summary TKA Peroneal Nerve Palsy is a rare, potentially devastating, complication of TKA that is most commonly seen following correction of a knee with a valgus and/or flexion deformity. Diagnosis is made clinically post-op with decreased sensation in peroneal nerve distribution with weakness if dorsiflexion of the ankle. Treatment is placing the knee in flexion immediately post-operatively. Observation and AFO in the presence of foot drop are recommended to monitor for recovery of the nerve. Neurologic Injury (Peroneal nerve) Introduction incidence 0.3%-2% risk factors preoperative valgus and/or flexion deformity tourniquet time > 120 min postoperative use of epidural analgesia aberrant retractor placement preoperative diagnosis of neuropathy (centrally or peripherally) prognosis 50% or more improve in time with no additional treatment Anatomy common peroneal nerve lying on lateral head of gastrocnemius at the level of the joint line distance from posterolateral corner of tibia to peroneal nerve is 9mm-15mm at this level Evaluation EMG obtain after 3 months if no improvement Treatment remove dressing and place knee in flexed position indications initial postoperative management in all cases noted in the immediate postoperative period ankle-foot orthosis indications complete foot drop late nerve decompression or muscle transfer indications no recovery after 3 months