This nonspecific condition affecting mainly the hip and stifle is characterized by degeneration of articular cartilage and eburnation of subchondral bone, joint effusion, and fibrosis with calcification of the joint capsule.
Many causes and predisposing factors influence the development of degenerative joint lesions. There is almost certainly an inherited predisposition to the condition. Certain conformations, eg, straight hocks in beef bulls, are also incriminated. Joint instability after trauma is a common cause. Nutritional factors involved in some cases, such as rations high in phosphorus and low in calcium, influence the strength of subchondral bone. Copper deficiency or fluoride poisoning also may act similarly. Forced traction of a calf in breech presentation can impede the blood supply to the hip joint, and arthritis may result. The role of infection is unclear. Infectious arthritis in calves usually produces severe changes in the hock, but degenerative arthropathy rarely involves this joint.
Bulls fed high-grain diets for show may become lame when as young as 6–12 mo, but most cases are first noticed at 1–2 yr.
Onset is gradual (later in bulls), and both hip joints are usually affected; stifle involvement is rare. Lameness to the point of incapacitation, with crepitation of degenerate joints, may develop in a few months; however, correlation between pathologic changes and clinical signs is poor. The earliest changes occur in the acetabulum and on the dorsomedial surface of the femoral head.
In the stifle, the medial condyle of the femur shows the earliest changes. Because degenerative arthropathy may result from any of several initiating factors, a specific diagnosis may be difficult.
Radiographic, cytologic, and microbiologic evaluation of the synovial fluid are useful diagnostic aids. Arthroscopy of articular surfaces and ligaments may help attain a definitive diagnosis and prognosis.
Changes in the joints are usually irreversible by the time of diagnosis. Palliative treatment of valuable breeding animals should be undertaken with the knowledge that the condition or predisposing factors may be inherited. The diet should be carefully analyzed and, if necessary, corrected. This is especially important in fast-growing animals, in which adequate exercise is indicated and overfinishing should be avoided.