Persistent knee instability following revision total knee arthroplasty

Instability is an important cause of failure following total knee arthroplasty (TKA). Knee stability needs to be optimal in both the coronal and sagittal planes. We describe failed revision TKA with persistent deformity and instability secondary to a deficient medial collateral ligament in a 71-year-old Chinese woman. Revision knee arthroplasty using constrained implants was performed on her with good result. During both primary and revision TKA, assessment of knee stability is critical. Constrained prosthesis would need to be considered when there is significant ligamentous deficiency.