Total Knee Replacement

There is a covering of tissue on the end of the bone called articular cartilage. Think of this as natures “Teflon”. All the joints have it and it’s a low friction bearing surface. Joints form the articular cartilage towards the end of growth in the late teens and thereafter the cartilage has a very poor capacity for repairing itself.

When all the cartilage has worn away and the bare bone underneath is exposed. This is the condition loosely known as osteoarthritis. Osteoarthritis is also characterised by extra bone forming, lumps in the joint and by stiffness around the joint, and by pain and sometimes inflammation and swelling.

Knee replacement is an operation which involves re-coating of the end of the bones of the kneecap with a metal coating. It does not involve chopping the knee out and putting in a hinge, as many people think, it is a resurfacing procedure and a maximum of 2cms of bone are removed from the femur and tibia combined. The total knee replacement itself is generally made of a steel alloy containing chromium and cobalt, consisting of a re-coating of the bottom of the femur and a small thin plate of the top of the tibia, and between the two surfaces the insertion of a bearing surface made of dense plastic (known as polyethylene). In quite a lot of cases the back of the kneecap is also recoated with a dome of plastic. In a total knee replacement the anterior cruciate ligament is generally sacrificed, but all other ligaments are preserved.

The results of total knee replacement are generally very good when done in patients who have reached the point of significant pain and disability with knee arthritis. Patients with a knee replacement generally speaking cannot run or do vigorous sports, such as skiing or squash, but are able to function at the level of golf, social tennis and fast walking, although, fast walking down slopes is frequently difficult after total knee replacement.

The operation involves an incision down the front of the knee generally around 10cms long and the opening up of the front of the knee and moving of the kneecap to one side exposing the bones of the knee. These are within the ligament envelope, and these bones are shaved and shaped using equipment designed to make sure the alignment is absolutely correct and recoated with the components, which come in a variety of sizes usually giving the surgeon about five and nine sizes depending on the system which is used. The operation usually takes between one and two hours, and is done under general or spinal anaesthetic.

Patients after knee replacement stay in hospital for an average of four nights, with a variation from two to seven. They are encouraged to get up immediately and walk on the first post-operative day.

Recovery after total knee replacement is unpredictable, some patients recovering very quickly and returning to driving at two weeks, and some taking a lot longer and returning to driving only at six weeks. Patients are encouraged to walk independently and discard crutches when able, but it’s fair to say that the knee after total knee replacement only starts to return to normal at around the three month mark and it takes up to six months for things to settle down completely.