Partial Knee Replacement

In the preceding few posts, I have covered complementary and alternative treatments for arthritis of the knee. (Insert link to previous posts) In patients with mild to moderate degenerative disease, these modalities when combined with traditional physical therapy, activity modification and anti-inflammatory medications may help preserve function and control symptoms for many years. Arthritis travels a slow and steady path, which for many patients, leads to surgery. 10% of Americans aged 80 years or older have undergone a knee replacement.

The traditional knee replacement consists of replacing diseased cartilage of the thigh bone (femur), leg bone (tibia) and the knee cap (patella) with metal components, with a plastic insert in between to create smooth motion of the new knee.

Recently, a procedure called a partial knee replacement (PKR) has grown in popularity throughout the US and the world. In this post I will answer 5 of the most common questions I’ve received about this procedure.

How is a partial knee different from a full knee replacement?

The knee joint consists of three compartments: the inside (medial) compartment, the outside (lateral) compartment, and the front (patellofemoral) compartment. The most common area of the knee affected by arthritis is the medial or inside compartment. A partial knee most often addresses this area, though it may be done for arthritis in the other two as well. In a PKR, only the area of the knee affected by cartilage loss is replaced with metal and plastic, leaving the rest of the knee’s cartilage alone. 

What are the benefits of a PKR compared to those of a TKR?

In a PKR, the important stabilizing ligaments which connect the thigh and leg bones are not cut as they are in total knee replacement. This may be one of the reasons patients with a partial knee replacement score higher in functional questionnaires and are more satisfied compared to patients who have had total knee replacement. (Kim, Journal of Arthroplasty 2017)

Because less of the normal bone of the knee joint is removed during surgery, typically the pain after surgery is less, and recovery is faster. Many studies have shown PKR to have a quicker and easier recovery compared with TKR, including a shorter hospital stay and less pain. 

How long will my partial knee last?

It is generally accepted that a partial knee is just as likely to last ten years as a total knee replacement. After ten years, the survivorship for partial knee replacement is slightly lower than that of total knee replacement. In one study, 91% of PKRs were still functioning well at 20 years after surgery. (Price, CORR 2011)

What are the risks of having partial knee replacement?

PKR, while a smaller operation, is still a major surgery and has all of the same risks as a total knee replacement procedure. Many studies suggest that PKR procedures have a higher likelihood of complications, including progression of arthritis in the other areas of the knee, loosening of the metal components and a greater likelihood of needing a revision operation when compared to total knee replacement. With appropriate patient selection, these risks can be mitigated.

Is partial knee replacement right for me?

PKR is a good option in patients with knee pain from arthritis without significant limb deformity, and who still have good motion of the knee. Patients with long standing, severe arthritis, certain inflammatory conditions such as rheumatoid arthritis, and patients who have limited motion of the knee may be better treated with total knee replacement. Speak to a surgeon who performs knee replacement if you think you may be a candidate.
- Evan J. Hawkins, MD, MBA

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