Sonography (US) is well suited for imaging the ankle and
foot. The superficial nature of the foot and ankle structures enable high
frequency transducers to be used, typically 12 MHz or greater. US should be considered a first line
examination for the ankle tendons including the Achilles, posterior tibial,
flexor hallucis longus, anterior tibial, and peroneal tendons. Sonography is highly accurate for tendon
tears, tendinosis, and tenosynovitis. The dynamic nature of US allows the ankle
ligaments to be imaged not only at rest, but also with stress to identify
ligamentous laxity or impingement. US
also readily identifies plantar fasciitis or plantar fibromatosis. While MRI is
more accurate for depicting internal derangement of the ankle joint, US is
useful for identifying effusions, synovitis, bursitis, and ganglion cysts. High
resolution US is also useful for identifying nerve abnormalities, and can
diagnose and guide treatment for Morton’s neuromas. Finally, US is the test of choice for
identifying radiolucent foreign bodies, a common occurrence in the foot.
