee joint cartilage was divided in 4 specific areas: the central and peripheral patella and medial and lateral tibial plateau., Results: The effect on proteoglycan synthesis in cartilage from these locations was similar in the in vitro and the in vivo experiments. Papain evoked more inhibition of the proteoglycan synthesis in tibial cartilage than in patellar cartilage. In contrast, iodoacetate caused more inhibition in patellar than in tibial cartilage. The central part of the patella was more vulnerable than the peripheral part of IL-1 alpha and iodoacetate, and both parts were equally sensitive to papain. Differences in sensitivity between central medial and central lateral tibial plateau were found only with iodoacetate, which inhibited proteoglycan synthesis medially more than laterally., Conclusion: Our results indicate that inhibition of proteoglycan synthesis in specific areas of the knee joint is stimulus dependent.

Objective: To determine in a cross sectional study the concentrations of stromelysin, tissue inhibitor of metalloproteinases (TIMP), and proteoglycan fragments in knee synovial fluid (SF) at different times after injury to cruciate ligament or meniscus., Methods: Joint fluid samples were obtained from patients with knee injury diagnosed by arthroscopy. Concentrations of stromelysin-1 and TIMP-1 were determined by immunoassay with monoclonal and polyclonal antibodies. Cartilage proteoglycan fragments were quantified by immunoassay with polyclonal antibodies or by dye precipitation., Results: Average concentrations of stromelysin increased 40-fold in association with injury, and after about 6 months decreased to a plateau level about 10-fold increased compared to a reference group with healthy knees. TIMP and proteoglycan levels also increased in similar temporal patterns, but less markedly. Increased average SF levels of these markers were maintained for at least 17 years after injury. SF from knees with injury contained a 1.5 to 2.5 molar excess of stromelysin over TIMP, while reference joint fluids contained a 2-fold molar excess of TIMP over stromelysin., Conclusion: The persistent changes in SF markers after joint injury may be associated with the cartilage destruction and frequent development of posttraumatic osteoarthritis in this group of patients.

Objective: To determine the influence of osteoarthritis (OA) on bone density measurements and whether OA at one site is associated with OA at other sites., Methods: Nonrandomized, cross sectional observational study; secondary analysis of a general population database. Sixty-four subjects derived from a longitudinal study of long distance runners and community controls had a complete peripheral radiographic evaluation for osteoarthritic changes in hands, knees, and lumbar spine. Forty-four of these were studied in 1984 with quantitative computed tomography (QCT) of L1, and 54 were studied in 1988 with 153-Gd dual photon absorptiometry (DPA) in the spine and total body. Thirty-four subjects had all measurements done., Results: Total body and lumbar spine DPA were positively correlated with radiological scores of OA in the spine and knees, with coefficients ranging between 0.467 to 0.530 (p < 0.001 in all cases). This correlation was principally associated with spinal spurs and knee sclerosis. Results of stepwise multiple linear regression modeling for QCT included age, spine sclerosis, knee sclerosis and knee spurs as the main predictors of bone mineral density (BMD). For DPA measurements, spine spur score was a useful regressor for all the models. Altogether, the percentage of variance accounted for by individual radiological OA variables was 27.4% for lumbar QCT, 27.3% for lumbar BMD, 7.3% for total spine BMD, and 45.2% for total body BMD. OA scores at different sites were not correlated, although repeated assessment at the same site showed very close correlation., Conclusions: All methods used to determine BMD showed a highly significant positive correlation between lumbar and knee radiological OA and bone mineral content both in the spine and the total body. Thus, our results support the hypothesis that OA is negatively correlated with osteopenia. OA, as seen in this population, was not a generalized condition, but rather, was site specific.

The resting intraarticular pressure and the type of arthropathy [rheumatoid arthritis (RA) or non-RA] have been examined for their importance as determinants of synovial fluid (SF) lactate concentration in patients with knee effusions. SF lactate concentration was higher in RA than in non-RA knees. This difference was not related to the resting intraarticular pressure at the time of sampling. After drainage of SF and saline lavage of the joint, the rate of increase of lactate in a fixed volume of intraarticular saline was examined under resting conditions. The rate of increase of the lactate concentration was significantly greater in RA joints. It is most likely that SF lactate concentration under resting conditions will reflect the lactate concentration during the preceding period of activity which, in turn, is probably a composite function of the extent of synovial hypoxia due to hypoperfusion and the type of arthropathy.

