Torn ACL - Causes

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What causes a torn ACL?

Most anterior cruciate ligament injuries occur due to injury, usually in a sport or fitness activity. The ligament gets stretched or tears when the foot is firmly planted and the knee locks and twists or pivots at the same time. This commonly occurs in basketball, football, soccer, and gymnastics, where a sudden change in direction stresses and damages the ligament. These injuries are usually noncontact, occur at low speed, and occur as the body is decelerating.

ACL injuries may also occur when the tibia is pushed forward in relation to the femur. This is the mechanism of injury that occurs because of a fall when skiing, from a direct blow to the front of the knee (such as in football) when the foot is planted on the ground, or in a car accident.

Risk factors for ACL injury in women

Women are more prone to ACL injuries than men. Women have slightly different anatomy that may put them at higher risk for ACL injuries:

  • The intercondylar notch at the end of the femur is narrower in women than men. When the knee moves, this narrower space can pinch and weaken the ACL.
  • Women have a wider pelvis than men, and this causes the femur to meet the tibia at a greater angle (called the Q angle). This increases the force that the ACL has to withstand with any twisting motion, increasing the risk of damage.
  • Genetic differences may put the female ACL at risk. Female muscles tend to be more elastic and decrease the protection that the hamstring muscles can provide to the ACL. Hormonal changes during menses may also affect elasticity. Moreover, female hamstrings react and contract a millisecond slower than in a male, increasing the risk of ACL damage when landing from a jump.
Return to Torn ACL (Anterior Cruciate Ligament Tear)

See what others are saying

Comment from: raymor, 19-24 Female (Patient) Published: January 27

I jumped out of the bed of a truck and slipped on ice when I landed. I felt a big pop and was in some serious pain. I couldn't put any weight on it for several days without my knee buckling or shifting. MRI showed the bad news two weeks later! Full tear of the ACL as well as a partial tear to the lateral meniscus.

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Comment from: Knowles, 19-24 Male (Patient) Published: April 11

I was playing Australian Rules football. I received a tackle from behind! My knee went straight into the ground and the tackler landed on my leg twisting my knee and foot. I felt a crack in my knee and thought I had broken my tibia. At first I got up and walked away from the incident, then in about 10 minutes my knee was huge and I could not bear weight on it at all! Scans revealed torn ACL and I require surgery!

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