One of the pioneers in modernizing simpler A.C.L. surgery is Dr. Gregory S. DiFelice, who has done A.C.L. repairs, instead of reconstructions, on about 250 patients during the last decade at the Hospital for Special Surgery in New York. Dr. DiFelice maintains that repair rather that reconstruction is especially helpful for children 18 and younger who are more likely than older patients to reinjure a reconstructed A.C.L. Over all, he said in an interview, the risk of reinjury with the repair method has been no greater than that following reconstruction.

Reconstruction involves removing the torn ligament and replacing it with a graft — a tendon surgically removed from the patient’s hamstring, quadriceps or kneecap, or sometimes taken from a cadaver — and attaching it with screws or buttons through tunnels drilled into the femur and tibia. As it heals, the grafted tendon develops scar tissue that results in a firm, reliable knee joint with an overall failure rate of about 5 or 10 percent.

But Dr. DiFelice said that when the damaged A.C.L. is removed, the patient loses the nerve endings within it that send signals to the brain about what the knee is doing. Also, range of motion may be compromised, and during the lengthy recovery that can take six to eight months or longer for the graft to be strong, thigh muscles atrophy and must be rebuilt before the patient can safely return to demanding activity.

Thus, Dr. DiFelice said he wants to encourage other practitioners and their patients to pursue the lesser surgery and shorter rehab whenever circumstances permit, especially when the full length of the A.C.L. tears directly off the bone. However, he explained that even when the torn ligament is not quite long enough to reach the bone, he’s developed an augmentation procedure to add a small strut to make it reach. Using this method, he said, he now has to resort to the standard reconstruction surgery for less than a third of the patients he sees.

There are at least two important caveats to this story:

1) Unlike the introduction of new prescription drugs, new surgical procedures are not subject to government approval and typically are not tested in controlled clinical trials, at least not until they have been used for years. So patients must rely on what surgeons tell them about the effectiveness of their procedures, supplemented perhaps by reports from patients.