Abstract
Alkaptonuria is a metabolic disorder characterized by homogentisic acid accumulation in connective tissue. Ochronotic arthropathy, a rare condition reported in alkaptonuria, mostly affects the knee joint. In this study we reported a 57-year-old male patient presented with bilateral hip pain. During the operation, black bone tissue and tendons were observed. We examined the patient for alkaptonuria after the operation and the diagnosis was confirmed. In fact, alkaptonuria was not detected until the operation. Therefore, our study suggests that orthopedic surgeons be suspicious of atypical arthropathy in order to avoid being overwhelmed by the appearance of black cartilage during surgery.