How are images oriented in musculoskeletal Ultrasound?
The convention in musculoskeletal US imaging is to have the notch of the transducer directed to the patient’s head or the patient’s left side. Images are described as being in “long axis” or “short axis” to the structure being imaged, corresponding to “longitudinal” and “transverse” planes in body imaging.
When describing the orientation of the transducer to a tendon, the terms long axis and short axis are preferred, because tendons and ligaments travel obliquely around the joints.
For example, if one is imaging the posterior tibialis tendon in the ankle, which courses vertically proximal to the medial malleolus but then travels anteriorly distal to the medial malleolus, the transducer would be oriented longitudinally with respect to the body, and then transversely as it follows the tendon distally. Meanwhile, the tendon is being imaged in “long axis” the entire time.