Does having one leg longer make you more likely to get injured?
We often get patients asking us if having one leg longer makes them more prone to injury. So in this blog, we will answer this question!
How common is leg length inequality?
A 2005 study found that 90% of the population has a leg length inequality, with an average difference of 5.2 mm. So we can see it's pretty common to have one leg shorter than the other. (Knutson 2005)
How is leg length measured?
There are various methods used to measure leg length, but the only way to measure your leg length accurately is via a standing radiograph of the entire leg. Other measures of leg length tend to be prone to error & inaccuracy.
How much a difference is considered relevant?
The same study mentioned above, concludes that leg length inequalities less than 15-20mm are likely nothing to be concerned about. And with only 6.4% of the population having a difference greater than 14mm, it's not that common to have a significant leg length difference. There are conditions in childhood that can result in significant leg length differences, but thankfully these are very rare.
What about leg length and injury?
If we head to the research again here, there is actually very little research to support that leg length inequalities cause injuries:
A 2018 study of high school cross country runners found that leg-length inequality was NOT associated with injury, with the exception that males with a leg-length inequality > 1.5 cm were a greater likelihood of incurring a lower leg (shin/calf) injury. (Rauh 2018)
A 2006 study of military recruits found NO difference in injury between those who had a leg length inequality compared to those who did not. (Goss 2006)
Regarding low back pain, whilst asymmetry in leg length can cause changes in spinal curvature, it is unclear if this actually contributes to low back pain, with limited research to support this.
The multifactorial nature of injuries...
As usual, with all injuries, there is often a combination of multiple factors that cause an injury. So whilst it's possible that large leg length inequalities COULD contribute to injury, there are more than likely other factors at play.
To conclude:
Most people (>90%) have different leg lengths
Significant differences in leg length (>14mm) are rare (6%)
Evidence does not support that significant leg length inequality is a major risk factor for injury
References
Goss DL, Moore JH, Slivka EM, Hatler BS. Comparison of injury rates between cadets with limb length inequalities and matched control subjects over 1 year of military training and athletic participation. Mil Med. 2006;171(6):522-525.
Knutson GA. Anatomic and functional leg-length inequality: a review and recommendation for clinical decision-making. Part I, anatomic leg-length inequality: prevalence, magnitude, effects and clinical significance. Chiropr Osteopat. 2005 Jul 20;13:11.
Rauh, M. J. (2018). "LEG-LENGTH INEQUALITY AND RUNNING-RELATED INJURY AMONG HIGH SCHOOL RUNNERS." Int J Sports Phys Ther 13(4): 643-651.