Recurrent dislocation of total knee arthroplasty: an unusual cause.

We report an unusual case of recurrent dislocation of posterior stabilized total knee arthroplasty (TKA) secondary to fracture of the polyethylene insert. Recurrent dislocation occurred 21 months after primary TKA. Fractured polyethylene insert was noted as an abnormal radiolucent shadow on postoperative radiographs and was confirmed by an arthrogram. At revision surgery, disintegration of the insert, including the tibial post, was found. We recommend careful scrutiny of the integrity of the polyethylene insert at the time of follow-up evaluation in cases of TKA dislocation.