Total Knee Replacement: What the Surgery Involves

Total knee replacement is a surgical procedure in which a surgeon removes the damaged surfaces of your knee joint and replaces them with artificial parts made of metal and plastic. The surgeon cuts away the worn cartilage and bone from the end of your thighbone, the top of your shinbone, and the underside of your kneecap, then attaches the artificial components—called prosthetics—to the remaining bone. The surgery typically takes between one and three hours, depending on the complexity of your case and whether you have had previous knee surgery.

The goal is to relieve pain and restore function to a knee that has been damaged by arthritis, injury, or wear over time. Most people who have this surgery have severe arthritis that has not improved with physical therapy, medication, or injections. After the surgery, your knee will feel different—not exactly like your original knee, but stable and usually much less painful than before.

Key Takeaways

  • Total knee replacement removes damaged bone and cartilage and replaces them with metal and plastic prosthetics that are cemented or press-fit into place.
  • The surgery takes one to three hours and is performed under general anesthesia or spinal anesthesia while you are asleep or numb from the waist down.
  • Most people stay in the hospital for one to three days after surgery, though some go home the same day depending on their health and support at home.
  • Recovery involves physical therapy starting within hours or days of surgery, with most people walking with information within a few days and returning to light activities within six weeks.
  • Artificial knee joints typically last 15 to 20 years, after which revision surgery may be needed if the prosthetic wears out or loosens.

How the Surgeon Prepares Your Knee

Before the actual replacement begins, your surgeon makes an incision down the front of your knee, usually 8 to 10 inches long. This gives the surgeon direct access to the joint. The surgeon then carefully removes the damaged cartilage and bone from the surfaces of your thighbone, shinbone, and kneecap. The amount removed is minimal—only the damaged layer—so that the prosthetic parts fit properly on the remaining healthy bone.

Once the damaged surfaces are removed, the surgeon tests the fit and alignment of the artificial components. Getting the alignment exactly right is critical because even small errors can cause the prosthetic to wear unevenly or cause pain and instability later. The surgeon uses special instruments and sometimes computer-assisted navigation to may support the prosthetic is positioned correctly relative to your leg's natural alignment.

Installing the Prosthetic Components

A total knee replacement has three main parts: a metal component that attaches to your thighbone, a metal or plastic component that attaches to your shinbone, and a plastic button that replaces the underside of your kneecap. The surgeon attaches these using bone cement (a fast-hardening adhesive) or by press-fitting them directly onto the bone, where they eventually bond naturally. Most surgeons use cement for at least some components because it provides when ready stability.

Between the metal components, the surgeon places a plastic spacer that acts like the cartilage your knee has lost. This spacer allows the joint to move smoothly and absorbs shock as you walk. Once all three components are in place and the cement has hardened, the surgeon checks that your knee bends and straightens properly and that the prosthetic is stable. The surgeon then closes the incision with stitches or staples.

Anesthesia and What to Expect Before Surgery

You will receive anesthesia so you do not feel pain during the procedure. Most people receive general anesthesia, meaning you will be asleep throughout the surgery. Some patients receive spinal anesthesia, which numbs you from the waist down while you remain awake or lightly sedated. Your anesthesiologist will discuss which option is best for you based on your age, overall health, and any previous reactions to anesthesia.

Before surgery, you will have blood tests, imaging, and a physical exam to make sure you are healthy enough for the procedure. You will be asked not to eat or drink for several hours before surgery. If you take blood thinners or other medications, your doctor will tell you which ones to stop and when. Arrange for someone to drive you home after surgery, since you will not be able to drive for several weeks.

Hospital Stay and Early Recovery

Most people stay in the hospital for one to three days after total knee replacement. Some hospitals and surgical centers now offer same-day discharge for patients who are young and healthy and have good support at home, but this is less common. During your hospital stay, nurses will monitor your pain, help you manage swelling with ice and elevation, and start you on physical therapy.

