Iliotibial tract

At a glance

English

Iliotibial tract

Latin (TA2)

Tractus iliotibialis

System

Connective tissue

Region

Lower limb

Side

Paired, left and right

About the iliotibial tract

The iliotibial tract, also called the iliotibial band or IT band, is a lengthwise thickening of the fascia lata, the deep fascia that wraps the thigh. It forms a strong, flat strap along the outer thigh, easily felt above the knee on the lateral side when the leg is straightened. It is not a muscle itself, but it serves as the shared tendon for two muscles that insert into it: tensor fasciae latae and the superficial part of gluteus maximus.

Above, it is attached to the tubercle on the outer lip of the iliac crest. Under tensor fasciae latae it splits to enclose that muscle, and its deep layer runs up to blend with the lateral part of the hip joint capsule. Below, it passes over the lateral femoral epicondyle and attaches to the anterolateral tubercle of the tibia, Gerdy's tubercle, with fibres to the patella and the lateral knee capsule. Along its whole length it is anchored to the linea aspera by the lateral intermuscular septum.

Through the muscles that pull on it, the tract helps abduct the thigh and steady the hip and knee. It braces the outer side of the knee in both extension and slight flexion, so it works throughout walking and running, and when someone leans forward with the knee slightly bent it is the main structure holding the knee against gravity. In relaxed standing with the weight on one leg, its pull drives the knee back into full extension and locks it, turning the limb into a firm pillar.

Iliotibial band syndrome is an overuse problem in runners, cyclists and walkers, causing pain on the outer knee, especially going downhill or after keeping the knee bent. It is worst at about thirty degrees of knee flexion, where the band crosses the lateral epicondyle, and is thought to arise from compression of a fat pad beneath it rather than friction over a bursa. Sudden increases in training, faulty foot posture or a leg-length difference add to the risk. The band is very stiff and barely stretches.

Function and supply

Begins at

Tubercle of the iliac crest, on its outer lip, with a deep layer to the lateral hip capsule; receives tensor fasciae latae and part of gluteus maximus.

Ends at

Anterolateral tubercle of the tibia (Gerdy's tubercle), with fibres to the patella and lateral knee capsule.

Function

Transmits the pull of tensor fasciae latae and gluteus maximus; braces the lateral knee and helps lock it in extension; steadies the hip.

Nerve supply

No motor nerve of its own; its muscles are supplied by the superior and inferior gluteal nerves.

Blood supply

No dedicated supply; small branches of the lateral circumflex femoral, superior gluteal and lateral genicular arteries reach it.