Iliotibial band: What is the function and how to manage discomfort? 🏃‍♂️🔍

Sports Med U | Educating Minds, Elevating Potential

The Iliotibial Band: A Complex Structure with Versatile Functions

Hutchinson, L.A., Lichtwark, G.A., Willy, R.W. and Kelly, L.A., 2022. The iliotibial band: a complex structure with versatile functions. Sports Medicine, 52(5), pp.995-1008

In today’s letter

• Overview of ITB function and diagnosis/treatment for ITB band syndrome

• Professional take away = A consistent recommendation for recovery involves incorporating progressive overload and graded exposure to challenging activities, while popular interventions such as foam rolling and stretching provide only temporary relief; hip strengthening exercises may offer a longer lasting discomfort relief

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Deep dive

Aim of study

• Collate anatomical and biomechanical information Inform knowledge of the mechanical function of the ITB to enhance understanding of ITBS aetiology, clinical examination, and treatment.

• Concentrate on factors influencing strain and tension in the ITB Specifically explore the roles of the in-series musculature in relation to ITB mechanics.

Background

• The iliotibial band (ITB) is a resilient, fibrous fascial tissue extending from the iliac crest to the lateral proximal tibia, playing a crucial role in the human erect posture.

• The functional roles of the ITB appear to be contingent on posture and activity selection, influenced by the interplay between two in-series muscles: the gluteus maximus (GMAX) and the tensor fasciae latae (TFL).

• Despite its significance, the precise mechanical function and basic anatomy of the ITB remain inadequately understood, contributing to ongoing research in the field.

• Functionally, the ITB is believed to operate as a stabilizing strut during walking, serving as both a hip and knee stabilizer, particularly in the frontal plane, with additional speculation about its potential role in storing elastic energy during walking.

• Runners commonly experience ITB pain, with a prevalence ranging from 5% to 14% of all running-related injuries, highlighting the clinical importance of understanding and addressing issues related to the iliotibial band

Anatomical variance

Evolutionary uniqueness

• Human GMAX muscle, significantly larger than in non-human primates, plays a vital role in enhancing trunk stabilization.

• The distinctive development of a prominent ITB in humans sets them apart anatomically from other primates, with the ITB being structurally different from the fascia lata found in other primate species.

• Unlike in other animals, the termination point of the tensor fasciae latae (TFL) in humans is at the superior thigh, inserting into the femur near the greater trochanter.

• The evolution of bipedality in humans is attributed to the combination of a well-developed GMAX, the shift in pelvic position from horizontal to vertical, and the formation of the unique ITB.

Muscular contribution

• The ITB's anatomy is interconnected with the in-series musculature, specifically the GMAX and TFL muscles.

• Muscles such as GMAX and TFL have direct insertions, either partially or fully, into the ITB, contributing significantly to the functional mechanics of the ITB.

• The TFL exerts an anterosuperior pull on the ITB to flex the hip, while the GMAX pulls posteriorly to extend the hip, highlighting the intricate interplay of these muscles in hip movement.

• Fascia, in general, is theorized to broaden muscle insertions by redistributing or redirecting force transmission within the musculature.

• The ITB, by broadening the insertion of the GMAX muscle and facilitating TFL muscle insertion, plays a pivotal role in transmitting forces from these muscles across both the knee and hip joints.

• Despite these insights, the specific functions of the ITB and the impact of variations in activation levels of the in-series muscles remain largely elusive.

Distal insertion

• While the distal insertion of the ITB is what makes it unique to humans, descriptions of this insertion vary widely

• Though the ITB’s insertion at Gerdy’s tubercle is unani- mous across all authors

• Other commonly published distal insertion points of the ITB are: (Image)

• Recent literature challenges the notion of the ITB as a distinct structure, suggesting it is essentially a thickening of the fascia lata, with unclearly distinguishable margins in cadaveric dissections.

• Inconsistencies in the literature regarding the distal insertions of the ITB create challenges in comprehending its function.

• Alternatively, diverse insertions may indicate distinct force transmission pathways within the ITB, reflecting its numerous potential mechanical functions influenced by posture and muscular activation.

Tensor fascia latae (TFL)

• The mechanical function of the TFL has posed challenges for researchers, leading to varying perspectives in the literature.

• While consensus suggests TFL contributes to hip internal rotation, hip flexion, and knee stabilization, its high electromyographic (EMG) activity in isolated abduction has sparked debate regarding its primary function.

• Despite some speculation about TFL's potential role in hip abduction, the prevailing view in the literature is that any force it applies at the knee is transmitted via the ITB, indicating a stabilisation role at the knee rather than an active contribution to joint movement.

• Gottschalk et al. proposed the concept of the ITB functioning as a "strut" during normal walking, providing frontal plane stabilization of the hip.

• Recent research by Neumann explored the theoretical potential actions of hip muscles and concluded that TFL, with its frontal plane moment arm, could play a role in stabilizing the pelvis in the frontal plane. The mechanical role of TFL likely depends on the posture of the ITB during force production, given its biarticular nature and shared insertion onto the ITB with a muscle opposing hip flexion (GMAX)

Gluteus maximus

• GMAX, recognized as a primary hip joint extensor, boasts substantial muscle volume and a significant hip extension moment arm in the sagittal plane.

