Osteoarthritis? Ochronotic arthritis! A case study and review of the literature.

Alkaptonuria is a rare disease in which the body does not have enough of an enzyme called homogentisic acid oxidase. Osteoarthritis is the most common degenerative joint disease. Ochronotic arthritis which resulting from the deposition of oxidized homogentisic acid within the connective tissues of peripheral joints has clinical feature that resembles those of osteoarthritis, but it has a unique manifestation. We reported a case of a patient of ochronotic arthritis, arthroscopic findings showed large areas of darkly pigmented full-thickness cartilage defects in the right knee, the whole meniscal parenchymatous tissue was also darkly pigmented. Histological investigation proved to be ochronosis.