Knee replacement problems: When is revision surgery needed?

A joint replacement can relieve the pain caused by advanced osteoarthritis of the knee in many people. But up to 20 out of 100 people who have the procedure continue to experience problems afterwards. That could have many possible causes, such as:

• An artificial joint that doesn’t fit well or hasn't been implanted properly
• Pinched soft tissue
• Problems with the kneecap
• An allergy to the artificial joint material or to the bone cement

It is normal for the knee to hurt a little for the first year following the surgery. Sometimes dissatisfaction with a prosthesis is down to having expectations that were too high.

The cause of the problem doesn't always have to do with the knee joint itself. Other possible causes include:

• Tendon problems
• Bursitis (an inflammation in the small, fluid-filled sacs often found near joints in the body)
• Pain extending from your back down to your leg (such as caused by a slipped disc, for example)
• Pain or muscle weakness caused by osteoarthritis of the hip
• Vascular disease of the leg
• Chronic pain disorder

Anxiety, worrying and mental illness such as depression can make the pain worse.

But it's important to know that you should only have revision surgery if a cause has been found for the problems – and if the procedure is expected to help. Sometimes it’s not possible to find a cause. The chances that revision surgery will be successful are low then.

An exact diagnosis needs to be based on a detailed discussion of the problem. The doctor needs to know exactly what’s wrong – such as where and how severely your knee hurts, how the pain feels, and when you experience it. After that, your knee, the alignment of your leg and your posture will be examined. Blood tests and x-ray imaging can help to rule out complications like infection and to check the position of the parts of the knee replacement.

Revision surgery is most commonly used when parts of the knee replacement have become loose. That could be due to any of the following causes, such as:

• Material wear and bone loss
• Heavy strain – for instance in some jobs, or from playing intensive sports or being very overweight
• Improper anchoring of the parts of the replacement joint

Problems caused by a loose knee replacement can only be treated with revision surgery. Sometimes there are reasons not to have revision surgery – for instance if someone is already very old and has a lot of other illnesses that would make surgery too risky.

An unstable knee can cause various problems. Your knee may feel like it could give way. Or it might be painful or swollen. Sometimes it is going down stairs that is especially difficult.

The possible causes of an unstable knee include the following:

• Ligament problems, such as a weak median (facing the other knee) collateral ligament or lateral (facing away from the other knee) collateral ligament
• Parts of the knee replacement that aren’t positioned correctly
• Illnesses such as rheumatism or muscle or nerve diseases
• Being very overweight

Revision surgery may be needed if you have an unstable knee This type of surgery involves making corrections, exchanging parts of the knee replacement, or implanting a knee replacement that offers better support (a non-constrained or semi-constrained prosthesis). Depending on the cause and the severity of the symptoms, other treatments might be suitable, such as physical therapy to strengthen your muscles, or a knee brace or splint (knee bandage or orthesis).

After surgery your kneecap can slip sideways out of its groove. That could be caused by weak or injured ligaments in your knee or by the knee replacement not being correctly positioned. Here there may be various treatment options as well, such as physical therapy, ligament or joint capsule surgery, or the exchange of parts of the knee replacement.

Sometimes osteoarthritis gets worse and damages the cartilage underneath the kneecap. That can cause pain in the front part of the knee, especially when standing up or climbing stairs. The inner side of the kneecap can be replaced in revision surgery. But pain in the front part of the knee might also be caused by something else, such as overuse. Surgery isn’t a good idea if that is the cause.

Sometimes you aren’t able to fully extend or flex your knee after getting a knee replacement. Possible causes include

• Parts of the knee replacement that aren’t positioned correctly
• Ligament problems
• Joint infections or adhesions (tissue sticking together)
• Pain

Another cause is inflammation, which causes the connective tissue in the knee to multiply. That can result in the formation of a solid, thick capsule that limits your range of motion. Doctors call this hardening of tissue arthrofibrosis (frozen knee).

Depending on the cause, a frozen knee can be treated with physical therapy, medication or special knee ortheses. Sometimes the knee is extended and flexed using an anesthetic to loosen the adhesions. This may also be done as part of arthroscopy (keyhole surgery). Revision surgery can’t always be prevented, though.

A second opinion can be particularly worthwhile for people who have so far only had a partial knee replacement. Because it is comparatively easy to replace a partial knee replacement with a full knee replacement, revision surgery is often recommended too hastily, even when it is not actually needed.

It's best to consult a doctor with a lot of experience if you'd like a second opinion on revision surgery for a partial knee replacement. That is important because problems with partial knee replacements are not always easy to assess. X-rays may show lighter areas around the parts of the replacement joint, for instance. They can be, but are not automatically, a sign that the partial knee replacement has become loose. These kinds of lighter patches are often normal side effects of the operation and don't require treatment. The quality of the examination and the x-ray imaging can also affect this assessment.

Urgent revision knee surgery is needed if there are acute complications or an emergency. This is particularly the case if

• the knee joint that has been operated on becomes infected, or
• a bone in the knee region is broken in an accident or fall.

A joint infection occurs after about 1 out of every 100 operations. Most joint infections develop during the first weeks or months after the joint replacement has been implanted. A reddened, painful and warm joint is a sign of an infection. The joint can also become stiff and swollen. Fever and a surgical wound that is not healing or is weeping (releasing fluid) can also be signs of a joint infection. It's important to seek medical advice quickly if you have these symptoms.

In rare cases, a knee replacement can become infected years after surgery if bacteria from other parts of the body spread to the joint through the blood. There is often no swelling or reddening at all in these sorts of late infections. Instead, the typical signs are chronic pain or problems caused by the knee replacement loosening.

A joint infection can sometimes be successfully treated at an early stage by cleaning the wound, rinsing the joint, and using antibiotics. Then the knee replacement doesn't have to be removed. But it might be necessary to exchange the knee replacement. Sometimes one operation is enough. Two procedures are often needed, though. In the first operation, the infected knee replacement is replaced by a dummy containing antibiotics. It remains in the joint for 2 to 6 weeks, depending on which germs have infected the joint. A new joint is implanted in the second procedure.