Knee Replacement

A knee replacement resurfaces the joint. Your surgeon removes the damaged surface of the thigh bone and the top of the shin bone along with a few millimetres of the bone beneath, then caps each with a shaped metal component. A smooth plastic bearing sits between the two and does the gliding work the joint's own lining used to do. The back of the kneecap is resurfaced in some knees and left as it is in others.

Most replacements are total, meaning the whole joint surface is resurfaced. Where the damage is confined to one side of the knee and the ligaments are intact, a partial replacement can be done through a smaller incision and removes less bone. Your surgeon decides between them from your standing X-rays and from the examination, and occasionally the final decision is made once the joint is opened.

The components are usually fixed to the bone with cement, which sets in minutes and allows you to stand on the leg the same day. A modern implant is built for many years of ordinary walking, stairs and daily activity. Younger and heavier patients place more demand on it, and your surgeon will factor that into the timing of the operation and the choice of implant.

The operation is normally done under a spinal anaesthetic, so you are numb from the waist down and awake, with sedation available if you would rather not follow what is happening. Most people feel pressure and movement and nothing sharp. A nerve block is often added to keep the knee comfortable into the first day.

Your surgeon makes an incision down the front of the knee, moves the kneecap aside, prepares the bone ends with guides or with computer or robotic assistance, and fits trial components to check the balance of the ligaments and the movement through the full range before the final implants go in. The operation itself takes around sixty to ninety minutes, and you are in theatre for longer than that either side.

This is an Inpatient procedure. You are usually admitted the morning of surgery or the night before, and you stay two to four nights. A physiotherapist will have you standing and taking your first steps with a walker the same evening or the next morning, and that early start is a deliberate part of the treatment. You go home walking with support, on blood-thinning treatment for a few weeks, and with a set of exercises and a follow-up date.

You will walk with a walker or crutches for two to four weeks and with a stick for a further two to four. Most people are walking unaided by six weeks. The exercises you are given matter more than anything else in the first six weeks, since the range of movement you establish early is broadly the range you keep.

Desk work is realistic at four to six weeks and manual work at around three months. You can drive when you can control the car in an emergency without hesitation, which is usually six weeks for a right knee and sooner for a left in an automatic, and your surgeon confirms it. Sleep is broken for the first few weeks and improves steadily.

The knee stays warm and swollen for three to six months, and it is normal for it to swell by evening well into that period. Most of the improvement arrives by three months, and the joint continues to settle and strengthen for a full year. Kneeling is uncomfortable for many people long term, and a patch of numbness on the outer side of the scar is permanent in most knees.