There is no absolute limit to the number of times a knee can be revised, and what usually stops us is extreme bone or soft tissue loss, persistent infection, or poor health of the patient. Patient recovery takes longer, and often requires expert rehabilitation.

Implants fail for many reasons, some of which are predictable. Ideally joint replacements should be followed up with X-rays and examinations at least every 5 years in order to pick up potential problems before they become more complex.

Failing implants usually become painful, although some may present with instability of the joint, stiffness and infection. There is a spectrum of complexity, and these are listed below.

This occurs in about 1% of all primary joint replacements. It can present with pain, swelling, stiffness, drainage of the wound, or may present many years down the line with painful loosening of the implants. Occasionally infection can come from a distant site such as dental surgery, chest infection, or urinary infection. Patients can become very unwell, requiring emergency surgery, but usually the onset of symptoms is slow.

Successful treatment usually requires eradication of the infection before a new knee can be considered. This means an initial operation to remove the infected implants, followed by a period of powerful antibiotic treatment, usually with a temporary knee in place. If the infection is successfully cleared, then a second operation can be carried out to implant a new knee replacement.

The treatment of infected joints is complex and requires expert management from both the surgeon and the infectious diseases physicians. Reconstruction is often difficult due to the destruction caused by the infection.

In our hands, the chance of successful eradication of infection in knees is more than 90%.

Patients can feel as if their knee replacement is going to give way, so that walking is difficult, or getting up from chairs or coming down stairs is problematic. Causes include poor component positioning, muscle weakness, implant wear, and loosening.

Careful assessment of the cause of the instability needs to take place before revision surgery is contemplated, otherwise recurrence of the problem is all too common.

If the implants are not quite in the correct place, this can lead to stiffness, instability, excessive wear or pain. Revision is often needed for this conditions, and must address the cause fully. This is a commonly under recognised condition that I have particular interest and experience in.

The majority of knee replacements that fail do so due to wear of the moving parts, which may be associated with bone loss and loosening of the components. These will usually become painful, but may result in fractures of the bone or instability of the joint.

Specialist implants are often required to deal with bone loss, instability and tissue loss.

Sometimes the bone or tissue loss is so great that a large piece of donated bone needs to be fixed to the patients’ knee along with a new knee replacement. The surgery is highly specialised, but is associated with satisfactory results in the medium term.

These are essentially the same as for primary knee replacement, but more common.

Transfusion is much more likely depending on the complexity of the surgery. About 25% of patients will require a blood transfusion.

Depends on the extent of the surgery and the health of the patient.

Risk to life is much higher with this kind of surgery than with primary joint replacement.

These implants wear at least as fast as primary implants, and loosening is more common. Hence each revision is likely to last a shorter time than the implant that preceded it.

Fractures are much more common, usually during removal of the old implants. Experienced revision surgeons should be able to anticipate and deal with these.

Also see the Related links on this page.