Q: I am the head athletic trainer at a large university.  We've started keeping some statistics that show our women are more likely to tear their ACLs and a large percentage of both men and women don't come back -- even after going through the whole rehab program. What do your experts have to say about why this may be?

A: Well, of course, most studies focus on only one sport at a time and don't usually compare athletes across the disciplines. So you may be on to something with your record keeping. Past studies do support your observations that in the U.S. and in Europe, women athletes tend to injure their anterior cruciate ligaments (ACLs) more often than men.

The main reasons for this are probably already well-known to you: women tend to have a larger Q-angle (altering joint biomechanics), greater joint laxity (looseness), and weaker musculature. Combined together, these factors can contribute to an increased risk of ACL tear or rupture.

Your question about return rates to sports is an intriguing one. There was a recent study looking into this just for soccer players (males and females). One-hundred (100) active soccer players (males and females) between the ages of 11 and 53 were included in the study.

This was a retrospective study, which means the athletes were contacted after their surgery and rehab to see what kind of results they had. Two-thirds had a bone-patellar-bone graft to reconstruct the anterior cruciate ligament (ACL). The other one-third had a hamstring graft. Information about the type of graft used is always important in these studies to see if it makes a difference in results.

Final, long-term results were measured by looking at number of patients who went back to full sports participation, how many were still actively playing soccer years later, and how many people had to have another knee surgery (either on the injured side or the opposite side).

They found some interesting patterns. First, the graft type (hamstring versus patellar) did NOT make a measurable difference. Second, female soccer players were more likely to experience reinjury or future injuries. Any athlete who injured the nondominant leg was at increased risk for recurrent ACL injuries. That's because after the injury, they put even more stress and strain on the dominant side -- eventually leading to an overuse injury. Slightly more than half of all injuries (57 per cent) affected the dominant leg in these 100 patients.

There was a general trend among all players but especially for the females of declining sports participation over time. In other words, more patients returned to the game and played during the first couple of years after surgery. But by the end of five to seven years, far fewer were engaged in sports play. This may be similar to what you are seeing in your study.

The reason(s) for this trend are unknown. The authors suggest that maybe women who finish college and go on to a career and/or family gradually give up sports. Men were more likely to say that fear of reinjury and the trauma and pain of the injury and surgery were the reasons why they did not stick with sports.

The fact that women are actually more likely to experience future injuries (compared with men) may have to do with differences in muscular strength and joint laxity between the sexes. Women tend to have greater joint laxity or looseness. Men tend to have tighter and stronger muscles on either side of the joint to support and protect it.

The authors summarize by suggesting greater emphasis on injury prevention for all soccer players (young and old, male and female). Studies reporting results of ACL injury prevention programs are favorable at this point. Future programs need to pay attention to those athletes at increased risk for ACL reinjuries or opposite leg ACL injuries. Females and athletes injuring the nondominant leg are the first groups to target with a prevention plan.

Reference: Robert H. Brophy, MD, et al. Return to Play and Future ACL Injury Risk After ACL Reconstruction in Soccer Athletes from the Multicenter Orthopaedic Outcomes Network (MOON) Group. In The American Journal of Sports Medicine. November 2012. Vol. 40. No. 11. Pp. 2517-2522.