The iliotibial tract or iliotibial band (ITB; also known as Maissiat's band or the IT band) is a longitudinal fibrous reinforcement of the
fascia lata
The fascia lata is the deep fascia of the thigh. It encloses the thigh muscles and forms the outer limit of the fascial compartments of thigh, which are internally separated by the medial intermuscular septum and the lateral intermuscular septu ...
. The action of the muscles associated with the ITB (
tensor fasciae latae
The tensor fasciae latae (or tensor fasciæ latæ or, formerly, tensor vaginae femoris) is a muscle of the thigh. Together with the gluteus maximus, it acts on the iliotibial band and is continuous with the iliotibial tract, which attaches to the ...
and some fibers of
gluteus maximus
The gluteus maximus is the main extensor muscle of the hip. It is the largest and outermost of the three gluteal muscles and makes up a large part of the shape and appearance of each side of the hips. It is the single largest muscle in the human ...
) flex, extend, abduct, and laterally and medially rotate the hip. 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. However, it has been suggested that this is only an illusion due to the changing tension in the anterior and posterior fibers during movement. It originates at the anterolateral
iliac tubercle
The iliac tubercle is located approximately posterior to the anterior superior iliac spine on the iliac crest in humans. The transverse plane that includes each of the tubercles (one from the left iliac tubercle and one from the right iliac tube ...
portion of the external lip of the
iliac crest
The crest of the ilium (or iliac crest) is the superior border of the wing of ilium and the superiolateral margin of the greater pelvis.
Structure
The iliac crest stretches posteriorly from the anterior superior iliac spine (ASIS) to the posterior ...
and inserts at the
lateral condyle of the
tibia
The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...
at
Gerdy's tubercle
Gerdy's tubercle is a lateral tubercle of the tibia, located where the iliotibial tract inserts. It was named after French surgeon Pierre Nicolas Gerdy (1797–1856).
Gerdy's tubercle is a smooth facet on the lateral aspect of the upper part of t ...
. The figure shows only the proximal part of the iliotibial tract.
The part of the iliotibial band which lies beneath the
tensor fasciae latae
The tensor fasciae latae (or tensor fasciæ latæ or, formerly, tensor vaginae femoris) is a muscle of the thigh. Together with the gluteus maximus, it acts on the iliotibial band and is continuous with the iliotibial tract, which attaches to the ...
is prolonged upward to join the lateral part of the capsule of the
hip-joint
In vertebrate anatomy, hip (or "coxa"Latin ''coxa'' was used by Celsus in the sense "hip", but by Pliny the Elder in the sense "hip bone" (Diab, p 77) in medical terminology) refers to either an anatomical region or a joint.
The hip region is ...
. The tensor fasciae latae effectively tightens the iliotibial band around the area of the knee. This allows for bracing of the knee especially in lifting the opposite foot.
The gluteus maximus muscle and the tensor fasciae latae insert upon the tract.
Clinical significance
The IT band stabilizes the knee both in extension and in partial flexion, and is therefore used constantly during walking and running. When a person is leaning forwards with a slightly flexed knee, the tract is the knee's main support against gravity.
Iliotibial band syndrome
Iliotibial band syndrome (ITBS) is the second most common knee injury, and is caused by inflammation located on the lateral aspect of the knee due to friction between the iliotibial band and the lateral epicondyle of the femur. Pain is felt most ...
(ITBS or ITBFS, for iliotibial band friction syndrome) is a common
thigh
In human anatomy, the thigh is the area between the hip (pelvis) and the knee. Anatomically, it is part of the lower limb.
The single bone in the thigh is called the femur. This bone is very thick and strong (due to the high proportion of bone ...
injury
An injury is any physiological damage to living tissue caused by immediate physical stress. An injury can occur intentionally or unintentionally and may be caused by blunt trauma, penetrating trauma, burning, toxic exposure, asphyxiation, o ...
generally associated with
running
Running is a method of terrestrial locomotion allowing humans and other animals to move rapidly on foot. Running is a type of gait characterized by an aerial phase in which all feet are above the ground (though there are exceptions). This is ...
. It can also be caused by
cycling
Cycling, also, when on a two-wheeled bicycle, called bicycling or biking, is the use of cycles for transport, recreation, exercise or sport. People engaged in cycling are referred to as "cyclists", "bicyclists", or "bikers". Apart from two ...
or
hiking
Hiking is a long, vigorous walk, usually on trails or footpaths in the countryside. Walking for pleasure developed in Europe during the eighteenth century.AMATO, JOSEPH A. "Mind over Foot: Romantic Walking and Rambling." In ''On Foot: A Histor ...
. The onset of iliotibial band syndrome occurs most commonly in cases of overuse. The iliotibial band itself becomes inflamed in response to repeated compression on the outside of the knee or swelling of the fat pad between the bone and the tendon on the side of the knee. ITB syndrome can also be caused by poor physical condition, lack of warming up before exercise, or drastic changes in activity levels. Until recent anatomical studies showed differently, the previously held belief was that the distal portion of the iliotibial band rubbed over a bursa, however this bursa was found not to exist. Additionally, the theory that the iliotibial band needs to stretch has been questioned as, in cadaveric studies under extreme load, the flexibility of the iliotibial band has been shown to be minimal with greater stiffness than capsular fibers.
[Akuthota V, Stilp SK, Lento P, Gonzalez P. Iliotibial band syndrome. In: Frontera W, Silver JK, Tizzo TD Jr, eds. Essentials of Physical Medicine and Rehabilitation, 2nd ed. St. Louis, MO: W.B. Saunders Elsevier, 2008: chap 60.]
Symptoms of iliotibial band syndrome may include pain on the outside of the knee at the beginning of exercise which persists through the exercise or specific movements like running downhill and having the knee bent for prolonged periods of time.
[
This syndrome is usually developed by people who suddenly increase their level of activity, such as runners who increase their mileage. Other risk factors for ITBS include gait abnormalities such as overpronation, leg length discrepancies, or ]bow-leggedness
Genu varum (also called bow-leggedness, bandiness, bandy-leg, and tibia vara) is a varus deformity marked by (outward) bowing at the knee, which means that the lower leg is angled inward ( medially) in relation to the thigh's axis, giving the ...
. ITB Syndrome is an overuse condition of the distal ITB near the lateral femoral condyle
The lateral condyle is one of the two projections on the lower extremity of the femur. The other one is the medial condyle. The lateral condyle is the more prominent and is broader both in its front-to-back and transverse diameters.
Clinical sign ...
and at Gerdy's tubercle
Gerdy's tubercle is a lateral tubercle of the tibia, located where the iliotibial tract inserts. It was named after French surgeon Pierre Nicolas Gerdy (1797–1856).
Gerdy's tubercle is a smooth facet on the lateral aspect of the upper part of t ...
. The most vulnerable range of knee flexion for this condition is at 30-40 degrees; this is where the ITB crosses the lateral femoral epicondyle.
Postural function
The IT band is of critical importance to asymmetrical standing (pelvic slouch). The upward pull on the lower attachment of the IT band thrusts the knee back into hyperextension, thereby locking the knee and converting the limb into a rigid supportive pillar.[Evans P. The postural function of the iliotibial tract. Ann R Coll Surg Engl. 1979 Jul;61(4):271-80. ]
References
{{Authority control
Lower limb anatomy