Ochronosis is a rare metabolic disorder characterized by homogentisic acid deposition in the large joints and spine, resulting in progressive degeneration. We present two cases of ochronotic arthritis of the knee subjected to cemented total knee arthroplasty (TKA). These cases were diagnosed intraoperatively and later confirmed with a histopathologic examination. Orthopedic surgeons should be aware of the condition as the intraoperative finding of darkened cartilage might surprise them. After a five-year TKA follow-up, both of our cases showed better mobility and function.