How Successful Is Arthroscopic Knee Surgery? It Depends on What It Fixes

You have knee pain, maybe an MRI that shows a tear, and someone has mentioned a knee scope. Before you agree to it, you want to know one thing: does it actually work?

The honest answer is that it depends on what the surgery is meant to fix. Arthroscopic knee surgery is not one operation. For some knee problems it is the right tool. For the most common reason it is done, a worn and arthritic knee in middle age or later, large trials found it does little more than a placebo procedure.

It works best when it fixes a specific mechanical problem, and it works poorly for wear and tear.

• For a worn, arthritic knee or a degenerative meniscus tear, the evidence is strong that it does not help much. A 2022 Cochrane review found that, in trials comparing it with a placebo procedure, it made little or no difference to pain or function three months after surgery. An international panel writing in The BMJ in 2017 made a strong recommendation against arthroscopy in nearly all patients with degenerative knee disease.
• For a specific problem in a knee that is not worn out, such as a torn ACL that leaves the knee unstable, a repairable meniscus tear, or a knee that is truly locked and cannot straighten, arthroscopic surgery is a standard treatment. The BMJ recommendation was written for worn, degenerative knees, not for these problems.

So the first question is not how well the surgery works in general. It is which of these two groups your knee belongs to.

In knee arthroscopy, the surgeon puts a small camera into the joint through a small cut and works with thin instruments through one or two more. The American Academy of Orthopaedic Surgeons (AAOS) says most knee arthroscopy procedures last less than an hour, and a generally healthy person usually goes home the same day.

The same technique is used for very different jobs. The AAOS lists, among others:

• Partial meniscectomy, trimming away a torn piece of the meniscus, the rubbery cushion between the thigh bone and shin bone
• Meniscus repair, stitching a tear so it can heal
• Reconstruction of a torn anterior cruciate ligament (ACL)
• Trimming or reconstruction of damaged cartilage
• Removal of inflamed joint lining

A success rate for "knee arthroscopy" mixes all of these together, which is why the number on its own tells you so little.

Knee arthroscopy has been studied hard, because it was done so often. The BMJ panel called it the most common orthopaedic procedure in countries with available data.

The BMJ panel did not consider knee problems that began after a major injury or young people with sports injuries, and it named a truly locked knee, one that cannot fully straighten, as the only possible exception to its recommendation. These are the situations where arthroscopic surgery is used on purpose.

Before any knee surgery, it helps to say out loud what you want it to do. Common goals are:

• Less pain day to day
• A knee that stops locking or giving way
• Getting back to a sport or a job that loads the knee
• Protecting the joint for the future

Arthroscopy is good at the second and third goals when there is a specific structure to fix. It is not a reliable way to get the first one when the cause is wear. The AAOS also cautions that some damage cannot be completely reversed with arthroscopic surgery and that a bigger operation may be needed later.

Recovery depends on which procedure you have, because a repaired tear has to grow back together, while a trimmed one does not.

• Partial meniscectomy: the AAOS puts healing at roughly 3 to 6 weeks.
• Meniscus repair: the AAOS puts rehabilitation at about 3 to 6 months.
• A minor scope: the AAOS says most people can drive 1 to 3 weeks after surgery and return to most physical activities after 6 to 8 weeks, sometimes sooner. A heavy job can take longer.

The AAOS calls the complication rate after knee arthroscopy very low and lists infection, blood clots, stiffness, bleeding into the knee, and swelling or bruising as possible problems. Low is not zero, and the Cochrane review lists deep vein thrombosis, pulmonary embolism and deep infection among the serious adverse events reported in the trials. That is one more reason not to have the operation when the evidence says it will not help.

If your knee pain comes from wear, the trials point to non-surgical care first. That usually means a structured exercise and physical therapy program to strengthen the muscles that support the knee, plus medicine for pain and swelling. An injection can calm a flare enough to keep you moving; our article on the cortisone shot for knee pain explains what to expect. When a worn knee stops responding to all of that, the conversation usually moves toward knee replacement rather than a scope.

Go to an emergency room now if a knee becomes hot, red and very swollen with a fever, or if, after any knee surgery, your calf becomes swollen and painful or you become short of breath or have chest pain.

See an orthopedic doctor soon if your knee locks and will not straighten, if it swelled up quickly after a twist or a pop, or if it keeps giving way under you. Those are the patterns that point to a mechanical problem rather than wear. After a scope, the AAOS advises talking to your doctor if your pain has not begun to improve within a few days.

The most useful thing you can have before deciding is a clear answer about what is causing your knee pain, based on an exam of your knee and how it behaves, not only on what an MRI report says. Mountain Spine & Orthopedics offers a complimentary MRI review and second opinion, and our orthopedic team will tell you plainly whether a scope is likely to help or whether another route makes more sense. You can read more about the procedure on our arthroscopic knee surgery page.