Background <p>Ochronosis is a rare metabolic disorder characterized by the deposition of homogentisic acid in connective tissues, leading to fragility and degeneration. Total knee arthroplasty (TKA) in ochronotic arthropathy is challenging due to compromised bone and soft tissue quality. Patellar tendon rupture during TKA in this context is an uncommon but serious complication.</p> Case Presentation <p>A 64-year-old male with severe degenerative knee arthropathy underwent left TKA. Intraoperatively, blackish discoloration of cartilage and tendons consistent with ochronosis was noted. During patellar eversion, a partial-thickness rupture of the friable patellar tendon occurred. The rupture was repaired. Postoperative recovery included early mobilization with a range-of-motion brace. At six months, the patient regained a knee range of motion from 0 to 120 degrees. Histopathology and biochemical testing confirmed ochronotic arthropathy.</p> Conclusion <p>This case highlights the risk of patellar tendon rupture during TKA in ochronotic patients due to altered tendon integrity. Preoperative recognition and cautious handling of tendons are crucial. Early repair and rehabilitation can lead to favorable functional outcomes. Preoperative tendon evaluation by ultrasonography may help anticipate such complications.</p>