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 Table of Contents  
Year : 2021  |  Volume : 4  |  Issue : 1  |  Page : 30-33

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

1 Baylor University, Honors College, Waco, TX, USA
2 Department of Physical Medicine and Rehabilitation, The Ohio State University, OH; Department of Physical Medicine and Rehabilitation, OhioHealth Riverside Methodist Hospital, Columbus, OH, USA
3 H. Ben Taub Department of Physical Medicine and Rehabilitation, Center for Trauma Rehabilitation Research, Baylor College of Medicine, Harris Health System, Houston, Texas, USA

Date of Submission20-Oct-2020
Date of Acceptance20-Oct-2020
Date of Web Publication10-Feb-2021

Correspondence Address:
Dr. Faye Y Chiou-Tan
H. Ben Taub Department of Physical Medicine and Rehabilitation, Baylor College of Medicine, Smith EMG Clinic, Harris Health System, 2525 Holly Hall, Suite #5203, Houston, TX, 77030
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jisprm.jisprm_32_20

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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.

Keywords: Anatomy, dancer, external rotation, injection, leg, torsion, ultrasound

How to cite this article:
Tan MC, Strakowski JA, Ughwanogho UO, Forrest EG, Chiou-Tan FY. Special anatomy series: Ultrasound visualization of torsional anatomic changes with external rotation of the lower limb. J Int Soc Phys Rehabil Med 2021;4:30-3

How to cite this URL:
Tan MC, Strakowski JA, Ughwanogho UO, Forrest EG, Chiou-Tan FY. Special anatomy series: Ultrasound visualization of torsional anatomic changes with external rotation of the lower limb. J Int Soc Phys Rehabil Med [serial online] 2021 [cited 2021 Apr 14];4:30-3. Available from: https://www.jisprm.org/text.asp?2021/4/1/30/309054

  Introduction Top

Torsional anatomy is a new concept mapping the twisting movement of muscles and tissues in positions other than anatomic neutral using musculoskeletal ultrasound. Previously, we documented the sonographic changes with the internal rotation in spastic hemiparesis of the upper and lower limbs specifically for the purpose of injection.[1],[2],[3],[4],[5],[6] Inspiration for the first series came when, as clinicians, we found it difficult to know the new positions of muscles for spasticity injection for the arm and leg. As noted in previous papers, “the usual anatomic references are of limited utility because they were not obtained in this spastic hemiparetic position. There (was) no anatomic reference in the literature for these spastic postures.”[4] As discussed in those articles, torsion is to be differentiated from the rotation in which both the origin and insertion turn at equal rates. In torsion, the origin and insertion rotate at different rates leading to twisting of structures as would be seen in a candy cane or barber's pole for example.[1] [Table 1] summarizes the changes found from these papers [Table 1].
Table 1: Summary of internal torsion changes of the upper limb

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Review of torsional concepts

Torsional concepts learned thus far from the previous papers[1],[2],[3],[4] can be summarized as:

  1. Structures previously in the cross section when in the anatomic position may become oblique or difficult to see after internal torsion. A previous example given is the tip of a needle which has an oblique rather than blunt cross-sectional cut. In addition, anisotropy can also cause less than optimal views or even “disappearance” of the structure
  2. Not all structures move equally for the same rotational movement
  3. One example is bunching and crowding of some muscles while stretching out of others. A second example of is the degree of movement. Structures near the origin of movement may move little whereas those far away may move greatly.

In this publication, we are reporting changes with external rather than internal rotation. This series is important for sports medicine and athletes such as with baseball players throwing a ball. In this article, we are reporting ultrasound images of the lower limb with the hip in external rotation (ER), which is utilized in the first position stance in ballet. The investigation is designed to improve the understanding of the positional relationships in this stance.

  Methods Top

This project was approved by the local institutional review boards of the academic medical school and the hospital. Informed consent from the subject was obtained before initiation of the study. Sonographic images were obtained in a healthy female subject.

Instrumentation and Ultrasonographer

A Fujifilm Sonosite machine was used for the images obtained in this paper. The ultrasonographer for this series (author JS) is double boarded by the American Registry for Diagnostic Medical Sonography (ARDMS) and neuromuscular ultrasound of the American Board of Electrodiagnostic Medicine (ABEM). He also is a question writer for both Boards, author of ultrasound textbooks and national/international lecturer in ultrasound. The senior author (FCT) is also an anatomic question exam writer for the ARDMS ultrasound board and boarded by the ABEM and current board member for the ABEM. Both are pushing the envelope in ultrasound research on this planet and hopefully others in collaboration with the national aeronautic space administration and space research.

Ultrasound survey

We performed a systematic survey of commonly imaged musculoskeletal structures of the lower limb.[7],[8] The bony acoustic landmark of the hip joint, anterior recess, and femoral neck was identified. In the anterior hip region, the acetabulofemoral joint, iliacus, psoas, rectus femoris, sartorius, and pubic symphysis were identified and analyzed. The greater trochanter, gluteus medius and minimus tendons, bursae, iliotibial band, and tensor of fascia lata were assessed in the areas of the lateral hip. The rectus femoris, vastus medialis, vastus intermedius, and the vastus lateralis were identified in the anterior thigh region. The femoral artery, vein and nerve, sartorius, gracilis, and adductor longus, brevis and magnus were evaluated in the medial thigh. In the posterior thigh region, the semimembranosus, semitendinosus, biceps femoris, and sciatic nerve were analyzed.

