Identifying changes in leg joints of female runners during puberty

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Females runners experience greater forces on their knee joints in the later stages of puberty than in the earlier stages. This discovery was made by a research team led by Associate Professor Adam Bryant from the Centre for Health, Exercise & Sports Medicine.

When the foot hits the ground during running, a force travels through the foot and up the leg. The size of the force that reaches each joint depends on an individual’s body characteristics – such as weight and height – as well as their muscle strength.

Knee injuries during puberty are more common for females than for males. This may be because bone and muscle grow at different times in each group. In females, but not males, growth of the long leg bones precedes muscle growth, so their muscle strength is comparatively lower. The research team proposed that this might make it harder for female adolescents to control their movement during running. It might also cause higher forces on the knees.

To test the hypothesis, the researchers stuck small reflective markers on the hips, knees, shins and feet of 91 females who were at different stages of puberty. Cameras tracked how the markers moved while the participants ran barefoot. A force plate was used to measure the impact on the ground as they ran. The researchers used this information to calculate the forces acting on the hip and knee joints.

They found that the forces affect the knee and hip joints differently depending on whether a female runner is pre-pubertal, pubertal or post-pubertal.

For example, the rotational force pushing the knee into a bent position was higher during and after puberty than before puberty. During running, this force causes high stress to structures at the front of the knee, such as the knee cap.

In addition, the rotational force pushing the knee outwards was higher after puberty than before puberty. This force causes a bowed knee and leg position during running. Biomechanists think that this contributes to knee-cap pain (or patellofemoral pain), which is common in females going through puberty.

There was no difference in the opposing rotational force that pushes the knee towards the body, or in the inwards rotation of the knee, between females at different stages of puberty.

The forces acting on the hips also changed during puberty. The researchers found that the force pushing the hip away from the body was higher before the onset of puberty than in later stages of puberty. In addition, the force pushing the hip to bend (causing forward movement of the thigh) was higher both before puberty and in early/mid-puberty.

Next steps

In collaboration with researchers from Griffith University, the research team has used data from this project to refine a model for calculating muscle and joint forces, which they developed together. They will use this to study how footwear affects the forces on knee joints in Australian Football League Women’s players, both on the field and in the laboratory.

Funding

• ARC Linkage Project (LP150101041)
• NHMRC Australian Government Research Training Program Scholarship (APP1075881)
• NHMRC Principal Research Fellowship (1058440)
• ARC Future Fellowship (FT130100175)
• NHMRC Career Development Fellowship (1053521)

Publication

Sayer TA et al (2018) Differences in hip and knee running moments across female pubertal development. Medicine & Science in Sports & Exercise 50(5): 1015–1020. doi: 10.1249/MSS.0000000000001525

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