Iliotibial Band – Origin, Nerve Supply, Function

Iliotibial Band/Iliotibial band Muscle or IT band (ITB) is a longitudinal fibrous sheath that runs along the lateral thigh and serves as an important structure involved in lower extremity motion. The ITB is also sometimes known as Maissiat’s band.  The ITB spans the lower extremity on its lateral aspect before inserting on Gerdy’s tubercle on the proximal/lateral tibia.

The iliotibial tract or iliotibial band (also known as Maissiat’s band or IT band) is a longitudinal fibrous reinforcement of the fascia lata. The action of the ITB and its associated muscles is to extend, abduct, and laterally rotate the hip. In addition, the ITB contributes to lateral knee stabilization. During knee extension, the ITB moves anterior to the lateral condyle of the femur, while ~30 degrees knee flexion, the ITB moves posterior to the lateral condyle.

Anatomy of Iliotibial Band Muscle

Proximally in the thigh, the ITB receives fascial contributions from the deep fascia of the thigh, gluteus maximus, and tensor fascia lata (TFL).[rx]  The TFL is the deep investing fascia of the thigh, encompassing the muscles of the hip and lower extremity around this region.[rx] Distally, the ITB becomes a distinct soft tissue layer of the lateral knee.[rx]

Regardless of the ITB condition, most patients experience complete resolution of symptoms following nonoperative management modalities alone.  However, surgical consideration is a potential option for chronic, recurrent, or recalcitrant cases that continue to persist despite exhausting of all nonoperative management options after several months.

Structure and Function of Iliotibial Band Muscle

Origin, insertion, and structure

The detailed anatomic structure of the ITB, TFL, and its origins, insertions, and variations have been debated for decades in the literature.  Huang delineated the proximal anatomy in a recent study from 2013.[rx]

Proximal anatomy

• TFL 

  • Separate origin of TFL fibers originates off the ilium and in between the superficial and intermediate IT layer origins
  • Distally, the TFL becomes a tendinous structure as it merges with the superficial and intermediate IT layers
  • Farther distal, the TFL tendinous fibers, including the superficial and intermediate IT layers, fuse as a single confluent structure near the level of the GT

Gluteal contributions

Distal anatomy

• Proximal to the knee joint, the ITB attaches to the intermuscular septum and supracondylar tubercle of the femur.  Proximal to the lateral epicondyle, there is an interposed fat layer between the ITB and the vastus lateralis.[rx]
• The ITB is more tendinous proximal to the lateral femoral epicondyle, and at the level of the epicondyle, the ITB contributes to lateral knee stability secondary to its anatomic position, intimal contact with the epicondyle, and relative to its location with respect to the lateral collateral ligament (LCL).[rx]

Function

Proximal ITB function includes[rx]:

• Hip extension
• Hip abduction
• Lateral hip rotation

Distally, ITB function depends on the position of the knee joint[rx]

• 0 degrees/full extension to 20 to 30 degrees of flexion

  • Active knee extensor

    • The ITB lies anterior to the lateral femoral epicondyle

• 20 to 30 degrees of flexion to full flexion ROM

  • Active knee flexor

    • ITB lies posterior relative to the lateral femoral epicondyle

Blood Supply of Iliotibial Band Muscle

The ITB, being a tendinous extension of the tensor fascia lata (TFL), shares the same arterial supply:

• Ascending branch of the lateral femoral circumflex artery (LFCA)
• Superior gluteal artery (SGA)
• The LFCA traverses the TFL as a single branch from the profundus femoris arterial system usually 6-10 cm distal from the anterior superior iliac spine (ASIS) directly into the muscle belly.
• The SGA is the largest branch of the posterior division of the internal iliac artery and exits the greater sciatic foramen where it divides into superficial and deep branches.
• The latter of which also provides collateral arterial blood supply to the TFL in addition to the gluteus medius and minimus muscles.[rx]

Nerves

• Analogous to the arterial blood supply, the ITB shares the innervation of the TFL and gluteus maximus via the superior gluteal nerve (SGN) and inferior gluteal nerve (IGN), respectively.
• The SGN arises from the ventral rami of nerve roots L4-S1 and originates from the lumbosacral nerve plexus.  Like the SGA, the SGN exits the pelvis via the greater sciatic foramen to innervate the TFL as well as the gluteus minimus and medius (both hip abductors and medial rotators). The IGN is comprised of the ventral rami of L5-S2 and provides innervation of the gluteus maximus muscle.[rx]

Muscles

• The TFL works in concert with the gluteus medius and minimus to medially rotate and abduct the hip, as well as assist in flexing the hip with the rectus femoris.[rx] The distal attachment of the ITB on Gerdy’s tubercle serves as a focal point of lower extremity abduction.[rx][rx]
• The gluteus maximus primarily serves to extend the hip, however, also contributes to hip abduction via the ITB tract. Again, the ITB is an extension of the tendinous insertions of these muscles, and a better understanding of each of their function, will, in turn, improve one’s understanding of the biomechanics of the ITB.[rx][rx]

Function

References