In pseudogout (calcium pyrophosphate deposition disease), which radiological finding distinguishes it from osteoarthritis?

• A Osteophyte formation at joint margins
• B Periarticular osteopenia
• C Calcification of joint cartilage (chondrocalcinosis) especially in menisci and triangular fibrocartilage ✓
• D Joint space narrowing predominantly in the lateral compartment of the knee

Explanation

Calcium pyrophosphate deposition (CPPD) disease characteristically deposits calcium pyrophosphate crystals in hyaline and fibrocartilage. On X-ray, chondrocalcinosis (linear calcification within articular cartilage) is the hallmark, seen most commonly in the medial menisci of the knee, triangular fibrocartilage complex of the wrist, and symphysis pubis. Osteoarthritis also causes joint space narrowing and osteophytes but lacks chondrocalcinosis. Periarticular osteopenia is a feature of rheumatoid arthritis. Synovial fluid shows rhomboid-shaped positively birefringent crystals under polarized light.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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