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Radiology · Musculoskeletal imaging: tuberculous arthritis
Sample itemA child from a rural area has months of knee swelling, night pain, low-grade fever and wasting of the thigh. A radiograph shows periarticular osteopenia, peripheral erosions and a joint space that narrows only slowly. What is the diagnosis?
Original practice item, not a recalled exam question. Nothing here is recorded.
The answer and the reasoning
B. Tuberculous arthritis
The Phemister triad of tuberculous arthritis is juxta-articular osteopenia, peripheral osseous erosions and gradual narrowing of the joint space, because the organism lacks proteolytic enzymes and cartilage is lost late. Pyogenic arthritis destroys cartilage rapidly. Haemophilic arthropathy shows dense effusion and epiphyseal overgrowth.
Option by option
A. Haemophilic arthropathy
Haemophilic arthropathy follows recurrent bleeding with epiphyseal enlargement.
B. Tuberculous arthritis (correct)
Correct. The Phemister triad with constitutional symptoms points to tuberculosis.
C. Pyogenic arthritis
Pyogenic arthritis gives rapid joint space loss and acute toxicity.
D. Juvenile idiopathic arthritis
Juvenile idiopathic arthritis causes a more uniform loss of space and no wasting with night pain.
Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.
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