The surgery itself takes 1 to 2 hours, but you will be at the hospital or surgical center for 4 to 6 hours total

The actual time a surgeon spends replacing your knee joint runs between 60 and 120 minutes. That is the time from the moment you are asleep under anesthesia until the incision is closed. But the total time you spend in the operating room, recovery area, and pre-op holding space is much longer — typically 4 to 6 hours from when you arrive until you leave.

The length of the surgery itself depends on several factors: whether this is your first knee replacement or a revision (replacing an implant that failed), the complexity of your knee damage, and how quickly your surgeon works. A straightforward first replacement on someone with no prior knee surgery usually takes closer to 60 minutes. A revision or a knee with severe arthritis or prior injury can stretch past 90 minutes.

Your surgeon will tell you a more specific estimate before the day of surgery, based on imaging and your medical history. Ask during your pre-op visit — this number matters for planning childcare, time off work, and arranging a ride home.

Key Takeaways

  • The actual surgical time is 1 to 2 hours, but plan for 4 to 6 hours at the facility including pre-op and recovery.
  • First-time knee replacements usually take 60 to 90 minutes; revisions and complex cases may run longer.
  • You will be under general or regional anesthesia the entire time and will not be awake during the procedure.
  • Recovery time in the post-op area is typically 1 to 2 hours before discharge, though some patients stay overnight.
  • Your surgeon can give you a more precise time estimate at your pre-op appointment based on your specific situation.

What happens before the surgeon starts

You arrive 1 to 2 hours before your scheduled surgery time. During this period, nursing staff will check your vital signs, review your medical history again, start an IV line, and have you change into a surgical gown. An anesthesiologist or nurse anesthetist will meet with you to discuss anesthesia options and answer questions about what to expect.

You will also sign final consent forms and may be given a mild sedative to help you relax. This pre-op time is not wasted — it is when the surgical team confirms your identity, marks the correct knee, and prepares your body for anesthesia. Do not rush this part. Tell the staff about any new symptoms, medication changes, or concerns since your last visit.

The actual replacement procedure and timing

Once you are asleep, the surgeon makes an incision (usually 8 to 10 inches long) down the front of your knee. They remove the damaged cartilage and bone from the end of your thighbone and the top of your shinbone, then fit the metal and plastic implant pieces into place. The surgeon tests the knee's movement and alignment, closes the incision with stitches or staples, and applies a sterile dressing.

The entire process — from incision to closure — takes 60 to 120 minutes depending on the factors mentioned above. Simpler cases move faster; complex anatomy or prior surgery slows the pace. Your surgeon's experience also matters; a high-volume knee replacement surgeon may work more efficiently than someone who does fewer procedures.

Recovery room time before you go home

After surgery, you move to a recovery area (sometimes called post-op or PACU — Post-Anesthesia Care Unit). You will still be groggy and may not remember much. Nurses monitor your heart rate, blood pressure, oxygen level, and pain. They manage nausea and pain with medication and help you wake up gradually.

This phase typically lasts 1 to 2 hours. Once you are alert enough to follow commands, your pain is controlled, and your vital signs are stable, you are cleared to leave or move to an inpatient room if you are staying overnight. Some patients go home the same day (outpatient surgery); others stay one night for observation and physical therapy to begin.

Factors that can make surgery take longer

A revision knee replacement — replacing an implant that has loosened, worn out, or failed — usually takes 30 to 60 minutes longer than a first replacement because the surgeon must remove the old implant and prepare the bone for a new one. Bone loss from the failed implant may require bone grafting or special implant designs, which adds time.

Severe arthritis, prior knee surgery, obesity, or stiffness in the joint can also extend surgical time. Patients with multiple medical conditions may need extra time for anesthesia management. Unexpected bleeding or bone quality issues discovered during surgery can add 15 to 30 minutes. Your surgeon cannot always predict these complications in advance, so the estimate given at your pre-op visit is an educated guess, not a may provide.

Outpatient versus overnight stay

Most knee replacements are now done as outpatient procedures, meaning you go home the same day. This requires a responsible adult to drive you home and stay with you for at least the first night. You must be alert, able to move your leg slightly, and have controlled pain before discharge.

Some patients stay overnight for medical reasons: uncontrolled pain, nausea, or medical conditions that make same-day discharge unsafe. Overnight stays add 12 to 24 hours to your time at the facility but do not change the length of the surgery itself. Ask your surgeon ahead of time whether they expect you to go home the same day or stay overnight.

What to expect in the days after surgery

The surgery is over in a few hours, but recovery takes weeks. You will have pain, swelling, and stiffness for the first 2 to 4 weeks. Physical therapy starts within days — sometimes before you leave the facility — and continues for 6 to 12 weeks. Most people can walk with a walker or crutches within a few days and return to light activities within 4 to 6 weeks.

Full recovery, including return to normal walking and most recreational activities, takes 3 to 6 months. Implants can last 15 to 20 years or longer, but this depends on your activity level and how well you follow post-op instructions. Your surgeon will schedule follow-up appointments at 2 weeks, 6 weeks, 3 months, and sometimes longer to track your progress.

Frequently Asked Questions

Can I eat or drink before knee replacement surgery?

No. You will be told to stop eating at midnight the night before and stop drinking clear liquids a few hours before surgery. This prevents vomiting while you are under anesthesia. Follow these instructions exactly — eating or drinking before surgery can be dangerous and may force the surgical team to postpone your procedure.

Will I be awake during the surgery?

No. You will receive general anesthesia (you are completely asleep) or regional anesthesia (your lower body is numb but you are sedated). Either way, you will not be conscious or feel pain during the procedure. You may not remember the pre-op or recovery areas either.

How long until I can drive after knee replacement?

Most surgeons recommend waiting 4 to 6 weeks before driving, and only after you have stopped taking prescription pain medication and can move your knee enough to operate the pedals safely. Check with your surgeon — the timeline depends on which knee was replaced and your healing progress.

What if my surgery takes longer than expected?

Your surgeon will contact your family if the procedure runs significantly longer than planned. Minor delays (15 to 30 minutes) are common and usually mean the surgeon is being thorough. Major delays are rare but can happen if unexpected bone loss or bleeding occurs.

Do I need someone to stay with me after surgery?

Yes. You must have a responsible adult with you for at least the first 24 hours after going home. You cannot drive, operate machinery, or make important decisions while pain medication is in your system. This person should help with basic tasks like getting to the bathroom and taking medication on schedule.