Total knee replacement or total knee arthroplasty, is a surgical procedure in which parts of the knee joint are replaced with artificial parts (prostheses). A normal knee functions as a hinge joint between the upper leg bone (femur) and the lower leg bones (tibia and fibula). The surfaces where these bones meet can become worn out over time, often due to arthritis or other conditions, which can cause pain and swelling.
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.
There are no absolute age or weight restrictions for total knee replacement surgery. Recommendations for surgery are based on a patient's pain and disability, not age. Most patients who undergo total knee replacement are age 50 to 80, but orthopedic surgeons evaluate patients individually. Total knee replacements have been performed successfully at all ages, from the young teenager with juvenile arthritis to the elderly patient with degenerative arthritis.
Surgical procedures differ depending on the patients needs and the surgeons approach, but generally the steps are as follows:
- The patients vital signs are checked to make sure blood pressure, heart rate, body temperature and oxygenation levels are normal and surgery can proceed. A mark is made on the knee undergoing surgery.
- Anesthesia is administered. The patient may receive general anesthesia (be put to sleep) or be given a regional anesthesia to block sensation from the waist down along with a relaxant. What type of anesthesia a patient receives is decided well ahead of time.
- The surgeon makes an incision down the center of the knee about 8 to 10 inches long, and then cuts through deeper tissue, including the quadriceps tendon and flips over the kneecap to access the femur and tibia. Alternatively, some surgeons make smaller incisions and use minimally invasive techniques for total knee replacement.
- To improve the surgeons ability to access to the joint, the knee is bent to 90 degrees.
- The surgeon uses a bone saw to remove the arthritically damaged areas at bottom of the femur and the top of the tibia. Each bone is reshaped to exactly fit its new prosthesis. Because these cuts must be precise, the surgeon uses either a metal jig or computer assistance to line up the cuts.
- A surgeon may resurface the back of the kneecap or patella and attach an implant. A polyethylene component may be attached to facilitate the patellas gliding against the new joint. Research has not shown a significant difference in outcomes for patients who received patella resurfacing and those who did not.
- Components are attached to the femur and tibia and patella, if applicable. How the components are attached to the bone will depend on what type of component is used. Most knee replacement surgeries use cemented components that are affixed using bone cement. Cemented and cementless components offer different advantages.
- A flexible cushion made of polyethylene is attached on top of the new tibia surfaces. This spacer acts as a shock absorber between the two new prosthetic surfaces.
- The leg is flexed and extended to test the fit of the components and the new knees range of motion.
- The surgeon straightens the knee to allow the components, cement and bone to bond together. Because the bone cement is fast acting, this takes only about 10 minutes.
- The surgeon will repair any deep tissue that was cut during surgery and then stitches the skin at the incision.
Hospital stay post-surgery
You will most likely stay in the hospital for several days.
After surgery, you will feel some pain. This is a natural part of the healing process. Your doctor and nurses will work to reduce your pain, which can help you recover from surgery faster.
Medications are often prescribed for short-term pain relief after surgery. Many types of medicines are available to help manage pain, including opioids, non-steroidal anti-inflammatory drugs (NSAIDs) and local anesthetics. Your doctor may use a combination of these medications to improve pain relief as well as minimize the need for opioids.
Be aware that although opioids help relieve pain after surgery, they are narcotic and can be addictive.It is important to use opioids only as directed by your doctor. As soon as your pain begins to improve, stop taking opioids. Talk to your doctor if your pain has not begun to improve within a few days of your surgery.
Your orthopedic surgeon may prescribe one or more measures to prevent blood clots and decrease leg swelling. These may include special support hose, inflatable leg coverings (compression boots) and blood thinners. Foot and ankle movement also is encouraged immediately following surgery to increase blood flow in your leg muscles to help prevent leg swelling and blood clots
A continuous passive motion (CPM) machine. Most patients begin exercising their knee the day after surgery. In some cases, patients begin moving their knee on the actual day of surgery. A physical therapist will teach you specific exercises to strengthen your leg and restore knee movement to allow walking and other normal daily activities soon after your surgery. To restore movement in your knee and leg, your surgeon may use a knee support that slowly moves your knee while you are in bed. The device is called a continuous passive motion (CPM) exercise machine. Some surgeons believe that a CPM machine decreases leg swelling by elevating your leg and improves your blood circulation by moving the muscles of your leg.
It is common for patients to have shallow breathing in the early postoperative period. This is usually due to the effects of anesthesia, pain medications and increased time spent in bed. This shallow breathing can lead to a partial collapse of the lungs which can make patients susceptible to pneumonia. To help prevent this, it is important to take frequent deep breaths. Your nurse may provide a simple breathing apparatus called a spirometer to encourage you to take deep breaths.
Recovery and Rehabilitation
A patients recovery and rehabilitation plan are crucial to the overall success of knee replacement surgery. A recovery and rehabilitation plan can help the patient: Leave the hospital sooner Regain knee strength and range of motion more quickly Resume independent living sooner Avoid potential complications Typically, knee replacement patients are able to leave the hospital within 1 to 5 days (often 2 or 3) and they can take care of themselves and resume most activities 6 weeks after surgery. The majority of patients are 90% recovered after 3 months, though it can take 6 months or longer before they are 100% recovered. Some knee replacement patients do not follow the typical recovery timeline. For example: Patients who did knee-strengthening exercises in preparation for surgery sometimes recover more quickly. Patients who are older, smoke, or have other medical conditions may take longer to heal. Deviation from the typical recovery timeline cannot always be predicted, but these differences are usually okay as long as the patient, doctor and physical therapist, continue to work together towards a full recovery.