Lateral patellofemoral impingement: a cause of treatable pain after TKA.

Multiple etiologies may cause anterior knee pain after total knee arthroplasty. While prior studies have addressed component positioning and surgical technique, no series in the literature describes lateral patellofemoral impingement as a source of the pain. Over a 2-year period at our institution, 18 patients with 19 painful total knee arthroplasties were diagnosed with lateral patellofemoral impingement. All underwent revision surgery with either lateral facetectomy or revision of the patellar dome. These patients were followed with Knee Society scores for 1 year. Knee Society scores were significantly improved at 8 weeks, 16 weeks, and 1 year. Lateral patellofemoral impingement should always be considered in the differential diagnosis of the painful total knee arthroplasty. This should be evaluated clinically through direct palpation of the lateral facet, and radiographically with the sunrise view. Lateral facetectomy or patellar revision can be performed with predictably good clinical results.