A knee replacement is a surgical procedure in which the diseased portions of the bones within the knee are replaced with a prosthesis. Knee replacements are typically a solution to pain from the three types of arthritis: osteoarthritis, rheumatoid arthritis, or post-traumatic arthritis. Rheumatoid arthritis is the result of inflammation in the knee joint and is the most common of the three types of arthritis. Osteoarthritis occurs with age and wear and tear on the joint as the cartilage protecting the bones begins to wear away causing the bones to rub against one another. Ligaments on the inside of the patella are shortened. It usually occurs in people over 50 years of age.
Post traumatic arthritis is often the result of a serious knee injury which fractures the bones and causes damage to the ligaments and cartilage.
To measure the severity of arthritis, four grades classify the extent of injury
- Grade 1—Early changes show fissuring in the cartilage (Breaks)
- Grade 2—More extensive thicker breaks in the cartilage
- Grade 3—intermittent loss of cartilage with breaks
- Grade 4—Exposed subchondral bone (below the cartilage)
The physician may advise total knee replacement for:
- Severe knee pain that limits daily activities (such as walking, getting up from a chair or climbing stairs)
- Moderate-to-severe pain that occurs during rest
- Chronic knee inflammation and swelling that is not relieved with rest or medications
- A bow-legged knee deformity
- Failure to obtain pain relief from medications, injections, physical therapy, or other conservative treatments
The goal of total knee replacement surgery is to relieve pain and restore the alignment and function of your knee.
- The surgery is performed under spinal or general anesthesia.
- An incision is made in the skin to expose the knee joint.
- The damaged portions of the femur bone are cut at appropriate angles.
- The femoral component is attached to the end of the femur.
- The surgeon then cuts or shaves the damaged area of the tibia (shinbone) and the cartilage. This removes the deformed part of the bone and any bony growths, as well as creates a smooth surface on which the implants can be attached.
- The tibial component is secured to the end of the bone with bone cement or screws.
- The surgeon then places a plastic piece called an articular surface between the implants to provide a smooth gliding surface for knee movement. This plastic insert will support the body’s weight and allow the femur to move over the tibia like the original meniscus cartilage.
- The femur and the tibia with the new components are then put together to form the new knee joint.
- The knee rear surface is also prepared to receive a plastic piece.
- When all the new components are in place, the knee joint is tested for range of motion.
- The entire joint is then irrigated and cleaned with a sterile solution.
- The incision is closed; drains are inserted, and a sterile dressing is placed over the incision.
Post operative Care
Rehabilitation begins immediately following the surgery.
- Knee immobilizers are used to stabilize the knee.
- A physical therapist will teach specific exercises to strengthen and restore knee movement.
- The physical therapist will also determine a home exercise program for leg muscle strength.
- Crutches or a walker will be prescribed.
- A continuous passive motion (CPM) machine can be used to move the knee joint. Continuous passive motion is a device attached to the treated leg that constantly moves the joint through a controlled range of motion.