Investigation of the association between human fascia lata thickness and its neighboring tissues' morphology and function using B-mode ultrasonography

The fascia lata is a membrane tissue which envelopes all thigh muscles and connects with the subcutaneous adipose tissues through loose connective tissues. It is presumable that the morphology of the fascia lata is strongly affected by the unique properties of underlying thigh muscles and subcutaneous adipose tissues. We aimed to investigate the relationships between characteristics of the fascia lata and adjoining adipose tissues and underlying muscles. Twenty healthy people were recruited (25 +/- 3 years, 167.1 +/- 8.5 cm, 62.5 +/- 13.2 kg). The thickness of the skeletal muscles (rectus femoris, vastus lateralis, biceps femoris, and semitendinosus), and their overlying fascia lata and subcutaneous adipose tissues were measured by B-mode ultrasonography. Isometric knee extension and flexion torque during maximal voluntary contraction were also tested. The fascia lata thickness demonstrated site-dependent differences (vastus lateralis: 0.91 +/- 0.20 mm > rectus femoris, biceps femoris, and semitendinosus: 0.56-0.69 mm, p < 0.01). Furthermore, there were large individual variations in the fascia lata thickness even in the same region of the thigh. The fascia lata showed positive simple correlations with height (rectus femoris: r = 0.39 p = 0.01, semitendinosus: r = 0.37 p < 0.05), body mass (rectus femoris: r = 0.59, p < 0.01, vastus lateralis: r = 0.47, p < 0.01, semitendinosus: r = 0.55, p < 0.01), corresponding muscle thickness (rectus femoris: r = 0.39, p < 0.05, semitendinosus: r = 0.74, p < 0.01) and knee extension (rectus femoris: r = 0.52, p < 0.01, vastus lateralis: r = 0.40, p < 0.01) and flexion (semitendinosus: r = 0.41, p < 0.01) torques. After adjusting for the influence of height and/or body mass, the fascia lata thickness showed a partial correlation only with the skeletal muscle thickness at the semitendinosus (r = 0.61, p < 0.01). The present study revealed that the fascia lata has site-specific differences of the thickness, which positively correlates with the underlying muscle thickness and corresponding joint torque. Furthermore, the fascia lata over the semitendinosus is associated with the underlying muscle characteristics independent of the physical constitution. It is assumed that the fascia lata has the plasticity and changes its thickness, which likely corresponds to the morphology of the neighboring tissues and underlying muscle function.