What is the early radiographic sign of hip osteoarthritis?

• A. Joint space narrowing
• B. Subchondral sclerosis
• C. Osteophyte formation
• D. Joint space widening

Answer: (A)

The main thing this question tests is what plain X-ray changes appear first when hip osteoarthritis starts. Cartilage is not visible on standard radiographs, so the earliest indicator is loss of cartilage thickness shown as a narrowing of the joint space between the femoral head and the acetabulum. As the disease progresses, the bone responds with subchondral sclerosis (increased bone density under the cartilage) and osteophyte formation at joint margins. Joint space widening is not typical of OA and would point away from degenerative changes. In summary, narrowing of the joint space is the first clear radiographic sign of hip OA, with sclerosis and osteophytes appearing later.