This article was informed by Flato et al’s ‘The iliotibial tract: imaging, anatomy, injuries, and other pathology’ published in 2017 in Skeletal Radiology. Find this article here: https://rdcu.be/b4w5s
What is the ITB?
The iliotibial tract/band (ITB) is a unique anatomical feature in humans which represents an adaptation to upright posture and bipedalism. Typically, between 1-3mm thick, it is a strong, superficial, and laterally positioned length of connective tissue belonging to the fascia lata of the thigh.
What is the specific anatomy of the ITB?
It is a coalescence of the fascial layers derived from TFL, gluteus maximus, gluteal aponeurosis (which covers gluteus medius) and the fascia lata. It also has 3 distinct layers: superficial, intermediate, and deep which eventually fuse together distal to the belly of TFL. The ITB originates from the iliac tubercle and inserts into the linea aspera of the femur via the fascia lata, as well as at many points of the lateral knee joint. These lateral knee insertions are functionally important and include the lateral epicondyle of the femur, the lateral patella retinaculum, Gerdy’s / lateral infracondylar tubercle, the fibular head, and the knee joint capsule. It is because of the diverse insertion of the ITB at the lateral knee that debate continues as to whether the ITB is technically a ligament of the femur or a muscle of the tibia!
What does the ITB do?
Through its muscular contributions (from TFL and gluteus maximus) the ITB extends, abducts, and laterally rotates the hip. It functions in postural support when standing asymmetrically by pulling one knee into extension when the pelvis is slouched, and aids in lateral knee stabilization via the lateral patellofemoral ligament complex. It improves antero-lateral knee stability as its condylar insertion is very close to the anterolateral ligament of the knee, and it can act in shock absorption by transmitting force from the knee more proximally towards the hip. Interestingly, the ITB may act alongside the ACL in restricting anterolateral subluxation through its capsule-osseous insertion.
When is the most tension going through the ITB?
During knee flexion range of motion, the fibers of the ITB are elongated differently. From 0-40 degrees of flexion the anterior fibres are tensioned, and from 50-90 degrees of flexion are the posterior fibres.
Does the ITB ever get injured?
Injury to the ITB usually results from repetitive stress or direct trauma. Here are some examples of injuries involving the ITB:
● Iliotibial band syndrome (ITBS): ITBS refers to pain over the lateral femoral condyle that is typically worse at 30 degrees of knee flexion. Usually associated with a history of repetitive activity and/or chronic overuse such as running or cycling. Pain will usually get worse throughout a bout of activity. Pain is usually felt between the lateral femoral condyle and Gerdy’s tubercle. Running downhill is a reliable aggravating factor. The theory that this is caused by rubbing of the ITB over the lateral femoral condyle resulting in friction and irritation of the ITB sub-ITB structures is still debated. It is not clear what direction the ITB moves over the condyle, nor how much it moves (if at all!). It is also unclear to what extent the sub-ITB structures play in the pain experience. Sub-ITB structures include cysts, bursae, fat pad or a synovial recess. There is a lack of evidence demonstrating changes in the IT tract itself in ITBS. Risk factors may include limb length discrepancy, genu varum, excessive foot pronation and hip adductor weakness.
● External snapping hip syndrome: a snapping, popping, or clicking sensation over the greater trochanter with hip motion. Can occur with or without pain. Presence of pain reflects bursitis or tendonitis. Occurs in the lateral hip due to the abrupt forward movement of the proximal ITB +/-gluteus maximus during hip flexion. Usually following chronic overuse of activities that involve extremes of hip range of motion. Common in athletes and dancers. Provocative test: flexion of an adducted thigh, external rotation of an adducted and IR hip.
● Proximal ITB syndrome: an overuse of enthesopathy at the origin of the ITB (iliac tubercle). Most patients report gradual onset of localized pain over the iliac tubercle. Females > males, athletes > non athletes.
● Iliotibial bursitis: It remains unclear whether a sub-ITB bursa is present prior to pain onset, but on MRI in people with chronic ITBS they show the presence of an inflamed sub-ITB bursa.
● Acute injury of the ITB: Most commonly a sprain, although this is a rare injury, occurring approximately in 2% of acute knee injuries and requires pure valgus force. This injury is seen in 70-74% of patients with an ACL tear or patella dislocation, it is very rare for a complete tear to occur. Tell me if I corrected this right for what you were trying to say.
● ITB insertional tendinosis: Not related to compression of sub-ITB structures but this is an enthesopathy-type injury typically caused by chronic repetitive stress, diffuse idiopathic skeletal hyperostosis (DISH), endocrine or other metabolic disorders.
● Distal avulsion fracture: Most commonly occurs following a direct blow angled posterolaterally with the knee extended. Usually this injury is accompanied by other posterolateral structures being injured. Patients present with point tenderness at the distal insertion of the ITB (Gerdy’s tubercle) as well as severe pain on weight bearing. ACL tear is commonly a concomitant injury.
● Segond fracture: This is a fracture of proximal tibia just below the lateral plateau that results from tension through the laterally positioned structures of the knee. These include the capsular-osseous layer of the ITB, the lateral collateral ligament, and the anterolateral ligament following varus stress with tibial internal rotation. 75%-100% of cases also have a concomitant ACL tear, 66-75% have medial meniscal tear. Typically presents as pain over the lateral joint line, swelling and anterolateral rotational instability.
● Morel-Lavelle lesion: a rare closed internal degloving soft tissue injury caused by severe pelvic or thigh trauma. This involves the separation of the subcutaneous layer from the deep fascia. May occur during contact sports or low-velocity crush injuries. Patients report painful swelling, ecchymosis, swelling and skin hypermobility.
Reference:
Flato, R., Passanante, G. J., Skalski, M. R., Patel, D. B., White, E. A., & Matcuk, G. R. (2017). The iliotibial tract: imaging, anatomy, injuries, and other pathology. Skeletal radiology, 46(5), 605-622.