Fig. 3

Parasagittal ultrasound image of thoracolumbar fascia at the L2-3 level. Left downward arrow: Thick echogenic layer representing the aponeurosis of the latissimus dorsi and abdominal muscles. Right upward arrow: Thin echogenic layer representing the aponeurosis surrounding paraspinal muscles. Between the arrows is a thin echolucent layer of loose connective tissue. Deep to the thin echogenic layer are paraspinal muscles. Shear strain represents differential motion (moving laterally on the image) between echogenic layers