KNEE IMPLANT FREQUENTLY ASKED QUESTIONS FAQs 

Q. What are the components of a knee implant in a total knee replacement?

Knee implant components are designed so that metal always articulates against plastic, which provides smooth movement and results in minimal wear. Depending on your specific case, up to three bone surfaces may be replaced during your total replacement of the knee. They include:
• the lower ends (condyles) of the thighbone,
• the top surface of the shinbone, and
• the back surface of the kneecap.

The three components of knee implants are:

1. Femoral Component: The metal femoral component curves around the end of the thighbone and has an interior groove so the kneecap can move up and down smoothly against the bone as the knee bends and straightens. Usually, one large piece is used to resurface the end of the bone. If only one side of the thighbone is damaged, a smaller piece may be used (unicompartmental knee replacement) to resurface just that part of the bone. Some designs, called posterior stabilized, have an internal post with a center cam. This works with a corresponding tibial component to prevent the thighbone from sliding forward too far on the shinbone when you bend the knee. Designs which do not have the center cam are called cruciate-retaining (CR).

2. Tibial Component: The tibial component is a flat metal platform with a polyethylene cushion. The cushion may have either a flat surface (cruciate-retaining) or a raised surface with a center cam (posterior-stabilized).

3. Patellar Component: The patellar component is a dome-shaped piece of polyethylene that duplicates the shape of the patella (kneecap).

Q. How is a knee implant affixed in the body?

Knee implant systems are affixed in the body in one of three ways:

1. Cemented with bone cement: A special type of acrylic bone cement may be used to secure some or all of the implant components to the bone. The bone cement takes about 15 minutes to set.

2. Cementless (biologic ingrowth): Implant components using cementless implantation have a special porous coating that allows tissue to grow into it for fixation.

3. Combination: In some cases, your surgeon may choose a combination of cement and cementless attachment, depending upon the implant components and the condition of the bone around the knee joint.

The decision as to whether to use a cemented or cementless component depends upon many factors, including the intended use of the product, surgeon philosophy and the patient’s condition.

Q. Will an implant set off a metal detector?

Knee implants may possible set off metal detectors as the implants are made of metal. You may be provided with a special card by your healthcare provider to keep in your wallet explaining that you have a knee implant.

Q. Who are some of the manufacturers of knee implants?

There are more than 150 knee replacement designs on the market today. The following manufacturers manufacture various knee implant systems for total knee replacement (TKR), partial knee replacements (PKR), patellofemoral joint replacements (PFJ), unicompartmental knee replacement, revision knee replacements and others. Click on the manufacturer name below to learn more about their products and models.

• Zimmer
• Biomet
• Johnson & Johnson DePuy
• Stryker
• Smith & Nephew

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