The human knee is one of the most used and abused joints in the body. It moves with every step we take and bears weight to some degree almost constantly. Athletes, such as hockey, football, basketball, soccer and tennis players are continually stressing their knees to point of destruction. Many walk away unscathed, but others are not so lucky.
Repeated sprains, strains, ruptures of the meniscus and tearing of tendons and cartilage can cause many rehabilitation procedures to be ineffective. When extensive damage occurs, whether it be through injury, disease or the effects of aging, a knee replacement may become the only option.
Complete and partial joint replacements are available to repair damage and improve the quality of life to individuals who may otherwise have reduced mobility and restricted activity. The degree of damage will determine which joint replacement is used.
A unicondylar, or partial, knee replacement replaces only the part of the knee affected by injury or disease. The pieces used to take the place of diseased bone are called prostheses. Partial replacements are less invasive needing only a 3 to 4 inch incision to accomplish the exchange. Rehabilitation is also quicker and less painful than a full replacement. A 4 to 6 week recovery time is normal with almost full range of motion after the knee is completely healed.
A complete knee replacement is much more extensive. An incision ranging from 10 to 14 inches is needed to replace the entire joint. Components in the prosthesis of a complete knee are made of metal and polyethylene. The metal pieces include those that replace the ends of the femur and tibia, while polyethylene is placed on the ends to form a smooth surface. Polyethylene is used to not only cushion the ends of the bones, but to provide a surface that allows the bones to glide across each other easily.
In a partial knee replacement the anterior and posterior cruciate ligaments are saved and replaced after the new compartment of the knee is positioned. In a complete knee replacement these ligaments are replaced with nylon cording or cadaver parts. The anterior and posterior cruciate ligaments are what stabilizes the knee and allows for range of motion. The ligaments and tendons within the knee allow for movements, such as walking, running and climbing. If they are damaged or torn, they may need to be replaced no matter what replacement is being performed.
The implanted components used in knee replacements are either cemented into place or attached to the bone itself so the bone remodel itself into the implant as it heals, holding it firmly in place.Screws and pegs may be used to reattach tendons and ligaments.
Because of the extensive work that is performed in complete knee replacement, healing and recuperation can take from 6 to 8 weeks.