MUSCLES:
Normal anatomy:
Fibers are grouped into fascicles separated by perimysium (fibrous tissue). The whole muscle is enclosed in epimysium.
Ultrasound:
Transverse - perimysium seen as echogenic dots or short lines scattered throughout the hypoechoic muscle fibre bulk. Intra and intermuscular septae are echogenic
Longitudinal - perimysium seen as oblique parallel echogenic stripe against hypoechoic muscle.
Dynamic scan - During contraction, muscle alters the shape and is hypoechoic with increased angulation of septae
Artefact - Beware of anisotropy, which results in marked hypoechogenicity, mimicing tear. To avoid this keep the transducer perpendicular to the muscle
TENDON:
Ultrasound:
Beware of anisotrophy all the time
Tendons are hyperechoic
LIGAMENTS:
Ultrasound:
Ligaments are hypoechoic
NERVE:
Ultrasound:
Multiple longitudinal hypoechoic bands representing fascicular bundles; separated by discontinuous bands of increased echogenicity, representing surrounding epineurium
References:
1. Lee JC et al. Sonography of Lower Limb Muscle Injury. AJR 2004; 182:341-351
2. Stuart RM et al. Sonography of Peripheral Nerve Pathology . AJR 2004; 182:123-129
