Medial patellar luxation induces cartilage erosion in dogs: a retrospective study of prevalence and risk factors.

Objective: To explain the relationship between cartilage erosion and medial patellar luxation (MPL) and to identify risk factors in dogs.

Methods: A retrospective review was conducted on 90 dogs (103 stifles) surgically treated for MPL between January 2006 and March 2024. Data collected included signalment, side of operated stifle, patellar luxation grade, symptom duration, and lameness score. Cartilage erosion was evaluated for extent and location on the patella and femoral trochlea. Statistical analyses were conducted to identify risk factors.

Results: The prevalence of cartilage erosion of the patella and femoral trochlea was 47.6% (49/103) and 54.4% (56/103), respectively, increasing with a higher grade of patellar luxation. Lesions were most prevalent in the distolateral patella and proximomedial trochlea, with generalized lesions more prevalent in grade IV. The extent of both lesions was significantly associated with age, patellar luxation grade, and symptom duration, while body weight significantly correlated only with the cartilage erosion of the patella. No significant correlation was observed with sex, side of operated stifle, or lameness score.

Conclusions: Many patients with MPL exhibited cartilage erosion in the patellofemoral joint, likely due to biomechanical mechanisms. Surgery can be indicated for patients with MPL, as it may prevent cartilage erosion while improving patellofemoral alignment and gait. When selecting surgical candidates, it is important to consider risk factors, such as patellar luxation grade, body weight, age, and symptom duration.

Clinical relevance: Early surgical treatment is recommended, especially for dogs with higher body weight and higher grade of MPL, to prevent cartilage erosion and secondary osteoarthritis.