The surgical team prepares you and removes the damaged knee joint

When you arrive for knee replacement surgery, an anesthesiologist will place you under general anesthesia or regional anesthesia (numbing from the waist down). Once you are asleep or numb, a surgical nurse will clean your knee with antiseptic solution and drape it with sterile sheets. The surgeon makes an incision, usually 8 to 12 inches long, down the front of your knee to reach the joint.

The surgeon then carefully moves the muscles and tendons to the side without cutting them. This gives clear access to the knee joint itself. You will not feel any of this—the anesthesia prevents pain and keeps you still during the procedure.

Key Takeaways

  • The surgeon removes the damaged cartilage and bone from your knee joint and replaces it with metal and plastic implants that mimic a healthy knee.
  • The entire surgery typically takes 1 to 3 hours, depending on the complexity of your case and whether both knees are being replaced.
  • Before you leave the operating room, the surgeon tests the new joint to make sure it moves smoothly and is aligned correctly.
  • You will spend time in recovery before moving to a hospital room, where physical therapy begins within hours or the next day.
  • Most people go home within 1 to 3 days, though some stay longer if they live alone or have other health conditions.

The surgeon removes damaged bone and cartilage

Once the joint is exposed, the surgeon uses specialized cutting guides and saws to remove the damaged cartilage and a thin layer of bone from the end of your thighbone (femur) and the top of your shinbone (tibia). The amount removed is carefully measured so the new implant will fit properly and your leg will be the correct length.

The surgeon also removes any bone spurs or damaged tissue inside the joint. If your kneecap is severely damaged, a portion of it may be resurfaced as well. This step is critical because the new implant can only work well if the bone surfaces are prepared correctly.

Metal and plastic implants are positioned and secured

The surgeon then places the metal components onto the prepared bone surfaces. The femoral component (a curved metal piece) goes on the thighbone, and the tibial component (a flat metal piece) goes on the shinbone. These are usually secured with bone cement, though some implants have a textured surface that allows bone to grow into them over time.

A plastic spacer is inserted between the metal pieces to create a smooth, gliding surface that mimics natural cartilage. The surgeon tests the fit and alignment by moving your knee through its range of motion. If everything feels stable and moves smoothly, the components are locked in place.

The incision is closed and you move to recovery

Before closing, the surgeon rinses the joint with sterile saline solution to remove any bone fragments or debris. The muscles and tendons are moved back into their normal position. The surgeon then closes the incision with stitches or staples and covers it with a sterile bandage.

You are then moved to the recovery room, where nurses monitor your heart rate, blood pressure, oxygen level, and pain. As the anesthesia wears off, you will begin to wake up. Most people feel groggy and may not remember much of the first hour. Pain medication is given as needed, and ice is applied to reduce swelling.

Physical therapy begins almost when ready

Within a few hours of surgery, or the next morning, a physical therapist will visit you to begin gentle movement exercises. These might include ankle pumps, quadriceps sets (tightening the thigh muscle), and short walks with a walker or crutches. Early movement prevents blood clots and stiffness and speeds recovery.

You will also learn how to use a continuous passive motion (CPM) machine if your surgeon recommends one. This device gently bends and straightens your knee while you rest, helping maintain flexibility. Most hospitals use these for a few hours each day during your stay.

Pain management and monitoring during your hospital stay

You will receive pain medication through an IV, by mouth, or through a nerve block (numbing medication injected near the surgical site). Your surgical team will adjust doses based on your pain level. Some swelling and bruising around the knee is normal and expected.

Nurses will check your incision regularly for signs of infection, monitor your leg for blood clots, and help you move around safely. You may wear compression stockings or use a sequential compression device (a sleeve that inflates and deflates around your calf) to prevent clots. Most people stay in the hospital for 1 to 3 days, though length of stay varies based on your age, overall health, and home situation.

What to expect when you go home

Before discharge, you will receive instructions on wound care, pain management, and exercises to do at home. You will need crutches or a walker for several weeks and should not drive while taking strong pain medication. Most people can put weight on the leg within days, but the timeline depends on your surgeon's recommendations and your individual recovery.

Outpatient physical therapy typically begins within 1 to 2 weeks and continues for 6 to 12 weeks. Your knee will continue to improve for up to a year after surgery as swelling decreases and you regain strength and flexibility. Full recovery usually takes 3 to 6 months, though some people need longer.

Frequently Asked Questions

How long does knee replacement surgery take?

Most knee replacements take 1 to 3 hours from the time you enter the operating room until the incision is closed. The exact time depends on the complexity of your case, whether both knees are being replaced, and any complications the surgeon encounters.

Will I feel pain during the surgery?

No. Anesthesia prevents you from feeling pain, seeing, or remembering the surgery. You will be unconscious or deeply sedated the entire time. Pain begins after anesthesia wears off, which is why pain medication is given in recovery.

What happens if something goes wrong during surgery?

Your surgical team monitors you constantly and is trained to handle complications. If the surgeon encounters unexpected bone damage or other issues, they adjust the procedure on the spot. Serious complications during surgery are rare, but your surgeon will discuss risks specific to your health before the procedure.

Can both knees be replaced at the same time?

Yes, some people have both knees replaced in one surgery, which takes longer (usually 2 to 4 hours total). Others have them done separately, weeks or months apart. Your surgeon will recommend the approach based on your age, overall health, and how damaged both knees are.

What kind of implant will I receive?

Your surgeon will discuss implant options with you before surgery. Choices include different materials, designs, and fixation methods (cemented or cementless). Your age, activity level, and bone quality influence which implant is recommended for you.