For many athletes, the scenario is all too familiar: a pop in a knee, followed by a sharp pain.

If testing shows a tear in the anterior cruciate ligament – a flexible cable of tissue that links the thigh bone and shin bone – they face the likelihood of surgery and months of physical therapy.

But Dr. Freddie Fu of the University of Pittsburgh says he’s “trying to challenge surgeons to think differently” with an innovative surgery for this common injury that he believes closely duplicates the anatomy of the uninjured ACL and may improve knee stability and function more than standard techniques.

The standard approach, used in most of the 100,000 ACL reconstructions in the United States each year, is to replace the torn ligament with a single bundle of tendon fibers, known as a tendon graft.

But Fu says using two separate bundles, placed near each other at different angles, is more effective.

“This is how nature is,” said Fu, who has been working with other researchers to investigate the surgery’s benefits.

He learned the technique from doctors in Japan and has performed it on about 200 patients since November 2003. He said this research may be the most important he has undertaken.

The double-bundle technique is “quite appealing and may become a step forward in patient outcomes,” said Dr. Douglas Jackson, medical director of the Orthopaedic Research Institute in Long Beach, Calif.

But research results are mixed on whether the surgery is better than the single-bundle technique.

Refinements to the single-bundle surgery have been shown to improve knee stability, said Dr. Gary Poehling, chairman of orthopaedic surgery at the Wake Forest University School of Medicine.

Although the double-bundle surgery better reproduces the unique three-dimensional configuration of a normal ACL, “no one knows whether it will hold up better in the long run than the single bundle,” said Dr. Nicholas DiNubile, an academy spokesman and clinical assistant professor at the Hospital of the University of Pennsylvania.

The ACL includes two bundles of fibers, the anteromedial, or AM, bundle and the posterolateral, or PL, bundle. The PL bundle is behind the AM bundle and often hidden by it during surgery. Jackson said the PL bundle usually was not adequately replaced in the single-bundle surgery.

Fu believes the PL bundle is important to controlling knee rotation and that the double-bundle surgery should result in better outcomes for injured athletes.