Tensor Fasciae Latae

legsTensor fasciae latae

The tensor fasciae latae is a small muscle at the front of your hip that pulls on the IT band. It abducts and flexes the hip, and it is the muscle people mean when they blame the IT band for something.

The TFL is a short, thick muscle at the front outer corner of the hip. It arises from the front of the hip crest, runs down for only a few inches, and then ends — not on bone, but on the iliotibial tract, the thick band of fascia that runs down the outside of the thigh to the knee.

That arrangement is unusual and is the whole point of the muscle. It cannot move the knee directly, but by tightening the IT band it makes that band a rigid strut down the side of the leg, which helps hold the knee steady when standing on one leg. The gluteus maximus pulls on the same band from behind.

Its own actions at the hip are abduction, flexion and internal rotation, which is a combination it shares with the front part of the gluteus medius. The two work together on every step.

It is a small muscle with a large reputation, largely because of the IT band. Complaints about a tight IT band and pain on the outside of the knee are commonly attributed to it, and that attribution is much less settled than its popularity suggests. What is not in doubt is the mechanical arrangement: this muscle tensions that band.

Training notes

It works during any hip abduction, so band walks, side-lying raises and cable abduction all load it alongside the gluteus medius and minimus.

It works hardest in abduction performed with the hip flexed, since that is the position where its own line of pull is most favourable — which is why abduction performed seated feels different from abduction performed standing or lying.

It is heavily involved in running and in any single-leg loading, where it stabilises the pelvis and tensions the IT band on every stride.

Nothing here is guidance on IT band pain or on foam rolling, both of which are questions for a professional. The useful takeaway is simply what the muscle attaches to and what it does.

Anatomy

Origin
  • Outer lip of the anterior iliac crest, between the anterior superior iliac spine and the tubercle of the crest
Insertion
  • Iliotibial tract, at about the junction of the upper and middle thirds of the thigh
Actions
  • Abducts the thigh
  • Flexes the thigh at the hip
  • Medially rotates the thigh
  • Tenses the iliotibial tract, contributing to lateral stability of the extended knee
Innervation
Superior gluteal nerve (L4–S1)

Tensor fasciae latae lies between the two layers of the fascia lata at the anterolateral hip, arising from the anterior part of the outer lip of the iliac crest and passing downward to insert into the iliotibial tract in the upper third of the thigh.

Its insertion into fascia rather than bone means it acts on the femur indirectly, through the tension it applies to the tract. Gluteus maximus inserts into the same structure from behind, and the two together determine its tension.

At the hip it acts with the anterior fibres of gluteus medius and minimus, sharing their nerve supply and their combination of abduction with medial rotation. Its flexion component distinguishes it from the posterior fibres of gluteus medius.

Its contribution to lateral knee stability through the iliotibial tract is well established mechanically. Its role in lateral knee pain syndromes is frequently asserted and considerably less well established, and is outside the scope of this page.

Under load

It is loaded by hip abduction, and preferentially so with the hip flexed, where its line of pull is most advantageous.

It is active throughout gait and running as part of the abductor mechanism controlling pelvic position in single-leg stance.

It contributes little to the visible contour of the hip, being small and lying deep to the fascia lata.

Exercises

Antagonists

Synergists