A full knee replacement removes the damaged surfaces of your knee joint and replaces them with artificial parts
A total knee replacement (also called total knee arthroplasty or TKA) is surgery to remove the worn cartilage and bone from your knee joint and install artificial components in their place. The surgeon removes the damaged ends of your thighbone and shinbone, along with the kneecap surface, then attaches metal and plastic implants that recreate the shape of a healthy knee. The artificial joint lets your knee bend and straighten again, usually with less pain than before.
This is different from a partial knee replacement, which replaces only one section of the knee when damage is limited to that area. A full replacement is used when arthritis or injury has damaged multiple compartments of the joint, or when other treatments have not relieved the pain enough to let you walk and move normally.
Key Takeaways
- A full knee replacement removes damaged bone and cartilage from all three compartments of your knee and replaces them with metal and plastic implants.
- The surgery typically takes one to three hours, and you will spend one to three days in the hospital before going home.
- Recovery involves physical therapy starting within days of surgery, with most people regaining basic function within three months and continued improvement for up to a year.
- Artificial knees usually last 15 to 20 years before wear requires a second surgery, though some newer designs may last longer.
- Your surgeon will discuss your medical history, current medications, and any previous surgeries before the operation to reduce the risk of complications.
Why surgeons recommend a full knee replacement
Your doctor will typically suggest a full knee replacement when your knee pain is severe enough to limit daily activities—walking, climbing stairs, getting in and out of a car—and when other treatments have not worked. Those other treatments usually include physical therapy, weight loss if relevant, anti-inflammatory medications, and injections of corticosteroids or hyaluronic acid into the joint.
The most common reason for a full replacement is osteoarthritis, where the protective cartilage in your knee wears away over time. Rheumatoid arthritis, where your immune system damages the joint, is another frequent cause. Severe knee injuries, fractures that did not heal properly, or damage from a previous surgery can also lead to enough joint destruction that replacement becomes the best option.
Your surgeon will order X-rays and sometimes an MRI to see how much damage exists and to confirm that a full replacement is the right choice for your situation. If only one part of your knee is damaged, a partial replacement may be an option that requires less surgery and recovery time.
What the surgeon does during the operation
The surgery begins with anesthesia—either general anesthesia (you are asleep) or regional anesthesia (your lower body is numb but you are awake). The surgeon makes an incision down the front of your knee, usually 8 to 10 inches long, to access the joint.
Once inside, the surgeon removes the damaged cartilage and bone from the ends of your thighbone, shinbone, and kneecap. The amount removed is carefully measured so the artificial parts will fit properly and your knee will be aligned correctly. The surgeon then cements or presses metal implants onto the thighbone and shinbone, and attaches a plastic spacer between them to act as the new cartilage surface. A plastic or metal component is also attached to the back of the kneecap.
The surgeon tests the knee's movement and alignment before closing the incision with stitches or staples. The whole operation usually takes one to three hours. You will have a bandage and often a drain tube to prevent fluid buildup, which is usually removed within a day or two.
Hospital stay and the first days after surgery
Most people stay in the hospital for one to three days after a full knee replacement. During this time, nurses will monitor your pain, manage swelling with ice and compression, and help you begin moving your knee gently. You will receive antibiotics to prevent infection and blood thinners to reduce the risk of clots in your legs.
Physical therapy starts almost when ready—often the day of surgery or the next morning. A therapist will help you bend and straighten your knee, teach you how to walk with crutches or a walker, and show you exercises to do at home. Your goal in these first days is to get your knee bending to at least 90 degrees and to be able to walk safely with information.
Pain and swelling are normal and expected. Your doctor will prescribe pain medication, and you will use ice and elevation at home to manage swelling. Most people can put weight on their new knee right away, though they need crutches or a walker for balance and safety at first.
Recovery timeline and physical therapy
Recovery from a full knee replacement is a gradual process that unfolds over months. In the first two weeks, your focus is on reducing swelling, regaining knee motion, and walking safely without crutches. By four to six weeks, most people can walk without assistive devices and begin climbing stairs with a rail.
Physical therapy continues for several months, either at a clinic or at home with a therapist visiting you. The exercises gradually increase in difficulty—from straightforward bending and straightening to walking longer distances, climbing stairs without a rail, and eventually returning to activities like swimming or cycling. By three months, most people have regained enough function for everyday tasks. Improvement continues for up to a year as strength builds and your brain adapts to the new joint.