At the level of the anterior tibiotalar joint recess, the tibialis anterior, extensor hallucis longus, anterior tibial artery and veins, deep fibular nerve, and extensor digitorum longus were analyzed. In the medial ankle region, the tibialis posterior, flexor digitorum longus, posterior tibial artery and veins, tibial nerve, flexor hallucis longus, and deltoid ligament were identified. The fibularis longus and brevis, the anterior talofibular ligament, calcaneofibular ligament, and anterior tibiofibular ligament were analyzed at the anterolateral ankle. The Achilles tendon, the posterior bursa, and the plantar fascia were observed in the posterior ankle and plantar region. In the calf, the soleus, medial and lateral heads of gastrocnemius, and the plantaris were identified. Areas inspected in the forefoot region included the dorsal joint recesses, the intermetatarsal spaces, flexor digitorum tendons, and plantar plates of the metatarsal phalangeal joints.[7],[8] These structures were chosen because they are commonly used for clinical assessment and therapeutic injections.[8] The transducer was placed on the anterior leg in both the short and long-axis views to create the images of each of the structures of interest. A pair of images was recorded for each structure. The first was recorded in the neutral position and the second with the hip in full ER. The images were compared and a video recording was made at each site to track the movement of the muscles, nerves, and other selected anatomic landmarks during ER.

  Results Top

Mid-thigh region

[Figure 1]a Observing the left thigh rotating from an anatomic neutral position to an externally rotated position, the rectus femoris moves laterally as the vastus lateralis along with the rectus femoris artery rotates posteriorly. The outline of the femur becomes less prominent as the rotation results in the loss of the bony landmark when the depth of the ultrasound image is fixed in the anterior plane.
Figure 1: Anatomic neutral and external rotation of the lower limb at the mid--thigh, distal thigh, mid-leg, and ankle. (a) Mid-thigh - short axis. (b) Distal thigh - short axis. (c) Mid-leg - short axis. (d) Ankle - short axis

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Distal thigh

[Figure 1]b Rotating the left hip from an anatomical neutral position to an externally rotated position results in the vastus medialis moving laterally to replace the rectus tendon and the vastus intermedius tendon. With the ultrasound depth fixed in the anterior plane, the bony landmark of the femoral condyle becomes visible with ER.


[Figure 1]c The bright cortical outline of the tibia and tibialis anterior is easily seen in a neutral position. As the leg rotates externally, the tibialis anterior is replaced by the medial structures, including the flexor digitorum longus, the soleus, and the medial head of the gastrocnemius.


[Figure 1]c, [Figure 1]d At the ankle, the extensor hallucis longus and the tibialis anterior tendons are moved posteriorly and laterally from a neutral position to an externally rotated position. This results in the extensor hallucis longus and the tibialis anterior tendons to be replaced by the tibia and tibialis posterior tendon.

  Discussion Top

Torsion refers to the twisting of an object due to applied torque. For our purposes, we are observing the measurable changes of the appearance of muscle and tendon on ultrasound due to hip and leg movement and resultant torsional stress. The torsion is created from rotational torque affecting opposing ends of the structure to different degrees. This can result in thickening or bunching, or even thinning and tightness, of the tendon and muscle depending on the nature of its position in relation to the joint movement.[1]

Importance of external rotation in dance

ER is an integral component of many types of dance.[9] More widely known in the dance community as turnout, ER of the hip, resulting in repositioning of the entire lower limb, is essential in the execution of movements and stability. It also reduces the biomechanical energy used to perform complex movements, allowing a dancer to look effortless. Not only does “turn out” allow a dancer to perform complex movements with ease, but it also is a form of stability.[10] A positive correlation has been found relating better scores on the Y Balance test to hip strength.[11] ER of both the hip of the supporting limb and the hip of the extended limb are equally important for balance. The supporting limb remains rotated to allow for movements to be executed on one limb while the extended limb remains rotated in anticipation for its next landing. In order to maintain extreme flexibility in the hip, dancers often perform exercises that strengthen the hip muscles, conventionally known as pliés, frog, and pretzel stretches.[12] Stretching before and after practice is essential in order for the dancer to increase flexibility and reduce muscle tension to prevent tearing. Hamilton et al. discusses the possibility of a “torsional component to the turned-out hip position in the elite female professional ballet dancers,”[9] suggesting that they are different in both genders relative to the normal population.