Physical therapy begins within hours or a day after surgery. A therapist will help you move your knee gently, teach you how to use crutches or a walker, and show you exercises to prevent blood clots and restore strength. You will likely be able to put some weight on your leg within a day or two, though you will need crutches or a walker for several weeks. Pain and swelling are normal and usually peak around day three or four after surgery.

Recovery Timeline and Return to Activity

The first six weeks after surgery are the most critical for recovery. During this time, you will attend physical therapy two to three times per week, continue exercises at home, and gradually increase how much weight you put on your leg. Most people can walk without crutches by four to six weeks after surgery, though walking distances will still be limited. Swelling and stiffness gradually improve over three to six months.

By three months after surgery, most people can return to light activities like walking, swimming, or stationary cycling. Return to more demanding activities—like hiking, tennis, or running—depends on your individual recovery and your surgeon's recommendations. Some people feel ready by six months; others take a full year. Your surgeon and physical therapist will guide you on what is safe for your specific situation. Artificial knees are designed for moderate activity, not high-impact sports.

Lifespan of the Prosthetic and Future Surgery

An artificial knee joint typically lasts 15 to 20 years, though some last longer and some wear out sooner depending on your activity level, weight, and how well you follow post-surgery guidelines. Over time, the plastic spacer can wear down, the cement can loosen, or the metal components can develop small cracks. When this happens, you may experience increased pain, swelling, or instability in your knee.

If your prosthetic wears out or loosens, you may need revision surgery to replace some or all of the components. Revision surgery is more complex than the original surgery because the surgeon must remove the old prosthetic and cement, which takes longer and carries slightly higher risks. However, revision surgery is a standard procedure and most people recover well. Planning your activity level after surgery can help extend the life of your prosthetic.

Risks and Complications

Like any surgery, total knee replacement carries risks. Blood clots in the legs are one of the most common complications, which is why you will receive blood-thinning medication and be encouraged to move your leg frequently. Infection is rare but serious and can occur in the weeks or months after surgery. Other possible complications include excessive bleeding, nerve or blood vessel damage, stiffness that limits how much you can bend your knee, and persistent pain or swelling.

Some people experience an allergic reaction to the metal components, though this is uncommon. A small number of people report that their prosthetic feels unstable or that they have chronic pain even after recovery. Most of these issues can be managed with physical therapy, medication, or additional surgery if needed. Your surgeon will discuss these risks with you before the procedure and explain what steps will be taken to prevent them.

Frequently Asked Questions

How long does total knee replacement surgery take?

The surgery itself usually takes one to three hours, depending on the complexity of your case and whether you have had previous knee surgery. Add another 30 to 60 minutes for preparation and anesthesia, and another hour or two in recovery before you return to your hospital room.

Will I be able to bend my knee after surgery?

Yes, but it takes time. Most people can bend their knee to about 90 degrees (a right angle) by six weeks after surgery. Full or near-full bending usually returns by three to six months with consistent physical therapy. The amount of bending you regain depends on how much you could bend before surgery and how dedicated you are to therapy.

Can I walk normally after total knee replacement?

Most people can walk normally without crutches or a walker by four to six weeks after surgery, though walking distances will be limited at first. By three months, many people walk without a limp. Some people notice a slight difference in how their knee feels compared to their natural knee, but this usually becomes less noticeable over time.

What activities should I avoid after knee replacement?

Avoid high-impact activities like running, jumping, and contact sports. Walking, swimming, cycling, and golf are generally safe. Your surgeon will give you specific guidelines based on your prosthetic type and your individual recovery. Staying active within these limits actually helps your prosthetic last longer.

How much pain will I have after surgery?

Pain is usually worst in the first few days after surgery, then gradually improves. You will receive pain medication to manage it, and ice and elevation help reduce swelling and discomfort. Most people report that post-surgery pain is less severe than the chronic pain they had before surgery from arthritis.