Synovitis Precedes Stifle Instability Associated with Cruciate Ligament Rupture

This chapter describes the characteristics of synovial inflammation in dogs with cruciate ligament rupture (CR) and its impact on cruciate ligament and joint degeneration. The synovial membrane is a specialized collagenous tissue lining the interior and all structures within a synovial joint, except articular cartilage. Synovitis is characterized by infiltration of the synovial membrane with inflammatory cells, resulting in vascularization and hyperplasia of the synovium. Objective evaluation of the synovial membrane is not routine in clinical veterinary practice or research, despite the increased use of arthroscopy and the importance of synovitis in joint disease. The value of synovial tissue assessment has been documented in humans with osteoarthritis (OA), rheumatoid arthritis, and other joint conditions. The synovium in stable stifle joints with early clinical or radiographic evidence of arthritis is inflamed. Radiographic arthritis correlates with arthroscopic observations of synovitis but generally underestimates the severity.