When people look into knee replacement for the first time, they soon notice there aren’t actually one but two main types of procedure. There are total knee replacements. And there are partial knee replacements. So… what’s the difference? And why would you have one or the other?
Let’s look in more detail.
Three compartments, two operations
Your knee is structured around three compartments: the lateral (outer), medial (inner) and patellofemoral (kneecap area). If your knee develops osteoarthritis, the damage could affect any one of those compartments, or all three together. A partial replacement (also known as a unicondylar or unicompartmental replacement) targets one of the compartments. A total replacement replaces the entire knee joint. Partial knee replacements are less common than totals. In 2019 there were 103,617 primary replacement procedures in England and Wales, and 11% of those were partials.
What are the advantages of a partial replacement?
Partial surgery places a smaller implant into your joint. Because it involves removing less material and tissue from the knee, it’s a smaller operation. This usually means less time in theatre and a shorter stay in hospital. It can also mean a quicker recovery. Studies suggest the complication and infection rates are lower for partials too (although the risks in both operations are low). It’s worth bearing in mind that partial implants are not usually as long lasting as totals, so in time a total replacement may be needed.
When do people have partial replacements?
This varies from patient to patient, so we would always assess your suitability carefully in clinic. But the pattern or extent of the arthritis is a key factor. A typical candidate for partial has painful bone-on-bone arthritis in one side of their knee, well-preserved other compartments, little or no deformity in the knee, and intact ligaments. For some years, partials were only recommended to younger, active patients, because they can allow for a greater range of movement than totals. But the evidence now says older patients can do very well with partial replacements too. So, age is not a defining factor.
Who has a total replacement?
If you’re a typical candidate for a total, you would have painful arthritis damage extending across the joint, and deformity in the knee that isn’t correctable – which means you’re unable to straighten it fully. In these cases, replacing the entire joint can help to restore function, stability and pain-free movement. On the other side, the operation and recovery times for total replacement are longer, it’s more expensive (though usually longer-lasting), and the new joint may feel artificial compared to the original knee. But for people who have been struggling with pain and reduced mobility, sometimes for years, the results can be dramatic.
For further reading
An NHS guide to knee replacement surgery
A 60-second guide to knee replacements
How long does it take to recover from a total knee replacement?
How to improve your recovery time after surgery