Iliotibial Band

For Medical Students

Structure and Location

The iliotibial band is a thickening of the fascia lata on the outer side of the thigh. It runs from the iliac crest to the tibia, crossing both the hip and the knee.

Tensor fasciae latae and part of gluteus maximus insert into it proximally, so it carries muscle pull as well as acting as a passive restraint.

At the knee it attaches to Gerdy's tubercle on the anterolateral tibia. 2.2.4 covers that tubercle.

It is more than a surface structure. Deep fibres run from the band to the lateral femoral condyle, and those are the Kaplan fibres that 2.11.2 covers.

A further expansion, the iliopatellar band, runs forwards to the patella and forms part of the lateral retinaculum. 2.12.4 covers that.

Relations

Superficial to it: skin and subcutaneous fat. It is the outermost structure of the lateral knee and is palpable along its whole course.

Deep to it: the lateral femoral condyle, with a small bursa between the two near the epicondyle.

Behind it: biceps femoris, with the common peroneal nerve behind that again. 2.10.5 and 2.10.6 cover them.

In front: the lateral retinaculum, which it blends with rather than meets.

Function

It stabilises the hip in single leg stance, which is its function above the knee.

At the knee it restrains internal rotation of the tibia and contributes to varus restraint.

Its line of pull moves as the knee flexes. In extension it lies in front of the axis of rotation and helps extend; past about 30 degrees it lies behind and helps flex. That shift is why the band behaves differently at different angles.

Clinical Relevance

Because it crosses two joints, a problem at the knee can arise from the hip. That is an anatomical fact with consequences for assessment.

The deep fibres to the femur are what make it a rotational restraint rather than only a passive strap, and 2.11.2 covers them.

It is the one lateral structure that can be followed by hand along its whole length, which makes it the simplest landmark on this side of the knee.

MRCS Level

Structure and Location

Describe it in three parts at the knee: the superficial layer running to Gerdy's tubercle, the deep layer attaching to the distal femur, and the capsulo-osseous layer running posteriorly and distally to the tibia behind Gerdy's tubercle.

The capsulo-osseous layer is the one most often left out. It is the deepest and most posterior part and it behaves as a ligament rather than as fascia.

Conventional teaching gives the band a width at the knee of the order of 25 mm superficially, narrowing as it approaches its tibial attachment.

It is continuous with the lateral intermuscular septum, which anchors it to the linea aspera along the length of the femur.

Relations

It is the whole of layer one on the lateral side, in the three layer scheme 2.10.4 uses.

The deep and capsulo-osseous layers lie against the capsule and against the lateral femoral condyle, so the band's deep surface is in contact with layer three.

A bursa separates the band from the lateral epicondyle, which is where friction problems arise.

In front it blends with the lateral retinaculum and the iliopatellar band, so there is no clear anterior border.

Blood Supply and Innervation

Supply is from the lateral superior genicular artery at the knee and from perforating branches of the profunda femoris along the thigh.

The band itself is relatively avascular in its mid substance, which is consistent with a structure that carries load rather than one that contracts.

Nerve supply is from the lateral articular branches and from cutaneous nerves in the overlying fascia. The band is well supplied with nociceptors near the epicondyle.

Function

The superficial layer anchors the band to the tibia and carries the tension that tensor fasciae latae and gluteus maximus generate.

The deep and capsulo-osseous layers restrain internal rotation of the tibia, and the capsulo-osseous layer carries most of that. 3.11.1 covers the proportions.

The change of lever arm through flexion means the band acts as an extensor near extension and a flexor in deeper flexion, which 3.11.1 also covers.

Clinical Relevance

Assess the hip when the lateral knee is painful, because the band crosses both joints and tension at one end is felt at the other.

Expect the band to contribute to rotational control as well as to coronal stability. That is what makes it relevant to anterior cruciate surgery at all.

Preserve the capsulo-osseous layer where an approach allows it, since it carries the rotational restraint the superficial layer does not.

Identify Gerdy's tubercle before any anterolateral work. It is the fixed landmark and 2.2.4 covers it.

FRCS Level

Relations

The band's continuity with the intermuscular septum means it is anchored to the femur along a length rather than at a point. Any procedure that tensions it is tensioning a structure attached to the whole femur.

Its deep layers and the anterolateral ligament occupy the same region, which is part of why the two have been described as the same structure by different authors. 2.11.3 and 2.11.5 cover that.

Its anterior blend with the retinaculum means a lateral release crosses the band's expansion, so the two procedures are not as separate as their names suggest.

Function

Treat the band as the main passive restraint to internal rotation at the knee, with the anterolateral ligament and the capsule contributing. That ordering is the current reading and 3.11.5 carries the evidence.

Its two joint course makes it the one knee structure whose tension can be altered by something above the knee, which matters when a lateral extra-articular procedure is being considered.

Over-tensioning it constrains rotation rather than simply restraining it, because the band has little compliance in its deep layers.

Clinical Relevance

Consider the band's deep layers rather than its surface when a rotational problem is being addressed. The superficial layer is the easiest to reach and the least relevant to rotation.

Assess hip abductor function in a knee with lateral symptoms, because the band's tension is set above the knee.

Plan any lateral extra-articular procedure around the capsulo-osseous layer and the Kaplan fibres, which 2.11.2 covers, and 7.30 carries the technique.

Avoid over-tensioning. A band with little compliance tightened too far does not restrain rotation, it removes it.