Does Having Different Leg Lengths Cause Injuries?

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

Reliable Predictors Of Running Injuries

You need a new pair of running shoes so you decide to go to a specialist running store to choose a pair that's suitable for you. The store manager at the specialist running store tells you to hop onto their in store treadmill and 'analyzes' your running gait.

He then proceeds to critique your running gait and its biomechanical implications. And suggests the most expensive running shoe (in the store) for you so you do not get injured. Is that a common scenario that happens?

Contrary to several long held beliefs, most biomechanical and structural factors are not reliable factors at predicting running injuries. 

Researchers studied 300 runners who have been injury-free for the past six months and found several more reliable factors (rather than biomechanical and structural factors) in predicting who would be more likely to get injured.

The runners' demographics, physiology, biomechanics, psychosocial issues and training were documented. Their hamstrings, quadriceps muscle strength, knee, ankle flexibility, arch height of their feet were tested. 

A gait analysis studied how their feet, knees and hips distribute forces while running

Any runner who reported an injury were followed up at six and twelve months later. After the first year, the researchers emailed the injured runners a biweekly questionnaire asking them what injuries they sustained in the past two weeks.

Those that were injured went to a doctor and physiotherapist who were part of the study for treatment.

Results of their study after the two year follow up indicate that female runners sustain injuries at a higher rate than male runners. Stiffness in the knee joint, which were more common in runners weighing more than 80 kg significantly increases the chances of an overuse running injury. 

The runners who were injured also reported significantly worse mental health related to their quality of life and more negative emotions compared to the non injured runners.

Most biomechanical, structural factors like arch height, overpronation, flexibility, Q-angle  (see picture above), lower limb strength, weekly mileage, footwear and previous injury are not reliable factors for overuse running injuries.

The researchers recommended that caution should be used when trying to alter what were commonly thought risk factors such as excessive pronation, poor flexibility, weekly mileage etc unless a runner has extreme values.

It appears from this study that the importance of biomechanics and anatomical structures assumed by doctors, physiotherapists, personal trainers and other clinicians are not as high risk as assumed. 

I feel that this does not mean they are not important. It is still important to consider the individual patient/ runner when assessing their condition. 

We still need to be aware of each patient's individual structural and biomechanical anomalies, but not to the point where we nitpick every discrepancy in strength, joint angle, foot position and range of motion.      

Reference

Messier SP, Martin DF, Shannon L et al (2018). A 2-Year Prospective Cohort Study Of Overuse Running Injuries: The Runners Injury Longitudinal Study (TRAILS). AJSM. 46(9): 2211-2221. DOI: 10.1177/0363546518773755

No Need To Stretch Or Foam Roll Your ITB?

You are a runner and you haven't been able to run more than 2 km before a sharp pain in your outer knee reduces your run to a hobble. Resting, icing and changing your running shoes made no difference. The sports doctor you saw just diagnosed you with the dreaded Iliotibial Band Syndrome (ITBS). He tells you that you need to stretch your Iliotibial band (ITB) and use a foam roller.

Sounds familiar? Well, this latest published paper on the ITB by Paul Giesler (2020) challenges common treatment approaches of stretching and massaging the ITB. Basically, he says that you do not want to stretch or foam roll your ITB.

Attachments of ITB at L knee

I've written about the ITB before in a few different posts. Except for Daniel Liberman and Carolyn Eng's study, most other articles seem to suggest that the ITB causes pain via a 'friction syndrome'. This is thought to be due to the ITB rubbing to and fro over Gerdy's tubercle on the outer shin bone while running due to hip weakness. 

Treatment is normally targeted at stretching the ITB (to reduce friction). Doctors will often suggest a steroid injection to reduce 'inflammation' (in the bursa) on the outer knee.  Giesler (2020) however,  suggested that ITB pathology is more likely to involve compression of sensitive structures beneath the ITB rather than friction.

also know as Iliotibial tract (ITT)

Since the ITB is a really broad, strong and complex structure with many attachments (picture above) along the hip, thigh and around the knee, it can provide stability for both the hip and knee. Like I wrote before, the ITB is actually thought to function like our Achilles tendon. To store and release energy like a spring. Therefore you cannot and would not want to stretch a spring. A coiled spring can release energy much better than a spring that is stretched out.

From Carolyn Eng's running simulation 

Hence the need to treat the cause of the problem rather than just treating the pain over the outer knee. Hip strength and control thus thought to be key in causing ITBS, especially weakness in hip increased hip adduction (dropping of the hip inwards) during loading. 

Runner on L has increased hip adduction

In runners/ patients with excessive hip adduction while running, progressive rehab and addressing potential causes should be adapted for individual runners, especially while running downhill and during longer runs. I've written on this topic specifically, you can read that article here.

So treatment should be to calm the symptoms (knee pain) and treat the cause. We don't get you to stretch your ITB or use the foam roller in our clinics, come see us if you want to run pain free.

The Paul Geisler (2020) article is free, click on the link under references if you want to read it.

References

Bramah C, Preece SJ Nimh G et al (2018). Is There A Pathological Gait Associated With Common Soft Tissue Running Injuries? AJSM. 46(12): 3023-3031. DOI: 10.1177/0363546518793657

Eng CM, Arnold AS, Liberman DE et al (2015). The Capacity Of The Human Iliotibal Band To Store Elastic Energy During Running. J Biomech. pii: S0021-9290 (15) 00354-1. DOI:10.1016/j.jbiomech.2015.06.017.

Geisler PR (2020). Iliotibial Band Pathology: Synthesizing The Available Evidence For Clinical Progress. J Ath Trg. DOI: 10.4085/JAT0548-19