Total knee replacement is a surgical procedure in which injured or damaged parts of the knee joint are replaced with artificial parts, called prostheses.
The knee is the largest joint in the body. It is commonly known as the "hinge" joint, because it allows the knee to flex (bend) and extend (straighten), similar to the hinge on a door. The knee also has the ability to rotate (turn) and translate (glide).
The knee joint is composed of the tibia (shin bone), the femur (thigh bone) and the patella (kneecap). Each bone is covered with a layer of cartilage that cushions, protects and keeps the bones from rubbing together. Ligaments (bands of tissues) connect the femur and tibia, while muscles and tendons stabilize the knee and enable it to move. The patella helps protect the knee joint and anchor the tendons while allowing movement.
Reasons for Knee Replacement
The most common causes of knee joint damage are:
Osteoarthritis: a disease in which there is a gradual deterioration, caused by time and usage of the cartilage between the femur and the tibia. Osteoarthritis occurs in most people over the age of 60, but it can occur in younger people, too, due to injury to the knee or a congenital joint deformity. Osteoarthritis causes pain, swelling, creaking and stiffness in the knee joint.
Rheumatoid arthritis: an autoimmune disorder (the immune system attacks the tissues of the body) in which the tissues surrounding the knee joint become inflamed, causing deterioration of cartilage and other parts of the knee. Rheumatoid arthritis usually starts in early adulthood or middle age, but in the case of juvenile rheumatoid arthritis, it can begin in childhood. Rheumatoid arthritis causes pain, swelling and stiffness in the knee joint.
Who Is A Candidate For Knee Replacement?
A person would be considered for total knee replacement if there is:
- Daily pain
- The pain is severe enough to restrict work, recreation and ordinary activities of daily living
- Significant stiffness in the knee
- Significant instability (constant giving way) of the knee
- Significant deformity (knock-knees or bow-legs) that hinders normal function of the knee
- Damage from arthritic conditions, such as osteoarthritis, rheumatoid arthritis or post-traumatic arthritis
After understanding the symptoms, limitations and progression of the knee problem, the doctor will perform a variety of tests that may include measuring the knee's range of motion, analyzing muscle strength and evaluating the legs for variances, such as bow-legs or knock-knees. Additionally, an x-ray of the knee will be done to assess the damage. From the medical history, physical examination and test results, the doctor will determine if total knee replacement is necessary.
Before surgery, joints adjacent to the damaged knee (such as the hip and ankle) are evaluated. Replacing a knee joint adjacent to a severely damaged joint may not yield significant improvement in knee function. All medications that the patient is taking prior to surgery are reviewed. Routine blood tests for liver and kidney function, as well as urine tests for signs of anemia, infection, or abnormal metabolism are given. A chest x-ray and an EKG are performed to exclude significant heart and lung disease which may preclude surgery or anesthesia.