Total Knee Replacement

The knee is a joint that brings together the lower end of the femur and the upper end of the tibia and the knee cap. The ends of each bone are covered with hyaline cartilage which allows the joint to move smoothly. The menisci are located between the femur and tibia. These C-shaped wedges act as “shock absorbers” that cushion the joint. Large ligaments hold the femur and tibia together and provide stability and allow the knee to flex and extend like a hinged joint, as well as some limited rotation.

The long thigh muscles give the knee strength. Once the cartilage on the ends of the bone wears off, as happens in osteoarthritis, then the exposed bone which has nerve endings rubs against itself and causes pain and swelling. If conservative treatments such as anti-inflammatory medications, physical therapy, corticosteroid or artificial joint fluid injections, fail to relieve the pain in an arthritic knee, then knee replacement may become necessary.

The most common causes of chronic knee pain include:

-Osteoarthritis: This is an age-related “wear and tear” type of arthritis. It usually occurs in people 50 years of age and older, but may occur in younger people, too. The cartilage that cushions the bones of the knee softens and wears away. The bones then rub against one another, causing knee pain and stiffness.
-Rheumatoid arthritis: This is an autoimmune disease in which the synovial membrane that surrounds the joint becomes inflamed and thickened. This chronic inflammatory state can damage the cartilage and eventually causes cartilage loss, pain, and stiffness. Rheumatoid arthritis is the most common form of a group of disorders termed “inflammatory arthritis.”
-Post-traumatic arthritis: This can follow a serious knee injury. Fractures of the bones surrounding the knee or tears of the knee ligaments may damage the articular cartilage over time, causing knee pain and limiting knee function.

There are four basic steps to a knee replacement procedure:

-Preparation of the bone: The damaged cartilage surfaces at the ends of the femur and tibia are removed along with a small amount of underlying bone.
-Positioning of the metal implants: The removed cartilage and bone is replaced with metal components that cap the ends of the cut bone, thus recreating the surface of the joint. These metal parts may be cemented or “press-fit” into the bone.
-Resurfacing of the patella: The under-surface of the patella (kneecap) is cut and resurfaced with a plastic button.
-Insert a spacer: A medical-grade ultra high molecular weight polyethylene plastic spacer is inserted between the metal components to create a smooth gliding surface.