The tensor fasciae latae is a small but clinically significant muscle at the anterior hip that transitions into the iliotibial band, transmitting its forces all the way to the lateral knee. Because it pulls the IT band taut during hip flexion and abduction, a shortened or overactive TFL is a key contributor to iliotibial band syndrome, the most common cause of lateral knee pain in runners. Its small size belies its outsized influence on lower limb biomechanics.
| Origin | Anterior superior iliac spine and outer lip of the anterior iliac crest |
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| Insertion | Iliotibial band at the junction of the proximal thigh, continuing distally to the lateral tibial condyle via the IT band |
| Nerve Supply | Superior gluteal nerve (L4, L5, S1) |
| Blood Supply | Superior gluteal artery |
| Actions | Abduction of the hip; Medial rotation of the hip; Flexion of the hip; Tensioning of the iliotibial band to stabilise the extended knee laterally |
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It works with the gluteus medius and minimus to abduct and medially rotate the hip, but its primary clinical significance is its effect on IT band tension. The TFL and gluteus maximus pull the band in opposite directions, and imbalance between them is central to IT band pathology at the lateral knee.
TFL tightness, usually combined with gluteus medius weakness, is a consistent finding in runners with IT band syndrome, patellofemoral pain, and hip flexor contracture. The Ober test assesses IT band and TFL flexibility by checking whether the adducted hip can drop to neutral position. Foam rolling the TFL muscle belly directly has better evidence than rolling the IT band itself, which cannot be meaningfully deformed by foam roller pressure.
The TFL is palpable as a firm contracted muscle belly just inferior and posterior to the ASIS during resisted hip abduction or flexion with medial rotation, in the region corresponding to the front trouser pocket of the hip.
Repetitive friction of the IT band over the lateral femoral epicondyle during running, producing lateral knee pain that appears consistently at the same distance into a run. TFL tension is a primary mechanical driver.
Acute muscle fibre tears at the ASIS origin from sudden hip flexion or abduction, producing anterior hip pain just below the ASIS that worsens with hip flexion and resisted abduction.
