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Current treatment algorithms for stable juvenile osteochondritis dissecans (JOCD) of the knee have not been established. For arthroscopically stable lesion, in-situ arthroscopic fixation with bioabsorbable pins was introduced as a more desirable approach because of less surgical morbidity and faster recovery. However, there is a paucity of literature that concludes on its efficacy. The aim of this study is to determine the efficacy and limitation of in-situ arthroscopic fixation on stable JOCD lesion in the knee. Ninety-six patients with 110 affected knees were reviewed. Subsequently, patients who underwent in-situ arthroscopic fixation for arthroscopically stable JOCD lesions were grouped for further analysis. Arthroscopic lesion stability was graded according to the Guhl's grading system from the surgical description of each lesion. The grade I and II were defined as 'stable' lesions. The lesion status was also evaluated with the MRI grading system described by Dipaola in preoperative images retrospectively. The grade I and II lesions were also defined as 'stable' and more than III as 'unstable'. Clinical outcomes were evaluated by the Lysholm score at the final office visit. If the patient had a revision surgery, the case was classified as a complete failure. There were 13 lesions in 13 patients with open physis treated with in-situ arthroscopic fixation using bioabsorbable pins. In this population, radiographical lesion status and the Lysholm score were significantly improved in 10 cases (preoperative: 77.5±11.2, postoperative: 98.9±3.1, P=0.002); however, we found three revision cases (failure rate, 23%). Of these revision cases, all lesions were graded as 'unstable' in MRI. In this series, the failure rate was 23% for in-situ arthroscopic fixation for arthroscopically stable JOCD lesion of the knee. Because of the potential risk for underestimation of lesion instability, we strongly suggest that this less invasive approach should be chosen with great care for the lesion that presents arthroscopically stable, but as unstable status on MRI., Level of Evidence: Level IV, case series.

We have developed a magnetic system for targeting cells in minimally invasive cell transplantation. Magnetically labeled MSCs (m-MSCs) with nanoscale iron particles can be guided into the desired region by magnetic force from an extracorporeal device. We reported that magnetic targeting of m-MSCs enhances cartilage repair in a mini-pig model. However, the detailed kinetics of these magnetically targeted m-MSCs remain unknown. For clinical use, this aspect should be clarified from a safety standpoint. We therefore investigated the spatial and temporal distribution of the fluorescently-labeled m-MSCs transplanted into the knee joint using in vivo fluorescence combined with three-dimensional computed tomographic imaging in a rat model. Although the intraarticularly injected m-MSCs were spread throughout the joint cavity in the absence of magnetic force, the magnetic force caused the injected m-MSCs to accumulate around the chondral lesion. Further examinations including ex vivo imaging, histological assessments and reverse transcription polymerase chain reaction revealed that transplanted MSCs were not present in any major organs after intraarticular administration, regardless of magnetic targeting. Our data suggest that m-MSCs can be accumulated efficiently into a chondral lesion using our magnetic targeting system, while none of the intraarticularly transplanted MSCs migrate to other major organs., (© 2015 Wiley Periodicals, Inc.)

We analyzed the mechanical and histological variables after the attachment of an autogenous tendon graft to cortical or cancellous bone. We reconstructed the medial collateral ligament of the knee in 33 Japanese white rabbits, using a bone socket procedure. The floor of the bone socket was cortical bone in group A and cancellous bone in group B. Mechanically, the pull-out test showed a tendency towards an increase in maximum failure load, with 10.9 N, 35 N and 37 N in group A, and 11 N, 18 N and 36 N in group B at 2, 4 (statistically significant difference) and 8 weeks after surgery, respectively. Histologically, the attachments were immature at 2 weeks. At 4 weeks, granulations had matured and Sharpey's fiber-like structures were seen. These fibers were more abundant in group A than in group B. At 8 weeks, the attachments in both groups were rather like the normal 4-zone structure. With time, tendon attachments matured in both groups. Our study showed that reattachment of tendons to cortical bone may be bettter than to cancellous bone.

We studied 16 women 21-23 years old with regular menstrual cycles (28+/-4 days) and no history of knee injury. From their basal body temperatures and the serum concentrations of estradiol and progesterone, the follicular, ovulatory, and luteal phases were delineated. Using a KT-2000 arthrometer, anterior displacement at 89 N and 134 N and anterior terminal stiffness (N/mm) at 134 N were measured two or three times every week over a 4-week period. Eight men 21-23 years old were also measured. In women the anterior displacement at 89 N varied between the follicular and the ovulatory phase and between the follicular and the luteal phase ( P<0.05) and at 134 N between the follicular and the luteal phase ( P<0.05). There were no statistical differences in the anterior displacement with time in men, nor in anterior terminal stiffness in either sex. We conclude that anterior cruciate ligament laxity in women might be dependent on the concentrations of hormones.

