The etiology of ankle pain includes pathology of the osseous structures, cartilage, tendons, and soft tissues. A number of modalities are available for evaluation of the ankle and foot. Gross soft tissue abnormalities, arthritic or degenerative disease, fractures, and malalignment are well evaluated with conventional radiography. For evaluation of complex fractures or cortical pathology, CT is usually performed. Occult fractures, cartilage abnormalities, soft tissue tumors, and bone marrow pathology including osteomyelitis are well evaluated with MR imaging. A variety of tendon, joint, and soft tissue pathology can be efficiently diagnosed by ultrasound (Table 1).

Sonographic evaluation of the ankle has distinct advantages and disadvantages. Advantages include direct correlation of sonographic findings with the patient's symptoms with rapid comparison with the asymptomatic ankle, dynamic imaging with the foot in multiple planes and positions, wide availability of sonographic equipment, lower cost when compared with MR imaging, and speed of the examination. Knowledge regarding the location of the pain and acuity of the injury usually narrows the differential diagnosis and allows for a more focused examination. A focused foot or ankle ultrasound can usually be performed more efficiently than MR imaging. Disadvantages of ultrasound include unfamiliarity with the scanning technique and appearance of ultrasound pathology, operator dependence, and limitation of imaging structures superficial to the bony cortex. This article reviews the current role of sonography in evaluation of the foot and ankle with emphasis on its advantages, limitations, and accuracy compared with MR imaging.