#1 – The Pelvis – The female pelvis is wider than the male pelvis. A wider pelvis causes a more forward tilted femur near the hips as the shin bone is angled toward the knee, resulting in knock-knees, which in turn, place a great amount of stress on the ACL.
#2 – Narrow Notch – Females have narrower intercondylar notch, through which the ACL passes through. It has been suggested that cutting and jumping movements with narrow femoral notches may weaken the ACL.
#3 – Smaller ACL – Women have smaller anterior cruciate ligament size, making it more vulnerable to fraying.
#4 – Hormones – Generally, women have greater knee laxity, which may be influenced by the hormones secreted in large amounts by the females. Receptors for estrogen and progesterone have been identified on the ACL; thus, hormonal fluctuations occurring during the menstrual cycle may influence the structure of the ACL. It was found that women are more susceptible to ACL tears during the ovulatory phase (days 5 through 12 of the menstrual cycle), when the estrogen and progesterone levels are high, increasing the laxity and susceptibility of the ligament to overstretching.
#5 Weaker Leg Strength – Women have lesser muscle strength and slower muscle reaction times when compared to men. A strong and fast-reacting hamstrings is vital to keep the ACL intact during abrupt changes of direction. In addition, women also tend to recruit or use their front thigh musles or quadriceps, increasing the risk of AC L injuries. The hamstrings protect the ACL by decreasing the stress applied on the knee as the lower leg moves forward. The quadriceps pulls the shin bone forward, consequently placing additional stress on the ACL.