Knee replacement is a surgery to relieve pain and improve mobility, most often in people with arthritis of the knee. Most knee pain is caused by one of the following types of arthritis:
- Osteoarthritis: Cartilage covering the bone surfaces in the knee wears out over time
- Rheumatoid arthritis: The membrane that surrounds the knee joint becomes inflamed and thickened, which leads to damage to the cartilage in the knee
- Post-traumatic arthritis: Arthritis develops in the knee after a knee injury
The knee joint is made up of three bones: the lower end of the thighbone, the upper end of the shinbone, and the kneecap. The bone surfaces where these three bones touch are covered with smooth cartilage that protects the bones and enables them to move easily in the joint.
Knee replacement surgery does not actually involve replacing any structures of the knee. It is a “resurfacing” procedure, in which only the surface of the bones is replaced with metal, plastic or ceramic.
Types of Knee Replacement Surgery
There are two types of knee replacement:
- Total knee replacement: All of the knee joint surfaces are replaced
- Partial knee replacement: Only the surface on one side of the knee joint is replaced
Total knee replacement surgery typically involves the following steps:
- Damaged cartilage surfaces at the ends of the thighbone and shinbone are removed along with a small amount of bone underneath the cartilage.
- Metal components replace the cartilage and bone that were removed. This recreates the smooth surfaces of the knee joint.
- The surface on the underside of the kneecap is cut and resurfaced with a plastic button.
- A plastic spacer is inserted between the metal components to create a smooth gliding surface.
Risks and Complications after Knee Replacement Surgery
- Infection at the incision site
- Infection deep around the resurfacing materials
- Blood clots in the leg veins or pelvis
- Nerve and blood vessel injury
- Continued knee pain
- Continued stiffness due to scar tissue in the knee
- Loosening of the resurfacing materials