Risks and complications in knee replacement are similar to those associated with all joint replacements. The most serious complication is infection of the joint, which occurs in <1% of patients. Risk factors for infection are related to both patient and surgical factors. Deep vein thrombosis occurs in up to 15% of patients, and is symptomatic in 2–3%. Nerve injuries occur in 1–2% of patients. Persistent pain or stiffness occurs in 8–23% of patients. Prosthesis failure occurs in approximately 2% of patients at 5 years.