The Phemister triad, classically described in tuberculous arthritis, consists of:

• A Subchondral sclerosis, osteophyte formation, and periarticular calcification
• B Juxta-articular osteoporosis, marginal osseous erosions, and gradual narrowing of the joint space ✓
• C Diffuse osteopenia, central bone destruction, and rapid loss of joint space
• D Periosteal reaction, sequestrum formation, and cloacae

Explanation

Phemister described three radiological features of chronic tuberculous arthritis: osteoporosis around the joint due to hyperaemia and disuse, erosions at the margins where synovium abuts bare bone, and slow cartilage destruction producing late joint space narrowing. Option A describes degenerative disease. Rapid cartilage loss with early space narrowing favours pyogenic arthritis, which destroys cartilage enzymatically within days, whereas tuberculous cartilage destruction is delayed because the mycobacterium lacks proteolytic enzymes.

Reference: Tuli's Tuberculosis of the Skeletal System, 5th ed.

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Written and medically reviewed by the StethoPrep medical team.