Knee Replacement Surgery (Total Knee Arthroplasty)
Introduction
Knee replacement surgery, also known as a total knee arthroplasty, is a common procedure used to reduce pain and improve movement in people with severe knee problems, especially arthritis. Over time or following a trauma, the cartilage in the knee joint can wear down leading to arthritis. This can cause knee pain and swelling that makes it difficult to walk, bend, or do everyday activities. When medicine, physical therapy, or other treatments no longer help, a doctor might suggest knee replacement surgery. Knee replacement surgery removes the damaged parts of the knee and replaces them with new, artificial parts (Figure 1), helping the knee move better and hurt less.
History of Knee Replacements
The first knee replacement surgeries were performed in the 1960s. Back then, the technology was new, and the materials were not as advanced as they are today. Modern knee replacements are made from strong, long-lasting materials such as metal alloys, medical-grade plastic (ex. ultra-high molecular weight polyethylene), and sometimes ceramic. These materials are designed to work smoothly together and hold up to years of use. The goal is to create a joint that feels as close to natural as possible.
Who is a Candidate for a Knee Replacement?
Most people who have knee pain do not need a knee replacement. Total knee arthroplasty surgery is usually recommended for people with severe arthritis or other problems with the knee joint that substantially limit their ability to move or enjoy life. Candidates for knee replacement surgery often have trouble walking, climbing stairs, or getting out of a chair. Doctors may suggest trying other treatments first, such as weight loss, exercise, medications, or injections. People who are very young, have certain infections, are morbidly obese, or have poor overall health (ex. poorly controlled diabetes) might not be good candidates for knee replacement surgery.
How is Total Knee Arthroplasty Surgery Performed?
During knee replacement surgery, the orthopaedic surgeon makes a cut at the front of the knee to reach the joint. The damaged bone and cartilage are removed, and the surfaces are cut using special jigs to fit the new parts (Figure 2). The new parts—a metal cap for the thigh bone (femur), a metal tray for the shin bone (tibia), and a smooth plastic piece in between—are placed and secured, often with special bone cement (ex. methyl methacrylate). The surgery usually takes one to two hours and is performed in a hospital or surgery center.
Knee Replacement Recovery
Recovery from knee replacement surgery takes time and effort. Today many patients undergoing a knee replacement are able to go home the same day of the surgery. However, some people will stay in the hospital for a day or two. Studies have shown that it is very helpful to start standing and walking with help soon after surgery -ideally the same day. Physical therapy is very important and begins almost right away. It helps patients regain strength, movement, and flexibility in their new knee. It often takes three to six months of dedicated rehabilitation effort for patients to achieve a good recovery, although improvements may continue for a year or more. It’s important to follow the doctor’s instructions, do the prescribed exercises, and keep moving to get the best results.
Potential Complications Following a Knee Replacement
Like any surgery, knee replacement has risks. Some possible complications include infection, blood clots, knee stiffness, pain that doesn’t go away, or loosening and implant failure over time:
Deep infection (periprosthetic infection) following a knee replacement
A deep infection after knee replacement is a serious problem, though it’s uncommon. Surgeons take many steps to lower the risk, such as checking for other infections, cleaning the skin carefully, and giving antibiotics through an IV. Even with these precautions, deep infections happen in about 0.5–2.0% of cases. To learn more about infections following a knee replacement click on the link: here.
Blood clots: deep vein thrombosis (DVT) or pulmonary embolism (PE)
A blood clot, also known as a deep vein thrombosis (DVT), is when blood gets thick and forms a clump inside a vein, usually in the leg. If a piece of the clot breaks off and travels to the lungs, it can block blood flow and cause a pulmonary embolism (PE), which can be very dangerous, even fatal. After knee replacement surgery, blood clots can happen because the patient may be resting and not moving around much, which slows blood flow in the legs. DVTs are fairly common after knee surgery, but doctors take steps to reduce the risk. These steps include giving blood-thinning medications such as aspirin, using compression stockings or devices, and encouraging patients to start moving and walking as soon as it is safe after surgery. Without any preventive measures the rate of blood clot formation in patients undergoing a knee replacement can be as high as 40%. However, with preventive treatment (prophylaxis) the rate of blood clot formation is only 1-3%.
Residual pain and dissatisfaction following knee replacement surgery
Unfortunately, 10-15% of patients report residual discomfort or dissatisfaction after undergoing knee replacement surgery. The reasons for this vary and can include factors like unrealistic expectations, implant positioning, underlying medical conditions, or nerve-related pain.
Loosening and failure of the prosthesis
A knee replacement subject to normal repetitive loads may become loose or wear out over time (usually many years), especially in very active patients. If the knee replacement fails due to loosening or another reason the patient may need another surgery to fix or replace the implant. For more information on loosening of the prosthesis following a knee replacement click on the link: here.
Surgeons take many steps to lower the chances of problems following a knee replacement, and most people have a smooth recovery and are very happy with the results. They often feel less pain and can move more easily than before. Many return to daily activities, like walking, gardening, or swimming. While high-impact sports like running or jumping should be avoided, low-impact activities are encouraged. Modern knee replacements can last 15 to 20 years or more in many cases.
Summary
In summary, knee replacement surgery is a safe and effective way to treat severe knee pain and improve quality of life. Thanks to improvements in materials and surgical techniques, more people than ever are benefiting from this procedure. With proper care and rehabilitation, patients can look forward to many years of better movement and less pain.
Edited by Amari Eubanks and Stephen Pinney MD, July 24th, 2025