The Surgery Itself Takes One to Three Hours

The actual surgical procedure for knee replacement usually lasts between one and three hours, with two hours being typical. The exact time depends on whether you are having a total knee replacement (both sides of the joint) or a partial one (just one side), how complex your knee damage is, and how quickly your surgeon works. A straightforward total replacement on a healthy patient might take 90 minutes; a partial replacement or a revision of an old implant can run longer.

The surgeon removes the damaged cartilage and bone, positions the metal and plastic implant pieces, and tests the joint to make sure it moves smoothly and stays stable. None of this can be rushed without risking poor alignment, which would cause pain or early failure of the implant. Your surgeon will take whatever time is needed to get it right.

Key Takeaways

  • The surgical procedure itself typically lasts one to three hours, with two hours being the most common length for a total knee replacement.
  • You will spend one to two hours in the operating room before surgery begins for positioning, anesthesia, and prep work.
  • Recovery in the post-operative area takes another one to three hours while anesthesia wears off and nurses monitor your vital signs.
  • Total time from when you arrive at the hospital to when you leave the operating area is usually four to six hours.
  • The first few weeks at home involve physical therapy and gradual return to activity, not a single recovery period.

What Happens Before the Surgeon Starts

Before the actual surgery begins, you will spend time in the pre-operative area. Nurses will check your blood pressure, heart rate, and oxygen levels, place an IV line, and ask you to confirm your medical history and any allergies. An anesthesiologist will talk with you about pain control and sedation options—most knee replacements use regional anesthesia (numbing from the waist down) combined with light sedation, though some patients receive general anesthesia instead.

You will then be moved to the operating room, positioned on the surgical table, and prepped with sterile draping. The surgical team will mark the surgical site and verify they are operating on the correct knee. This entire pre-operative phase takes 60 to 120 minutes. Nothing happens in an operating room without deliberate steps, and rushing this part increases infection risk and other complications.

Recovery Time in the Post-Operative Area

After the surgeon closes the incision, you move to the post-operative recovery area (sometimes called the PACU, or post-anesthesia care unit). Nurses monitor your heart rate, blood pressure, oxygen level, and pain while the anesthesia wears off. They will help you wake up gradually, check that you can move your toes and feel your legs, and manage any nausea or discomfort with medication.

This phase typically lasts one to three hours. You cannot leave until you are alert enough to follow commands, your vital signs are stable, and your pain is controlled. Some patients move faster than others depending on how they respond to anesthesia. Once you are ready, you will either go to a hospital room (if you are staying overnight) or to a discharge area (if you are going home the same day).

Total Time at the Hospital on Surgery Day

From the moment you arrive at the hospital to the moment you leave the operating area, plan on four to six hours. This includes check-in, pre-operative prep, the surgery itself, and post-operative recovery. If you are having outpatient surgery (same-day discharge), you may spend another hour or two in a discharge area while final paperwork is completed and you receive instructions for home care.

If you are staying overnight, you will be moved to a hospital room after recovery. Many hospitals keep knee replacement patients for one night to manage pain, start physical therapy, and make sure there are no when ready complications. Some patients go home the same day, depending on the surgeon's preference, your age, your overall health, and whether you have someone at home to help you.

Physical Therapy Starts Right Away

Physical therapy begins within hours of surgery, while you are still in the hospital or recovery area. A therapist will help you move your knee gently, straighten and bend it as much as pain allows, and walk a few steps with crutches or a walker. These early movements prevent stiffness and blood clots, and they hurt—but they are necessary.

You will continue physical therapy at home or in an outpatient clinic for weeks or months after surgery. The first two weeks are the most intense, with therapy three to five times per week. Gradual improvement continues for three to six months, and some people continue to gain strength and range of motion for a full year. This is not a single recovery period but a series of milestones: walking without crutches (usually two to six weeks), climbing stairs (four to six weeks), driving (four to six weeks if you had the right knee and are not taking strong pain medication), and returning to normal activities like shopping or light exercise (eight to twelve weeks).

Factors That Make Surgery Longer or Shorter

A partial knee replacement (unicompartmental replacement) often takes less time than a total replacement because only one side of the joint is replaced. A revision surgery—replacing an implant that has worn out or failed—usually takes longer because the surgeon must remove the old implant and bone cement, which adds 30 minutes to an hour to the procedure.

Your surgeon's experience matters too. An experienced surgeon who performs dozens of knee replacements per month may work faster than one who does fewer, but speed is not the goal—precision is. Complications during surgery, such as unexpected bone loss or difficulty positioning the implant, will extend the time. Your age, weight, and overall health can also affect how long the procedure takes, though not always in the direction you might expect. A healthy 75-year-old may have a faster surgery than an overweight 55-year-old with multiple medical conditions.

What to Tell Your Surgeon Before Surgery

Let your surgeon know if you take blood thinners, have had previous knee surgery, have significant arthritis in your other knee, or have any metal implants elsewhere in your body. Tell them about any allergies to medications or latex. If you smoke, mention that—smoking slows healing and increases infection risk. These details help your surgeon plan the procedure and anticipate complications.

Ask your surgeon directly how long they expect your surgery to take. They have done hundreds of these procedures and can give you a realistic estimate based on your specific situation. If your surgery takes longer than expected, the surgical team will contact your family in the waiting area to let them know you are still in the operating room and doing fine.

Frequently Asked Questions

Can I go home the same day as my knee replacement surgery?

Yes, many patients do go home the same day, though some surgeons prefer to keep patients overnight. Same-day discharge depends on your age, overall health, pain control, and whether you have someone at home to help you for the first few days. Ask your surgeon what their standard practice is before surgery.

Why does it take so long if the surgery is only two hours?

The two-hour surgical time does not include anesthesia setup, positioning, prep work, or recovery. Add one to two hours before surgery and one to three hours after, and you are at four to six hours total. This is normal and expected.

Will my surgery take longer if I am older?

Not necessarily. Age alone does not determine surgical time. A healthy 80-year-old with straightforward knee damage may have a faster surgery than a 55-year-old with complex bone loss or previous knee surgery. Your surgeon will assess your individual situation.

What if my surgery takes longer than expected?

The surgical team will update your family if the procedure is taking longer than planned. This usually means the surgeon is being thorough or encountered something unexpected—not that something has gone wrong. Complications during surgery are rare, and taking extra time to get the implant positioned correctly is better than rushing.

When can I start walking after knee replacement surgery?

Physical therapists will help you walk within hours of surgery, usually with crutches or a walker. Most patients walk without crutches within two to six weeks, depending on pain, swelling, and strength. Your therapist will guide you through each stage.