Knee replacement, also known as knee arthroplasty, is a surgical procedure to replace the weight-bearing surfaces of the knee joint to relieve pain and disability. It is most commonly performed for osteoarthritis, and also for other knee diseases such as rheumatoid arthritis and psoriatic arthritis. The knee is a hinge joint which provides motion at the point where the long bones of the upper and lower leg meet. In a knee replacement surgery, the damaged bone and cartilage is removed and replaced with artificial components made of metal alloys, high-grade plastics and polymers.