Stifle joint alterations associated with canine patellar luxation: A clinical and histopathological study

The abnormal placement and movement of the patella outside the trochlear groove in patellar luxation affected the stifle joints, resulting in microscopic and macroscopic alterations in the soft tissue and bony structures of the canine stifle joint. This study focuses on the histopathological changes in articular cartilage and joint capsule from the affected joint and the gross, macroscopic lesions observed intra-operatively during surgical correction. Erosive lesions of the articular cartilage were noted in different subdivisions of the stifle joint. The articular cartilage and joint capsule from two control dogs were also histologically assessed. The articular cartilage and joint capsule in affected dogs showed inflammatory and degenerative changes. The articular cartilage sections showed statistically significant loss of safranin-o stain uptake and % loss of chondrocytes in Group III (Grade 4) cases. The gross macroscopic alterations revealed articular cartilage erosive lesions, primarily on the distal patella and lateral trochlea, as well as osteophytosis in the joints. The study reports higher changes in stifle joint structures with the progression of the luxation grade.