Part of designing a knee replacement is a keen understanding of the materials used to replace the normal knee joint surfaces. Second, the design attempts to create an implant that will replicate a normal knee as best possible. By doing so, the patient will be able to participate in the same activities before and after surgery.
Rotating knee replacement implants are also called mobile-bearing implants or rotating platform implants.
Rotating Knee Replacement Implants
The rotating knee replacement implants not only swing back and forth (like a hinge), but the knee can also rotate inwards and outwards (a twisting motion). Because a normal knee joint rotates a small amount, the rotating knee replacements are intended to more closely replicate normal knee motion. Rotating knee implants generally cost more than the traditional fixed-bearing implants.
Why Does This Rotation Matter?
The hope is that by acting more like a normal knee joint, the rotating knee replacements will have fewer stresses on the implant than traditional knee replacement implants. With less stress on the implant, the plastic part of the knee replacement may last longer.
All joint replacements are limited in that they tend to wear out over time. Knee replacements usually last at least 20 or more years, but they do not last forever. This is a problem for all who have the surgery, but especially for those who have knee replacements at a younger age (less than 60 years old). These people will likely wear out their knee replacement during their lifetime.
The American Academy of Orthopaedic Surgeons notes that mobile-bearing implants are more often chosen for younger, active, or overweight people. As well, it is important that the person has good support from the ligaments and soft tissues of the knee for a rotating implant to be successful.
These designs have gone through generations of development, with newer versions introduced and marketed over the years. This complicates the question as to whether rotating knee replacements work better or last longer than traditional knee replacements.
Some surgeons will argue that rotating implants are worse, believing that the additional motion can lead to faster wear of the implant over time. A 2011 study of rotating implants that had to be removed from patients due to complications found as much wear on the surfaces as those of fixed implants.
Newer designs may last longer than the first or second generation of these implants, but you must wait for long-term studies to be sure.
Should I Have the Rotating Knee Replacement?
There are some studies that show the rotating knee replacements work as well as traditional knee replacements, but a 2015 Cochrane review of 19 studies notes only moderate- to low-quality evidence of this, and therefore could not reach a firm conclusion.
Fortunately, rotating knee replacements look and act much like traditional knee replacement implants. The surgery is the same, and the recovery is the same. Some surgeons feel that ligament balancing of a rotating knee replacement is more difficult than a traditional knee replacement, but this is not agreed upon by all surgeons.
There may be a difference between the rotating knee replacements and traditional knee replacements, but it is likely a small difference. You can discuss with your surgeon if this is a difference that should matter to you.
