Peroneal nerve palsy after total knee arthroplasty. The prognosis for peroneal palsy after total knee arthroplasty (TKA) is poorly defined. Twenty-six postoperative peroneal palsies occurred after 8998 TKAs performed between 1972 and 1985. Eighteen patients had complete and eight had incomplete peroneal palsies. Twenty-three had both motor and sensory deficits, and three had only motor deficits. At an average of 5.1 years (range, one to 11 years) after arthroplasty, recovery was complete for 13 palsies and partial for 12. Complete recovery was more likely in those palsies that were incomplete initially. Patients with palsies that were initially partial had significantly higher knee scores than those with complete palsies, and patients whose eventual recovery was complete had significantly higher knee scores than those with incomplete recovery. This new prognostic information should be useful for surgeons who encounter this unfortunate yet persistent complication of TKA. 