What are Knee Implants?
Knee implants are artificial devices that form the essential parts of the knee during a knee replacement surgery. The knee implants vary by size, shape, and material. Implants are made of biocompatible materials that are accepted by the body without producing any rejection response. Implants can be made of metal alloys, ceramic or plastic, and can be joined to the bone. The metals used include stainless steel, titanium, and cobalt chrome; whereas, the plastic used is polyethylene.
Components of a Knee Implant
The components of a knee implant replicate the natural shape and structure of the knee joint. The components used may depend on the size of your body and vary from patient to patient. There are 3 components in a knee implant:
- The femoral component is generally made of metal and curves around the thighbone. It has a channel that allows the kneecap to move up and down as the knee is in motion.
- The tibial component is usually a flat metal platform with a plastic (polyethylene) cushion. The metal portion has a stem that goes into the tibia for stability. The plastic portion, also known as a spacer, acts as a cushion between the femoral and tibial metallic components.
- The patellar component is a dome-shaped device made of polyethylene that replicates the patella.
Types of Knee Implants
The type of implant used may depend on your bone quality and health of the ligaments surrounding the knee.
- Posterior cruciate ligament retaining implants: PCL retaining implants can be used if you have a healthy posterior cruciate ligament. Unlike PCL substituting designs, PCL retaining implants do not have the center post and cam design. The femoral and tibial components have grooves to hold the posterior cruciate ligament.
- Posterior cruciate ligament (PCL) substituting implants: The posterior cruciate ligament stabilizes the knee against forces that push the tibia towards the femur. PCL substituting implants are used if your PCL is injured. The PCL substituting implants are provided with a raised surface on the cushion of the tibial component, which acts as a center post, fits into a cam in the femoral component and duplicates the actions of the injured PCL.