Total Knee Replacement

How is it replaced?

A total knee replacement is a surgical procedure used to replace the ends of the bones that form your knee joint that have become damaged from osteoarthritis. Because your entire knee joint needs to be accessed during a total knee replacement, an open procedure will be performed in which an incision is made down the front of your knee. The ends of your femur and tibia bones that form your knee joint will be shaved down and resurfaced with metal caps, forming new joint surfaces to “replace” your knee joint.

Implant Decision

The implants used to replace the ends of your bones within your knee joint can vary depending on what type of material and what type of structure your implants contain. Choosing the type of implants to use for your total knee replacement will be decided upon by your surgeon depending on what type is most appropriate for you.

Metal on Plastic

Most implants used for a total knee replacement are made of metal. Metal caps will be used to replace the damaged ends of the femur and tibia bones that form the knee joint, while a plastic spacer made of polyethylene will be inserted between the metal implants to provide cushioning within the joint. 

This plastic spacer replaces the cartilage that normally cushions the knee joint and will allow the metal ends of the knee replacement to move smoothly to mimic the natural motion of the knee joint. In some cases, the plastic attaches directly to the tibia bone so that only the end of the femur is capped with a metal implant. The back of the patella (kneecap) is often also lined with a plastic dome to resurface the back of the patella to allow it to glide smoothly over the knee replacement parts.

The metal caps are fixated to the ends of the femur and tibia either with a bone cement made of polymethylmethacrylate or through press-fitting in which the ends of the femur and tibia are contoured to fit and grow into the grooves of the implants, fusing the metal to the bone over time.

Ceramic on Plastic

If full metal implants cannot be used for a total knee replacement due to a metal sensitivity or allergy, ceramic implants or ceramic-coated metal implants may be used. These implants are used to replace the damaged joint surfaces of the femur and tibia bones the same way metal implants are used with the placement of a plastic spacer in between. Ceramic implants can also be secured through cement fixation or press-fitting.

Posterior Stabilized

During a total knee replacement, the anterior cruciate ligament (ACL) of the knee, which prevents excessive forward movement of the shin or hyperextension of the knee, is removed as the structure of the knee replacement provides enough stability to act as a substitute.

The posterior cruciate ligament (PCL) of the knee, which prevents excessive backward movement of the shin or excessive bending of the knee, may also need to be removed if it is damaged or gets in the way during surgery. If the PCL is removed, a posterior stabilized implant which contains a post in the middle of the tibia portion will be used. This post serves as a physical stopper that limits the motion of the knee with bending in order to substitute for the removed PCL.

Cruciate Sparing

If the PCL is able to stay intact within the knee during a total knee replacement, a cruciate sparing implant will be used. This type of implant contains a cutout groove in which the PCL will sit in order to maintain its function in stabilizing the knee.

Surgery Recovery Timeline

Full recovery from a total knee replacement can take between 6-12 months to return to unrestricted activity. If you have a sedentary job, you can generally return to work 4-6 weeks after your surgery. Jobs that require prolonged standing, walking, or bending can require you to take off 12 weeks or more depending on your progress with rehabilitation and how physically demanding your job duties are.