Occasionly, knee replacements need revising (doing again). The key to successful revision is obtaining the correct diagnosis of the cause of failure.These can be for a variety of reasons:

1) Wear-

Modern knee replacements should last at least 10 to 20 years but occasionally they fail sooner. Usually this wear will become evident as pain,perhaps swelling and instability. The wear particles cause loosening of the prosthesis in the bone and destruction of bone. For this reason all replacement joints are best x-rayed at intervals of about 5 years even if causing no problems.

2) Infection-

Infections should be very rare. It usually gets into the joint at the time of initial surgery but can get in via blood transmission from a distant infection. This is called haematogenous infection and becomes commoner if the joint becomes loose.

Unfortunately, once the infection is in the joint, it will not be cured with antibiotics alone and surgery is required. If it is caught early, within 2 weeks then debridement and wash out together with appropriate antibiotics is often effective. If it is diagnosed late then the joint will have to be removed and redone (revised). This can be done as a 2 stage or 1 stage procedure, although a 2 stage procedure remains the gold standard.

3) Instability-

Instability may develop due to failure of the knee ligaments, wear or mechanical failure in the components or surgical error.

4) Stiffness-

A knee replacement may be stiff for a variety of reasons. Sometimes it is due to surgical errors, but it can also be due to problems with physiotherapy, patient factors such as bleeds into the joint or abnormal collagen production. In many cases it is due to a low grade infection. It must be remembered that in many cases stiffness is not a sign of problems and persistance with the exercises will produce an improvement for up to 18 months following surgery.

5) Pain-

Painful knees are often stiff and the causes are very similar. Again diagnosis of the cause is the key to effective treatment.

A revision knee replacement is a much more complicated undertaking than a primary(1st time) knee replacement. It will take about 3hrs on average. The results can be very good.

There is no fixed limit on how many times a knee can be revised, but the surgery gets harder and more complicated each time.