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My cousin says she had a unicompartmental knee replacement that didn't work out very good. She's suggesting I just skip that option and go right for the full knee replacement. She's had hers a good 10 to 12 years. Have things improved enough since then that I can give it a try?

The unicompartmental knee arthroplasty (UKA) was designed to replace half the joint when only one side was worn away and arthritic. In its early days there were high rates of failure and revision surgeries. Today, studies show excellent medium-to-long-term results. There are fewer reoperations, less joint degeneration, and more evenly balanced knees. Plus patients have an increased chance to remain active (or increase activity level). Improved surgical techniques have been demonstrated. In the early days of UKAs, it was easy to overcorrect a knee deformity and end up with a failed surgery. Getting the right patient, using the most appropriate implant for that individual, and maintaining proper limb alignment are now understood to be a necessary part of the equation for success. Correct limb alignment refers to the fact that it can be very easy to insert the implant with too much rotation or tilt to one side or another. The surgery can be done with an open incision, which gives the surgeon a better view of the joint and easier time of aligning the implant. Or it can be done as a minimally invasive procedure with just a three-inch incision. It's harder for the surgeon to see what he or she is doing with minimally invasive surgery. But the fact that it can be done successfully with less disruption of the surrounding muscles makes the minimally invasive approach very attractive. The stay in the hospital is shorter and the cost is less. Third, changes have been made in the implant design that have improved results. The polyethylene (plastic) platform that the implant sits on is thinner than it used to be. Finding the right balance of thickness has been a challenge that is yet to be overcome completely. The surgeon aims for correction of any deformities but tries to ere on the side of undercorrection instead of overcorrection. The slope (or curvature) of the implant has been changed over the years. Surgeons were able to see that an increased slope led to a higher rate of implant loosening. And they've discovered that the slope makes a difference when the ACL isn't present or is damaged. In such cases, an implant with a neutral slope is selected. Different types of implants have been developed. Some sit right on top of the bone. These are called resurfacing designs. Others require a portion of the bone surface to be removed to make an inset design for the implant. There's also the fixed-bearing versus the mobile-bearing implant. This feature describes how much the implant pieces move and rotate against each other. The mobile-bearing unit seems to be winning out. It has a larger area of contact to spread out the load resulting in lower wear rates. Mobile-bearing units are more difficult to get the right balance of knee flexion and extension. This requires a perfect soft-tissue balance to achieve. So you can see, there have been many improvements that might warrant consideration of this approach. You can rely on your surgeon for his or her best recommendations for you and your particular situation. Not all people are good candidates for this approach. Some people really do need a total knee replacement right off the bat.

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