I am a high school athlete doing a science project on ACL injuries in girls and women. So far I've found that females are at greater risk for ACL injury than males. Are they also more likely to reinjure themselves later?

Teasing this kind of information out of the literature can be difficult. Other variables must also be considered such as age and level of activity. Treatment of the torn ACL has also changed over the last 20 years, affecting the results for both men and women.

In general, more ACL tears are repaired surgically early on. Early ACL repair allows young patients (especially athletes) to return to full activities.

Several studies have been done looking at the rate of reinjury in two groups of patients: those who have an ACL repair and those who don't. The consensus at this time is that gender isn't a factor in reinjury.

It looks like age is more of a predictive factor. The younger, active patients who don't have ACL repair reinjure the knee later. Meniscus and joint cartilage are damaged most often. If you have access to a medical or public library, check out these two articles for more information:

Warren R. Dunn, MD, MPH et al., The Effect of Anterior Cruciate Ligament Reconstruction on the Risk of Knee Reinjury. In The American Journal of Sports Medicine. December
2004. Vol. 32. No. 8. Pp. 1906-1914.

Barber-Westin SD, et al. A Rigorous Comparison Between the Sexes of Results and Complications After Anterior Cruciate Ligament Reconstruction. In Arthroscopy. Vol. 12. Pp. 462-469, 1996.