Ultrasonography of the lower leg: technique, anatomy and pathologic conditions

Ultrasonography (US) is a useful modality for examining the lower leg, particularly in patients who have sustained muscular, tendinous or bony injuries. This paper will demonstrate the proper technique for US examination of each compartment of the lower leg. The bones, muscles and tendons of the lower leg (i.e., patellar tendon, superficial posterior fascial compartment [gastrocnemius, plantaris, soleus], deep posterior fascial compartment [tibialis posterior, flexor digitorum longus, flexor hallucis longus], lateral fascial compartment [peroneus longus, peroneus brevis], anterior faccial compartment [tibialis anterior, extensor digitorum longus, extensor hallucis longus], tibia and the fibula) will be reviewed with respect to their surface anatomy, US appearance and common pathologic conditions. A linear array high-frequency (at least 7.5 MHz) transducer should be used. One with variable centre frequency is useful to allow the examination of both deep and superficial areas in the same patient without switching transducers. Power Doppler is used to identify areas of increased blood flow, often due to inflammation or active healing. The transducer must be maintained perpendicular to the long axis of tendons to avoid anisotropy artifacts, which give a false appearance of decreased echogenicity. Structures should be followed from origin to insertion in the long and short axes. (author)