By Eric Foch, PhD

The mixed findings of several cross-sectional studies seem to suggest that no specific biomechanical variables are unequivocally associated with iliotibial band syndrome in either men or women, which underscores the importance of assessing each patient individually

Running is a popular choice of physical activity among exercisers, as well as germane to the conditioning of athletes and military populations. Running confers musculoskeletal health benefits,^1,2 but the likelihood of a runner sustaining an overuse injury is high. Previous prospective investigations indicate that the overuse injury rate among runners during a 12-month period ranges from 56% to 85%.^3-6 A similar overuse injury rate of 74% was reported in a more recent retrospective investigation in collegiate cross country runners.⁷

The knee is the most commonly injured anatomical location, accounting for 25% to 42% of all reported running-related overuse injuries.^4,8 Iliotibial band syndrome (ITBS) is the most common cause of lateral knee pain and the second most common injury sustained by runners.⁸ Furthermore, women are two times more likely to develop ITBS than men.⁸ Gender differences in biomechanics during running have been reported between healthy female runners and male runners.^9,10 Female runners exhibit greater hip adduction,^9,10 hip internal rotation,¹⁰ and knee abduction^9,10 angles than men during stance. Collectively, throughout the stance phase of running, women demonstrate different lower extremity alignment in the frontal and transverse planes compared with men. The differences in movement patterns between genders may suggest the existence of different etiologies of ITBS for men and women.

Functional anatomy of the iliotibial band

The iliotibial band functions to stabilize the lateral hip and knee, as well as limit hip adduction and knee internal rotation.¹¹ Greater hip adduction and knee internal rotation angles during knee flexion and extension may increase the tensile and torsional strain experienced by the iliotibial band.¹² A combination of increased tensile strain, torsional strain, or both may damage the iliotibial band over the course of many miles run.¹³

Furthermore, increased strain may compress a highly innervated fat pad that lies between the iliotibial band and lateral femoral epicondyle. Compression of this fat pad also may be a source of pain associated with ITBS.¹²

Kinematics of ITBS in female runners

Prospective evidence indicates that female runners who later develop ITBS exhibit greater peak hip adduction and knee internal rotation angles during stance at baseline, compared with female runners who remain uninjured.¹⁴ This hip and knee movement pattern may contribute to the pain associated with ITBS.

Prospective studies are the gold standard for experimental design, in particular for determining cause and effect relationships between variables. However, conducting a prospective investigation is costly in terms of participant recruitment and adherence.¹⁴ Alternatively, cross-sectional investigations are less time-consuming and can provide insight into determining associations between biomechanics during running and ITBS injury status. No ITBS study has investigated whether runners’ biomechanics postinjury are the same as before their first incidence of ITBS. However, approximately half of runners who experienced an overuse injury reported a previous injury to the same anatomical site.¹⁵

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The results of previous cross-sectional investigations differ with respect to associations between greater hip adduction or knee rotation and current or previous ITBS in women.^16-20 Women with previous ITBS indeed exhibit greater peak hip adduction and knee internal rotation angles compared with controls.¹⁶ However, the literature also reports less hip adduction motion in women with previous ITBS^17,19 and current ITBS²⁰ compared with healthy women. Additionally, a 2015 study found that women with current ITBS exhibit greater hip external rotation angles in late stance compared with healthy women, a finding that has not been reported elsewhere.²⁰ At the knee, internal rotation angles have been reported to be similar between healthy runners and those with previous ITBS^17,19 and current ITBS.²⁰

The current theory that excessive frontal and transverse plane hip and knee motion influences iliotibial band mechanics is elegant in its simplicity. However, the equivocal findings in the literature suggest that determining how biomechanics during running are related to ITBS in women is considerably more complex. Greater peak hip adduction and knee internal rotation angles may be predictors of ITBS in women. But the differences in findings among studies with respect to excessive peak hip adduction and knee internal rotation angle in women with ITBS may indicate that a female runner’s injury status does affect the way she runs.

For example, in women with previous ITBS, decreased hip adduction angle may be a compensatory running strategy developed after ITBS symptoms have abated¹⁹ or a way to limit pain while the injury is current.²⁰ Running with the hip in a less adducted position may decrease the tensile strain experienced by the iliotibial band, thereby lessening the pain.^12,17,19

Kinematics of ITBS in male runners

Relative to the body of literature that reports biomechanical factors associated with ITBS in women, few studies have investigated ITBS in men. Specifically, no prospective ITBS investigations of male runners have been reported. Additionally, running biomechanics have been compared only between men with current ITBS and healthy male runners,^20,21 and men with current ITBS exhibit greater peak hip internal rotation and knee adduction during early stance than controls.²¹ The combination of excessive hip internal rotation and knee adduction may elongate the iliotibial band, increasing iliotibial band strain.

Distal to the iliotibial band, ankle internal rotation is different between male runners with current ITBS and healthy male runners.²⁰ However, since greater ankle internal rotation suggests a decrease in tibial internal rotation relative to the foot, it is unclear how less tibial internal rotation would negatively affect the iliotibial band. It may be a protective mechanism through which male runners with ITBS limit iliotibial band strain. These two studies suggest that, for male runners, both proximal and distal kinematic factors may be associated with the etiology of ITBS.

Hip strength and its association with ITBS

Researchers have hypothesized that increased hip adduction during the stance phase of running may demand greater eccentric activity from the gluteal musculature.^14,16 This greater eccentric activity would be reflected in the magnitude of the hip abduction moment. During running, peak hip abduction moment has been reported to be similar among female runners who later developed ITBS, those with current ITBS, those with a history of ITBS, and healthy women,^14,16,18,19 but has not been studied in men with current ITBS.

