Knee replacement, also called knee arthroplasty or total knee replacement, is a surgical procedure to resurface a knee damaged by arthritis. Metal and plastic parts are used to cap the ends of the bones that form the knee joint, along with the kneecap. This surgery may be considered for someone who has severe arthritis or a severe knee injury. Knee replacement surgery is not typically recommended if you are younger than 50. While recommendations for surgery are based on a patient’s pain and disability, most patients who undergo a total knee replacement are age 50-80.