Prosthetics

Large hinges were used in early examples of knee joint replacements. Operations for knee joint replacement, today, are implants within the joint using metal and plastic parts used to cover the worn parts of cartilage in the joint. The objective is to save as much of the joint as possible. This procedure is used mostly for elderly patients suffering from osteoarthritis or rheumatoid arthritis. Younger people are usually not advised to have a knee prosthesis because it reduces the range of movement for the knee and usually will not withstand the strains of vigorous use.

In the operation to install the knee prosthesis the flat undersurfaces of the knee joint are exposed. The lower end of the femur (thigh bone) is smoothed down to accept the prosthesis and then holes are drilled to fasten it. Likewise, the upper end of the tibia (leg bone) is prepared and the back part of the patella (knee cap) is prepared to accept the patellar component of the prosthesis. The parts are then cemented and tested to see if the joint movements are proper. The knee prosthesis consists of the femoral component and the tibial component along with the patella component.

The main purpose of the knee joint replacement procedure is to reduce pain and to restore some movement to the joint. The outcome of the operation lacks certainty and the duration of the prosthesis is limited. Research continues to find better cements and materials for the joints as well as designs that come closer to the actual joint.