Synovial fluid (SF) samples, all containing monosodium urate crystals, obtained from 18 asymptomatic knees of 12 patients with gout, were serially analyzed before and one month after treatment with 1 mg/day of oral colchicine. Before treatment, the SF contained 612 [confidence limits (CL) = 282, 942] cells/mm3, while after treatment these values decreased to 274 (CL = 73, 471) cells/mm3 (p less than 0.005). In all cases, pretreatment cell counts were higher than the corresponding posttreatment values. The percentage of polymorphonuclear leukocytes also diminished from a pretreatment value of 13.0 (CL = 7, 19) to 4.5 (CL = 2, 7) after colchicine administration (p less than 0.005). These results strongly suggest the presence of baseline subclinical joint inflammation which is reduced by colchicine. The preventive effect of this drug on the occurrence of new attacks may relate to its effect in reducing the baseline inflammation of the asymptomatic joints.

The prevalence and clinical evolution of popliteal cysts in children with knee arthritis is not well known. Using ultrasonography, we studied 44 children with clinically detectable knee effusions secondary to juvenile rheumatoid arthritis (n = 35), spondyloarthritis (n = 3) and psoriatic (n = 2), septic (n = 2) and lupus (n = 2) associated arthritis. Popliteal cysts, defined as anechoic or hypoechoic masses measuring at least 1 cm in 2 of 3 dimensions, were identified in 27 children (61%). Of the 30 children with bilateral arthritis, 11 (37%) had bilateral cysts. The size of the cysts ranged from 1 to 40 cm3 (median 3.0 cm3). There was a significant correlation between the presence of a cyst and popliteal pain and the size of the suprapatellar effusion (p less than 0.001) but not the child's age or underlying diagnosis (p greater than 0.05). A cohort of 25/27 children with cysts were followed prospectively with serial sonograms for 18-24 months. The resolution of the cyst followed that of the suprapatellar effusion in those children whose arthritis improved or resolved. Two children (8%) had rupture of the popliteal cysts. Popliteal cysts are readily documented in children with knee effusions using ultrasonography, and their presence and evolution correlates with the size of the suprapatellar effusion.

The levels of serum keratan sulfate (KS) were measured in 9 dogs who underwent anterior cruciate ligament transection. They rose in some animals as early as 7 days after surgery, long before any decrease in the articular cartilage content of KS containing proteoglycans could be measured; and they reached their maximum in most dogs by Day 21 and remained elevated for at least 13 weeks. In contrast, the serum levels of the KS epitope showed no increase in sham operated control animals. Analysis of synovial fluid suggested an increase in the catabolism of cartilage proteoglycans in the operated joint contributed significantly to the increased levels of serum KS.

We describe a woman with recurrent synovitis in one or both knees treated with intraarticular corticosteroid injections and two 6-day courses of methylprednisolone tablets. She later developed osteonecrosis of her distal femora and proximal tibiae. Her course was complicated by persistent synovitis associated with a large quantity of necrotic fat in the joint fluid.

We describe 3 patients with painful intraarticular knee effusions composed of a viscous milky white suspension of monosodium urate crystals, in the absence of any cellular component. Two patients presented with acute bilateral knee pain. One patient presented with unilateral knee pain of gradual onset. All 3 patients had a history of ethanol abuse. Two patients had a history of gout. Two patients had chronic renal insufficiency, hypertension, and congestive heart failure. One patient had alcoholic cirrhosis. Two patients' pain responded to colchicine. One patient's discomfort was relieved only by repeated arthrocentesis. We conclude that intraarticular free urate can cause painful joints in the absence of an apparent inflammatory response.

The impact of daily, orally administered nonsteroidal antiinflammatory drugs (NSAID) or a steroid on arthritic knee joints of mice with 1-3 weeks of antigen induced arthritis (AIA) was examined by light microscopy. Prophylactic drug effects on inflammatory cell infiltrate in synovium and joint cavity were evident only in mice treated with prednisolone (0.2-5.0 mg/kg). Treatment with diclofenac, piroxicam (both 0.5-7.5 mg/kg) or tiaprofenic acid (3-30 mg/kg) did not change these phlogistic features significantly. Striking, however, was the protective effect of piroxicam on bone apposition, a common trait in murine AIA. Among the other drugs, minor antiosteophyte effects were exerted only by prednisolone. Histological assessment was also performed on osteocyte death which was almost exclusively confined to menisci and tibial subchondral bone. Because of variability in occurrence and intensity, no clear picture emerged from drug effects on this lethal feature. Combined data from this and a previous pharmacological study, directed at chondroprotective effects, points to prednisolone as the best antiinflammatory and joint protective drug.

Cholesterol crystals were demonstrated in synovial fluids from 4 patients with knee osteoarthritis and recurrent synovial effusions. Large crystals (10-80 micros) were readily identifiable by their characteristic plate-like morphology. Some fluids also contained numerous smaller (1-5 microns) irregular, rod and needle shaped crystals. Identification of these crystals as cholesterol was established by x-ray diffraction analysis (2 fluids) and by ultrastructural studies (1 fluid). This study documents the occurrence of cholesterol crystals in osteoarthritic effusions, but their precise pathogenetic significance remains unclear.

