This involves placing a metal prosthesis into the knee with a high density plastic insert that acts as a new bearing for the knee. Unfortunately, knee replacements can wear or loosen over time. This is not as big of a problem in an elderly patient, but a 45-year-old, active patient may need a revision operation if a total knee replacement fails.
Various non-surgical options exist for treatment of osteoarthritis in younger patient populations. Cortisone, viscosupplementation, specialized knee braces, physical therapy, anti-inflammatory medications and activity modification all have potential roles in the treatment of osteoarthritis, and should be considered before proceeding with any surgical intervention..
I believe that the procedure you are referring to is the "partial" knee replacement. As you would expect, this operation does not replace all of the cartilage surfaces in the knee, but only addresses the problematic area of arthritis -- normally this would be the inner or medial aspect of the joint. This can be a great operation, but not all patients fit the criteria that help to make this operation successful. One of the main issues is that since the surgery only replaces part of the knee, any arthritis in the remaining joint will still be there after the surgery. Therefore, your surgeon will take x-rays and on occasion use an MRI to study the knee to see if the rest of the joint surfaces look great. This operation has the benefit of a shorter hospital stay, it can be less painful than a complete knee replacement, and the recovery can be easier.
Many orthopedic surgeons are performing partial knee replacements. This surgery adds to our list of possible options available to younger patients with troubling osteoarthritis.