Factors that increase your risk of anterior cruciate ligament (ACL) injuries include:

• Playing sports that involve sudden changes in direction or cutting around other players or obstacles, such as skiing, football, soccer, basketball, baseball, and tennis.
• Making accidental movements that may twist your knee, such as falling off a ladder, jumping from an extreme height, stepping into a hole, or missing a step on a staircase.
• Losing muscle tone in legs (from aging or inactivity).
• Having unbalanced leg muscle strength, such as if the muscles in the front of your thigh (quadriceps) are stronger than the muscles at the back of your thigh (hamstrings).
• Previous ACL injuries, especially if your knee occasionally gives out (chronic ACL deficiency).

Women have more ACL injuries than men; in sports, women injure their ACL 4 to 6 times as often as men.⁴ There are several theories for the increased incidence in women athletes, including differences in men's and women's hormone levels and how they use muscles.