Een man met pijn en zwart kraakbeen

Diagnose in beeld
David Visser en Jan A.N. Verhaar

A male with black cartilage

A 52-year-old men suffered from osteoarthritis of the knee. During knee replacement surgery, the remaining cartilage appeared black. This discoloration and early degeneration of the cartilage is characteristic for the metabolic disorder alkaptonuria in which homogentisic acid accumulates in the body.

Conflict of interest and financial support: none declared.