Pseudomeniscal synovial impingement after unicondylar knee arthroplasty

Unicondylar knee arthroplasty (UKA) is a well-established treatment option for unicompartmental knee arthrosis. Although UKA achieves high success rates, surgeons should be aware of many potential sources of persistent postoperative pain. Common causes include septic or aseptic loosening, a loose body, implant failure, and chronic regional pain syndrome. Tibial plateau stress fracture, meniscus rupture, and cement extrusion have also been reported as infrequent causes of persistent pain. We encountered 2 patients in whom persistent pain after UKA was attributed to synovial impingement mimicking a meniscus tear, and we refer to this as pseudomeniscal synovial impingement. This article presents the clinical histories and histologic findings of 2 patients fitted with a mobile-bearing UKA system and a fixed-bearing UKA system, respectively. These patients were successfully treated by arthroscopic excision.