Problems after knee replacement: When is revision surgery needed?

Joint replacement surgery 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. This can be caused by various things, including:

• 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 knee implant comes from having too high expectations.

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 small, fluid-filled sacs near the knee joint)
• Pain from your back down to your leg (caused by a slipped disc, for example)
• Pain or muscle weakness caused by osteoarthritis of the hip
• Vascular (blood vessel) disease in the leg
• Chronic pain disorder

Anxiety, worrying and mental health problems like depression can make the pain worse, too.

Sometimes doctors can't find a cause. Then revision surgery isn't very likely to help.

To diagnose the problem properly, the doctor will need to talk with you first. They will ask exactly what symptoms you have – such as where and how bad your knee hurts, what the pain feels like, and when you experience it. After that, they will take a close look at your knee, the alignment of your leg and your posture. Blood tests and x-rays can help to rule out complications like an infection and to check the position of the different parts of the knee replacement.

Revision surgery is most commonly done because parts of the knee replacement have become loose. That could happen for one of the following reasons, for example:

• Wear-and-tear of the implant material and bone loss
• Heavy strain – for instance, in some jobs, from playing intense sports or being very overweight
• Implant parts not fixed in place properly

Problems caused by a loose implant can only be treated with revision surgery. But sometimes there are reasons not to have revision surgery – like 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. For example, the knee may feel like it could give way. Or it might be painful or swollen. Sometimes it's mainly difficult to go down stairs.

The possible causes of an unstable knee include the following:

• Ligament problems, such as a weak collateral ligament on one or both sides of the knee
• Parts of the knee implant that are in the wrong position
• Illnesses such as rheumatoid arthritis or diseases affecting the muscles or nerves
• Being very overweight

An unstable knee may need to be treated with revision surgery. This type of surgery involves making corrections, exchanging parts of the implant, or replacing the first implant with one that offers better support (a 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 orthosis).

After surgery, your kneecap may slip sideways out of its groove. That can happen if the ligaments in the knee are weak or injured, or if the knee replacement implant isn't in the right position. There are various treatment options here, too – like physical therapy, surgery on the ligament and joint capsule, or exchanging parts of the implant.

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 back 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, like overuse. In that case, surgery isn’t a good idea.

Sometimes you aren’t able to fully bend or stretch your knee after getting a knee replacement. Possible causes include the following:

• Parts of the implant aren’t in the right position
• Ligament problems
• Joint infections or adhesions (tissue sticking together)
• Pain

Another cause is inflammation, which makes more connective tissue grow in the knee. This may lead to the development of a solid, thick capsule that limits the movement of the knee. Doctors call this hardening of tissue "arthrofibrosis" (frozen knee).

Depending on the cause, a frozen knee can be treated with physical therapy, medication or a special knee orthosis. Sometimes the knee is stretched and bent to loosen adhesions. This is done under anesthesia. It can be done during arthroscopy (keyhole surgery), too. Revision surgery on the implant can’t always be avoided, though.

A second opinion can be particularly worthwhile for people who have only had a partial knee replacement so far. Because it's relatively easy to do a full knee replacement after a partial knee replacement, this kind of revision surgery is often recommended too readily, even when it's not actually needed.

If you'd like a second opinion on revision surgery after a partial knee replacement, it's best to consult a doctor who has a lot of experience. That's important because it's not always easy to assess problems with partial knee replacements. For instance, x-rays may show lighter areas around the implant. These areas may be – but aren't always – a sign that the partial knee replacement has become loose. The lighter areas are often a normal result of the operation and don't need to be treated. The quality of the examination and the x-ray images can also affect the outcome of the assessment.

Urgent revision surgery is needed if there's an acute complication or an emergency. This is particularly the case if

• the knee joint becomes infected or
• a bone around the knee is broken in an accident or fall.

The joint becomes infected after about 1 out of every 100 operations. Most joint infections develop during the first few weeks or months after joint replacement surgery. If the knee looks red, hurts and feels warm, that could be a sign of an infection. It may also become stiff and swollen. Other signs include a fever and a poorly-healing surgical wound that may be "weeping" (releasing fluid). It is important to seek medical advice immediately 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 bloodstream. When this happens, there is often no swelling or redness at all. Instead, it tends to cause chronic pain or problems because parts of the implant have become loose.

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 implant doesn't have to be removed. But sometimes the implant has to be exchanged. One operation may be enough. Two procedures are often needed, though: In the first operation, the infected implant is replaced by a "dummy implant" containing antibiotics. That stays in the joint for 2 to 6 weeks, depending on which germs have infected the joint. Then a new joint is implanted in the second operation.