Ochronotic Surprise during Total Knee Replacement! A Case Report.

Introduction: Alkaptonuria is a rare autosomal recessive metabolic disorder characterized by accumulation of homogentisic acid (HGA) due to an inherited deficiency of the enzyme HGA oxidase. Unlike rheumatoid arthritis which affects the small joints of the hands and feet, ochronotic arthropathy predominantly involves the large weight-bearing joints such as hips, knees, and spine. The knee is the most common joint to be affected. Ochronotic arthropathy is usually managed conservatively, but for severely affected hip and knee joints, replacement is considered. Case Report: This report describes a case of 57-year-old male who presented with bilateral knee osteoarthritis who was incidentally diagnosed with ochronosis intraoperatively during total knee arthroplasty, its challenges faced and post-operative functional outcome after 18 months follow-up. Conclusion: This case report highlights the need for high index of suspicion for preoperative diagnosis of ochronotic arthropathy. Difficult spinal anesthesia should be anticipated. Friable and stiff tendon due to ochronotic involvement can put the extensor tendon at risk of rupture during retraction of patella intraoperatively. Post-operative active quadriceps rehabilitation should be done with caution due to friable tendon.