Clicking Noise From a Knee Replacement

Many patients who undergo knee replacement surgery will describe noises that come from their replaced joint. People commonly mention a clicking or clunking coming from their knee replacement when they walk, and they often worry that something is wrong with their knee replacement. Is it a problem to hear clicking after knee replacement surgery?

Most often, no, it is not a problem. It is not unusual for people to be able to hear or feel their knee replacement after they have surgery. Usually, a little reassurance that nothing harmful is taking place is all that is needed in these situations. Your surgeon can examine your knee, and possibly obtain tests such as an x-ray, to ensure nothing is wrong with the implant.

Noises can come from a number of possible sources, including the metal and plastic implants, tendons, and fluid around the knee. Determining the source of the noise is something your surgeon can help you with. However, take comfort in that fact that many patients describe clicks and other noises that come from their knee replacement.

That said, sometimes noises coming from a replaced knee should be evaluated by your surgeon:

• New noises coming from the replaced knee: Most often, noises and clicks coming from a knee replacement tend to diminish over time. New noises should be evaluated by your surgeon.
• Noises associated with pain: Painless noises are often normal, but when pain, deformity, or swelling is associated with the noise, that's a good sign the knee needs evaluation.

Most knee replacements are made of four separate parts. While there are some subtle variations, the most common knee replacement has two metal parts and two plastic parts. The four parts of a knee replacement are:

1. Femoral component: the femoral component is the metal cap that is fitted to the end of the thigh bone, the femur. The femoral component is a U-shaped cap that covers the end of the bone, wrapping around the front and the back. There are different shapes to the femoral component that can be based on patient size, and how much stability is needed to reconstruct the normal knee function.
2. Tibial component: the tibial component is also made of metal, and sits on top of the shin bone, the tibia. The tibial component has a part that extends into the hollow center of the bone to support the flat top tray of the tibial component.
3. Patellar component: while not every patient ends up with a replacement part on the kneecap, those that do will have a plastic (polyethylene) patellar component. This part replaces the inner half of the kneecap--the top of the kneecap that you feel under your skin is not replaced.
4. Polyethylene spacer: between the metal femoral and tibial components is a piece of plastic made of polyethylene called a spacer. This allows for smooth movement of the knee joint back and forth. There are variations in the shape and thickness of the polyethylene components to match each particular patient and situation.

Each of these implanted parts is held within the bone either with cement or wedged tightly into place so that bone can grow into the implant. Different implants are designed to be held in place in different ways, and your surgeon may have a preference for a particular type or brand of implant.

The noise that most people detect after knee replacement is the result of the metal and plastic implants contacting each other and making an audible 'click.' These parts of a typical knee replacement are not actually connected to each other, rather the knee joint is held together by your body's own ligaments, muscles, and tendons. As these structures move, there can be some movement in the joint allowing the metal and plastic parts to click into one another.