No difference in hip abduction moment in women with ITBS may suggest that this population is characterized by differences in the timing of gluteal muscle activation rather than the magnitude of the activity.¹⁴ However, the activation of two primary hip abductors, the gluteus medius and tensor fasciae latae, have not been directly measured in previous ITBS studies.

In healthy female and male runners, there is no difference between genders for peak, average, and onset timing of gluteus medius muscle activation during running, even though women demonstrated greater peak hip adduction than men.⁹ It was concluded that the timing of gluteal muscle activation likely does not play a significant role in overuse injuries associated with hip adduction.⁹

The hip abduction moment during running is a submaximal measure of strength. A maximal measure of hip abduction strength may provide insight into biomechanical factors associated with ITBS even if it is not measured during running. Findings in the literature on this topic are mixed. Maximal isometric hip abductor weakness has been reported in groups that consist of both male and female runners with current ITBS^11,22 and of only male runners with current ITBS.²¹ However, women with previous ITBS exhibit less isometric hip abductor strength compared with female runners with current ITBS and with healthy runners.¹⁹

In the latter study, women with current ITBS flexed the trunk more toward the stance limb in the frontal plane compared with female runners with previous ITBS and healthy runners. This may represent a compensatory strategy on the part of female runners with current ITBS to reduce the demand on the hip abductors.¹⁹ Consequently, less hip abductor strength in runners with previous ITBS may be a residual effect of greater trunk ipsilateral flexion that was used during running when previously injured.¹⁹ Therefore, treatment for ITBS should target trunk motion, as well as hip abductor strength, even after the pain associated with ITBS has diminished.

Whereas a handful of studies in the ITBS literature have examined hip abductor strength in runners, only one has investigated hip external rotation strength.²¹ The hip external rotators play an important role in maintaining transverse plane control of the hip.²³ During running, hip external rotator weakness may result in a decreased ability to limit hip internal rotation, thereby increasing iliotibial band strain.²³ Indeed, male runners with current ITBS who demonstrate increased hip internal rotation compared with controls also exhibit less isometric hip external rotator strength than healthy men.²¹

Collectively, these results provide evidence that men and women should be considered separately when investigating strength differences associated with ITBS. When treating patients with ITBS, strengthening the lower extremity musculature as a whole through multijoint exercises could aid in preventing any new or further strength deficiencies.

Hip strength training in runners

The reported findings that excessive hip and knee movement patterns during running are associated with ITBS and may play a role in its etiology suggest that, potentially, runners with ITBS who do exhibit greater hip and knee motion than healthy runners may benefit from strength training. However, few studies have examined this possibility.

One study has investigated the effect of strengthening the hip abductors and external rotators in healthy female runners with no history of ITBS but who exhibited excessive hip adduction during running.²⁴ After a six-week training program of three sessions per week, the women significantly increased their hip abductor and external rotator strength. However, hip and knee kinematics remained unchanged following the program.²⁴ These findings indicate that, to improve form during running, there is not anything to suggest that increasing lower extremity strength alone is beneficial.

Gait retraining

Recently, the concept of implementing gait retraining strategies to alter joint kinematics in runners with knee overuse injuries has been studied, with promising results.²⁵ Eight women with patellofemoral pain were provided with real-time kinematic feedback on hip adduction angle during the stance phase of running for eight sessions. Feedback was gradually removed over the last four sessions. At the one-month follow-up session, the women still demonstrated improved lower extremity pelvis and hip alignment during the stance phase of running.²⁵ This improvement in hip mechanics was associated with a reduction in pain.

Outpatient orthopedic physical therapy clinics often do not have the luxury of a 3D motion capture system. However, verbal instructions and feedback can be provided by the clinician to the runner; for example, giving the instruction, “attempt to run with your knee pointing straight ahead,”²⁵ during treadmill running. This may be an effective and economical feedback measure to alter biomechanics during running. Additionally, in a 2014 study, healthy male and female runners were able to decrease peak hip adduction angles by landing with their feet on pieces of tape placed along a runway.²⁶ Instructing a runner to land with her feet wider apart during running may also be a simple yet effective feedback measure to improve lower extremity alignment during stance.

Conclusion

Researchers have made considerable efforts to understand biomechanical risk factors associated with overuse running injuries in order to improve treatment and prevention. However, there has been no significant decrease in injury rates during the past 30 years.⁷ The alterations to biomechanics during running seen in studies of runners with other overuse injuries may also be beneficial to runners with ITBS, and to women in particular. However, the mixed findings of several cross-sectional ITBS studies seem to suggest that no specific biomechanical variable are unequivocally associated with ITBS in either men or women. For example, not all runners with current or previous ITBS exhibit greater hip adduction during running or hip abductor weakness compared with healthy runners.

Collectively, there is likely not a generalizable gait retraining or rehabilitation intervention for male and female runners with current ITBS. The findings reported in the literature should be used as a guide for clinicians treating patients with ITBS. What the literature indicates is that hip strength and atypical trunk, hip, and knee movement patterns are associated with ITBS. Therefore, when a clinician is presented with a runner with ITBS symptoms, these biomechanical factors should be assessed, and a patient-specific rehabilitation plan can be developed and implemented accordingly.

Eric Foch, PhD, is an assistant professor of biomechanics at Central Washington University in Ellensburg.

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