Knee replacement surgery typically lasts between one and three hours, depending on whether you're having one knee or both replaced at the same time

A standard total knee replacement on a single knee usually takes about 90 minutes to two hours from the moment you're in the operating room until the surgeon closes the incision. If you're having both knees replaced during one surgery session—called bilateral knee replacement—plan on two to three hours. The exact time depends on your anatomy, how damaged your knee is, whether you've had previous knee surgery, and how quickly your surgeon works.

The time in the operating room is only part of your day at the surgical facility. You'll spend time in pre-op getting prepared, time in recovery waking up from anesthesia, and time in post-op before you go home or to a hospital bed. The entire process from arrival to discharge typically takes six to eight hours.

Key Takeaways

  • A single knee replacement takes 90 minutes to two hours in the operating room, while both knees take two to three hours.
  • Your total time at the surgical facility will be six to eight hours, including pre-op, surgery, and recovery time.
  • Complications during surgery, previous knee procedures, or bone damage can extend operating time by 30 minutes or more.
  • Recovery from the surgery itself is different from recovery of your knee function, which takes weeks to months of physical therapy.

What happens during the surgery itself

Once you're asleep under anesthesia, the surgeon makes an incision down the front of your knee, usually four to six inches long. They remove the damaged cartilage and bone from the ends of your femur (thighbone) and tibia (shinbone), then fit the metal and plastic replacement parts into place. The surgeon tests the new joint to make sure it moves smoothly and is properly aligned before closing the incision with stitches or staples.

The actual replacement of the joint surfaces takes most of the time. Preparing the bone surfaces so the new parts fit correctly, cementing or pressing the components into place, and making sure everything is aligned properly all require precision work. A surgeon who has done thousands of these procedures may work faster than one doing their first hundred, but speed is less important than accuracy—a misaligned knee replacement can cause problems years later.

Why some surgeries take longer than others

If you have severe arthritis that has deformed your knee bone, the surgeon may need extra time to reshape the bone properly. Previous knee surgery—even arthroscopy or a meniscus repair years ago—can create scar tissue that takes longer to work through. Obesity, very tight muscles, or bone density issues can also add time.

Complications discovered during surgery, such as unexpected bone loss or ligament damage, may require the surgeon to use different techniques or larger implant sizes. If you're having both knees done at once, the second knee sometimes takes longer because you're already partway through the anesthesia window and the surgeon may need to work more carefully.

The difference between surgery time and recovery time

It's important to separate what happens in the operating room from what happens after. The surgery itself is finished in two to three hours, but your recovery from anesthesia takes another hour or two in the post-op area. You'll be groggy, your leg will be numb from the regional anesthesia block (if you had one), and nurses will monitor your blood pressure, heart rate, and oxygen levels.

Recovery of your knee function—being able to walk, climb stairs, or return to normal activities—is a much longer process. Most people spend two to three months doing physical therapy before they can walk without a cane or walker. Full recovery, where you have normal strength and range of motion, often takes six months to a year. This is why your surgeon will tell you the surgery is just the beginning of your treatment.

What to expect in pre-op and recovery areas

You'll arrive at the surgical facility one to two hours before your scheduled surgery time. In pre-op, a nurse will check your vital signs, an anesthesiologist will review your medical history and explain the anesthesia options, and you'll sign final consent forms. You may receive a sedative to help you relax before being wheeled into the operating room.

After surgery, you'll wake up in the post-op recovery area with your leg in a compression bandage and possibly in a cooling device to reduce swelling. A nurse will give you pain medication and help you start moving your leg gently. Most people are alert enough to go home or to a hospital room within two to four hours, though you won't be able to drive or make decisions for the rest of that day because of the anesthesia.

Planning your day around surgery timing

If your surgery is scheduled for early morning—7 or 8 a.m.—you'll typically be home or in a hospital room by mid-afternoon. If it's scheduled for afternoon, you may stay overnight for monitoring. Ask your surgeon's office what time you need to arrive and whether you should expect to stay overnight. Some facilities do same-day discharge for knee replacement; others keep patients overnight as standard practice.

Arrange for someone to pick you up and stay with you for at least the first 24 hours. You'll be on pain medication and won't be able to care for yourself independently. Have your home prepared before surgery—crutches or a walker ready, a ground-floor bedroom or bathroom if stairs are difficult, and ice packs in the freezer for swelling.

When surgery takes longer than expected

If your surgeon discovers during the operation that your knee is more damaged than the pre-op imaging showed, or if there are unexpected complications, the surgery may run 30 minutes to an hour longer. Your surgical team will contact your family in the waiting room to let them know. Longer surgery doesn't automatically mean a worse outcome, but it does mean more time under anesthesia and potentially more swelling afterward.

Some surgeons also take extra time to use computer-assisted navigation or robotic guidance systems to position the implant with greater precision. These technologies can add 20 to 40 minutes to the procedure but may improve long-term alignment and implant lifespan. Ask your surgeon whether they use these tools and whether they're included in your surgery plan.

Frequently Asked Questions

Can I eat or drink before surgery?

No. You'll receive instructions to stop eating at midnight and stop drinking clear liquids a few hours before surgery. This prevents you from vomiting while under anesthesia, which can be dangerous. Follow these instructions exactly—eating or drinking before surgery can cause your operation to be postponed.

Will I be awake during the surgery?

No. You'll receive general anesthesia, which puts you completely to sleep, or regional anesthesia (a spinal or epidural block) plus sedation. Either way, you won't be aware of the surgery. Your anesthesiologist will monitor you throughout and adjust medications as needed.

What if I need both knees replaced—do they do them at the same time?

Some surgeons will replace both knees in one session if you're healthy enough; others prefer to do them separately, weeks or months apart. Bilateral surgery is faster overall but means more anesthesia and a longer recovery period. Discuss this with your surgeon based on your age, overall health, and how much pain you're in.

How much blood do I lose during knee replacement?

Most people lose less than one unit of blood (about one pint) during knee replacement surgery. Your surgeon may use a tourniquet to reduce bleeding during the procedure. If you're concerned about blood loss or need a transfusion, discuss this with your surgeon beforehand—some people bank their own blood before surgery.

Can I watch a video of my surgery?

Many surgeons record the procedure. Ask your surgeon's office whether they do this and whether you can receive a copy. Watching your surgery can help you understand what was done and why certain movements may feel different during recovery.