Qualitative macroscopic and microscopic evaluation of the knee joint in a dog osteoarthritis experimental model 90 days after cranial cruciate ligament transection

Cranial cruciate ligament transection (CCLT) is a well accepted experimental method used for initiating osteoarthritis (OA) in the canine femoro-tibial joint. The aim of the present study was to evaluate qualitatively gross and microscopic OA lesions 90 days after experimental CCLT in twenty-one young mature female beagle dogs. The femoral trochlear ridges showed the highest osteophyte score while the patella had the smallest. The medial femoral condyle exhibited higher osteophyte score than the lateral femoral condyle. Meniscal damages were observed only on the medial meniscus of five operated knees. Gross cartilage lesions (fibrillation) were seen in decreasing order of frequency on medial and lateral tibial condyles, lateral femoral condyle, femoral trochlea, medial femoral condyle and finally patella. Histologically, the superficial layer of the cartilage was fibrillated and discontinuous. Most of the cells were rounded and organised tangentially to the surface. In the transitional and deep layers, some chondrocytes were moderately hypertrophic and some clusters of chondrocytes were observed in the deep layer only. Concerning the synovial membrane, thickening of the mesothelium and a high density of collagen were observed and the ratio of thickness "mesothelium/ fibers" was between 1/0.15 and 1/0.10 in operated knees and 1/0.05 in control knees. The images provided here might be used as references for further work on disease modifying OA therapies.