Knee Replacement

Knee Arthritis

When the hyaline cartilage covering the ends of the bones in a synovial joint degenerates, this is termed arthritis. There are many causes, but sometimes we do not know what started the process, in which case it is termed 'Primary osteoarthritis'. An example of a well-known underlying cause of joint degeneration is rheumatoid arthritis.

Whatever the cause, the hyaline cartilage progressively becomes dull or soft and begins to break up. This makes the articulating surfaces rough and triggers a series of reactions in the joint and surrounding tissues. The joint may swell, grate or catch and the patient will eventually experience disabling pain.

In the advanced phase, knee arthritis is best treated by knee replacement (vide infra).

Advances are taking place all the time in terms of repairing, transplanting or regenerating hyaline cartilage in the knee, but the indications for such techniques are currently very narrow and some of the available techniques are less than reliable in practice. The most suitable candidates are usually young, high demand athletes with a small, isolated lesion.

When the knee articulating surfaces reach an advanced state of degeneration or wear, then the most sensible or reliable long-term solution is knee replacement. This can be Unicompartmental, or Total.

Unicompartmental knee replacement (UKR) is considered less invasive and conserves bone, as well as some of the important ligaments. It is not suitable for all osteoarthritic knees and there is debate or controversy about patient selection. Think of UKR as a 'half knee replacement'. The major drawback is the possibility that other compartments of the knee may continue degenerating after a UKR, requiring conversion to a Total Knee Replacement (TKR) later on. Such a revision procedure may be more difficult and the results inferior as compared to a well-performed primary TKR. Against this must be balanced the advantages of bone and ligament preservation with UKR, the possibility of using a smaller scar, and perhaps a faster initial recovery.

So the arguments for and against in any particular case are complex and best made in consultation with a surgeon who has your full history, has examined you and seen your x-rays.

Below is a model of a unicompartmental knee replacement (UKR) on the left with a total knee replacement (TKR) on the right for comparison.

Total Knee Replacement: How it is done [opens new window, please wait for pdf document to load]