Total knee replacement surgery, also known as total knee arthroplasty, is a surgical procedure that helps relieve pain and restore function in severely diseased knee joints. During the procedure, an orthopedic surgeon cuts away damaged bone and cartilage from the thighbone, shinbone and kneecap, and replaces it with an artificial joint, or prosthesis. The new, artificial joint replicates the knee’s natural ability to roll and glide as it bends. The goal is to improve mobility by relieving pain and improving function of the knee joint.
What causes the knee to become damaged?
The most common cause of chronic knee pain and disability is arthritis.
- Osteoarthritis occurs when the cartilage cushioning the bones of the knee wears away and the bones rub directly against each other, causing pain and stiffness.
- Rheumatoid arthritis is a chronic inflammatory disease that causes joint pain, stiffness, and swelling.
- Post-traumatic arthritis follows a serious knee injury when the bone and cartilage do not heal properly. The irregularities lead to more wear on the joint surfaces.
A knee joint also may need replacement because of an injury or normal wear and tear.
Who is a candidate for total knee replacement surgery?
The decision to have total knee replacement surgery is a joint one made by the patient, the patient’s primary care doctor, the patient’s family and an orthopaedic surgeon. Recommendations for surgery are based on the extent of the patient’s pain, disability and total health status.
Patients may benefit from knee replacement surgery if
- their severe pain limits everyday activities, including walking, going up or down stairs, and getting in and out of chairs.
- they are unable to sleep at night because of the pain.
- they receive little relief from non-surgical treatments, such as physical therapy, cortisone injections, other surgeries or anti-inflammatory drugs.
- they suffer side effects from pain medications.
- they have chronic knee inflammation and swelling that doesn’t improve with rest or medications.
- they have significant stiffness which limits the knee’s ability to straighten or bend.
- their knees have significant instability and constantly give way.
- they have a significant knee deformity, such as a joint that bows in or out.
Most patients who undergo total knee replacement are usually age 60 to 80, but orthopaedic surgeons evaluate patients individually. Recommendations for surgery are based on a patient’s pain and disability, not age. Patients as young as age 16 and older than 90 have undergone successful total knee replacement.
What are the benefits of total knee replacement surgery?
It’s important to know that an artificial knee is not a normal knee, nor is it as good as a normal knee. However, most people who undergo knee replacement surgery experience a dramatic reduction of knee pain and significant improvement in their ability to perform common activities. Most patients with stiff knees before surgery will have better motion after a total knee replacement. Remember, though, that total knee replacement won’t make an individual into an athlete or allow someone to do more than he or she could before the knee became arthritic or damaged. Following surgery, most patients are told to avoid some types of activity for the rest of their lives, including jogging and high impact sports.
How does knee replacement surgery work?
During a total knee replacement, surgeons reshape the knee joint. First, diseased bone and cartilage are removed. This includes the lower end of the thighbone (femur), the upper end of the shinbone (tibia), and the backside of the kneecap (patella). These surfaces are replaced with a metal shell on the end of the femur, a metal and plastic trough on the tibia, and if needed, a plastic button in the kneecap. Doctors usually secure the new knee joint components to the bones with surgical cement. The artificial knee then mimics natural knee motion and function.
The procedure usually takes about two hours to perform.
Most patients begin exercising their knee the day after surgery. A physical therapist will teach specific exercises to strengthen the leg and restore knee movement to allow walking and other normal daily activities soon after surgery.
Full recovery from the surgery takes three to six months, depending on the type of surgery, the overall health of the patient, and the success of the rehabilitation.
In some cases, doctors are able to use special tools and a smaller incision for a minimally invasive surgery when replacing the knee. Generally, recovery time is less and pain is lower when using this type of surgery.
With normal use and activity, every knee replacement develops some wear in its plastic cushion. Excessive activity or weight may accelerate this normal wear and cause the knee replacement to loosen and become painful. However, with appropriate activity modification, knee replacements can last for many years.