Total knee arthroplasty in a patient with nail-patella syndrome (NPS).

Nail-patella syndrome (NPS) or hereditary onycho-osteodyaplasia is a rare genetic condition involving a mutation in the LMX1B gene affecting nails, elbows, knees, and pelvis. Due to the regulatory functions of the gene in many developmental processes through the body, patients with NPS experience wide-ranging musculoskeletal problems including patellar instability, fingernail anomalies, iliac exostoses/horns, and elbow abnormalities. The patellar changes often involve aplasia, hypoplasia, and chronic dislocation. Due to these musculoskeletal involvement, arthritis of joints can occur in patients with NPS causing severe pain and disability. This is a case report of a patient with NPS who underwent a total knee arthroplasty for symptomatic knee arthritis.