Prevalence of lymphoplasmacytic synovitis in dogs with naturally occurring cranial cruciate ligament rupture.

OBJECTIVE: To determine the prevalence of lymphoplasmacytic synovitis (LPS) in dogs with naturally occurring cranial cruciate ligament (CCL) rupture and compare clinical, radiographic, cytologic, and histologic findings in dogs with and without LPS.
DESIGN: Cross-sectional study. ANIMALS: 110 dogs with naturally occurring CCL rupture. PROCEDURES: Histologic examination of synovial biopsy specimens obtained at the time of surgical treatment was used to identify dogs with LPS. Clinical, radiographic, cytologic, and histologic findings were compared between dogs with and without LPS.
RESULTS: 56 (51%) dogs had histologic evidence of LPS. There were no significant differences in age, body weight, duration of lameness, severity of lameness, severity of radiographic signs of degenerative joint disease, extent of CCL rupture (partial vs complete), or gross appearance of the medial meniscus between dogs with and without LPS. Mean tibial plateau angle was significantly lower in dogs with LPS than in dogs without LPS, and dogs with LPS were significantly more likely to have neutrophils in their synovial fluid. Lymphocytes were seen in synovial fluid from a single dog with LPS. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that LPS was common in dogs with naturally occurring CCL rupture. However, only minor clinical, radiographic, cytologic, and histologic differences were identified between dogs with and without LPS.