With the soccer and netball seasons over, the steady stream of knee injuries presenting to the emergency department has eased. I thought this may be a good time to share some information about a common knee injury, the ACL tear, and discuss some ways of preventing these injuries.
We've all heard about anterior cruciate ligament, or ACL, tears ending careers in professional athletes. But most of us are unaware that the highest risk group is recreational female athletes aged 15 to 25. This group is five times more likely to suffer ACL tears than men. These injuries typically occur in sports involving sudden changes of direction, such as soccer, hockey and netball, but can also result from hard landings after jumps or even direct blows to the knee.
The ACL is located in the middle of the knee, connecting the back of the femur (thighbone) to the front of the tibia (shinbone).
Knees are weak and wobbly joints and it's up to the ligaments to keep the knee from buckling. The ACL acts as a tether, keeping the shin from sliding forward of the thigh.
There are lots of theories as to why females are especially susceptible, but it probably comes down to several factors. Female hips are wider than men's, creating a slant to the thighbones that makes women a few degrees more knock-kneed than men. Under the strain of landing from a jump, this increased angulation forces the knee inward, straining the ACL.
Female athletes have weaker and slower-to-activate hamstring muscles than men. Hamstrings act as shock absorbers for the ACL and when they're weaker the ligaments have to absorb more of the strain. Weaker muscles combined with increased flexibility and more mobile joints also contributes to increased risk of ACL tears in women.
Oestrogen, which affects the stretchiness and strength of connective tissue, also probably plays a role in ACL tears.
Whatever the mechanism, the rates of ACL tears among young female athletes are high and are increasing. For many this will mean time off and a lengthy rehabilitation; for others it will mean surgery or giving up their chosen sport. Next week we'll discuss preventing ACL tears.