Mild to moderate inflammation of the femorotibial and femoropatellar joints of unknown origin is common. Severity of lameness varies. Synovitis and capsulitis may result from athletic sprain of the joints. Mild trauma to the articular cartilage, menisci, or any of the ligaments of the stifle may produce mild to moderate synovitis. Mild synovitis usually responds to rest and intra-articular and systemic anti-inflammatory drugs. If joint inflammation and lameness persist, further diagnostic investigation and arthroscopic examination are advisable to assess concurrent or causative injuries and to prevent ongoing degenerative joint disease and development of osteoarthritis.
Osteoarthritis of the femorotibial or femoropatellar joints may follow any of the causes of stifle lameness described and usually results in persistent lameness of varying severity. Diagnosis is confirmed with intra-articular anesthesia and radiography. Radiographic changes include periarticular remodeling with osteophyte formation and remodeling of the joint margins (particularly the medial tibial plateau), changes in the subchondral bone, narrowing of the joint space, and dystrophic mineralization of the soft tissues. The prognosis for athletic soundness in horses with osteoarthritis of the stifle is poor, and treatment is usually palliative. Newer techniques for arthroscopy and regenerative therapy may offer some hope for severely affected joints.