What Actually Happens During Knee Replacement Surgery

Knee replacement is one of the most commonly performed orthopaedic operations, and one of the most consistently successful in terms of pain relief.

Who it is for

The usual reason is osteoarthritis that has worn the cartilage away to the point where bone meets bone. The decision is driven less by what an X-ray shows than by what the pain is doing to daily life — whether it wakes you at night, prevents walking a normal distance, or no longer responds to weight management, physiotherapy and pain relief.

Most surgeons exhaust non-surgical options first, because a replacement has a finite lifespan and revision surgery is harder than the original.

The operation

The damaged surfaces at the end of the femur and the top of the tibia are removed and replaced with metal components, separated by a plastic spacer that acts as the new cartilage. The back of the kneecap may also be resurfaced.

It typically takes one to two hours under spinal or general anaesthetic. Partial knee replacement, where only one compartment is damaged, is a smaller operation with quicker recovery but is suitable for fewer people.

Recovery, realistically

Most people stand and walk with support the same day or the next. Hospital stays are often one to three days. Crutches or a frame are usual for a few weeks.

The honest timeline is longer than people expect: six weeks to manage most daily activities, three months for substantial improvement, and up to a year for the final result. Swelling and stiffness at six months is normal, not a sign of failure.

Physiotherapy is not optional. Range of motion achieved in the first six weeks strongly predicts the long-term result, and it is uncomfortable work.

How long implants last

Registry data suggests the large majority of knee replacements are still functioning at fifteen to twenty years. Younger and more active patients wear implants faster, which is part of why surgeons often advise waiting where it is tolerable.

Risks worth knowing

Infection, blood clots, persistent pain, stiffness requiring manipulation, and implant loosening over time. Serious complications are uncommon but not rare, and your own risk depends on age, weight and other conditions — that conversation belongs with your surgeon.

This article is general health information, not medical advice. Talk to a qualified doctor about your own situation.