The basic steps of a knee replacement

A knee replacement removes the damaged parts of your knee joint and replaces them with artificial components made of metal and plastic. The surgeon makes an incision down the front of your knee, usually 8 to 10 inches long, to reach the joint. They then remove the damaged cartilage and bone from the end of your thighbone, shinbone, and kneecap, and cement or screw the artificial parts into place. The whole procedure typically takes 1 to 2 hours in an operating room.

The artificial knee has three main parts: a metal component that replaces the end of your thighbone, a plastic spacer that sits between the thighbone and shinbone, and a metal or plastic component that replaces the surface of your kneecap. Once all pieces are secured, the surgeon closes the incision with stitches or staples and wraps your knee in a bandage.

Key Takeaways

  • The surgeon removes damaged bone and cartilage from your thighbone, shinbone, and kneecap, then cements or screws artificial metal and plastic components into place.
  • The procedure takes 1 to 2 hours and is done under general anesthesia, meaning you are asleep during the surgery.
  • Most people stay in the hospital for 1 to 3 days after surgery, though some go home the same day depending on their health and the surgeon's approach.
  • Physical therapy begins within days of surgery and continues for weeks or months to restore strength and movement in your knee.
  • Full recovery typically takes 3 to 6 months, though some people need up to a year to regain full function.

Before surgery: preparation and anesthesia

Before your surgery date, your surgeon will order blood tests, X-rays, and sometimes an EKG to make sure your heart and lungs can handle the procedure. You will meet with an anesthesiologist who will review your medical history and decide what type of anesthesia to use. Most knee replacements use general anesthesia, which puts you to sleep, though some surgeons use regional anesthesia that numbs only your leg.

The night before surgery, you will be told to stop eating and drinking at a specific time, usually after midnight. You should arrange for someone to drive you home and help you for the first few days, since you will not be able to drive or care for yourself when ready after. Wear loose, comfortable clothing to the hospital and leave jewelry, watches, and other valuables at home.

Removing the damaged joint surfaces

Once you are asleep, the surgeon makes an incision along the front of your knee. They carefully cut through the skin, fat, and muscle to reach the joint capsule. The surgeon then opens the joint to see the damaged surfaces clearly.

Using specialized cutting guides and saws, the surgeon removes the damaged cartilage and a thin layer of bone from the end of your thighbone. They then remove the damaged cartilage and bone from the top of your shinbone. The surgeon also assesses your kneecap and may resurface it or replace it depending on the damage. This step is critical because the amount of bone removed must be precise so the artificial components fit correctly and your knee bends and straightens properly.

Placing the artificial components

After the damaged surfaces are removed, the surgeon tests the fit of the artificial components using trial pieces. They position the metal component on your thighbone, the plastic spacer between the two bones, and the component for your shinbone, checking that your knee bends and straightens smoothly and that your leg is properly aligned.

Once the fit is correct, the surgeon cements or screws the permanent components into place. Most surgeons use bone cement, a fast-hardening adhesive that bonds the metal to your bone. Some newer techniques use cementless components with a special surface that allows your bone to grow into them over time. The surgeon may also add a plastic or metal component to resurface your kneecap, depending on the damage and your surgeon's preference.

Closing the incision and when ready recovery

After all components are find, the surgeon checks the joint one more time to may support everything moves correctly. They then close the incision with stitches or staples and explore a sterile bandage. Your knee may be wrapped in a compression bandage or placed in a brace to reduce swelling and protect the joint.

You will wake up in the recovery room with a nurse monitoring your heart rate, blood pressure, and oxygen level. You will likely feel groggy and may have some pain, which the medical team will manage with medication. Most people are moved to a hospital room within a few hours. Physical therapy often begins the same day or the next morning, with a therapist helping you move your knee gently and teaching you how to use crutches or a walker.

Hospital stay and early healing

Most people stay in the hospital for 1 to 3 days after knee replacement, though some hospitals now send patients home the same day if they meet certain criteria and have support at home. During your stay, nurses will help you manage pain, prevent blood clots with compression stockings or blood-thinning medication, and monitor your incision for signs of infection.

Physical therapy is a major part of your hospital stay. A therapist will help you bend and straighten your knee, teach you how to walk safely with crutches or a walker, and show you exercises to do at home. Your goal during this time is to regain enough movement and strength to go home safely. Before you leave, your surgeon will give you instructions on wound care, medication, activity limits, and when to return for a follow-up visit.

Recovery at home and long-term healing

Once you are home, you will need to keep your incision clean and dry, take pain medication as directed, and continue physical therapy exercises several times a day. Swelling and bruising are normal and may last for weeks. You can use ice packs for 15 to 20 minutes at a time, several times a day, to reduce swelling. Elevating your leg above heart level also helps.

Most people can put weight on their new knee within days of surgery, though you will need crutches or a walker for several weeks. You can usually return to light activities like walking and sitting within 3 to 6 weeks, but you should avoid high-impact activities like running or jumping for at least 3 to 6 months. Full recovery, including regaining full strength and range of motion, typically takes 3 to 6 months, though some people need up to a year.

Frequently Asked Questions

How long does the incision take to heal?

The outer incision usually closes within 2 to 3 weeks, and stitches or staples are removed around that time. However, the deeper layers of tissue and bone continue to heal for several months. You should keep the incision clean and dry during the first few weeks and avoid soaking it in water until your surgeon says it is safe.

What happens if the artificial knee wears out?

Artificial knees typically last 15 to 20 years or longer, depending on your activity level and body weight. If your artificial knee wears out or becomes loose, you may need a second surgery called a revision, which replaces the worn components. This surgery is more complex than the first replacement and requires longer recovery.

Can I bend my knee fully after surgery?

Most people regain 110 to 120 degrees of knee bending, which is enough for normal activities like walking, climbing stairs, and sitting in a chair. Some people achieve full bending of 130 degrees or more. The amount of bending you regain depends on how much movement you had before surgery, how well you do physical therapy, and your individual healing.

Will I set off metal detectors after knee replacement?

Your artificial knee may trigger metal detectors at airports or other security checkpoints. You can ask your surgeon for a card that explains you have an artificial joint. Most security personnel will allow you through after a pat-down search, though you may want to inform them before you enter the detector.

What activities should I avoid after knee replacement?

You should avoid high-impact activities like running, jumping, and contact sports indefinitely, as these can damage the artificial joint and loosen the components. Most surgeons recommend walking, swimming, cycling, golf, and other low-impact activities. Always check with your surgeon before starting any new activity.