Tensor fasciae latae
A small muscle at the front of the hip that pulls on the IT band — and is not the same thing as the IT band.
- Type
- Muscle
- Region
- Hip
- Standard name
- m. tensor fasciae latae
- Origin
- Anterior superior iliac spine and the adjacent outer lip of the iliac crest
- Insertion
- The iliotibial tract, about a third of the way down the thigh
- Actions
- hip flexionhip abductionhip internal rotation
- Verify
- TA2 2602 TA98 A04.7.02.010
What it is
A short, flat muscle at the front-outer corner of the hip, running from the bony point at the front of your pelvis down into the iliotibial tract, which it tensions. Its name is literally its function: the tensioner of the fascia lata.
It is small — a few inches long — and it does not reach the knee. What reaches the knee is the iliotibial tract it pulls on.
It shares that tract with gluteus maximus, which inserts into the same structure from behind. The two pull the band from opposite corners.
What it does
Three things at once, because of where it sits: it flexes the hip, abducts it, and rotates it inwards. It also tensions the iliotibial tract, which contributes to steadying the knee from the outside.
Its role in gait is to assist in keeping the pelvis level and swinging the leg forward. It works alongside gluteus medius for the stabilising job, and directly against gluteus maximus for rotation and extension.
What loads it
Hip flexion and abduction together — bringing the knee up and out. Walking, running, and anything on one leg.
It is loaded incidentally in almost everything the hip does, and deliberately by very little.
What is commonly got wrong about it
Confusing it with the IT band. These are constantly conflated. Tensor fasciae latae is a muscle at the top of the hip; the iliotibial tract is a sheet of dense connective tissue running the length of the thigh. One pulls on the other. "Tight TFL" and "tight IT band" are used interchangeably online and they are not the same structure.
The idea that the IT band can be stretched or rolled longer. The tract is extremely stiff connective tissue, engineered to resist lengthening — that resistance is the whole point of it. Foam rolling it may well change how it feels, and there are reasonable explanations for that involving the nervous system rather than the tissue, but the claim that you are lengthening or "releasing" the band is not supported by what the tissue is made of.
That it is the cause of lateral knee pain. Pain on the outside of the knee is common, particularly in runners, and it gets attributed to this muscle and this band with far more certainty than is warranted. The mechanism is genuinely contested in the literature. It is also, straightforwardly, a thing to see a physio about rather than read about.