The Black Knee: A Rare Case of Knee Ochronotic Arthopaty in an Elderly Patient with Unknown Alkaptonuria

Alkaptonuria and consequent ochronotic arthropathy are often a challenging diagnosis to carry out. Most of times patients are not aware of their illness and the surgeon discovers the diagnosis intraoperatively thanks to typical synovium and cartilage blackish color. We report the case of a 79 years old patient who found his alkaptonuria out after knee arthroplasty initially performed for degenerative knee joint. Diagnosis was supposed to be alkaptonuria intraoperatively by the signs and confirmed after surgery with histological examination and laboratory tests.