The prevalence of pathological calcifications in the menisci and articular cartilage of both knees was investigated macroscopically and radiologically in 130 consecutive autopsies. The mean age of the subjects was 72 +/- 13 years. Only 8 subjects were less than 50 years old. All had been admitted to hospital and no patient had a history of joint disorders. Half of the patients were male. Calcifications were found in 27 (20.7%) cases, all over 60 years of age. There were 15.4% males and 26.1% females affected. The incidence of intraarticular calcifications in females increased from 11.1-37.5% and in males from 20-29.4% for the 60-69 year age group and the over 80-year age group, respectively. One third of affected cases had only meniscal and 2/3 had both meniscal and chondral calcifications. Isolated meniscal calcifications were found more often in 1 and mixed meniscal and chondral calcifications were found in both knees. Severe destructive articular cartilage lesions were observed significantly more often in joints with intraarticular calcifications than in joints of age matched subjects without calcifications. Joints with calcifications showed little evidence of synovial inflammation. Similarly, no specific relationship was found between the presence of crystal and amyloid deposits in the knees examined.

Monosodium urate (MSU) crystals were shown in synovial (SF) fluid taken from the asymptomatic knee joints of 11 out of 13 patients with tophaceous gout. Intracellular crystals were identified in some cases. Examination of synovial biopsies taken concurrently revealed MSU crystals in 2 out of 6 cases. The results show that MSU crystals can be found in SF and synovium in the absence of acute gout. This implies that additional factors are important in the pathogenesis of gouty inflammation.

Metabolic variables in samples of synovial fluid (SF) from 33 rheumatoid arthritis (RA) knees were analyzed. These variables were correlated with radiological destruction and SF proteoglycan concentrations. SF acidosis correlated with radiological involvement (rs = 0.62, p less than 0.002), but not with proteoglycan concentrations. A weak correlation was found between SF acidosis and granulocyte concentrations (rs = 0.37, 0.02 less than p less than 0.05). Metabolic variables covaried as expected. Samples from right and left knees from the same patients correlated regarding cellular and metabolic variables. Our results indicate insufficient nutritional supply in RA joints with increasing radiological involvement.

Newly synthesized and endogenous proteoglycans of human osteoarthritic knee cartilages were studied in short term explant culture. There were more newly synthesized proteoglycans than endogenous uronic acid containing proteoglycans found in the A1 fraction generated by associative CsCl density gradient centrifugation. Thirty-five percent of the proteoglycans in the A1 fraction were shown to elute in the void volume on Sepharose CL-2B, under associative conditions. Reduction and alkylation of the A1 fraction indicated that the endogenous proteoglycan monomer was hydrodynamically smaller than the newly synthesized macromolecule. This was confirmed by a Sepharose CL-2B chromatography of the A1D1 fraction. In comparison to endogenous proteoglycans, the newly synthesized proteoglycan monomers were less capable of forming stable aggregates with exogenous hyaluronic acid. We also found a statistically significant decrease (p less than 0.05) in the amount of already existing proteoglycan subclass when compared to the amount of newly synthesized proteoglycans in the most dense A1D1 fraction. By contrast, a statistically significant increase (p less than 0.05) in the amount of endogenous vs newly synthesized proteoglycans was seen in the A1D2 fraction but not in fractions of a lower buoyant density.

Increased intraarticular hydrostatic pressure (Pia) may inhibit juxtaarticular muscle function, obstruct blood supply to joint structures and promote anoxic joint destruction in chronic arthritis. Joint capsular stiffness together with synovial fluid volume determines Pia at rest. Seventeen knee joints with effusive arthritis and different degrees of radiological cartilage involvement in 13 patients with chronic arthritis were examined. Since capsular elastance was difficult to standardize, we introduce a measure of joint capsular stiffness where the intraarticular volume yielding a pressure of 50 mm Hg (V50) is used. After normalization of injected volumes according to the V50, pressure volume curves became similar. Intraarticular hydrostatic pressure and maximal voluntary isometric extensor torque were measured simultaneously, while altering the intraarticular fluid volume in 9 knee joints. In 5 of these, quantified electromyography (EMG) of the vastus medialis and lateralis portion of the quadriceps muscle was also monitored. Progressive inhibition of extensor torque and EMG was found as the intraarticular pressure volume was increased in both intact and destroyed joints. No difference in inhibition was found for the 2 portions of quadriceps muscle tested. Increased intraarticular hydrostatic pressure Pia levels between 200 and 1150 mm Hg were observed during maximal voluntary activation of extensor muscles. The reproducibility was good for all variables studied. In a few instances evidence of intraarticular compartmentalization was found at low volumes. We conclude that the V50 is a convenient expression of capsular stiffness. Furthermore, increasing Pia caused by joint effusion inhibits knee extensor muscle function and impairs synovial blood flow. Awareness of these relations will facilitate more rational therapeutic approaches in chronic arthritis.