Several muscles are utilized during ER of the hip while performing this maneuver. This includes the obturator internus and externus, piriformis, superior and inferior gemelli, and quadratus femoris. The gluteus maximus and adductor magnus also assist in hip ER. The biceps femoris and semitendinosus are also important for stabilization on the side of supporting limb. Dancers are predisposed to musculoskeletal injury if “turnout” is executed with insufficient ER of the hip. Insufficient “turnout” can result in prepatellar bursitis and other soft-tissue overuse of the anterior knee as well as a multiple of foot and ankle injuries.[13]

Advantages of external rotation for diagnostic ultrasound

The majority of diagnostic ultrasound is performed supine in the anatomic neutral position. However, ER during ultrasound enables the physician to better observe and diagnose problems in certain muscles that are otherwise obstructed in the neutral positions. For example, disruption of the normal echotexture of the plantaris can be viewed in ER. This muscle should be routinely examined in athletes who perform jumping maneuvers due to its propensity for injury. Rotation of the hip joint allows the ileus psoas tendon to move laterally with respect to the bursa, facilitating better view of other muscles and tendons.

Advantages of external rotation for treatment

ER is often a valued position when doing ultrasound injections as well. Arthrocentesis of the hip joint in an externally rotated position allows a more visible view of the femoral neck. The piriformis tendon injection in an externally rotated position facilitates visualization of the insertion point of the tendon. Other procedures in the popliteal fossa or medial leg and ankle are more easily performed with hip ER. The impact of this positioning on the target structures can be appreciated by assessing them dynamically with internal and ER of the hip and inspecting the relative torsional deformation of the surrounding structures.

  Conclusion Top

Awareness of torsional anatomy of the lower limb is important for recognizing altered positions and patterns of stress on muscles in ER. This enhances the clinician's knowledge and understanding of elite dancer sport mechanisms and diagnostic abilities when assessing injuries. This position also useful for a number of therapeutic injections. Prior knowledge of the altered locations of the structures could facilitate more accurate ultra-guided needle insertion.


The authors wish to acknowledge Ms. Donna Cusack, Ms. Diane MacPhee, and Dame Christine Lacey, MBE from the world of Scottish Highland dancing for their contributions to this article.

  References Top

Chiou-Tan FY, Cianca J, Pandit S, John J, Furr-Stimming E, Taber KH. Procedure-oriented torsional anatomy of the proximal arm for spasticity injection. J Comput Assist Tomogr 2015;39:449-52.  Back to cited text no. 1
Chiou-Tan FY, Cianca J, John J, Furr-Stimming E, Pandit S, Taber KH. Procedure-oriented torsional anatomy of the forearm for spasticity injection. J Comput Assist Tomogr 2015;39:820-3.  Back to cited text no. 2
John J, Cianca J, Chiou-Tan FY, Furr-Stimming E, Taber KH. Procedure oriented torsional anatomy of the hand for spasticity injection. J Comput Assist Tomogr 2017;41:336-8.  Back to cited text no. 3
Chiou-Tan FY, Robinson LR, John J, Cianca J, Taber KH. Procedure oriented torsional anatomy of the carpal tunnel. J Comput Assist Tomogr 2018;42:492-5.  Back to cited text no. 4
Cianca J, Dy R, Chiou-Tan FY, John J, Taber KH. Torsional anatomy of the lower limb: The appearance of anatomy in hemispastic position. J Comput Assist Tomogr 2018;42:982-5.  Back to cited text no. 5
Strakowski J, Chiou-Tan FY, Forrest L, Ughwanogho U, Taber KH. Ultrasound visualization of torsional anatomic changes from external rotation of the anterior shoulder. J Comput Assist Tomogr 2019;43:519-23.  Back to cited text no. 6
American Institute of Ultrasound in Medicine. AIUM Practice Parameter for the Performance of a Musculoskeletal Ultrasound Examination American Institute of Ultrasound in Medicine Website. Available from: http://www.aium.org/resources/guidelines/documentation.pdf.  Back to cited text no. 7
Jacobson JA, Fundamentals of Musculoskeletal Ultrasound. Ch. 6, 8. Philadelphia: Elsevier/Saunders; 2018l. p. 223-283, 328-405.  Back to cited text no. 8
Hamilton WG, Hamilton LH, Marshall P, Molnar M. A profile of the musculoskeletal characteristics of elite professional ballet dancers. Am J Sports Med 1992;20:267-73.  Back to cited text no. 9
Grossman G, Krasnow D, Welsh TM. Effective use of turnout: biomechanical, neuromuscular, and behavioral considerations. J Dance Education • Volume 5, Number 1, 2005. Available from: http://www.citraining.com/Effective-Use-of-Turnout.html.  Back to cited text no. 10
Wilson BR, Robertson KE, Burnham JM, Yonz MC, Ireland ML, Noehren B. The relationship between hip strength and the Y Balance Test. J Sport Rehabil 2018;27:445-50.  Back to cited text no. 11
Gribbin S. Available from: http://www.studiofitonline.com/.[Last accessed on 2020 Jun 17].  Back to cited text no. 12
Rehmani R, Endo Y, Bauman P, Hamilton W, Potter H, Adler R. Lower extremity injury patterns in elite ballet dancers: Ultrasound/MRI imaging features and an institutional overview of therapeutic ultrasound guided percutaneous interventions. HSS J 2015;11:258-77.  Back to cited text no. 13


  [Figure 1]

  [Table 1]


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