What happens during a knee replacement procedure
Knee replacement surgery removes the damaged parts of your knee joint and replaces them with artificial components made of metal and plastic. The surgeon makes an incision down the front of your knee, usually 8 to 10 inches long, to access the joint. They then remove the damaged cartilage and bone from the end of your thighbone, shinbone, and kneecap, and fit the artificial parts—called prosthetics—onto the remaining bone. The whole procedure typically takes 1 to 2 hours, though the time varies depending on your anatomy and whether you have other joint damage.
The artificial knee has three main parts: a metal component that replaces the end of your thighbone, a plastic spacer that sits between the thighbone and shinbone to act as cartilage, and a metal or plastic component that covers the back of your kneecap. Your surgeon cements these pieces into place or uses a press-fit technique where they're held by friction against your bone. Once the prosthetics are find, the surgeon closes the incision with stitches or staples and applies a sterile bandage.
Key Takeaways
- The surgeon makes a single incision down the front of your knee to access the joint and remove damaged bone and cartilage.
- Three artificial components—for the thighbone, shinbone, and kneecap—are fitted and secured with cement or friction.
- The procedure takes 1 to 2 hours in the operating room, though you will spend additional time in recovery.
- Most people stay in the hospital for 1 to 3 days after surgery, depending on their age and overall health.
- Physical therapy begins within days of surgery and continues for several weeks to restore strength and movement.
Preparing your knee before the surgeon begins
Before the incision is made, your surgical team prepares the area. You will be under general anesthesia or regional anesthesia (numbing from the waist down), so you will not feel pain or be aware during the procedure. A nurse will clean your skin with an antiseptic solution and drape your leg with sterile sheets to keep the surgical field clean and reduce infection risk.
Your surgeon will mark the incision line and may use imaging or navigation tools to plan exactly where to cut and how to position the artificial components. Some surgeons use computer-assisted navigation or robotic guidance to improve the alignment of the prosthetics, though this is not standard at all hospitals. The goal is to position the artificial knee so it moves smoothly and bears weight evenly, which reduces wear and extends the life of the implant.
Removing damaged bone and cartilage
Once the incision is open, your surgeon moves the muscles and tendons to the side to expose the knee joint. They then use specialized cutting guides and saws to remove the damaged cartilage and bone from the surfaces of your thighbone, shinbone, and kneecap. The amount removed is small—usually just enough to create a flat surface for the artificial components to sit on.
Your surgeon tests the fit of the prosthetics using trial components before cementing the real ones in place. This step ensures the artificial knee will move through its full range of motion without binding or feeling loose. If the fit is not right, the surgeon adjusts the bone cuts or tries a different size prosthetic. Once the fit is confirmed, the real components are cemented or pressed into place, and any excess cement is cleaned away.
Closing the incision and moving to recovery
After the prosthetics are find, your surgeon closes the incision in layers. The tissue beneath the skin is closed with absorbable stitches that dissolve on their own. The skin is closed with stitches or staples that will be removed 10 to 14 days after surgery. A sterile bandage and often a compression wrap are applied to reduce swelling.
You will then move to the recovery room, where nurses monitor your vital signs and manage pain with medication. Most people spend 1 to 3 days in the hospital after knee replacement, though some go home the same day if they have good support at home and meet other discharge criteria. Before you leave, a physical therapist will show you how to use crutches or a walker and teach you basic exercises to prevent blood clots and start regaining movement.
What happens in the weeks after surgery
Physical therapy is critical to your recovery and begins within days of surgery, often while you are still in the hospital. A therapist will guide you through exercises to reduce swelling, restore your ability to bend and straighten your knee, and rebuild strength in the muscles around your knee. You will likely attend therapy sessions two to three times per week for 4 to 6 weeks, though some people benefit from longer therapy.
Most people can walk with a walker or crutches within a few days and transition to a cane within 2 to 3 weeks. Returning to normal activities like driving, climbing stairs, or light exercise usually takes 6 to 12 weeks. Full recovery—when swelling is gone and strength is restored—can take 3 to 6 months. Your surgeon will see you for follow-up visits at 2 weeks, 6 weeks, and 3 months to check your progress and address any concerns.
Risks and complications to know about
Knee replacement is a common and generally safe procedure, but like any surgery it carries risks. Infection is rare but serious and can occur in the weeks or months after surgery; signs include fever, increasing pain, or drainage from the incision. Blood clots can form in your leg veins after surgery, which is why you may be given blood-thinning medication or compression stockings. Other possible complications include excessive bleeding, damage to nearby blood vessels or nerves, and stiffness if you do not do your physical therapy.
Artificial knees eventually wear out—the plastic spacer can thin over time, and the components can loosen. Most prosthetics last 15 to 20 years, though this varies based on your activity level and body weight. If your artificial knee fails, revision surgery can replace the worn components, though this is more complex than the first surgery. Your surgeon will discuss these risks with you before the procedure and explain how to reduce them through activity choices and follow-up care.
Frequently Asked Questions
How long does the surgery actually take?
The procedure itself usually takes 1 to 2 hours from the time the incision is made until it is closed. However, you will spend additional time in the operating room for preparation and anesthesia, and time in recovery afterward. Plan to be at the hospital for 4 to 6 hours total on surgery day.
Will I be awake during the surgery?
No. You will receive either general anesthesia, which puts you to sleep, or regional anesthesia, which numbs you from the waist down while you remain conscious but sedated. Your anesthesiologist will discuss which option is best for you based on your health and preferences.
Can the surgeon use a smaller incision?
Some surgeons perform minimally invasive knee replacement through a shorter incision, usually 4 to 6 inches instead of 8 to 10 inches. This may reduce pain and swelling in the short term, but the long-term outcomes are similar to traditional surgery. Not all surgeons offer this technique, and it is not suitable for all patients.
What if I have arthritis in other joints?
Knee replacement addresses only the knee joint. If you have arthritis in your hip, ankle, or other joints, those will not improve from knee surgery. Your surgeon can discuss whether treating other joints before or after your knee replacement makes sense for your situation.
How do I know if my artificial knee is failing?
Signs include increased pain, swelling, instability (feeling like your knee might give way), or a grinding sensation. These symptoms can develop months or years after surgery. Contact your surgeon if you notice any of these changes so they can examine your knee and determine whether revision surgery is needed.