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This study aimed to examine the effects of an episode of in vivo cyclic loading on rat knee articular cartilage (AC) under medium-term observation, while also investigating relevant factors associated with the progression of post-traumatic osteoarthritis (PTOA). Twelve-week-old Wistar rats underwent one episode comprising 60 cycles of 20 N or 50 N dynamic compression on the right knee joint. Spatiotemporal changes in the AC after loading were evaluated using histology and immunohistochemistry at 3 days and 1, 2, 4, and 8 weeks after loading (n = 6 for each condition). Chondrocyte vitality was assessed at 1, 3, 6, and 12 hours after loading (n = 2 for each condition). A localized AC lesion on the lateral femoral condyle was confirmed in all subjects. The surface and intermediate cartilage in the affected area degenerated after loading, but the calcified cartilage remained intact. Expression of type II collagen in the lesion cartilage was upregulated after loading, whereas the superficial lubricin layer was eroded in response to cyclic compression. However, the distribution of superficial lubricin gradually recovered to the normal level 4 weeks after loading-induced injury. We confirmed that 60 repetitions of cyclic loading exceeding 20 N could result in cartilage damage in the rat knee. Endogenous repairs in well-structured joints work well to rebuild protective layers on the lesion cartilage surface, which may be the latent factor delaying the progression of PTOA., (© 2020 Orthopaedic Research Society. Published by Wiley Periodicals LLC.)

The aim was to use repeat delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) to estimate glycosaminoglycan (GAG) content in reparative cartilage after osteochondral autogenous transfer (OAT). The study group comprised 7 knees of 7 patients that were examined three times by dGEMRIC, at 3, 6, and 12 months using a 1.5 Tesla MRI system in both OAT operated and nonoperated condyles at 90 min after the injection. The gadolinium diethylene triamine pentaacetic acid (Gd-DTPA)(2-) containing contrast medium (0.2 mmols/kg) was injected intravenously. The mean T1 values of the plug cartilage at 3, 6, and 12 months after OAT was 230 ± 40, 213 ± 31, and 230 ± 23 ms (mean ± SD), respectively. There were differences between the plug and control cartilage at 3 (p < 0.01) and 12 (p < 0.05) months after OAT, but not at 6 months (p = 0.089). No T1 changes were detected between the plug cartilage at the different time points after OAT. The fact that the GAG content of the OAT plugs were maintained for 12-month study period suggest that no major deterioration of load-bearing properties occurs in the cartilage after the OAT., (Copyright © 2011 Orthopaedic Research Society.)

Although osteochondral grafting surgery is believed to replace damaged cartilage with healthy-looking normal cartilage, no study focuses on ultrasound quantification of those cartilage immediately after the surgery. It is unknown whether the ultrasound properties of damaged cartilage from trauma or osteonecrosis are same with each other. We have examined ultrasound properties of damaged cartilage, adjacent intact cartilage and plug cartilage during osteochondral grafting surgery for 15 knees of 15 patients, mean age of 43.4 (range, 14-61) years. Results showed that signal intensities of ultrasound (a measure of superficial cartilage integrity) of intact cartilage, damaged cartilage, and plug cartilage were 1.91 (arbitrary unit), 0.40, and 2.13, respectively, in 11 knees of 11 patients of traumatic cartilage lesions. Interval between signals of ultrasound (a parameter related to thickness) were 2.79 (micros), 1.90, and 2.85, respectively. The signal intensity and the interval between signals of plug cartilage were 533% (P < 0.01) and 150% (P < 0.01) of damaged cartilage, respectively. In four knees of four patients of osteonecrosis, the signal intensities of intact cartilage, damaged cartilage, and plug cartilage were 1.25, 0.30, and 1.39, respectively. The interval between signals were 2.36, 2.00, and 2.69, respectively. The signal intensity and the interval between signals of plug cartilage were 463% (P < 0.01) and 135% (P < 0.05) of damaged cartilage. We conclude that ultrasound properties of the damaged cartilage from trauma or osteonecrosis did not differ a lot especially in the late stages of osteonecrosis and that the osteochondral grafting surgery replaced the damaged cartilage with plug cartilage that had greater superficial cartilage integrity and greater thickness parameter immediately after the surgery. Long-term effect of the osteochondral grafting surgery should be verified in further study.