Authored by Jayant Row in Health
Published on 05-23-2009
Osteoarthritis is generally caused when the cartilage that allows the joints to move painlessly is degraded. This causes the bones within the joint to rub against one another. This could cause further bone growth that makes the movement of the joint even more painful. This degradation takes a lot of time, and this is why generally it is only older people who suffer from such joint problems. This could also be caused by defects in the cartilage and ligament tears that are often caused by excessive strain. Sportsmen and very active people can develop this at a younger age.
Knee arthroplasty, more commonly termed knee replacement, is the surgical procedure commonly suggested for people having such degenerative arthritis. The surgery involves replacing the damaged parts of knee joint surfaces. Plastic or metal components shaped to the requirement of the joints are used. There are times when the entire knee has to be replaced. At other times a partial replacement to change only affected parts is suggested by the orthopedic surgeon.
The surgery involves exposing the front of the knee and detaching the muscles from the patella. The patella is then displaced to one side, and ends of the femur and tibia are cut to shape using guides. The metal or plastic components are then fixed onto the bones with PMMA cement. The femur implant would have a round ended implant which would be similar to the natural shape of the bone. The tibia component is flat. Then a slightly dish shaped high density polythene insert is placed between the two implants so that there is no metal to metal contact. Ligaments are then reattached ensuring their proper balance so that there is a full range of movement possible for the operated knee.
The knee is divided into three parts or compartments. The inside part of the knee is known as the medial. The outside part is called the lateral. The third part is the joint between the knee bone and the thigh bone. This is called the patellofemoral. When wear and tear is confined to only one of these compartments, surgeons prefer that they replace only the affected part. This is called partial or unicompartmental knee replacement. This knee replacement technique requires smaller incisions, shorter hospital stay, and easier post operative rehabilitation.
Knee replacement is considered a major surgery. Preoperative tests are performed for blood, EEG and chest X-Rays. Blood may be required during the operation for transfusion. Very accurate and detailed X-Rays are also taken of the knee area so that the size of the components to be used for the replacement is determined. Certain blood thinning drugs are completely stopped.
After the operation the patient would need to move around on weight bearing crutches or use a walker. These aids would be needed until the muscles are fully healed and have recovered their strength. The quantity of hospitalization needed by the patient would depend on the patient’s general health but is rarely more than a week. It takes at least two weeks for the knee to gain full mobility, but it is at least 6 weeks before the surgeon would recommend that the full weight be taken by the operated knee. It may take another 6 weeks before the operated patient is able to return to normal life.
