The human knee forms a hinge joint connecting the upper leg bone (the femur) with the lower leg bones (the tibia and fibula). If the areas where these bones come together become worn due to arthritis or other conditions, the affected surfaces can become painful and swollen. One option for alleviating this pain is a total knee replacement, which is a surgical procedure in which the natural structures in the knee are replaced with artificial ones. Patients usually undergo this type of surgery after other, nonsurgical treatments—such as weight loss, bracing or support devices, physical therapy, or medications—have failed. Aside from providing pain relief, this surgery can help improve function in the knee joint, thus enhancing the patient’s quality of life. About 700,000 knee replacement surgeries occur in the US every year. The surgery itself usually lasts two to three hours, with the patient under anesthesia. After the surgery is complete, patients usually remain in the hospital for two to four nights, during which time they receive pain medication and medication to reduce the risk of blood clots in the legs. Soon after surgery, patients can begin moving their feet and ankles. After the initial recovery period, patients begin physical therapy to improve range of motion and strengthen muscles in the legs—especially those that support the knee joint.