A 40-year-old woman presents with pain and swelling over the left ankle for 8 months. There is a small sinus tract over the lateral malleolus discharging serous fluid. Radiograph shows periarticular osteoporosis, marginal erosions, and preserved joint space. Which feature distinguishes tuberculous arthritis of the ankle from pyogenic arthritis?

• A TB arthritis preserves joint space longer despite marginal erosions ✓
• B TB arthritis shows early marked joint space narrowing
• C Pyogenic arthritis spares the joint space until late
• D Pyogenic arthritis shows periarticular osteoporosis as the earliest sign

Explanation

In tuberculous arthritis, the joint space is preserved relatively longer because the synovium is primarily involved and cartilage destruction is slow. Marginal erosions and periarticular osteoporosis appear early. Pyogenic arthritis rapidly destroys cartilage, causing early marked joint space narrowing. Periarticular osteoporosis is a feature of TB, not pyogenic infection.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.