Osteoarthritis, or degenerative joint disease, is a slow, progressive articular disease that is characterized clinically by the gradual development of joint pain, stiffness, and limitation of motion. The most prominent pathological change is the degeneration of articular cartilage.
Osteoarthritis is classified as: Primary (or idiopathic) when it occurs without a known predisposing factor; or Secondary when it follows an identifiable local or systemic underlying cause.

The radiographic abnormalities of osteoarthritis include: loss of joint space, appearance of subchondral bone cysts, formation of osteophytes, and eburnation (sclerotic bone formation).

Osteoarthritis of the hip, also known as malum coxae senilis, usually occurs in older individuals. It may be unilateral or affect both sides. However approximately 100% of patients with unilateral osteoarthritis in the hip will progress to bilateral disease.