Total knee replcement surgery has evolved into an extremely precise and varied procedure. It has become so specialized, that only certain areas of the knee joint might be replaced without sacrificing normal joint surfaces elsewhere.
Total Knee Replacement
A total knee replacement refers to the resurfacing of all the major joint surfaces that come in contact with each other during motion and weight-bearing. These areas commonly consist of the femur (thigh bone), tibia (shin bone) and patella (knee cap).
With the use of very specialized cutting jigs, the ends of the two major bones, as well as the under-surface of the patella, are cut, shaved and contoured to provide an exact fit by the prosthetic implant components.
In a total knee replacement, none of the original joint cartilage surface remains after cutting and shaping.
Partial Knee Replacement
Partial, or unicondylar, knee replacement refers to the resurfacing of select areas of the knee joint, typically on only one side. Frequently, there are cases of severe arthritis that affect only one side, or compartment, of the knee, while all other surfaces remain normal and relatively healthy.
The implant components consist of a metallic "condyle" that is attached to the end of the femur, and the tibial component, which is attached only to the affected area of the shin bone joint surface.
The patella, or knee cap, is typically not resurfaced during a uni-compartmental or partial knee replacement.
Patellofemoral Replacement
In very select cases, it might be necessary to resurface only the patella and the femoral "notch," or the groove of the femur over which the patella glides during knee flexion (bending). Typically, the remainder of the joint surfaces are healthy and not in need of replacing.
Typical candidates for this type of procedure are the relatively young adult patient with either post-surgical or post-traumatic injury to the knee, which has caused a very localized defect in the joint surface of one of the condyles, as well as other adult patients with extremely localized degenerative arthritis.