The amount of time before you can return to work depends on your job. If you sit at a desk, you may return in four to six weeks. If your work requires standing, walking, or physical labor, recovery may take longer. Your surgeon will give you specific guidance based on your job and your progress in therapy.
Risks and complications to know about
Like any surgery, a full knee replacement carries risks. Infection is one of the most serious—it can happen in the wound or deep in the joint. Signs include increasing redness, warmth, swelling, drainage, or fever. Infection is rare (less than 2 percent of cases) but requires prompt treatment with antibiotics or, in severe cases, another surgery.
Blood clots in the legs are another possible complication. Your doctor will prescribe blood thinners and may recommend compression stockings to reduce this risk. Swelling, pain, or warmth in your calf should be reported to your doctor right away.
Other complications include stiffness (when the knee does not bend as much as expected), implant loosening over time, and wear of the plastic spacer. Some people experience persistent pain or swelling that takes longer to resolve. Nerve or blood vessel injury during surgery is rare but possible. Your surgeon will discuss your individual risk factors before the operation.
How long artificial knees last and when revision surgery may be needed
Most artificial knee implants last 15 to 20 years before the plastic spacer wears down enough that a second surgery becomes necessary. This timeline varies based on your age, weight, activity level, and the specific implant used. Younger, more active people may wear out their implants faster. Newer implant designs and materials may extend this lifespan, though long-term data is still being collected.
A revision surgery—replacing the worn implant with a new one—is more complex than the original surgery because the surgeon must remove the old implant and sometimes repair bone that has worn away. Recovery from revision surgery is typically longer than from the first replacement.
You can extend the life of your implant by maintaining a healthy weight, avoiding high-impact activities like running or jumping, and staying active with low-impact exercise like walking, swimming, and cycling. Your surgeon will give you specific guidance about which activities are safe for your new knee.
Preparing for surgery and what to expect beforehand
Before your surgery, your surgeon will order blood tests and an EKG (heart tracing) to make sure you are healthy enough for the operation. Tell your surgeon about all medications you take, including blood thinners, aspirin, and supplements. Some medications need to be stopped before surgery, while others should be continued.
You will meet with an anesthesiologist to discuss which type of anesthesia is best for you. If you smoke, quitting before surgery reduces infection risk and helps healing. Your surgeon may ask you to lose weight if your BMI is very high, as this reduces stress on the new joint and lowers complication risk.
The night before surgery, you will be told not to eat or drink after midnight. Arrange for someone to drive you home and help you for the first few days—you will not be able to drive while taking pain medication or using crutches. Set up your home beforehand: place frequently used items at waist height, remove tripping hazards, and arrange a comfortable place to rest with your leg elevated.
Frequently Asked Questions
Can I bend my new knee all the way like a normal knee?
Most people regain 110 to 120 degrees of bending, which is enough for walking, climbing stairs, and sitting in a chair. A fully normal knee bends to about 135 degrees, so some people do not regain complete motion. Physical therapy in the first weeks is critical—knees that do not bend well early on often stay stiff. Talk to your surgeon about your specific goals.
Will I be able to kneel or sit cross-legged after knee replacement?
Many people can kneel on their new knee, though some find it uncomfortable. Sitting cross-legged depends on how much your knee bends and your personal comfort. These activities are usually possible but may take several months of recovery. Your physical therapist can work with you on these specific movements if they are important to you.
What activities should I avoid after knee replacement?
Avoid high-impact activities like running, jumping, and contact sports, as these wear out the implant faster. Low-impact activities like walking, swimming, cycling, golf, and bowling are generally safe. Your surgeon will give you a specific list based on your implant type and your overall health. Some people do return to light hiking or recreational activities, but this should be discussed with your surgeon first.
Will I set off metal detectors with my new knee?
Most knee implants do contain metal, and you may trigger a metal detector at an airport or security checkpoint. Your surgeon will give you a card to carry that identifies your implant. Show this card to security, and they will usually allow you through or perform a pat-down instead of sending you through the detector.
How much does a full knee replacement cost?
The cost varies widely depending on your location, hospital, surgeon, and insurance coverage. In the United States, the total cost (including surgery, hospital stay, and follow-up care) typically ranges from $35,000 to $60,000 before insurance. Medicare covers most of the cost for people over 65. If you have private insurance, your out-of-pocket cost depends on your deductible and coverage plan. Ask your surgeon's office for a cost estimate based on your specific situation.