The basic surgical steps during a knee replacement

A knee replacement takes between one and three hours. The surgeon makes an incision down the front of the knee, usually 8 to 10 inches long, to reach the joint. Once inside, they remove the damaged cartilage and bone from the ends of the thighbone and shinbone, then cement or screw metal and plastic components into place to recreate the joint surface. The plastic spacer sits between the metal parts and mimics the cartilage that has worn away.

The surgeon tests the new joint's movement and alignment before closing the incision with stitches or staples. You will be asleep under general anesthesia or regional anesthesia (numbing from the waist down) during the entire procedure. A surgical team including an anesthesiologist, nurses, and surgical technicians will be present throughout.

Key Takeaways

  • The surgeon removes damaged bone and cartilage, then attaches metal and plastic components to recreate the knee joint surface.
  • The incision runs down the front of the knee and is typically 8 to 10 inches long, though minimally invasive techniques use shorter cuts.
  • The procedure takes one to three hours, and you will be unconscious under anesthesia the entire time.
  • Most people spend one night in the hospital, though same-day discharge is becoming more common at some facilities.
  • Physical therapy begins within hours or days after surgery and continues for weeks to months to restore movement and strength.

What the surgeon removes and what gets implanted

The damaged surfaces of the thighbone (femur) and shinbone (tibia) are cut away and reshaped to fit the metal implants. The surgeon removes only the diseased bone and cartilage, leaving healthy bone intact. The kneecap (patella) may also be resurfaced with a plastic button, though some surgeons skip this step if the kneecap surface is still healthy.

The metal components are typically made of cobalt-chromium or titanium alloys. The plastic spacer is usually made of ultra-high-molecular-weight polyethylene, a durable plastic that can withstand years of walking and bending. These materials are chosen because they resist wear and do not trigger immune reactions in the body. The implants are held in place either with bone cement (acrylic) or with a porous surface that allows bone to grow into it over time.

Incision size and surgical approaches

The standard approach uses a single incision down the middle of the knee, typically 8 to 10 inches. This gives the surgeon a clear view of the joint and room to work precisely. Some surgeons use a minimally invasive technique that makes a smaller incision, usually 4 to 6 inches, using specialized instruments and sometimes a camera (arthroscope) to guide the work. Smaller incisions may mean less muscle damage and faster recovery, though the implant quality and alignment are what matter most for long-term results.

A few surgeons also offer robotic-assisted surgery, where a robot arm helps position the implants with high precision based on a pre-operative scan. The surgeon controls the robot and makes the final decisions. This approach does not change the incision size significantly but may improve how well the implant aligns with your anatomy.

What happens in the recovery room and first 24 hours

After surgery ends, you move to a recovery room where nurses monitor your blood pressure, heart rate, oxygen level, and pain. You will wake up gradually as the anesthesia wears off. Your leg will likely be in a compression bandage or ice pack to reduce swelling. A catheter (thin tube) may be placed in your bladder if you cannot walk to the bathroom, though many hospitals avoid this now.

Pain medication is given intravenously or by mouth as you wake. Most people feel significant pain in the first hours, which is normal. Nurses will help you move your toes and ankle to prevent blood clots. On the same day or the next morning, a physical therapist will visit to help you stand and take a few steps, even though this feels difficult. Many hospitals now send patients home the same day or after one night, while others keep patients for two nights depending on age, overall health, and how well pain is controlled.

Physical therapy and movement in the first weeks

Physical therapy is not optional—it begins in the hospital and continues at home or in an outpatient clinic for weeks or months. In the first week, the focus is on reducing swelling, regaining the ability to straighten the leg fully, and bending the knee to at least 90 degrees. You will do exercises lying down, sitting, and standing. Ice and elevation help control swelling. Most people use crutches or a walker for the first two to six weeks.

