Knee replacement involves shaping or cutting the ends of the femur (thigh) and tibia (shin) bones and replacing them with a metallic or polyethylene (plastic) component to the bearing surface. The surface of the patella (kneecap) can also be replaced.
Components can be fixed to the bone either by using bone cement or coating the components in such a way that bone grows onto and into their surface.
A total knee replacement replaces all parts of the knee – both the medial (inner side of the leg) and lateral (outer side of the leg) compartments, and sometimes the patella as well. This procedure usually involves a hospital stay of 2-3 nights and rehabilitation exercises are important to get movement back despite pain potentially persisting for 6-8 weeks.
A partial knee replacement may replace just one part of the knee. A medial unicompartmental replacement is more common than a lateral replacement. This is a smaller operation than a total knee replacement and generally means a shorter hospital stay and quicker recovery.
Patellofemoral replacement involves resurfacing of only the patellofemoral compartment, which is between the patella and the femur.
Physiotherapy will begin on the first day following surgery. The physiotherapist will guide the patient through the various phases of rehabilitation, which may include using a CPM (continuous passive motion) machine to slowly bend and straighten the knee. Upon discharge, patients will be walking with the aid of two elbow crutches and will be independent in terms of showering and dressing. The main problem patients face after a knee replacement is getting movement back. Pain levels can vary considerably in individuals, but most people find the period from 24-72 hours after surgery the most difficult. It is important to keep working on the exercises, particularly bending the knee. The knee could be warm and swollen for some time post-surgery. This usually settles significantly within three months, although swelling may persist for a further few months. It is also normal for the skin on the lateral (outside) side of the incision to be numb. It is important to note that improvement occurs for up to 18 months after surgery.