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 action of the muscles associated with the ITB ( tensor fasciae latae and some fibers of

gluteus maximus The gluteus maximus is the main extensor muscle of the hip in humans. 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 ...

) 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 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 superolateral margin of the greater pelvis. Structure The iliac crest stretches posteriorly from the anterior superior iliac spine (ASIS) to the posterio ...

and inserts at the lateral condyle of the

tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...

at Gerdy's tubercle. The figure shows only the proximal part of the iliotibial tract. The part of the iliotibial band which lies beneath the tensor fasciae latae is prolonged upward to join the lateral part of the capsule of the

hip-joint In vertebrate anatomy, the hip, or coxaLatin ''coxa'' was used by Celsus in the sense "hip", but by Pliny the Elder in the sense "hip bone" (Diab, p 77) (: ''coxae'') in medical terminology, refers to either an list of human anatomical regions, ...

. 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 (ITBS or ITBFS, for iliotibial band friction syndrome) is a common

thigh In 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 tissu ...

injury Injury is physiological damage to the living tissue of any organism, whether in humans, in other animals, or in plants. Injuries can be caused in many ways, including mechanically with penetration by sharp objects such as teeth or with ...

generally associated with

running Running is a method of terrestrial locomotion by which humans and other animals move quickly on foot. Running is a gait with an aerial phase in which all feet are above the ground (though there are exceptions). This is in contrast to walkin ...

. It can also be caused by

cycling Cycling, also known as bicycling or biking, is the activity of riding a bicycle or other types of pedal-driven human-powered vehicles such as balance bikes, unicycles, tricycles, and quadricycles. Cycling is practised around the world fo ...

hiking A hike is a long, vigorous walk, usually on trails or footpaths in the countryside. Walking for pleasure developed in Europe during the eighteenth century. Long hikes as part of a religious pilgrimage have existed for a much longer time. "Hi ...

. 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. ITB Syndrome is an overuse condition of the distal ITB near the lateral femoral condyle and at Gerdy's tubercle. 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