The cruciate ligament of the knee receives its nutrition from a direct vascular supply and by permeation of nutrients from the synovial fluid. The contributions of these two routes as nutritional pathways are not known in detail. In this study, we injected [3H]methyl glucose as a tracer intravenously or directly into the knee of rabbits. Tracer concentrations in plasma, synovial fluid, the posterior cruciate ligament (PCL), and the lateral collateral ligament (LCL) were analysed by a pharmacokinetic compartment model. The contribution of [3H]methyl glucose permeation from the synovial fluid during steady state was calculated at 44.3% in the PCL and at 39.0% in the LCL. Although these results indicated that more than half the nutrition for both ligaments is provided by its vascular supply, synovial fluid permeation is also an important transport route for small molecules for the PCL and the LCL, which is an extra-articular structure.

Changes in the permeability of horseradish peroxidase (HRP) and the histology of the rabbit anterior cruciate ligament (ACL) caused by knee immobilization were studied. The knees of adult rabbits were immobilized for 2-8 weeks by a long leg cast with the knee flexed at 120 degrees, and some joints were allowed to be remobilized for 4 weeks after 6 or 8 weeks' immobilization. After 1 ml of HRP was injected into the knee joint and allowed to permeate into the ACL, the degree of permeation at the mid-portion of the ACL between femur and tibia was visualized with diaminobenzidine tetrahydrochloride. The ACL was examined histologically by light and transmission electron microscopy. Although the HRP permeated into almost the entire area of the transverse section of the non-immobilized normal ACL, as the period of immobilization increased, the extent of permeation gradually decreased. The decrease was significant from week 4 to week 6 and from week 6 to week 8. Degenerative change with necrosis of cells at the central area of the ACL was noted in the 6-week immobilization group, and the 8-week period of immobilization increased the extent of this degeneration. Although the permeation recovered in both the 6-week and 8-week immobilization groups 4 weeks after remobilization, there were fewer cells with a normal morphology in the central area in the 8-week immobilization group than in the control. These results suggest that long-term immobilization adversely affects the ACL.

We report a case of lipoma arborescens of both knee joints. In the face of chronic joint hydrops, it is important to consider lipoma arborescens in the differential diagnosis and to try to make early diagnosis, using magnetic resonance imaging or another means of examination.

Deep-frozen allogeneic meniscal grafts for the treatment of articular cartilage defects were performed experimentally. Osteochondral defects 3 mm in diameter were created bilaterally on the medial femoral condyles of 50 Japanese white rabbits. A meniscus was then grafted into the defect in the left knee, and the right knee was left untreated. At various periods from 2 to 24 weeks postoperatively, the rabbits were killed and macroscopic and histologic examinations were performed. Two weeks after operation, the grafted meniscus was bonded to the floor of the defect. After 12 weeks, chondrocytes producing matrix granules was shown by electron microscopy. After 24 weeks, a congruous articular surface was formed. With time, cellular elements infiltrated into the graft from the surrounding tissues, and gradually increased in penetration. Weight bearing in the early stage after operation did not degrade the grafted menisci, and no changes were shown in the opposing cartilage of the tibia. Deep-frozen allogeneic menisci may be useful as a biological implant to repair articular cartilage defects in this model.

Osteochondral defects in the knee joints of five patients caused by trauma or osteochondritis dissecans were repaired using deep-frozen allogeneic meniscal grafts. Three patients were male and two were female, with a mean age of 26.4 years. The mean follow-up period was 31 months. Postoperative magnetic resonance imaging (MRI) at all periods clearly showed a smooth and congruous articular surface, although the signal intensity of the grafted meniscus was not the same as that of the articular cartilage. Second-look arthroscopy performed approximately 1 year after surgery demonstrated that the grafted meniscus was well bonded to the grafted site, not sunken; there was no gap between the grafted meniscus and the surrounding articular cartilage, indicating that the grafted meniscus functions as a part of the articular surface. Histologic examination revealed that host cells had infiltrated into the meniscus and that cells surrounded by thin collagen fibrils were morphologically similar to fibrochondrocytes. Thus, the acellular grafted meniscus regenerated as meniscal tissue and formed an articular surface, although hyalinization did not occur. Our results suggest that deep-frozen allogeneic meniscal grafting is a useful method to repair osteochondral defects in the knee joint.

Chondral lesions of the knee joint, which have been detected via arthrotomy or arthroscopy, were examined prospectively and retrospectively through a review of previously obtained magnetic resonance images (MRIs). The study group was composed of 34 men and 29 women whose average age was 24.6 years. Of these 63 patients, there were 72 articular cartilage lesions in 65 knees. On retrospective analysis, the sensitivity of MRI, which was defined as a true positive reading for softening, fragmentation, erosion, and/or a full-thickness loss of cartilage, was 14.3%, 57.3%, 75.0%, and 100%, respectively. Although the sensitivity to early changes of chondral lesions was low, indicating the limitation of MRI at the present stage, it has been demonstrated that MRI can delineate intracartilaginous changes associated with softening and thickening of cartilage that cannot be detected even with arthroscopy. Therefore, it may be worthwhile to perform an MRI as well as arthroscopy to clarify the pathogenesis of internal derangement of the knee.