March 6, 2017

What is a partial knee replacement?

Knee | Total Joint Replacement

This post is part of The Ultimate Guide to Total Knee Replacement

Partial knee replacement surgery may be necessary when the pain and function of your knee is not allowing you to have a great quality of life and non-surgical treatments are no longer helping you.

During a partial knee replacement (also called unicompartmental knee replacement) only a portion of the knee is resurfaced. This procedure is an alternative to total knee replacement for patients whose disease is limited to just one area of the knee.

Because partial knee replacement surgery is done through a smaller incision, patients usually spend less time in the hospital and return to normal activities sooner than total knee replacement patients.

Read on to learn about partial knee replacement surgery and how to make the most of your recovery.

Anatomy of the knee

To best understand the need for partial knee replacement surgery, it helps to know the different components of the knee. A joint is a special structure in the body where the ends of two or more bones meet. The thigh bone (femur) and the shin bone (tibia) meet to form the knee joint. The knee cap (patella) covers and protects the front of the knee joint.

The joint lining (synovium) makes fluid that lubricates the joint cartilage covering the ends of the bones. This cartilage cushions the knee for smooth, easy movement.

The knee is a major weight-bearing joint and is held together by muscles and ligaments that allow your leg to bend and straighten so that you can walk and climb stairs.

When you have knee arthritis, the cartilage wears away, causing the bones to grind together. This produces pain, loss of motion and swelling.

Causes of pain

The need for partial knee replacement surgery almost always starts with knee pain. The most common cause of chronic knee pain and disability is knee arthritis.

Most knee pain is caused by one of three kinds of arthritis: osteoarthritis, rheumatoid arthritis or post-traumatic arthritis.

  • Osteoarthritis: Mostly related to old age, it usually occurs in people over 50 years old, but can occur in younger people as well. The cartilage that cushions the bones of the knee softens and wears away. The bones then rub against one another causing knee pain and stiffness.
  • Rheumatoid arthritis: The synovial membrane that surrounds the joint becomes inflamed and thickened. This chronic inflammation damages the cartilage and eventually causes cartilage loss, pain and stiffness in the knee. This is the most common form of a group of disorders referred to as inflammatory arthritis.
  • Post-traumatic arthritis: This follows a serious knee injury. Fractures of the bones surrounding the knee or tears of the knee ligaments may damage the articular cartilage over time, causing knee pain and limiting knee function.

Physician examination

To determine if you need partial knee replacement surgery, your total joint surgeon will ask you for a complete medical history, ask questions about your pain and how long you have been experiencing it, and conduct a physical examination. An X-ray or MRI can confirm the best treatment options.

Make an appointment with a joint replacement specialist

Partial knee replacement surgery procedures

There are three compartments in a knee joint: a medial and lateral compartment between the ends of the femur (thigh) and tibia (shin) bones and a third compartment behind your kneecap.

If only one of the compartments in your knee joint is affected by arthritis, it is possible that a total joint specialist can do a partial knee resurfacing in just that one compartment, leaving the other two healthy compartments alone.

When it involves the medial or lateral compartment between the femur and tibia bones it is called a unicondylar knee replacement (UKR). When it is the compartment behind the kneecap, it is called a patellofemoral replacement (PFR).

The terms replacement and arthroplasty are often used interchangeably. UKR and PFR can provide durable pain relief and many patients feel like they still have their own knee because a total joint surgeon only resurfaced one compartment.

In appropriately selected patients, UKR and PFR have an excellent long-term track record, but still not quite as good as a total knee replacement because the compartments that are not resurfaced will often wear out over time and cause pain again.

If this happens, then the UKR or PFR is removed and converted to a full knee replacement, which can be done with excellent results.

Your physician will evaluate you to determine which partial knee replacement surgery is best for you.


Following partial knee replacement surgery, you may have a brace on your knee for a day until your leg wakes up from the anesthesia. Physical and occupational therapists will help you with your activities of daily living. This includes how to get to the bathroom, get dressed and go up and down steps using either a walker or crutches.

The goal of knee replacement recovery is to help you become safe on your own so you can return home, even if you live alone; most of the time this is on the second day after surgery. They will also teach you a few exercises that you will continue to do after you leave the hospital.

You will do the exercises on your own. Pumping your ankles up and down is helpful in decreasing the chances of blood clots by keeping the blood moving in your legs. Tightening your thigh and buttock muscles is also helpful. You will have support stockings on both legs after surgery to help minimize swelling. Move around often after surgery.

Following partial knee replacement surgery, the focus is on getting good range of motion and controlling your pain and swelling the first month. Then you will progress to strengthening exercises once you have good range of motion and your pain and swelling are under control.

When can I return to normal activities?

Resumption of normal activities after partial knee replacement surgery is highly dependent on the individual patient. You should go at your own speed depending on how you feel. The first two weeks are the most difficult.

General guidelines suggest around three weeks after surgery, most patients are driving a car and using a cane to walk. Most people are able to return to a sedentary type of job at five weeks and a more physically demanding job at seven weeks after surgery. You can work from home whenever you feel like it.

Your leg will be swollen after partial knee replacement surgery. Travel is restricted to within two hours of home for the first month in order to decrease the risk of developing a blood clot in your leg.

Many patients get back to activities such as walking for exercise, swimming, riding a bike and golfing by six weeks after surgery even though they still have some discomfort, increased warmth and increased swelling.

You will fatigue easily and will not sleep well for the first month after surgery, but this will improve with time. Patients are encouraged to increase your activities as you can tolerate. Don’t be afraid to push yourself.

Many surgeons ask their patients to avoid running and jumping activities after partial knee replacement surgery, as this can cause the implant to prematurely fail.

Learn more about joint replacement surgery at OrthoIndy

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Schedule an appointment

Your well-being is important to us. If you have knee pain and are considering knee replacement surgery, schedule an appointment with one of our orthopedic specialists to review your options.

If your injury or condition is recent, you can walk right into one of our OrthoIndy Urgent Care locations for immediate care. For rehabilitation and physical therapy, no referral is needed to see one of our physical therapists.

The Ultimate Guide to Knee Pain Relief cover

The Ultimate Guide to Knee Pain Relief

Take control of your knee pain, learn about treatment options, and find out if surgery might be able to help you get back to normal.

Download the guide

Schedule an Appointment Call OrthoIndy 317.802.2000

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