You'll usually be admitted to hospital on the day of your operation. The surgeon and anaesthetist will usually come and see you to discuss what will happen and answer any questions you have.
Most people would have seen their surgeon at a pre-assessment clinic and had the chance to the operation.
A senior-level surgeon, consultant or registrar will do the operation. They may be helped by junior doctors. You should be told at your pre-operative assessment who will be doing the operation. Ask if you're not told.
Knee replacement surgery is usually performed either under general anaesthetic (you're asleep throughout the procedure) or under spinal anaesthetic or epidural (you're awake but have no feeling from the waist down).
The worn ends of the bones in your knee joint are removed and replaced with metal and plastic parts (a prosthesis) which have been measured to fit.
You may have either a total or a partial knee replacement. This will depend on how damaged your knee is. Total knee replacements are the most common.
Read more information about what happens on the day of your operation.
In a total knee replacement, both sides of your knee joint are replaced. The procedure takes 1 to 3 hours:
You're likely to still have some difficulty moving after your operation, especially bending your knee. Kneeling may be difficult because of the scar.
If only one side of your knee is damaged, you may be able to have a partial knee replacement. This is a simpler operation, which involves a smaller cut and less bone being removed. It's suitable for around 1 in 4 people with osteoarthritis.
The advantages of partial knee replacement include a shorter hospital stay and recovery period. Blood transfusions are also rarely needed. This type of joint replacement often results in more natural movement in the knee and you may be able to be more active than after a total knee replacement.
Talk to your surgeon about the type of surgery they intend to use and why they think it's the best choice for you.
In some cases, there may be other types of surgery you can have, including:
If only your kneecap is damaged, an operation called a patellofemoral replacement or patellofemoral joint arthroplasty can be performed. This is a simpler surgery with a faster recovery time. However, the long-term results are still unclear and it's not suitable for most people with osteoarthritis.
This is usually used for partial knee replacements.
The surgeon makes a smaller cut than in standard knee replacement surgery. Specialised instruments are then used to manoeuvre around the tissue, rather than cutting through it. This should lead to a quicker recovery.
Read the NICE guidance on mini-incision surgery for total knee replacement.
The surgeon performs this operation using computerised images, which are generated by attaching infrared beacons to parts of your leg and to the operating instruments. These are tracked on infrared cameras in the operating theatre. Results so far suggest that this may enable the new knee joint to be positioned more accurately.
Most hospitals don't yet have the equipment to do this and only around 1 in 100 knee replacements are performed in this way.
This is a more recent advance in knee replacement surgery. A guide is created using MRI scans. This helps to create the best fitting prosthesis for each patient.
The potential advantage is that the prosthesis may last longer, as the most accurate fitting is used. However, as this is a new technique, the results and long-term effects aren't fully known yet.