Knee pain can be caused either by arthritis or traumatic injury. The decision to undergo knee replacement surgery is based on the severity of the patient’s pain and the extent of their disability. Knee replacement is the most common joint replacement procedure performed in the United States. Most knee replacement surgeries occur in the age range of 60 to 80 years, with more than half a million people having knee replacement surgery annually in the United States.
Some common causes of knee pain and reduction of function include injury of the ligaments, bursae or tendon. Injury can also affect the menisci and bones forming the joint. Pain can arise from diseases or conditions that involve the joint, the nerves innervating the knee and bones and soft tissue around the knee. In fact, the knee joint is the most commonly involved joint in rheumatic disease. The most common reason for knee replacement surgery is osteoarthritis, which involves destruction of the cartilage.
Before going the surgical route, patients should try appropriate treatment options including weight loss, area strengthening, activity modifications, anti-inflammatory medications, joint supplements, corticosteroid injections and hyaluronic acid injections. Physical therapy may be used to reduce pain and improve mobility, strength and function until arthroplasty takes place. After failing to achieve adequate relief from these options, a knee replacement may be in order.
Knee arthroplasty involves resurfacing the injured, worn-out surfaces of the knee and replacing the cartilage and bone with metal and plastic. The prosthetic pieces consist of three components: the femoral component, made of a highly polished strong metal; the tibial component, made of a durable plastic often held in a metal tray; and the patellar component, which is also made of plastic.
Occasionally the damage to the knee only involves one area and doesn’t require replacement of the entire knee apparatus. This is known as a unicompartmental knee replacement. The knee joint has three compartments: the medial (inner) compartment, the lateral (outer) compartment and the patellofemoral (kneecap) compartment. If the damage is limited to either the medial or lateral compartment, that compartment may be replaced with the unicompartmental knee implant. Only about 6 percent to 8 percent of knee replacement surgeries are unicompartmental.
Since the prototypical prosthetic knee was designed in the early 1970s, many improvements in design, surgical technique and fixation methods have improved the life expectancy of the replaced joints. Now 85 percent of knee implants will last 20 years.
Minimally invasive total knee replacement involves making a smaller incision than with traditional methods. This potentially offers a smaller scar, a shorter hospital stay and quicker recovery time.
American Academy of Orthopedic Surgeons
Journal of the American Medical Association
By Jared Combs, Staff Writer