• Its involvement extends to external hip joint rotation, hip abduction, and notably, tensioning of the iliotibial band (ITB).

• Due to its extensive physiological cross-sectional area, prominent hip extension moment arm, and a substantial proportion of fibers inserting onto the ITB, GMAX is likely capable of transmitting greater force through the ITB compared to the tensor fasciae latae (TFL) in the sagittal plane.

• The biomechanical role of the GMAX muscle portion that inserts on the ITB remains a subject of considerable debate.

Knee stability

• The insertions of GMAX and TFL into the ITB have sparked speculation among researchers regarding their potential impact on lateral knee stabilization.

• Notably, attachments to the patella play a stabilizing role against medial dislocation, offering a mechanism for patellar stability.

• The ITB's attachments to the anterior and lateral tibia serve to resist anterolateral subluxation, particularly crucial in the pivot shift mechanism of an ACL-deficient knee.

• Knee stabilization mechanisms involving the ITB are contingent on factors such as attachment location, loading, mechanical behaviour and posture.

• In a fully extended knee, ITB insertions alone do not prevent anterior dislocation in an ACL-deficient knee.

• Beyond 30° of knee flexion, ITB attachments demonstrate the ability to reduce anterior translation in an ACL-deficient knee, notably in the pivot shift mechanism.

• Cadaveric studies form the basis of much of the cited research, presenting a limitation as the forces applied through the ITB are passive, overlooking potential substantial forces from GMAX or TFL during dynamic activities like walking and running.

• The precise contribution of the ITB to knee stability remains challenging to discern without a comprehensive understanding of how forces are applied in various postures.

Knee compression forces

• Knee joint stability can be achieved by the ITB's resistance to external adduction moments and the application of knee compression force to the femur through ITB tensioning.

• Magnetic resonance images show compression in the tissues between the distal ITB and the lateral femoral epicondyle during ITB tensioning.

• The current theories regarding the origin of iliotibial band syndrome (ITBS) suggest a compression syndrome, indicating that the enhanced knee joint stability may lead to potentially unfavorable excessive compression, especially in the presence of varus knee torques.

Ex vivo and In vivo Material Properties and Elastic Function

Material properties

• Understanding the material behavior of the ITB is crucial to understand its roles in human locomotion and stability.

• The ITB serves as a connection point for muscles (GMAX and TFL) to bones (pelvis, femur, and tibia), suggesting tendon-like material properties that contribute to joint stability and potential involvement in elastic energy storage and release, like the Achilles tendon.

• Although the general material properties of the ITB are well-documented, the overall mechanical behaviour of the entire structure remains less transparent.

• Tensioning of ITB fibres during hip extension occurs anterior to posterior, leading to varied tension across different regions of the band based on movement patterns.

• The transmission of forces within the ITB is likely diverse, influenced by the specific muscles generating forces, which, in turn, is contingent on leg posture and the necessity for force generation at any given moment.

Elastic function

• Human legs feature spring-like tendons, optimising the economical storage and release of energy during movement.

• Energy-saving structures include the Achilles tendon, plantar fascia, ITB, and peroneus longus.

• The Achilles tendon plays a predominant role, contributing around 35-40% (35 J) of positive work during the stance phase of running.

• Research indicates that the ITB can store up to 5% of the total positive work in a moderately paced run, roughly 14% of the work contributed by the Achilles tendon.

• Eng et al.'s model suggests that the posterior ITB (portion with GMAX muscle insertion) can transmit larger forces than the anterior (portion with TFL muscle insertion), leading to greater energy absorption.

• Assessing the energetic contributions of soft tissues is challenging due to the numerous degrees of freedom and difficulties in directly accessing their kinetic contributions to motion..

Clinical Significance

Pathomechanics of Iliotibial Band Syndrome (ITBS)

• ITBS is a prevalent overuse injury with significant impact on athletes.

• Lateral knee pain, often exacerbated by band tension during activities like single-leg stance, characterizes ITBS.

• ITBS ranks as the most common relative overuse injury at the lateral knee, constituting approximately 12% of all running-related injuries, with notable contributions to cycling and military-related injuries.

• Two proposed mechanisms explain how the mechanical behavior and function of the ITB contribute to ITBS.

• Historically viewed as a friction injury, it was believed that cyclic loading during activities like running and cycling caused the band to traverse the lateral epicondyle, leading to irritation of the innervated fatty tissue underneath.

• Recent questioning of the friction mechanism by Fairclough et al. suggests that the illusion of friction is created by sequential load shifting of ITB fibers from anterior to posterior during tensioning.

• A new theory, supported by magnetic resonance imaging (MRI), proposes that when the knee is flexed beyond 30°, the band compresses medially against the lateral femoral epicondyle, causing irritation to the highly innervated fat between the band and bone.

• This compression mechanism suggests that ITBS should be classified as a compression syndrome rather than a friction injury.

Running kinematics

• Noehren et al. and Friede et al. found that Individuals developing ITBS showed increased hip adduction and knee internal rotation during running compared to controls

• Runners with prior ITBS histories, as per Foch et al.'s research, exhibited reduced hip adduction in comparison to healthy controls.

