ACL Injuries


  • The tibia, patella, and femur are the three main bones that meet to form the knee joint.
  • The knee joint is held together by ligaments and tendons.
  • The medial collateral ligament (MCL) and the lateral collateral ligament (LCL) control the sideways motions of the knee, and the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) control the back and forth motion of the knee.
  • The ACL and PCL are found inside the knee joint and form an “X” like figure.
  • The ACL prevents the tibia from sliding out in front of the femur and provides rotational stability.


ACL tears and sprains are a common knee injury and can be caused by changing direction rapidly, landing from a jump incorrectly or with a hard impact, direct contact or collision, stopping suddenly, or slowing down while running.

For ACL injuries sustained through non-contact sources, Carter et al. (2016) showed a greater risk for ACL injury when there was an increase in internal rotation position of the tibia relative to the femur. Greater risk for ACL injury has been seen when torque is applied that causes internal rotation with a combination of valgus where the knee bows inward. There are numerous anatomical contributors to ACL injury that we do not control (Carter et al., 2017).

Through multiple studies, it has been shown females could be at greater risk for ACL sprain or tear due to differences in muscle strength, physical condition, and neuromuscular control. There is no exact or definitive link between gender or age that increase risk for ACL injury. A good way to try to prevent ACL injury is by targeting weak muscles groups that could increase risk. Weak hips have been shown to create “knock-kneed landing positions; therefore, improving strength and joint range of motion can help decrease risk for injury or rehabilitate an individual following an injury. Specific training could include jump routines, learning to pivot properly, and proper education to teach an individual how to prevent valgus maneuvers.

The most beneficial way to prevent injury is through preseason screening programs to assess risk factors and then trying to perform neuromuscular training prior to athletic participation.









Anterior Cruciate Ligament (ACL) Injuries. (2014). OrthoInfo. Retrieved from–conditions/anterior-cruciate-ligament-acl-injuries

Carter, J.C., Sturnick, D.R., Vacek, P.M., DeSarno, M.J., Argentieri, E.C., . . ., Beynnon, B.D. (2016). Relationship between geometry of the extensor mechanism of the knee and risk of anterior cruciate ligament injury. Journal of Orthopaedic Research, 35(5), 965-973. doi:

McCambridge, T. & Myer, G.D. (2010). ACL injuries. Orthopedics, 33(1), 1-2. Retrieved from

By Alexandra Moore and Alee Vladyka, ATC