What runners need to know about leg length discrepancy

Brodie Sharpe

Has someone told you your injuries are due to a leg length discrepancy? It can be a concerning, dis-empowering thought for any runner. But do athletes need to be concerned? Let’s look at the research to find the answers.

Assessing leg length for runners

A paper titled ‘Methods for Assessing Leg Length Discrepancy’ found that without scans, the most reliable method to determine leg length is to measure the distance between the hip bone (ASIS) & ankle bone (medial malleolus). However, a CT scanogram is reported as a sensible alternative when considering accuracy, cost and radiation exposure.

Leg length relevance:

If a runner is found to have a leg length difference with accurate testing, then they share this finding with 90% of the population. That’s right, 90% of humans (with studies including 2.68 million people) will have some form of leg length difference. Additionally, research then found the average difference was 5.2mm and deemed insignificant.

Link to running injury

A leg length difference under 20mm is not likely to cause symptoms that require treatment and reviewing these massive population studies, only 1 in 1000 show a difference greater than 20mm. Then reviewing the research findings above, this would fit our current understanding of running injuries, because our body does an amazing job at adapting to a wide range of running styles. As a result, we should focus on load management and avoiding rapid changes so our body can adapt and stay healthy, rather than handing our control over to a false, dis-empowering narrative.

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