The knee is the most critical joint in the body involved in all processes of locomotion, and is easily injured and vulnerable to repetitive stress. Total knee replacement surgery reconstructs both sides of the knee joint. Partial knee replacement reconstructs only one side of the joint, or one aspect of the joint. The proper medical term is arthroplasty, meaning to form or shape a joint. The first knee replacement was performed in 1968.
The knee replacement uses what is known as a prostheses, an artificial component which mimics the natural joint. The makeup of the knee prostheses has developed over the years and vary, made from a combination of metal, plastic and/or ceramic. Scientists are now developing even better compounds made from zirconia and carbon. Some prostheses even have robotic capabilities to help the user move.
The Surgical Procedure
The surgery may take up to 5 hours for one knee. Anesthesia will be administered by epidural, spinal or general means. Surgical methods vary and improve over time but generally, the surgeon will cut through the top part of the knee and into the joint compartment. The surgeon must cut only the tendons and ligaments necessary and cut off the ends of the bones. He or she shapes and prepares the surface of the ends of the femur and tibia to prepare for attaching the prostheses, either with or without cement. He or she then repairs tendons, ligaments and muscles as needed. The final steps are to check that the knee moves naturally, and then close the incision.
The Hospital Stay and Complications
The patient usually stays in the hospital for 5-10 days after the surgery. Complications can include scar tissue, infection, pain or numbness in knee, hip and back, bleeding, dislocation, deep vein thrombosis. Problems during surgery such as other broken bones or torn tendons, ligaments and muscles may complicate matters. Bone marrow could get into the lungs and cause breathing problems. Having two knees replaced at the same time can lengthen the hospital stay and increase complications. The prosthesis itself may malfunction.
Recovery after surgery varies depending on the physical condition of the person prior to the surgery and the specifics of the surgery itself. Generally, most people are walking after about 6 weeks and continue to seek outpatient physical therapy for another 1-2 months. Swelling and pain is common during that time.
How Long does the Implant Last?
The lifespan of the implant varies. Generally, most knee prostheses last 10-15 years. 85 percent of the joint implants will last 20 years. New materials are being developed and tested with longer lifespans. Methods of cementing the implants are being studied but cementless knee replacements have not been used long enough to have sufficient data. Because the prostheses life span is relatively short, younger people are not encouraged to have total knee replacement surgery until all other options have been tried or the pain is too much. Repeated knee replacements may send the person to a wheelchair.
Because total knee replacement surgery requires the uses of a prostheses which will wear out in 20 years, younger people are advised to make lifestyle changes before considering surgery. Eliminating risky activities, losing weight, increasing appropriate exercise, dietary changes, and examining the work environment for stressors may help. Medication, braces, orthotics and minimally invasive knee surgery can work. Other therapies can include acupuncture, chiropractic, hypnosis and meditation.
American Academy of Orthopedic Surgeons, Joint Replacement
Encyclopedia of Surgery, Knee Replacement
WebMd, Arthritis: Knee Replacement Surgery