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Objective To compare equine synovial fluid (SF) from injured and control joints for cartilage boundary lubrication function; concentrations of the putative boundary lubricant molecules hyaluronan (HA), proteoglycan 4 (PRG4), and surface-active phospholipids (SAPLs); relationships between lubrication function and composition; and lubrication restoration by addition of HA. Methods Equine SF from normal joints, joints with acute injury, and joints with chronic injury were analyzed for boundary lubrication of normal articular cartilage (kinetic friction coefficient [μkinetic]). Equine SF samples were analyzed for HA, PRG4, and SAPL concentrations and HA molecular weight distribution. The effect of the addition of HA, of different concentrations and molecular weight, on the μkinetic of equine SF samples from normal joints and joints with acute injury was determined. Results The μkinetic of equine SF from joints with acute injury (0.036) was higher (+39%) than that of equine SF from normal joints (0.026). Compared to normal equine SF, SF from joints with acute injury had a lower HA concentration (−30%) of lower molecular weight forms, higher PRG4 concentration (+83%), and higher SAPL concentration (+144%). Equine SF from joints with chronic injury had μkinetic, PRG4, and SAPL characteristics intermediate to those of equine SF from joints with acute injury and normal equine SF. Regression analysis revealed that the μkinetic value decreased with increasing HA concentration in equine SF. The friction-reducing properties of HA alone improved with increasing concentration and molecular weight. The addition of high molecular weight HA (4,000 kd) to equine SF from joints with acute injury reduced the μkinetic to a value near that of normal equine SF. Conclusion In the acute postinjury stage, equine SF exhibits poor boundary lubrication properties, as indicated by a high μkinetic. HA of diminished concentration and molecular weight may be the basis for this, and adding HA to deficient equine SF restored lubrication function.

Objective To evaluate the interleukin-1 inhibitor rilonacept (Interleukin-1 Trap) for prevention of gout flares occurring in the first few months following initiation of urate-lowering therapy. Methods In this double-blind study, adult patients with hyperuricemia and gout were randomized to receive rilonacept administered subcutaneously once per week (loading dose 320 mg followed by 160 mg weekly) or placebo, and started on allopurinol (300 mg/day, titrated to serum urate

To investigate the prevalence of arthritis and associations with arthritis in American Indian and Alaska Native populations.Data on self-reported, doctor-diagnosed arthritis from the baseline visit of 9,968 American Indian and Alaska Native adults from Alaska and the Southwest US were included. The prevalence of arthritis and univariate and multivariate associations between arthritis and demographic characteristics, health-related factors, and treatment are described.The prevalence of self-reported arthritis increased with age. The age-sex adjusted prevalence was high in Alaska (26.1%) and low in the Southwest US (16.5%) as compared with the US population (21.5%). In both centers, arthritis was associated with age, lack of employment, chronic medical conditions, and poorer self-reported overall health. Arthritis was associated with female sex in Alaska only, whereas education, marital status, and urban residency were associated with arthritis in the Southwest US. In both centers, self-reported physical health measured by the Short Form 12 Health Survey was lower in people with arthritis, and mental health was not associated with arthritis. More frequent use of antiinflammatory medications was reported with arthritis in both centers, but increased use of traditional medicine and healers were associated with arthritis only in Alaska.Compared with US rates, the prevalence of self-reported arthritis was higher among Alaska Native people and lower in a Southwest American Indian population. Some factors associated with arthritis differ between the 2 populations.

Objective To characterize histologic alterations and inflammatory infiltrates in the synovium of patients with chronic septic arthritis (SeA). Methods Synovial membranes from patients with SeA (9 specimens; disease duration >4 weeks) were compared with specimens from patients with septic joint prosthesis loosening (septic total arthroplasty [SeTA]; 9 specimens), rheumatoid arthritis (RA; 25 specimens), osteoarthritis (25 specimens), and normal histology (10 specimens). Sections were stained with hematoxylin and eosin, tissue gram stain, and immunostains for von Willebrand factor (vWF; blood vessels), Ki-67 (dividing cells), CD15 (neutrophils), CD3 (T cells), CD20 (B cells), CD38 (plasma cells), and CD68 (macrophages). Results Gram stains were positive in all SeA and SeTA specimens. Mixed polymorphonuclear and mononuclear infiltrates predominated in SeA and SeTA. SeA could be differentiated from RA by higher densities of CD15+ cells (SeA:RA ratio 6.5:1; P < 0.001) or Ki-67+ cells (ratio 2.1:1; P = 0.012). The inflammatory infiltrate of SeTA was similar to SeA but contained fewer CD3+ cells (SeTA versus SeA 0.26:1; P = 0.009) and a tendency toward fewer CD20+ cells. Mean vascular density was strikingly increased in SeA (SeA:normal ratio 3.0:1; P < 0.001) and, to a lesser extent, in the vascularized areas of the SeTA specimens (SeTA:normal ratio 1.9:1). Ki-67/CD31 double immunostains demonstrated proliferating endothelial cells in small subintimal blood vessels, suggesting angiogenesis. Receiver operating characteristic curve analysis identified higher densities of CD15+ and Ki-67+ cells and vWF-positive vessels as histologic markers that differentiated SeA from RA. Conclusion This first analysis of the synovium in patients with chronic pyogenic arthritis identified dramatic neovascularization and cell proliferation, accompanied by persistent bacterial colonization and heterogeneous inflammatory infiltrates rich in CD15+ neutrophils, as histopathologic hallmarks.

To determine whether the synovial fluid (SF) constituents hyaluronan (HA), proteoglycan 4 (PRG4), and surface-active phospholipids (SAPL) contribute to boundary lubrication, either independently or additively, at an articular cartilage-cartilage interface.Cartilage boundary lubrication tests were performed with fresh bovine osteochondral samples. Tests were performed using graded concentrations of SF, HA, and PRG4 alone, a physiologic concentration of SAPL, and various combinations of HA, PRG4, and SAPL at physiologic concentrations. Static (mu(static, Neq)) and kinetic (mu(kinetic, Neq)) friction coefficients were calculated.Normal SF functioned as an effective boundary lubricant both at a concentration of 100% (mu(kinetic, Neq)= 0.025) and at a 3-fold dilution (mu(kinetic, Neq)= 0.029). Both HA and PRG4 contributed independently to a low mu in a dose-dependent manner. Values ofmu(kinetic, Neq)decreased from approximately 0.24 in phosphate buffered saline to 0.12 in 3,300 mug/ml HA and 0.11 in 450 mug/ml PRG4. HA and PRG4 in combination lowered mu further at the high concentrations, attaining amu(kinetic, Neq)value of 0.066. SAPL at 200 mug/ml did not significantly lower mu, either independently or in combination with HA and PRG4.The results described here indicate that SF constituents contribute, individually and in combination, both at physiologic and pathophysiologic concentrations, to the boundary lubrication of apposing articular cartilage surfaces. These results provide insight into the nature of the boundary lubrication of articular cartilage by SF and its constituents. They therefore provide insight regarding both the homeostatic maintenance of healthy joints and pathogenic processes in arthritic disease.