Partial or total knee replacement? What 10 years of data tell us

Your knee has three compartments: the inner (medial) side, the outer (lateral) side, and the joint behind the kneecap. Arthritis doesn't always affect all three. When it's limited to one, replacing the whole knee can be more surgery than you need.

Who is a candidate

According to the American Academy of Orthopaedic Surgeons, you may be a candidate for a partial knee replacement if your arthritis is limited to one compartment. It's usually not recommended if you have inflammatory arthritis, significant stiffness or ligament damage.¹ Pain that sits mostly on the inside or outside of the knee points toward a partial replacement; pain across the whole knee points toward a total.

When one part of the knee is out of alignment and wearing faster than the rest, it can affect the cartilage in the other compartments too. A partial replacement corrects the worn compartment and keeps the healthy parts of your knee.

How partial compares with total

The TOPKAT trial randomized 528 patients with arthritis on the inner side of the knee to partial or total replacement. At five years, partial knee replacement was as good as total knee replacement and more cost-effective, and more partial knee patients said they would have the operation again.² Ten-year results, published in 2025, found that about 5% of knees in each group had needed revision surgery, and partial knee replacement had fewer complications.⁵

The AAOS lists quicker recovery, less pain after surgery and less blood loss among the advantages of a partial knee, and notes that many patients say it feels more natural.¹ That matches what I see. With partial knee replacement, people get a much more natural-feeling knee, and that's part of the reason they recover faster.

How long do robotic partial knees last?

A partial knee implant is small, so where it sits matters, and that's where robotic assistance helps. A four-center study of Mako partial knee replacements found 97% of implants still in place at a mean of 5.7 years, with 91% of patients satisfied or very satisfied.³ At ten years, 91.7% remained in place and 91% of patients were still satisfied.⁴

The trade-off

If arthritis later develops in another compartment, a partial knee can be converted to a total knee replacement. And occasionally, I find during surgery that a partial replacement isn't suitable and perform a total instead. We discuss both possibilities before surgery.

Finding out which fits you

An exam and standing X-rays usually show which compartments are worn. Explore the knee diagram on this site to see how each compartment points toward a different operation, then let's look at your own X-rays together.