Peroneal nerve palsy after total knee arthroplasty (TKA) occurs with an incidence of 0.3%-4%. Patients will typically present acutely / subacutely with a foot drop (inability to dorsiflex), inability to extend the toes, and/or numbness overlying the dorsum foot, based on the common peroneal nerve distribution to the anterior and lateral compartments of the lower leg musculature and sensory nerves in this area. It affects men and women equally.

Risk factors for peroneal nerve palsy after TKA include aberrant retractor placement, preoperative valgus deformity, preoperative flexion contracture, extended tourniquet time, epidural anesthesia for pain control, previous laminectomy, and preoperative neuropathy.

The peroneal nerve can become injured from traction, direct injury, or prolonged ischemia.

• Traction: Correction of a preoperative valgus deformity and/or flexion contracture (tight lateral structures) to a neutral alignment can stretch the nerve, causing neuropraxia or injury from ischemia as a result of fascial compression at the time of realignment.
• Direct injury: During surgery, the nerve can be directly injured by an errant saw cut or placement of a retractor along the posterolateral corner of the tibia.
• Ischemia: Prolonged tourniquet time can cause direct or indirect ischemic injury to the nerve from constricted blood flow to the limb during surgical intervention in an already systemically compromised extremity (preoperative vascular disease).
• Tight postoperative dressings may cause nerve compression.