Fabellar impingement after total knee replacement--a case report.

An unusual postoperative knee pain caused by fabellar impingement after total knee replacement is described. A 68-year-old woman with knee arthrosis had large fabellae in both knees. She had total knee replacements of both knees. One knee developed fabellar impingement to the knee prosthesis, while the other knee was free of symptoms due to simultaneous fabellectomy during knee replacement. At 3-month postoperative follow-up, pain and local tenderness at posterolateral aspect of the left knee was noted during flexion up to 90 degrees. Physical examination revealed a tender fabella on the posterolateral part of the left knee. The lateral radiograph of the knee revealed a large fabella impinging on the prosthesis. The symptoms and signs were alleviated after surgical excision of the fabella. Careful evaluation of the preoperative lateral radiograph of the knee is necessary to detect a large fabella. If it is present and larger than 1 cm, excision during knee replacement is recommended.