Knee replacement removes the damaged parts of your knee joint and replaces them with artificial components

Knee replacement is surgery to remove the worn or damaged surfaces of your knee joint and install artificial parts in their place. The surgeon cuts away the damaged bone and cartilage from your thighbone, shinbone, and kneecap, then attaches metal and plastic implants to the remaining bone. The artificial joint mimics the shape and movement of a healthy knee.

Most people have this surgery because arthritis has worn away the cartilage that normally cushions the joint, causing bone-on-bone contact, pain, and stiffness. Some people need it after a severe knee injury that cannot be repaired. The surgery typically takes one to three hours, and you go home the same day or stay overnight.

Key Takeaways

  • Knee replacement removes damaged bone and cartilage and replaces them with metal and plastic implants that restore joint function.
  • The surgery is most common for people with advanced arthritis who have not found relief from physical therapy, injections, or medication.
  • Recovery takes several months, with most people walking without a cane within four to six weeks and returning to normal activities within three to six months.
  • Artificial knees typically last 15 to 20 years, though some last longer, and revision surgery is possible if the implant wears out.

Why people have knee replacement surgery

Osteoarthritis is the most common reason. This type of arthritis develops when the cartilage that covers the ends of your bones gradually wears away over time. As the cartilage thins, bone rubs directly on bone, causing pain, swelling, and loss of movement. If rest, ice, physical therapy, weight loss, and anti-inflammatory medication do not reduce the pain enough to let you walk, climb stairs, or sleep, your doctor may recommend surgery.

Rheumatoid arthritis, a condition where your immune system attacks joint tissue, can also damage the knee severely enough to require replacement. Traumatic injury—a serious fracture or ligament tear that cannot be repaired—is a less common reason. Some people develop post-traumatic arthritis years after an injury and eventually need replacement.

Your doctor will typically suggest trying other treatments first. These include weight loss, physical therapy to strengthen the muscles around your knee, corticosteroid or hyaluronic acid injections, and oral pain relievers. Only when these have not worked well enough do most surgeons recommend replacement.

What happens during the surgery

You receive anesthesia so you are asleep and feel no pain. The surgeon makes an incision down the front of your knee, usually 8 to 10 inches long. They remove the damaged cartilage and bone from the ends of your thighbone and shinbone using special cutting guides to may support the surfaces are shaped correctly.

The surgeon then cements or presses metal implants onto the prepared bone surfaces. A plastic spacer is inserted between the metal parts to act as the new cartilage. In most cases, the surgeon also replaces the underside of your kneecap with a plastic button. The incision is closed with stitches or staples.

Some surgeons use computer navigation or robotic information to position the implants more precisely. Others use traditional instruments. Both approaches produce good long-term results. The choice depends on your surgeon's training and your specific knee anatomy.

Recovery and what to expect afterward

You will have pain and swelling for the first few weeks. Pain medication, ice, and elevation help manage this. A physical therapist will visit you in the hospital or at home to teach you exercises and how to walk with a walker or crutches. Most people walk with information within a day or two of surgery.

By four to six weeks, most people can walk without a cane and climb stairs with a railing. By three to six months, many return to driving, light work, and recreational activities like golf or swimming. Full recovery—when swelling is gone and strength is restored—typically takes six to twelve months.

You will have follow-up appointments with your surgeon at two weeks, six weeks, three months, and one year. Physical therapy continues at home or in a clinic for several months. Stiffness is common in the first weeks but usually improves with consistent movement and stretching.

How long artificial knees last

Most knee implants last 15 to 20 years. Some last longer, especially if you are not very active or are younger at the time of surgery. The plastic spacer wears down over time, similar to how a tire wears, and metal can loosen from the bone. Revision surgery—replacing the worn implant with a new one—is possible but more complex than the first surgery because the surgeon must remove the old implant and work with bone that has already been cut.

Your activity level affects how long your implant lasts. High-impact activities like running or jumping put more stress on the joint and may shorten its lifespan. Low-impact activities like walking, swimming, and cycling are gentler on the implant. Your surgeon will discuss which activities are safe for you.

Risks and complications

Serious complications are uncommon but possible. Infection occurs in fewer than 2 out of 100 surgeries. Blood clots can form in your leg veins after surgery, though blood thinners reduce this risk. Stiffness, where the knee does not bend or straighten as much as expected, happens in a small number of people and may require additional physical therapy or surgery.

The implant can loosen, shift, or wear out faster than expected. Nerve or blood vessel injury during surgery is rare but can cause numbness, weakness, or swelling. Persistent pain after surgery occurs in a small percentage of people and may be due to scar tissue, implant position, or other factors. Your surgeon will discuss these risks with you before the operation.

Preparing for knee replacement surgery

Your surgeon will order blood tests and imaging to assess your overall health and the condition of your knee. Tell your doctor about all medications you take, especially blood thinners, because some must be stopped before surgery. Arrange for someone to drive you home and help you for the first week or two.

Physical therapy before surgery, sometimes called prehabilitation, can strengthen your leg muscles and improve your range of motion, which may speed recovery. Your surgeon's office will give you specific instructions about eating and drinking before surgery, when to stop taking certain medications, and what to bring on surgery day.

Alternatives to knee replacement

If you are not ready for surgery or want to try other options first, several alternatives exist. Physical therapy and strengthening exercises can reduce pain and improve function, especially in early arthritis. Weight loss reduces stress on the joint. Anti-inflammatory medications like ibuprofen or naproxen can manage pain, though long-term use carries risks.

Corticosteroid injections into the knee joint reduce inflammation and pain for weeks to months. Hyaluronic acid injections, sometimes called viscosupplementation, add lubrication to the joint. Partial knee replacement, where only the damaged part of the joint is replaced, is an option for some people with arthritis in only one section of the knee. Arthroscopic surgery to clean out loose cartilage fragments may help temporarily but does not stop arthritis from progressing.

Frequently Asked Questions

How long does knee replacement surgery take?

The surgery itself usually takes one to three hours. You will spend additional time in the operating room for anesthesia and preparation, and time in recovery before going to your hospital room or home. Plan for a total of four to six hours at the surgical facility.

Will I need a blood transfusion during knee replacement?

Most people do not need a transfusion. Your surgeon may use techniques to minimize blood loss, such as explore a tourniquet to your leg during surgery or using medications that help your blood clot. If blood loss is significant, a transfusion is possible but uncommon.

Can I have both knees replaced at the same time?

Some surgeons perform bilateral knee replacement in one surgery if both knees are severely damaged and you are in good overall health. Recovery is more demanding because both legs are affected. Others prefer to do one knee at a time, spacing them weeks or months apart, so you can use one leg to help you move during recovery.

What activities can I do after knee replacement?

Low-impact activities like walking, swimming, cycling, golf, and bowling are generally safe. High-impact activities like running, jumping, and contact sports put more stress on the implant and may shorten its life. Your surgeon will give you specific guidance based on your age, health, and the type of implant you received.

Do I need to take antibiotics before dental work after knee replacement?

Current guidelines recommend antibiotics before dental procedures only if you have signs of infection or weakened immunity. Ask your surgeon whether you need them, as recommendations vary by individual circumstances. Inform your dentist that you have a knee implant.