Medial Partial Knee Replacement

Why the inner side wears first

Standing and walking load the inner compartment more than the outer one, so that is where wear commonly begins. Patients often describe pain along the inside of the knee, worse on stairs or after standing, and a leg that has begun to bow slightly.

When imaging and examination agree that the damage is confined to that compartment, resurfacing it alone becomes a reasonable option to discuss.

What is kept, and what that means

A medial partial replacement leaves the outer compartment, the kneecap compartment, and the cruciate ligaments alone. Those ligaments carry much of the knee’s sense of position, and keeping them is the reason the operation behaves the way it does.

The American Academy of Orthopaedic Surgeons lists the advantages over a total replacement directly: quicker recovery, less pain afterward, less blood loss, and a lower risk of infection and blood clots. Because the healthy bone, cartilage and ligaments stay, many patients report the knee feels more natural, and range of motion may be better.

In the TOPKAT randomised trial, 528 patients with arthritis confined to this compartment were assigned to a partial or a total replacement. At five years the two groups scored the same, with a similar rate of re-operations, and the authors recommended partial replacement as the first choice for this pattern of arthritis.

What would point to a total knee instead

Arthritis in more than one compartment, an unstable or absent anterior cruciate ligament, a leg that has bowed substantially and no longer corrects, significant stiffness, or inflammatory arthritis such as rheumatoid disease all point away from a partial.

A total knee replacement addresses the whole joint at once, and when wear is already spreading that is the right operation. The question is which one fits your knee, not which one is the bigger commitment.

What to try before either operation

Surgery is not the first step. Targeted strengthening and physical therapy, activity adjustment, weight management where it applies, anti-inflammatory medication where it is safe for you, and selected injections all remain real options, and they still help some people with arthritis limited to one compartment.

Choosing to wait, with a plan, is a reasonable decision. The consultation exists to tell you where you stand, not to schedule an operation.

The risks, and what a later operation involves

Partial knee replacement carries the risks any joint replacement does: infection, blood clots, stiffness, and loosening or wear that needs another operation later. It also carries one risk a total knee does not: arthritis can progress in the compartments that were left alone.

If that happens, the partial can usually be converted to a total knee replacement. That is a second operation with its own recovery, and it belongs in the decision at the start rather than as a surprise later.