The fascia lata is the deep fascia, or dense connective tissue, that surrounds the thigh muscle. It attaches to the hip bone and sacrum and runs down the lateral side of the thigh as a dense collection of fibers called the iliotibial band or iliotibial tract. The fascia lata then connects to the patella and crural fascia of the lower leg. The iliotibial band interests surgeons as a source of grafts. When the iliotibial band becomes inflamed because of demanding activities, the resulting condition is called iliotibial band syndrome (ITBS) and is a common injury among runners.
Like fascia throughout the rest of the human body, the fascia lata wraps around the muscles of the outer thigh and divides them into individual compartments. The fascia lata also connects the thigh muscles to key points on the pelvis, femur, patella and tibia. The structure that results from these bundles and connections provides support to the thigh muscles, making it possible for them to fulfill their respective duties.
As part of its duties, the fascia lata reinforces the hip joint's group of abductor muscles. These are the muscles that are responsible for moving the lower limbs of the body laterally — out to the sides. The abductor group is also responsible for keeping a person's stride from collapsing when taking a step. If the force of the step is especially intense, as in running, or if the abductors are especially weak, friction can build up near where the iliotibial band runs over the epicondyle of the femur.
ITBS occurs when enough friction builds up in the iliotibial band, leading to irritation. It usually is treated conservatively with rest, stretching and the application of heat before exercising and icing the iliotibial band afterward. Physical therapy is another popular treatment. ITBS can be prevented by strengthening the abductor muscles, and in the case of runners, changing the running stride to lessen the force on the iliotibial band.
Grafts from fascia lata have been used successfully in various fields of surgery, such as heart valve replacements, eyelid reparations and surgical treatments for urinary incontinence. The popularity of fascia lata in these operations is again because of the iliotibial tract that possesses an especially high concentration of strong connective tissue fibers. During a fascia lata harvesting operation, a surgeon will cut a select section of fibers from the iliotibial band, leaving the majority of the fibers intact.