What is the primary pathological process in osteoarthritis?

• A. Degeneration of articular cartilage with subchondral bone remodeling and osteophyte formation
• B. Increased synovial fluid due to autoimmune inflammation
• C. Crystal deposition in joints
• D. Infection of joint space

Answer: (A)

Osteoarthritis is driven by degeneration of the joint’s articular cartilage with subsequent remodeling of the underlying subchondral bone and the development of osteophytes. The primary event is cartilage breakdown from mechanical wear and tear, which reduces the smooth, lubricated surface of the joint. As cartilage deteriorates, chondrocytes try to repair, but the matrix—rich in proteoglycans and collagen—is gradually lost, leading to fissuring and erosion. The exposed subchondral bone responds by becoming sclerotic and, over time, may form cysts. End-stage changes include marginal bone spurs, or osteophytes, that develop as the joint attempts to stabilize itself. This sequence narrows the joint space and causes pain and functional limitation.

In OA, inflammation exists but is not driven by autoimmune processes; it’s typically mild and secondary. This is why the description involving autoimmune synovial inflammation isn’t the primary pathology. Similarly, crystal deposition or joint infection would point to different disease processes (crystal arthropathy or septic arthritis) rather than the degenerative pattern seen in osteoarthritis.