By week three to four, many people can walk without assistive devices on flat ground. By week six to eight, stairs and light activity become possible. Full recovery—meaning the strength and endurance to return to normal daily tasks—typically takes three to six months. Some people continue to see gradual improvement for up to a year. Pain and stiffness usually decrease steadily during this time, though some discomfort with activity is normal in the first months.

Swelling, bruising, and wound care

Swelling peaks around day three to five after surgery and can last for weeks. Bruising around the incision and down the shin is common and fades over several weeks. The incision itself will be closed with stitches or staples that are removed around two weeks after surgery. Until then, keep the area clean and dry. Your surgeon will give you specific instructions on when you can shower or bathe.

Some fluid may drain from the incision in the first days—this is normal. Watch for signs of infection: increasing redness, warmth, pus, or fever above 101°F. These are rare but require when ready medical attention. Compression stockings or sequential compression devices (sleeves that inflate and deflate) may be used to prevent blood clots, especially if you are at higher risk.

Pain management and medication after surgery

Pain peaks in the first week and gradually decreases. Most surgeons prescribe opioid pain medication (such as oxycodone or hydrocodone) for the first one to two weeks, along with over-the-counter options like acetaminophen or ibuprofen. Some surgeons use nerve blocks—injections that numb the area around the knee—to reduce pain in the first 24 to 48 hours without relying solely on opioids.

Ice and elevation are your most effective tools for pain control. explore ice for 15 to 20 minutes several times a day reduces swelling and numbs the area. Keeping your leg elevated above heart level when sitting or lying down also helps. As weeks pass, most people transition to over-the-counter pain relief and eventually need nothing. If pain worsens after improving, or if you develop new symptoms, contact your surgeon.

Return to daily activities and long-term function

Most people can return to light desk work within two to four weeks if they can keep their leg elevated. Driving is usually safe once you stop taking opioid pain medication and can control the knee well enough to brake safely—typically four to six weeks. Returning to exercise depends on the activity: walking on flat ground is usually safe by week six to eight, while running, jumping, or high-impact sports may take four to six months or longer.

A knee replacement is designed to last 15 to 20 years or more with normal use. "Normal use" means walking, swimming, cycling, and everyday activities—not running marathons or playing competitive sports. Excessive impact can wear out the plastic spacer faster. Most people report that their new knee feels stable and allows them to do the activities they could not do before surgery because of arthritis pain.

Frequently Asked Questions

Will I feel the implant moving inside my knee?

No. Once healed, the implant is fixed in place and moves as part of your knee joint. You may feel the scar tissue or have occasional clicking or popping sounds, which is normal. Some people report a slight awareness of the implant early on, but this usually fades as swelling decreases and you become accustomed to the new joint.

Can I bend my knee fully after surgery?

Most people regain 110 to 120 degrees of bending, which is enough for walking, stairs, and sitting in a chair. Full bending (130+ degrees) is less common but possible. The amount of bending you achieve depends on how much bending you had before surgery, your effort in physical therapy, and individual healing. Your surgeon can discuss realistic expectations based on your situation.

What if I fall on my new knee after surgery?

Once fully healed (usually three to six months), the implant is very durable and can withstand normal falls. In the first weeks, falls are a serious concern because the muscles are weak and the incision is still healing. Use assistive devices, remove tripping hazards, and ask for help until you have regained strength and balance. If you fall and experience severe pain or swelling, contact your surgeon.

Will I need another surgery on this knee in the future?

Most knee replacements last 15 to 20 years. Some people need a revision surgery to replace worn components, but this is not may provide. Revision surgery is more complex than the first surgery but is possible. Avoiding high-impact activities and maintaining a healthy weight can extend the life of your implant.

Can I set off metal detectors with a knee replacement?

Yes, the metal components will trigger metal detectors at airports and security checkpoints. You can request a pat-down instead of walking through the detector, or inform security in advance. Most airports are familiar with this and will not delay you. You may want to carry a card from your surgeon stating you have an implant, though this is not required.