A runner came to our clinic this past week with a brand new pair of orthotics as he was found to have a leg length discrepancy of half a centimetre (cm). He ran the Singapore Stan Chart marathon last week with them and ended up with a slight injury.
I had previously written about how it is very common to have a leg length discrepancy (LLD) and that most of the time it did not matter for most people. I had not provide any references to justify my post then so please allow me to do so now.
Actually, 90 percent of people have a LLD of up to 1 cm (Gordon and Davis, 2019). Knutson et al (2005) also reported that that the most people have an average leg length difference was 0.52 cm and for majority of people this difference does not matter unless there is a difference of 2 cm or more.
What about runners? Would having different limb lengths cause an injury for runners? Many healthcare professionals insist LLD can cause injuries and will often prescribe orthotics to correct this discrepancy.
While running, there is only single leg stance phase (where one foot contacts the ground) and some flight time (where both feet are off the ground) before the other foot contacts the round. At no point is both feet on the ground at the same time when we run (running does not have double leg stance phase unlike walking).
LLD actually has a greater effect on double leg stance (both feet contacting the ground) activities. During single leg stance activities, the effect is lessened as the gluteal (or buttock) muscles, especially gluteus medius work to stabilize the pelvis.
Hence, running is less likely to be affected by leg length differences and studies have shown that LLD was not associated with the development of a running injury (Hespanol et al, 2016).
Rauh et al (2018) did find that male runners with a LLD greater than 1.5 cm had a greater chance of developing a lower leg (shin/ calf) injury.
Now you know that LLD of up to 1 cm are very common and unlikely to cause pain in many cases, especially runners. There is also insufficient strong evidence when to start treatment and it should not be based solely on the length of the LLD.
If the gluteus muscle is weaker on the left (pictured), it can cause a functional leg leg difference and cause that side of the pelvis to drop lower. If the difference is above 2 cm, there is a higher chance that biomechanics are affected and can cause problems. Majority of people do not have this.
What about differences of 1 to 2 cm? Personally I believe if it ain't broken, don't fix it. Meaning only if a patient or runner's condition is causing pain then we it may be worth exploring if changing hip or leg strength helps.
References
Gordon J, Eric MD, Davis DE (2019). Leg-Length Discrepancy : The Natural History (And What We Really Know). J Ped Ortho. 39():p S10-S13. DOI: 10.1097/BPO.0000000000001396
Kuntson GA (2005). Anatomic And Functional Leg-Length Inequality: A Review And Recommendation For Clinical Decision-Making. Part 1, Anatomic Leg-Length Inequality: Prevalence, Magnitude, Effects And Clinical Significance. Chiro Man Therap 13,11. DOI: 10.1186/1746-1340-13-11
Hespanhol Junior LC, de Carvalho AC, Costa LO et al (2016). Lower Limb Alignment Characteristics Are Not associated With Running Injuries In Runners: Prospective Cohort Study. Eur J Sp Sci. 16(8): 137-144. DOI: 10.1080/17461391.2016.1195878
Rauh MJ (2018). Leg-Length Inequality And Running-Related Injury Among High School Runners. Int J Sp PT. 13(4): 643-651. PMID: 30140557
No comments:
Post a Comment