I had an ACL repair two years ago that seems to have failed. Should I just leave it? Or should I have the repair repaired?

Surgeons agree that not all ACL repairs that fail must be revised. Revision surgery is saved for patients with a chronically unstable and/or painful knee. If you have pain with everyday activities or you are unable to enjoy sports activities, then you may be a good candidate for revision surgery.

It's not clear yet who are the best candidates for revision surgery. Studies are being done to identify risk factors that might suggest a revision operation is (or isn't) going to help. These are called predictive factors of outcome.

About 10 per cent of revision cases also fail. According to a recent report from a Sports Injury Center in Rome, Italy, this may be because of errors in surgical technique.

Sometimes the tunnel drilled to thread the tendon graft through is too big. In other cases, the graft is attached in the wrong place and gets pinched during knee motion. The wrong graft tension or not attaching the graft properly can also result in failed surgery.

Until it's clear who should have revision surgery for a failed primary (first) ACL repair, symptoms and function are the main factors used in making the decision to have a second operation.