Knee arthroscopy (keyhole knee surgery): what it can and cannot fix

What a knee arthroscopy is

The surgeon makes two or three small cuts around the knee and passes in a thin camera and fine instruments. It is usually a day-case operation under general or spinal anaesthetic. Because the cuts are small, recovery is quicker than open surgery, but the knee still needs exercises and time.

Problems it can help

• A torn meniscus that makes the knee lock, catch or give way, especially after a twisting injury in a younger person
• A loose body: a piece of bone or cartilage floating in the joint and jamming it
• Repairing a meniscus tear where the tissue has a good blood supply and can heal
• Reconstructing a torn anterior cruciate ligament (ACL), which is done with arthroscopic help
• Some cartilage injuries from sport, and taking samples if the diagnosis is unclear

What it does not fix

Osteoarthritis, the slow wear of the joint that causes most knee pain in people over 50, is not improved by arthroscopy. UK guidance advises against arthroscopic washout for osteoarthritis unless the knee is truly locking from a loose body or flap. Many people are still told their knee needs to be "cleaned". If your X-ray shows arthritis and your main problem is aching pain, ask whether exercise, weight loss and physiotherapy have been tried, or whether a knee replacement is the real question.

A degenerative meniscus tear, the kind found on MRI in many middle-aged and older knees without a clear injury, usually does about as well with physiotherapy as with surgery. An MRI showing a tear does not by itself mean you need an operation.

Questions to ask before you agree

• What exactly do you expect to find, and what will you do about it?
• Is my main problem locking and catching, or pain from arthritis?
• What happens if I try physiotherapy first?
• How long until I can walk normally, drive and return to work, in my case?

After the operation

Most people go home the same day and walk soon after, sometimes with crutches for a short period. Swelling settles over weeks, and physiotherapy restores strength. If a meniscus was repaired rather than trimmed, recovery is slower and you may be told not to bend or put full weight through the knee for a time. Your surgeon will tell you which applies. Fever, a hot red knee or calf pain and swelling after the operation need urgent review.

Common questions