The surgery itself usually takes 1 to 2 hours, but you'll spend 3 to 4 hours at the surgical facility total

The actual time a surgeon spends replacing your knee joint runs between 60 and 120 minutes. That's the time from when you're asleep under anesthesia until the incision is closed. But the clock starts earlier and stops later. You'll arrive 1 to 2 hours before surgery for paperwork, vital signs, and anesthesia prep. After the surgeon finishes, you'll spend 1 to 2 hours in recovery while the anesthesia wears off and nurses monitor your vital signs. Plan to be at the surgical center or hospital for 3 to 4 hours total, even though the actual replacement takes less than half that time.

The exact length depends on your surgeon's experience, the complexity of your knee, and whether you have other joint damage the surgeon finds once they open your knee. A straightforward first knee replacement on someone without previous knee surgery typically takes closer to 60 minutes. If you're having both knees done in one session, add another 45 to 90 minutes for the second knee.

Key Takeaways

  • The surgical procedure itself lasts 1 to 2 hours, but you'll be at the facility for 3 to 4 hours when you include prep and recovery time.
  • Arrival time, anesthesia setup, and post-surgery monitoring add 2 to 3 hours to your total time at the surgical center.
  • Your surgeon's experience and the condition of your knee joint affect how long the replacement takes, with simpler cases running closer to 60 minutes.
  • You cannot drive or make decisions for 24 hours after surgery because of the anesthesia, so arrange transportation before your surgery date.

What happens during the 1 to 2 hours of actual surgery

The surgeon makes an incision down the front of your knee, usually 8 to 10 inches long. They move the kneecap aside to reach the joint underneath. Using specialized cutting guides, they remove the damaged cartilage and bone from the ends of your thighbone and shinbone. This removal and shaping takes the bulk of the time—the surgeon has to create a smooth surface that matches the metal and plastic components they're about to attach.

Once the bone surfaces are prepared, the surgeon cements the metal implants (usually a cobalt-chrome alloy) onto the thighbone and shinbone. They test the fit and alignment by moving your knee through its range of motion. If everything tracks correctly, they insert a plastic spacer between the metal parts to act as your new cartilage. The surgeon then closes the incision with stitches or staples, applies a sterile dressing, and you move to recovery.

The entire sequence—exposure, bone removal, implant placement, testing, and closure—is choreographed. Surgeons who perform knee replacements regularly develop a rhythm that keeps the time predictable. A surgeon doing 5 to 10 knee replacements per week will typically finish faster than one doing 1 or 2 per month, though speed is never the goal; precision is.

The hours before surgery: arrival, paperwork, and anesthesia setup

You'll be asked to arrive 1 to 2 hours before your scheduled surgery time. A nurse will check your blood pressure, heart rate, and oxygen level. You'll answer questions about your medical history, current medications, and any allergies—information the surgical team needs even though you've already provided it multiple times. This redundancy is intentional; it's a safety check.

An anesthesiologist or nurse anesthetist will meet with you to discuss the anesthesia plan. Most knee replacements use general anesthesia (you're fully asleep), though some surgeons use regional anesthesia (numbing from the waist down while you're sedated). The anesthesia team will place an IV line in your arm and may give you a mild sedative to help you relax. You'll change into a surgical gown, remove jewelry and dentures if you have them, and use the bathroom one last time before heading to the operating room.

Recovery time at the surgical facility after surgery ends

When surgery is finished, you move to the post-anesthesia care unit (PACU), sometimes called the recovery room. You'll wake up gradually over 30 to 60 minutes as the anesthesia wears off. A nurse will check your vital signs every 15 minutes at first, then less frequently as you become more alert. They'll manage any pain with medication and monitor your surgical dressing for bleeding. You may feel groggy, nauseous, or confused—all normal reactions to anesthesia.

Once you're alert enough to drink water without nausea and your vital signs are stable, you'll move to a discharge area if you're having outpatient surgery, or to a hospital room if you're staying overnight. Most people spend 1 to 2 hours in recovery before they're ready to leave. You cannot drive, sign documents, or make medical decisions for at least 24 hours after general anesthesia, so your ride home must be someone else.

Why the timeline varies from person to person

A patient with a straightforward knee replacement—no previous surgery, no arthritis in other parts of the joint, good bone quality—might be in the operating room for 60 to 75 minutes. A patient with a complex case—previous knee surgery, severe arthritis, bone loss that needs to be rebuilt, or implants that need to be removed first—might take 90 to 120 minutes or longer. The surgeon cannot predict the exact time until they see the inside of your knee.

Your age, overall health, and body composition also affect timing. An older patient with osteoporosis may require more careful bone handling. A patient with a very muscular leg may take longer to expose the joint. A patient on blood thinners may bleed more during surgery, requiring extra time for hemostasis (stopping the bleeding). None of these factors make the surgery riskier if your surgeon is experienced, but they do affect how long it takes.

Anesthesia time can also vary. Some patients wake up quickly from anesthesia; others take longer. This is partly genetic and partly related to your age and medications. The surgical team cannot rush this process—waking you too quickly can cause nausea and confusion, so they let it happen at its own pace.

What to expect in the days after you leave the surgical facility

You'll go home with a surgical dressing, pain medication, and instructions for wound care. Your knee will be swollen and stiff for the first few weeks. Physical therapy usually starts within a few days—either at a clinic or at home with a therapist visiting you. The goal is to restore your range of motion and strength so you can walk, climb stairs, and return to daily activities.

Most people can put weight on the leg when ready after surgery, though walking will be slow and painful at first. You'll use crutches or a walker for the first 1 to 2 weeks. Swelling peaks around day 3 to 5 and gradually improves over 6 to 8 weeks. Full recovery—when you can walk without a limp and return to most activities—typically takes 3 to 6 months. Some people continue to improve for up to a year.

Frequently Asked Questions

Can I eat or drink before surgery?

No. You'll be told to stop eating at midnight the night before surgery and stop drinking clear liquids 2 hours before your arrival time. This is critical—food or liquid in your stomach during anesthesia can cause serious complications. Follow your surgical team's instructions exactly, even if you're hungry or thirsty.

Will I be awake during any part of the surgery?

No. General anesthesia means you're completely asleep and unconscious. You won't remember anything from the time the anesthesia starts until you wake up in recovery. Some surgeons use regional anesthesia (numbing the leg while you're sedated), but you still won't be aware of the surgery happening.

What if surgery takes longer than expected?

Your surgeon will contact your family if the procedure is taking significantly longer than planned. This usually means they found unexpected bone damage or arthritis and are taking extra time to address it properly. A longer surgery is not necessarily a sign of a problem—it often means your surgeon is being thorough.

Do I need to stay overnight in the hospital?

Many knee replacements are done as outpatient surgery, meaning you go home the same day. Some hospitals or surgical centers keep patients overnight for monitoring. Your surgeon will tell you which applies to your situation based on your age, health, and home support. Even outpatient patients can request to stay overnight if they're uncomfortable going home.

When can I drive after surgery?

You cannot drive for at least 24 hours after general anesthesia, and most surgeons recommend waiting 1 to 2 weeks until you can safely operate the pedals and react quickly. Check with your surgeon and your insurance—some policies won't cover accidents that happen before your surgeon clears you to drive.