What is a knee replacement actually made of, and is my whole knee removed?

The parts of a knee replacement

• The femoral component: a curved metal cap, usually cobalt-chrome alloy, shaped to the end of the thigh bone
• The tibial component: a flat metal tray, often cobalt-chrome or titanium alloy, on top of the shin bone
• The insert: a highly durable polyethylene plastic that sits on the tray and acts as the new gliding surface
• The patellar button: a plastic dome sometimes placed on the back of the kneecap, depending on its condition and the surgeon's assessment

In a partial knee replacement, only one side of the joint is resurfaced with a smaller version of these parts.

How it is fixed to the bone

Most knee replacements are fixed with bone cement, an acrylic material that sets within minutes and holds the components firmly from the day of surgery. Some designs are uncemented, with a textured surface into which the bone grows over the following weeks. Both methods are well established, and the choice depends on bone quality, the implant design and the surgeon's experience.

Metal allergy and other common concerns

Some people are allergic to nickel in jewellery. True problems with a knee implant because of metal allergy are rare, but if you have a known, significant metal allergy, tell your surgeon, as implants with special coatings or alternative alloys are available.

The implant may trigger airport metal detectors. Body scanners and security staff are used to joint replacements, so a medical card is not usually needed, but you can carry a note if it reassures you. MRI scans can generally be done safely with a knee replacement, though the metal may blur images close to the joint.

Choosing the implant for your knee

Implants come in many sizes and several designs, for example whether the cruciate ligament at the back of the knee is kept or replaced by the shape of the implant. Dr. Gelber selects the design and size after examining your knee and measuring on X-rays, and he can explain the choice at your consultation at Aman Hospital.