Tensor Fasciae Latae, otherwise known by its abbreviation TFL, is a thin muscle of the hip region located on the thigh just inferior and lateral to the anterior superior iliac spine (ASIS).
Despite its small size, the TFL is largely important with a number of functions, including hip abduction, internal rotation, and hip flexion. The muscle gets its name from an additional function: to tense the fasciae latae.
What is Fasciae Latae?
To understand TFL, we must first explore the fascia.
Fascia is a sheet of fibrous tissue that envelops the body beneath the skin; it encloses muscles and groups of muscles and separates their several layers or groups. The fasciae latae is the deep fascia of the thigh, beginning around the pelvis at the iliac crest and ending just below the knee at the tibia.
At the lateral thigh, the fascia thickens and forms what we know to be the IT band (the iliotibial tract) and encircles the tensor fasciae latae.
TFL Function and Facts
Origin: ASIS and outer edge of iliac crest
Insertion: Iliotibial tract
Innervation: Superior gluteal nerve (L4, L5, S1)
Its various functions and anatomical positioning make TFL a complex muscle that is both poorly understood and often overlooked when clients consider the source of their pain.
The TFL is grouped with the gluteal muscles (maximus, medius and minimus) and shares a fascial connection with gluteus maximus as they both insert at the IT band. Together with gluteus maximus, the TFL stabilizes the hip joint. Along with gluteus medius and minimus, TFL is involved in both hip abduction and hip internal rotation.
Additionally, TFL works as a hip flexor in conjunction with the psoas, iliacus, rectus femoris, hip adductors, and sartorius. Hip flexion is thought to be TFL’s primary function, as it is most active during the acceleration phase of running.
As its name reminds us, the tensor fasciae latae acts as a stabilizer, working to maintain fascial tension during movement. For example, the TFL indirectly plays a role in stabilizing the knee by tautening the IT band and bracing the knee when the opposite foot is lifted.
TFL has a tendency to be overworked, in part due to its many functions. If gluteus medius (a historically weak muscle) doesn’t do its part in hip abduction, the TFL may be overused. Similarly, if the psoas is underactive in hip flexion, the TFL will take over. It is not unlikely for someone to simultaneously have a weak gluteus medius, an underactive psoas AND a slow-firing gluteus maximus in which case TFL is overactive in each of its varying functions.
Because of its connection to the IT band, TFL dysfunction can also contribute to IT band syndrome. In this case, it may present as knee pain or a taut IT band. Since IT band discomfort is such a common complaint and highly misunderstood, we should always consider the TFL in these instances.
A positive Trendelenburg test (hip drop on the contralateral side of a single leg stance) or valgus knees in an overhead squat assessment can both indicate an overactive TFL.
Tensor Fasciae Latae has many jobs and often doesn’t have the support it needs. By regularly massaging and stretching TFL, and targeting the surrounding muscles so that they can step up and do their part, we may be able to help our clients not only to feel better, but to move more efficiently.
fascia. (n.d.) Medical Dictionary for the Dental Professions. (2012). Retrieved January 3 2021 from https://medical-dictionary.thefreedictionary.com/fascia