What to Know About Partial Knee Replacement

Medically Reviewed by Dany Paul Baby, MD on October 18, 2022
5 min read

Your knee contains several compartments made of cartilage, bone, and connective tissues. When a compartment is damaged, your doctor might suggest unicompartmental knee arthroplasty — more commonly referred to as a partial knee replacement surgery. Partial knee replacement surgery can, for example, help fix joint issues and minimize pain for people with knee damage caused by osteoarthritis

Keep reading to learn more about partial knee replacement surgery, including its benefits, risks, recovery, and more. 

Your knee contains three distinct areas, called compartments:

  • The lateral compartment on the outside of your knee
  • The medial compartment on the inside of your knee (the point where it bends)
  • The patellofemoral compartment, which makes up the front of your knee, located between your thigh bone (femur) and kneecap

If you have osteoarthritis, one or more of those compartments may need to be replaced to restore normal, painless functioning. The medial compartment is the most commonly affected by osteoarthritis, so most partial knee replacements are performed there. This is a possible alternative to undergoing total knee replacement surgery, available to those who have received damage to only one part of their knee.

The procedure was first performed in the 1970s and has recently become more popular. Advancements in surgical techniques and implant design quality now allow doctors to perform the surgery more safely and effectively. 

Osteoarthritis is the most common form of arthritis. About 30% of people in the U.S. have osteoarthritis in their knees. It occurs when the cartilage in your joints becomes damaged, often due to natural wear and tear. While there is no cure for osteoarthritis, surgery to replace damaged joint tissues can help people function more normally and live with less pain. 

Partial knee replacement is one type of surgery used to treat osteoarthritis.  During the procedure, your surgeon will only remove the damaged parts of your knee and replace them with specially designed implants. 

Not everyone with osteoarthritis will need (or benefit from) a partial knee replacement. Your doctor will talk to you about your specific healthcare needs and goals. Most people who are good candidates for partial knee replacement surgery will have:

  • Damage in only one part of their knee
  • Functional ligaments
  • Good range of motion
  • Overall knee stability

Your doctor may instead suggest a total knee replacement if you have any damage to your ligaments, arthritis that affects more than one of your knee compartments, or the inability to bend or move your knee.

Of course, even with modern imaging technology and diagnostic methods, there is a possibility that your knee has more damage than your exam results show. Some people who expect to undergo a partial knee replacement procedure might actually require total knee replacement surgery. Your doctor will talk to you about this possibility and make the final decision during surgery.

If your doctor recommends surgery, you will meet with an orthopedic surgeon who will assess how much the osteoarthritis has affected your knee. This examination will involve:

  • Pinpointing what part of your knee is experiencing the most pain
  • Assessing how well you can move or bend your knee (range of motion)
  • Imaging scans such as x-rays or an MRI to see where your knee is damaged

You can expect partial knee replacement surgery to last between 1 to 2 hours. During the operation, your surgeon will make a short incision in the front of your knee to better see all three compartments and ensure your ligaments are not damaged. The surgeon will then make a final decision about whether a partial or total knee replacement is needed.

If you are still a good candidate for partial knee replacement, your surgeon will remove the damaged cartilage and bone. They will insert implants that will form an artificial joint. These metal implants can either be cemented in place or left unattached so your bones will eventually hold them in place. Plastic spacers are then placed between the metal joints to allow your knee to bend smoothly and naturally.

Partial knee replacement carries the same risks as any other surgical procedure. These risks can include:

  • Infection
  • Blood clots
  • Damage to blood vessels
  • Nerve damage
  • Ongoing pain

Partial knee replacement might also be an incomplete measure, and you will require additional surgeries in the future if your osteoarthritis spreads to other compartments or if the implants move out of place.

Immediately after surgery, you will move to a recovery room. Depending on your medical needs, you might stay at the hospital for several hours or overnight.

Your healthcare providers will give you pain medication to help keep you comfortable so your body can begin to heal. Most people will be given non-steroidal anti-inflammatory drugs (NSAIDs) or local anesthetics to control any pain.

Your doctor will encourage you to stand or walk as soon as possible after your surgery. You might want to use crutches, a walker, or a cane until you feel stable enough to walk alone. A physical therapist will meet with you and show you exercises you can do to strengthen your muscles and improve your range of motion.

Partial knee replacement recovery will be shorter and less painful than the recovery period following total knee replacement surgery. Most people have healed enough to return to their normal activities around 6 weeks after surgery. During the healing process, you will attend regular appointments with your orthopedic surgeon to check for complications and make sure you are healing well.

As with any medical treatment, there are both risks and benefits associated with a partial knee replacement procedure, so make sure you talk to your doctor about your individual healthcare needs and goals. 

There are several advantages of having a partial knee replacement rather than a total one. Many people report that their knee moves and bends more naturally than it would if they had a total knee replacement. Additionally, the surgery only removes damaged tissue, so it's simpler, shorter, and uses a smaller incision. There is less risk of complications like blood loss, blood clots, and infection. People with a partial knee replacement often experience less pain and swelling, so their recovery period is generally quicker and easier.

The biggest con related to partial knee replacement is the potential for needing more surgery in the future. This usually happens when the osteoarthritis spreads and affects other parts of your knee. It's also possible for the joint to wear out over time due to daily use. If you are heavier or engage in high-impact sports, the chance is greater.