• Studies reveal a gradual decline in peak hip adduction angle during prolonged runs, possibly indicating strategies to alleviate pain.

• These findings suggest that runners may adopt altered patterns to reduce strain on the ITB once pain becomes evident.

Diagnosis of ITB syndrome

• Runners experiencing (ITBS) commonly report lateral knee pain situated approximately 2–3 cm proximal to the lateral tibiofemoral joint line, specifically around the lateral femoral condyle.

• The onset of ITBS pain is typically insidious, often following a recent surge in running loads, marked by increased running distance or a higher volume of downhill running.

• Individuals with particularly irritable ITBS may feel pain during stair descent in the stance limb, coupled with hip extension and knee flexion as the (TFL) muscles contract eccentrically to aid in lower limb control.

• To ensure an accurate diagnosis, alternative sources of lateral knee pain, including patellofemoral pain, lateral meniscal lesions, lateral synovial plica syndrome, and distal femoral bone stress injuries, should be ruled out through specific clinical assessments and screenings.

• Gluteal tendinopathy and lumbar radiculopathy, conditions that commonly refer pain to the lateral thigh and knee, should also be considered and ruled out in patients presenting with suspected ITBS.

The nobles test

• The diagnostic evaluation for suspected ITBS relies primarily on the Noble compression test

• In the Noble compression test, manual pressure is applied to the lateral knee, specifically 1–2 cm proximal to the lateral femoral condyle, while the knee is passively extended through a range of motion from 60° to full extension.

• A positive result in the Noble compression test involves the reproduction of lateral knee pain when the knee is positioned at approximately 30° of knee flexion. However, caution is advised in interpreting test results as the Noble compression test has unknown positive and negative likelihood ratios.

The Ober’s Test

• Clinicians frequently use the Ober test to evaluate ITB "tightness."

• Both the classic and modified versions of the Ober test are based on the assumption that an injured ITB is tighter than a healthy ITB, yet neither version seems to effectively measure ITB "tightness."

• A positive result in either Ober test is associated with restrictions in the hip capsule and the musculature of the gluteus medius and minimus.

• Neither version of the Ober's test is particularly helpful in diagnosing ITBS or assessing ITB "tightness." 

• Individuals with ITBS commonly exhibit hip abductor weakness.

• The weakness in hip abductors is considered a consequence of ITBS rather than a contributing factor.

• Due to the absence of prospective studies and an unclear relationship between hip abduction strength and ITBS, it is hypothesized that pain arising from distal compression in the highly innervated tissues within the ITB may hinder proximal hip musculature.

• The tensor fasciae latae (TFL) and gluteus maximus may adaptively engage in a strategy to diminish tension in the ITB.

• The presence of hip weakness is concurrent with ITBS rather than being a causative factor in the onset of this injury

Treatment of ITBS

• Scientific literature on ITBS treatment is primarily composed of narrative reviews or case series, often of low quality.

• Despite the limited quality of available literature, a consistent recommendation for recovery in individuals with ITBS involves incorporating progressive overload and graded exposure to progressively challenging activities.

Foam rolling & stretching

• Foam rolling of the ITB is a common recommendation for runners dealing with ITB "tightness" or ITBS.

• Despite its popularity, the flexibility changes induced by foam rolling are brief or minimal, and any pain relief achieved through this method is temporary, lasting only a few minutes.

• Stretching the ITB poses challenges, particularly in the context of evaluating ITB "tightness," as seen in the Ober test.

• A recent study by Friede et al. employed shear-wave elastography to investigate ITB stiffness in both healthy participants and those experiencing ITBS symptoms after a 6-week training period.

• Surprisingly, the study found no discernible differences in ITB stiffness between healthy individuals and those with ITBS.

Hip strength

• Hip strengthening is a common recommendation for individuals dealing with ITBS.

• A hip-strengthening program showed concurrent resolution of hip weakness and pain in runners with ITBS; however, caution is advised in attributing causation to hip weakness since it typically follows the onset of ITBS.

• Notably, hip strength does not seem to correlate with hip adduction during running, contrary to a prevalent belief among clinicians.

• Furthermore, engaging in hip strengthening exercises does not lead to a reduction in hip adduction during running.

• An alternative explanation for the pain relief experienced in individuals with ITBS following hip strengthening could be that targeted loading exercises, like intensive hip strengthening, have the potential to alter central pain processing and diminish local hyperalgesia.

Runnining biomechanics

• Targeting running biomechanics to alleviate suspected increases in ITB strain and subsequent compressive loads on the lateral knee holds promise.

• A study by Meardon et al. employed a subject-specific musculoskeletal model during running, revealing that adopting a wider step width effectively reduces ITB strain.

• Providing feedback on step width can be easily achieved using a full-length mirror during treadmill running.

• Another effective intervention involves increasing running cadence (stride frequency), as it has been shown to reduce both ITB strain and strain rate in a comparable musculoskeletal model.

• Encouraging an uptick in running cadence can be seamlessly implemented during routine, in-field runs through the use of commercially available wearable devices