Risks & Complications Of Knee Replacement

Knee replacement is a major surgical procedure but most people do well and are pleased with the outcome. As with any major operation there are potential risks and complications (on this page).

Follow-up after knee replacement

After it’s all done, what further care should I expect?

Age and knee replacement

Surgeons may be less willing to replace the knee of someone under 60 years of age. Why is this?

Ideal candidates are older and of sedentary lifestyle because they are less likely to stress the joint excessively and cause it to fail. Artificial joints have a finite lifetime and if they have to be revised (done again) the operation is much more difficult technically than the initial (primary) operation.

However, the indications for this operation have widened to include younger and more active patients due to the good results obtained with older people. In one study of 114 replaced knees at an average age of 51 years, 94% of the femoral and tibial components survived (remained in the patients and worked at least moderately well) for 18 years.

There is no maximum age for knee replacement but the person needs to be well enough to cope with a major operation and the subsequent rehabilitation.

Risks and complications

• Fat Embolism occurs when the fat from the marrow cavity enters the bloodstream and can cause serious problems. Having both knees done at once increases the likelihood of this occurring.

• Nerve damage after knee replacement is more common in those who have epidurals, people who have had lumbar operations and those people with knock knees and inability to straighten the knee pre-operatively. The overall occurrence of this problem has been reported to be 0.58% after knee replacement.

• The occurrence of arterial complications is from 0.03% to 0.2% of knee replacements. It is more likely in those with calcification of the arteries in the area and those people in whom the foot pulses cannot be felt.

• Fractures around the prosthesis (artificial joint) can occur during the operation or afterwards,and how they are managed depends on whether they are displaced (not in line) and whether the joint replacement is itself affected.

• Excess bone formation (heterotopic ossification) occurs in some cases and causes a restriction in range of movement of the knee after operation.

• Recurrent bleeding(haemarthrosis) into the knee joint can occur but the cause may not be clear. Treatment may include aspiration (drawing the blood off with a needle), ice, resting and stopping of any anticoagulants.

• The skin may be numb to the outside of the operation scar and this does not usually improve.

• Loosening of the metal components may occur over time or due to trauma. This may cause few problems or be serious enough to have the joint revised. In a paper by Li, Zamora and Bentley, the rate of knee revision due to this problem was 2.7%.

• Infection is a rare complication but a serious one. Li, Zamora and Bentley reported a 3.4% revision rate due to this. Infection may occur soon after the operation or many years afterwards. Treatment may initially be with antibiotics but surgical revision of the joint is often needed in these cases.

• Thromboses (blood clots) may form in the veins of the legs or pelvis and cause inflammation, swelling and pain. A serious condition can result if some of a clot breaks off and enters the circulation (eg pulmonary embolism). Treatments include wearing support stockings, using footpumps while people are in bed, getting people up and about soon after surgery and using anticoagulant drugs.