The basic steps of knee replacement surgery
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, typically 8 to 10 inches long, to reach the joint. Once inside, they remove the damaged cartilage and bone from the ends of your thighbone, shinbone, and kneecap. The artificial parts—called prosthetics—are then fitted and secured in place, either with cement or by allowing bone to grow into them naturally.
The entire procedure usually takes 1 to 2 hours in the operating room. You will be under general anesthesia, meaning you are asleep and feel nothing during the surgery. A surgical team monitors your heart rate, blood pressure, and oxygen levels throughout. Once the prosthetics are in place and the surgeon confirms everything is aligned correctly, the incision is closed with stitches or staples, and you move to recovery.
Key Takeaways
- The surgeon removes damaged bone and cartilage from your thighbone, shinbone, and kneecap, then attaches metal and plastic prosthetics to replace them.
- The incision is made down the front of the knee and is typically 8 to 10 inches long, allowing the surgeon to access the joint directly.
- The surgery takes 1 to 2 hours under general anesthesia, and the prosthetics are secured either with surgical cement or by allowing bone to grow into them.
- After surgery, you will spend time in recovery and typically stay in the hospital for 1 to 3 days before going home to begin physical therapy.
- Most people begin walking with information the day after surgery and start formal physical therapy within days to regain strength and movement.
Preparing your knee before the incision
Before the surgeon makes the main incision, the surgical team prepares your knee by cleaning the skin with an antiseptic solution and draping the area with sterile sheets. The anesthesiologist confirms you are fully asleep and unable to feel pain. The surgeon then makes a single incision down the front of the knee, usually starting above the kneecap and extending below it. This anterior approach—cutting through the front—is the most common method because it gives the surgeon clear access to all three parts of the joint that need to be replaced.
Once the incision is open, the surgeon moves aside the muscles and tissues around the knee without cutting them. This protects the soft tissue and allows it to heal more easily after surgery. The surgeon then exposes the knee joint itself, where the thighbone, shinbone, and kneecap meet.
Removing damaged bone and cartilage
The surgeon uses specialized cutting guides and saws to remove the damaged surfaces of the bones. The thighbone is cut at a specific angle to match the shape of the artificial component that will replace it. The shinbone is also cut to the correct shape and size. These cuts are precise—often measured to within a millimeter—because the alignment of the prosthetics directly affects how well your knee will function after surgery.
The damaged cartilage is scraped away completely, exposing the underlying bone. If bone has worn away significantly, the surgeon may need to add bone cement or a bone graft to build up the surface before attaching the prosthetic. The kneecap is also resurfaced by removing its damaged cartilage and preparing it to receive a plastic component on its undersurface.
Fitting and securing the prosthetic components
Once the bone surfaces are prepared, the surgeon tests the fit of the prosthetic components. A temporary trial prosthetic is placed to check the alignment and make sure your knee bends and straightens smoothly. The surgeon moves your leg through its range of motion to may support the components are positioned correctly. If adjustments are needed, the surgeon removes the trial piece and makes small cuts to the bone until the fit is right.
When the alignment is correct, the permanent prosthetics are secured in place. Most surgeons use surgical cement—a fast-hardening adhesive—to bond the metal components to your bone. The cement fills the space between the prosthetic and the bone surface, creating a strong, lasting bond. Some surgeons use cementless prosthetics instead, which have a porous surface that allows your bone to grow into them over several weeks. Both methods are effective, and your surgeon will choose based on your age, bone quality, and other factors.
Closing the incision and moving to recovery
After the prosthetics are secured and the cement has hardened, the surgeon checks the knee one final time to confirm everything is in place. The tissues and muscles around the knee are repositioned, and the incision is closed with stitches or staples. A sterile bandage is applied, and you are moved to the recovery room while still under anesthesia.
In recovery, nurses monitor you as the anesthesia wears off. You will likely feel groggy and may experience some pain, which is managed with medication. Most people stay in the hospital for 1 to 3 days. During this time, you will begin moving your knee gently and may start walking with a walker or crutches, often with the help of a physical therapist. Pain and swelling are normal and gradually decrease over the first few weeks at home.
What happens in the weeks after surgery
Physical therapy begins within days of surgery and continues for several weeks. A physical therapist guides you through exercises designed to restore strength, flexibility, and balance. Early on, the focus is on reducing swelling and regaining the ability to straighten and bend your knee. As healing progresses, exercises become more challenging, helping you walk normally and climb stairs again.
Swelling peaks around 2 to 3 weeks after surgery and then gradually subsides. You will wear compression bandages or a compression sleeve to help control swelling. Ice and elevation also help reduce inflammation. Most people can return to light activities like walking and gentle stretching within 4 to 6 weeks. Full recovery—when you can return to most normal activities without pain—typically takes 3 to 6 months, though some people continue to improve for up to a year.
Common variations in surgical technique
While the basic steps are the same, surgeons may use different approaches depending on your anatomy and the condition of your knee. Some surgeons use a shorter incision, called a minimally invasive approach, which may reduce tissue damage and speed recovery slightly. Others use computer-assisted navigation or robotic guidance to improve the precision of bone cuts and prosthetic placement. These technologies help may support the components are aligned exactly, which can improve long-term outcomes.
The choice of prosthetic design also varies. Some prosthetics are designed to move more like a natural knee, while others prioritize stability. Your surgeon will recommend the type that best matches your needs and activity level. Regardless of the specific technique or prosthetic used, the fundamental goal remains the same: remove the damaged joint surfaces and replace them with components that allow pain-free movement.
Frequently Asked Questions
How long does the surgery actually take?
The surgery itself typically takes 1 to 2 hours from the time you enter the operating room until the incision is closed. However, you should plan to be at the hospital for several hours total, including time for preparation, anesthesia, surgery, and recovery. Your surgeon can give you a more specific timeline based on your individual situation.
Will I feel pain during the surgery?
No. General anesthesia keeps you completely asleep and unable to feel pain during the procedure. The anesthesiologist monitors your vital signs throughout to may support you remain safely asleep. You will not remember the surgery or feel anything until you wake up in recovery.
What is the difference between cemented and cementless prosthetics?
Cemented prosthetics are bonded to your bone when ready using surgical cement, providing stability right away. Cementless prosthetics have a porous surface that allows your bone to grow into them over several weeks, creating a natural bond. Both methods work well. Your surgeon chooses based on your age, bone quality, and activity level.
Can the surgeon fix my knee without replacing it?
If your knee damage is limited to one area, your surgeon may recommend a partial knee replacement, which replaces only the damaged compartment. If damage is widespread, a total replacement is usually necessary. Your surgeon will discuss which option is best for your specific knee condition.
What happens if the prosthetic becomes loose after surgery?
Prosthetics can loosen over time due to wear or bone loss, though this is uncommon in the first several years. If loosening occurs, revision surgery can replace the worn components. This is why regular follow-up appointments with your surgeon are important—they can detect problems early through X-rays before you experience significant pain or instability.