Posterior knee dislocation after total knee arthroplasty in a patient with multiple sclerosis. A case report.

A patient with multiple sclerosis (MS) and severe osteoarthritis of the right knee with valgus deformity developed early in the postoperative period a posterior dislocation of the knee after total knee arthroplasty (TKA), due to severe spasm of her hamstring muscles. At revision surgery the posterior cruciate retaining prosthesis was exchanged for a non-linked constrained knee prosthesis. Technical considerations are described for this rare complication, which remains a serious clinical challenge for the orthopaedic surgeon.