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Patients with arthritis of the knee can undergo different types of knee replacement surgeries if they are not responding to medication. This article outlines 6 things you need to know about unicompartmental (partial) knee replacement.

Arthritis, a condition that is characterized by joint pain, inflammation and stiffness, does not currently have a cure. However, several treatment methods can help reduce symptoms and improve joint function. In particular, patients with arthritis of the knee can undergo surgery to help ease pain and improve knee function. In patients with arthritis of the knee, the cartilage between the bones of the knees starts to wear away, causing the bones to rub against each. This can be extremely painful. Hence, one of the treatment methods for arthritis of the knee is knee replacement surgery. There are four major types of knee replacement surgeries, one of which is known as a unicompartmental or partial knee replacement surgery.

These are six things you should know about unicompartmental or partial knee replacement surgery.

1. A unicompartmental or partial knee replacement is only for patients with arthritis limited to one portion of the knee

All types of knee replacement surgeries involve resurfacing of the damaged bone and cartilage with metal and plastic compounds. A unicompartmental or partial knee replacement is similar to a total knee replacement except that only one part of the knee is resurfaced as opposed to the whole knee. There are three different sections or parts of your knee:

  • Medial (inside of the knee)
  • Lateral (outside of the knee)
  • Patellofemoral (the front of the knee)

Only patients who have arthritis that affects one area of their knee are eligible for this type of surgery.

2. There are several advantages to a unicompartmental or partial knee replacement

Since a unicompartmental knee replacement is conducted through a smaller incision than a total knee replacement, patients who undergo this surgery spend less time in recovery, less time being hospitalized, and are able to return to their normal life sooner. Additionally, during the surgery, patients experience less blood loss and after the surgery, patients have less pain.

Furthermore, in a unicompartmental knee replacement, the bone, cartilage, and ligaments in the part of the knee that is not affected by the arthritis are kept in their original condition. Thus, patients who undergo unicompartmental knee replacement are more likely than patients that are undergo a total knee replacement to say that their knee feels more natural and works better.

3. There are several disadvantages of undergoing a unicompartmental or partial knee replacement

It is well known that if you undergo a total knee replacement, you will likely feel pain relief after. However, the pain relief is less predictable in patients with partial knee replacement. Another disadvantage associated with a partial knee replacement is the possibility of needing more surgery. While you may have limited disease at the point in time in which you choose to undergo partial knee replacement, your arthritis may spread later on, requiring you to get a total knee replacement.

4. What makes you eligible for a partial knee replacement

It is extremely important to pick the right candidate to undergo this surgery as proper selection can lead to excellent results in the long-term but the surgery can lead to severe complications if conducted in the wrong type of patient.

Generally, patients who undergo a partial knee replacement tend to have osteoarthritis that is advanced and non-surgical treatment methods (i.e. medication or physical therapy) are no longer effective at relieving their pain. Importantly, in order to be eligible for the surgery, you must only have arthritis that is limited to one compartment of your knee. Characteristics that make you ineligible for the procedure include having inflammatory arthritis, knee stiffness, and ligament damage.

5. You will be thoroughly evaluated by an orthopedic surgeon before you undergo the surgery

The surgery is conducted by a type of specialist known as an orthopedic surgeon and they can help determine whether you are an appropriate candidate for a partial knee replacement. First, the doctor will ask questions about your health, knee pain, and knee functioning. Then, the doctor will evaluate exactly where the pain stems from and from what portion of your knee. If the pain comes from only one portion of the knee, then you may be a candidate for a partial knee replacement. The doctor will also test the range of motion of your knee as well as the quality of your ligaments. If the ligaments are not healthy, then you won’t be a candidate for a partial knee replacement. The doctor may also conduct several imaging tests including X-rays to see the extent of joint damage and an MRI to evaluate the cartilage.

6. You may not find out if you are eligible for a partial knee replacement until you are in surgery

On the day of your surgery, you will be admitted to the hospital and then the doctor will discuss your anesthesia options, which will include general anesthesia or spinal anesthesia (in which you are awake but numb). The actual surgery will last between one and two hours. First, the surgeon will inspect the joint. Then, he or she will make an incision in the front of the knee and explore the knee for the extent of the damage. If they find that the arthritis is limited to one portion of the knee and your ligaments are healthy then they will go ahead and conduct a partial knee replacement. If they find that you are not suitable for the surgery then instead, they will perform a total knee replacement.

  • Emerson Jr, Roger H., and Linda L. Higgins. "Unicompartmental knee arthroplasty with the oxford prosthesis in patients with medial compartment arthritis." JBJS 90.1 (2008): 118-122.
  • Carr, Andrew J., et al. "Knee replacement." The Lancet 379.9823 (2012): 1331-1340.
  • Newman, John H., Christopher E. Ackroyd, and Nilen A. Shah. "Unicompartmental or total knee replacement? Five-year results of a prospective, randomised trial of 102 osteoarthritic knees with unicompartmental arthritis." The Journal of bone and joint surgery. British volume 80.5 (1998): 862-865.
  • Photo courtesy of SteadyHealth

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