ACL Injuries and Female Athletes

ACL Injuries and Female Athletes

The anterior cruciate ligament (ACL) is one of the most commonly injured areas of the knee. For those of you who have sustained one, will know it's a difficult (but not impossible one to come back from). There are roughly 1000 new ACL injuries every year in Ireland. So with approximately an 80% success rate from surgery, that's almost 200 people every year who may not play sport again! Not even beginning to talk about the implication to movement alone, work etc. So let's talk about it in more detail.

Ligaments are structures of connective tissue that join two bones together to make a joint more stable. The knee joint is one of the load bearing joints in the lower body. It is the meeting point of three bones, the femur, the tibia and the patella (knee cap). The ACL is a ligament which joins the underside of the femur to the top of the tibia and it's main role is to prevent the femur from moving in front of the tibia. There are several other structures around the knee such as the MCL, PCL and LCL but the ACL is the most commonly cited injured area. 

Figure 1. Anatomy of the Knee

The majority of injuries sustained happen through abnormal loading of the knee, combined with the following factors:

1. Reduced knee and hip flexion - poor landing mechanics.
2. Increased knee valgus - knee caves in.
3. Internal rotation of the hip - hip rotates towards the centre of the body.
4. External rotation of the tibia.
5. Muscle imbalances between the quadriceps and the hamstrings - a quad dominant contraction usually places more stress on the ACL.

These happen during the following scenarios:

1. Landing.
2. Deceleration.
3. Side-stepping or cutting.

They are also exacerbated by the present of an opponent nearby. Think of two players jump to compete for a header or during throw in of a football match and one lands heavy on one knee with their knee caved in and hip internally rotated, with the additional weight of their opposite number, the stress placed on the ACL is too great, and then it ruptures/tears.

Figure 2. Infographic adapted from @YLMSportScience outlining the mechanisms of injury.

Why Are Females At Greater Risk?

While both males and females suffer from ACL injuries, the risk is 2 to 6 times higher in females. There are several reasons for this:

1. Greater Q angle compared to males - 8 to 10° vs >15°
2. Increase in certain sex hormones increase the flexibility of the joints.
3. A reduction in muscle strength compared to males means that some stresses are transferred from the muscle to the ligament.
4. Also, in some females, the femoral attachment for the ligament is reduced compared to males. This essentially means that the ACL has limited room to move.
5. Rapid increase in body weight relative to muscle mass increases the stress on the body.
6. Sex hormones also mediate cyclic changes in joint laxity (reducing stiffness and ability to absorb force) across the menstrual cycle.

Prevention > Treatment

With females more at risk of injury, why isn't there more done about it? Or what can be done? Integrating an injury prevention programme during the warm up section of your session (for both males and females) is a good place to start. Exercises that focus on increasing the strength around the hip and the knee, improving landing mechanics, improving postural control, normalising the ratio of quadriceps to hamstring strength, improving their ability to absorb force, developing their deceleration/acceleration mechanics and improving their reactive COD (change of direction) and agility are all proven strategies to reduce the risk of ACL injuries in both males and females, with adolescence females more at risk.

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To read more about the youth athletes (including several female athletes) we've helped over recent years then head over to this link