Girls, Boys and Knees

For Young Learners

Clinical Relevance

Start with the observation, because it is solid. In sports that involve cutting and landing, netball, football, basketball, skiing, female athletes tear the anterior cruciate ligament more often than male athletes playing the same sport at the same level. This has been found repeatedly, in different countries and different sports.

The explanation is less settled, and several things probably contribute at once.

Shape. A wider pelvis means the thigh bone runs inwards at a slightly steeper angle to reach the knee. That angle creates a small sideways pull on the kneecap and changes how forces reach the joint.

Movement patterns. On average, female athletes tend to land in a more upright position with the knees closer together. That position puts the knee in a more vulnerable spot at exactly the moment the forces are highest. The phrase people use is dynamic valgus, which just means the knee collapsing inwards.

Muscle balance. The hamstrings at the back help protect the ACL by resisting the shin sliding forward. If the quadriceps at the front are much stronger than the hamstrings, that protection is weaker.

Hormones. Rates appear to vary across the menstrual cycle in some studies. This is genuinely unresolved, and you will find researchers who disagree about how much it matters.

Here is the part that matters most. Movement patterns can be trained, and muscle balance can be built. The training programmes that reduce injury rates work particularly well in female athletes, which tells you something important: this is not a fixed fact about bodies. It is partly a gap in what people get taught.

Historically, girls' sport has had less access to strength and conditioning coaching than boys' sport. Some of the difference in injury rates may be a difference in coaching rather than a difference in knees.