Joints Replacement

You can’t move like you used to. It’s painful to walk the dog, climb a flight of stairs, or simply get out of a chair. You’ve tried medicines, injections, and physical therapy. Nothing seems to work. If that’s the case, it could be time to consider knee replacement surgery.

In a healthy knee, the end of the femur glides smoothly over the tibia, cushioned by the layers of cartilage. However, if the cartilage is worn away it can make the joint painful and stiff. An artificial knee may help improve mobility and reduce pain.

Total knee replacement is a surgical procedure in which the bone surfaces and cartilage that have been damaged or worn away are removed and replaced with artificial surfaces ('implants' or 'prostheses') made of metal or a plastic material. Both left and right sides of the knee joint - the inside ('medial compartment') and outside ('lateral compartment') - are resurfaced with metal prostheses in a total knee replacement. The resultant artificial joint is designed to move, as far as possible, like a natural healthy knee.

Cause

The most common cause of chronic knee pain and disability is arthritis. Although there are many types of arthritis, most knee pain is caused by just three types: osteoarthritis, rheumatoid arthritis, and post-traumatic arthritis.

Osteoarthritis
This is an age-related "wear and tear" type of arthritis. It usually occurs in people 50 years of age and older, but may occur in younger people, too. The cartilage that cushions the bones of the knee softens and wears away. The bones then rub against one another, causing knee pain and stiffness.
Rheumatoid arthritis
This is a disease in which the synovial membrane that surrounds the joint becomes inflamed and thickened. This chronic inflammation can damage the cartilage and eventually cause cartilage loss, pain, and stiffness. Rheumatoid arthritis is the most common form of a group of disorders termed "inflammatory arthritis."
Post-traumatic arthritis
This can follow a serious knee injury. Fractures of the bones surrounding the knee or tears of the knee ligaments may damage the articular cartilage over time, causing knee pain and limiting knee function.

Different Types of Surgery

Total knee replacement

This is the most common form. Your surgeon replaces the surfaces of the thigh bone and shin bone that connects to the knee.

Partial knee replacement

If arthritis affects only one side of your knee, this surgery may be a possibility. However, it’s only right for you if you have strong knee ligaments. Partial knee replacement can be performed through a smaller cut than is needed for total knee replacement.

Kneecap replacement

This replaces only the under-surface of the kneecap, but some surgeons advise against this procedure, because total knee replacement surgery has a higher rate of success.

Complex (or revision) knee replacement

This procedure may be needed if you have very severe arthritis or if you’ve already had two or three knee replacement surgeries.

Implant Components

Implants are made of metal alloys, ceramic material, or strong plastic parts. Up to three bone surfaces may be replaced in a total knee replacement:

The lower end of the femur. The metal femoral component curves around the end of the femur (thighbone). It is grooved so the kneecap can move up and down smoothly against the bone as the knee bends and straightens.

The top surface of the tibia. The tibial component is typically a flat metal platform with a cushion of strong, durable plastic, called polyethylene. Some designs do not have the metal portion and attach the polyethylene directly to the bone. For additional stability, the metal portion of the component may have a stem that inserts into the center of the tibia bone.

The back surface of the patella. The patellar component is a dome-shaped piece of polyethylene that duplicates the shape of the patella (kneecap). In some cases, the patella does not need to be resurfaced.

Components are designed so that metal always borders with plastic, which provides for smoother movement and results in less wear of the implant.