Acute locking in revision total knee arthroplasty due to disengagement of the locking screw.

Acute locking of the joint in a replaced knee joint is very rare. This report describes an acute locking episode of a revised modular total knee replacement, occurring more than 2 years after surgery. A disengaged screw from the modular femoral component had lodged in the joint at the inferior pole of the patella and required urgent arthroscopic removal. There was no subsequent failure of the stem-condylar junction, nor loosening of the femoral component.