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Special anatomy series: Ultrasound visualization of torsional anatomic changes with external rotation of the lower limb

Objective: The objective of this article is to describe ultrasound imaging changes in the lower limb as it moves from the neutral anatomic position to external rotation (ER) position. This includes sonographic differences related to both positional changes and tissue torsion. Methods: Sonographic images were obtained in a 28-year-old healthy elite female highland dancer. Both short- and long-axis sonographic images were obtained with the transducer placed over the structure of interest with the hip in both neutral and externally rotated positions. Cine video was also recorded at each site to assess dynamic imaging changes in real time. Results: Ultrasound evaluation of the lower limb during ER allowed assessment of the appearance of positional change and torsion on the tissues from this movement. At mid-thigh, the vastus lateralis was replaced by the rectus femoris. At distal thigh, the rectus tendon was replaced by the vastus medialis. In mid-leg, the tibialis anterior was replaced by the soleus. At the ankle, the extensor hallucis and tibialis anterior tendons are replaced by the tibia and tibialis posterior tendon. Conclusion: The patterns of change with ER of the hip can be identified with ultrasound in multiple muscles throughout the lower limb. This provides the potential to be used as a tool for assessing appropriate movement patterns for performance and preventing injury in dancers and other athletes who repeatedly perform this maneuver.