Your ACL (anterior cruciate ligament) runs through the center of your the knee and is highly susceptible to rips and tears. Women have two- to six-times more risk of ACL injuries because, for starters, they have wider hips, which adds pressure to the inside of the knee. Plus, estrogen and other female hormones might be responsible for loosening joints, increasing the odds of a tear. And then there are high heels, which tip the body forward, putting extra force on the knees and making the ACL work even harder.

MORE: ACL Injuries in Women