Fig. 1.

A 61-year-old female patient underwent mobile medial unicompartmental knee arthroplasty (UKA) for medial compartmental osteoarthritis. (A) Anterior dislocation of mobile bearing occurred 31 months after medial UKA. (B) A 4-mm bearing was replaced with a 7-mm bearing. (C) Valgus limb alignment was observed with use of the thicker bearing. (D) Recurrence of bearing dislocation was noted 10 months after bearing exchange. Intraoperatively, medial collateral ligament was found to be lax. (E) Conversion to total knee arthroplasty was performed.