Knee Replacement Risks & Complications

There is a very small risk of life threatening complications, as a result of cardiac events, stroke, or a pulmonary embolism (clot on the lung). The latest data suggests the overall risk is about 1 in 300.

There is always bleeding when you replace the knee. With modern techniques it is rare for patients to need a blood transfusion, but you will be asked to consent to have a blood transfusion in case we have problems with excessive bleeding.

Our results show that infection occurs in less than 1% of our patients. With careful surgery in a clean hospital, antibiotics and careful wound closure we aim to minimise infection as much as we can. If it happens it can be very serious, because if the infection gets into your new joint, we can’t treat it with antibiotics and we may have to remove the joint and start again.

This is very major surgery and the long-term results will not be as good as they would have been if the infection hadn’t occurred. If you do have problems with your wound which don’t settle down quickly we should review you earlier than planned in the clinic.

Deep vein thrombosis (DVT) means clot in the veins in the leg and this can occur after any surgery on the lower limb. These do not usually cause long-term problems, but can cause a pulmonary embolism (PE), which can be very serious. If you get a clot you may require treatment with blood thinning drugs for a few weeks.

The risk of a DVT is about 5%, but these are often asymptomatic. The risk of a PE is about 0.5% and this will cause breathlessness and breathing difficulties and can be life threatening. We do all we can to prevent blood clots. You wear special stockings, sometimes we use special pumps on the lower leg to encourage blood flow and you are given blood thinning injections or tablets for 21 days after the operation.

The nerves supplying your leg are near to the knee joint and can be stretched or bruised during surgery. If this happens you may have some altered sensation and weakness or paralysis in your leg, usually your ankle and foot. Although this is usually very short-term, in extremely rare cases it can lead to permanent weakness at the ankle and foot (foot drop). The risk of a serious nerve injury is about 1 in 500.

The main blood vessels supplying your leg are very close to the back of your knee. Damage to these structures is extremely rare, but is very serious, resulting in excessive bleeding and interruption of the blood supply to the leg. This requires emergency repair of the blood vessels to deal with it.

Fracture of the bones very rarely occurs during a knee replacement. This will usually be seen and dealt with during the operation, but does make the surgery more complex and may mean a different post-operative rehabilitation. Occasionally a fracture is only seen on the X-ray taken after the operation. This may require another operation to deal with it, or alterations to the post-operative regime.

You will have a scar down the front of your knee. On the outside of this scar you will have a numb patch – everyone will have this and it is unavoidable. Most people do not notice this after a while, but occasionally the scar or the skin in this are remains sensitive. Many people never find it comfortable to kneel after a knee replacement.

Stiffness after knee replacement is rare, but can be very troublesome. You will need to work hard with the physiotherapist in the early post-operative period to get the knee moving.

Occasionally (<1% of our patients) you will need a manipulation under anaesthetic to obtain the bend we and you are hoping for.

Although knee replacement is generally a very successful operation, not everyone is happy with their new knee. The knee can remain painful and stiff and usually doesn’t feel like a ‘normal knee’. The literature indicates that 10% of people are a bit disappointed with their new knee and 5% of people feel the knee is worse than before the operation.

Artificial joints are likely to eventually wear out, causing recurrent pain and the need for the operation to be re-done (revision), which is often more complicated that the first-time procedure. The available data suggests that the type of joint we plan to use has a very good chance of lasting at least 20 years.