A recent article just published online in the American Journal of Sports Medicine shows a definite connection between hip strength and the incidence of ACL injury. It turned out that athletes with decreased hip strength were more likely to have ACL injury. http://ajs.sagepub.com/content/early/2015/12/07/0363546515616237
More and more data indicates also that hip strength is critical to preventing and treating patellofemoral pain. This study is a landmark in that it shows a true role for prevention as well as treatment.
