Uncompartmental knee replacement (UKR), also known as partial knee replacement or half knee replacement is an excellent option in patients where joint damage is confined to one section of the knee. There are 3 main “compartments” of the knee, the medial compartment, the lateral compartment, and the patellofemoral compartment.
Uncompartmental knee replacement involves replacing the surfaces of both the tibia and femur (in the case of medial or lateral UKR), or femur and patella (in the case of patellofemoral joint replacement). The remainder of the knee is left alone, except for the removal of any osteophytes, which are bone growths resulting from arthritis. Importantly, the cruciate ligaments, which are sacrificed in total knee replacement, are kept. This helps maintain normal joint motion and joint position sense.
UKR has many benefits over total knee replacement. The operation is smaller that having a total knee replacement, and as such is associated with
Patients report a much more “normal” feeling knee, as more of the knee is preserved, and the knee rotates in a more normal motion. Studies on UKR have shown a greater proportion of highly satisfied patients when compared to total knee replacement, and fewer dissatisfied patients. Patients report a higher level of activity, and an increased ability to perform more difficult and strenuous activities.
UKR targets only the failing areas of a joint and is a more individualized treatment for a patient’s knee arthritis. Total knee replacement, although very successful, is a one-size-fits-all solution.
Not everyone is suitable for UKR. It is very important to perform a thorough assessment prior to proceeding with surgery, involving a careful history of the pain and symptoms, physical examination, x-rays, and perhaps an MRI scan.
UKR is suitable for your knee if
UKR may be seen as a single-step solution to patients with isolated single compartment arthritis. Typically, these patients are older, and lower in their activity levels. Alternatively, it can be used in younger patients as a smaller intervention allowing better function and earlier return to activity. This might be considered to be a staged intervention where years later a total knee replacement may need to be performed if the UKR were to wear out. Young patients who have this option can potentially enjoy the benefits of UKR while they are more active, and have a total knee replacement later in life when activity levels tend to be less.
Rates of UKR have fallen in Australia due to a perception that they are not as successful as Total Knee Replacement. The Australian National Joint Replacement Registry shows that there is a higher risk that a UKR will have to be re-done compared to a total knee replacement. After 10 years, 15.2% of UKR’s will have been re-done, compared with 5.5% of total knee replacements. The most common reasons for this are the implants loosening, or arthritis affecting the other areas of the knee.
Some of this difference in re-do rates may be because surgeons are more likely to revise a failing UKR than a failing total knee replacement because the surgery is more straightforward.
Regardless, it is important that UKR is done in a carefully selected patient, and by a surgeon with experience and a particular interest in UKR. Multiple studies have highlighted that surgeons with a higher rate of UKR have better overall results.
Yes. Bilateral surgery is very well tolerated and is often the best way to proceed if the knees are equally affected. Of course, your general health would need to be taken into account to see whether the anaesthetic and surgery could be performed safely.
Usually around 3-4 nights following surgery for single sided surgery, and 4-5 nights for bilateral surgery.
I am happy for my patients to drive when their knee is bending well, and they are not in pain, and are off any sedating medications. Typically this is around 1-2 weeks following UKR surgery. Typically, office workers will return to work after 2-4 weeks and manual worker at around 4-6 weeks.
The risks of UKR include (but are not limited to):