Architecture of the Short External Rotator Muscles of the Hip

Kevin C. Parvaresh, Charles Chang, Ankur Patel, Richard L. Lieber, Scott T. Ball, Samuel R. Ward*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


Background: Muscle architecture, or the arrangement of sarcomeres and fibers within muscles, defines functional capacity. There are limited data that provide an understanding of hip short external rotator muscle architecture. The purpose of this study was thus to characterize the architecture of these small hip muscles. Methods: Eight muscles from 10 independent human cadaver hips were used in this study (n = 80 muscles). Architectural measurements were made on pectineus, piriformis, gemelli, obturators, quadratus femoris, and gluteus minimus. Muscle mass, fiber length, sarcomere length, and pennation angle were used to calculate the normalized muscle fiber length, which defines excursion, and physiological cross-sectional area (PCSA), which defines force-producing capacity. Results: Gluteus minimus had the largest PCSA (8.29 cm2) followed by obturator externus (4.54 cm2), whereas superior gemellus had the smallest PCSA (0.68 cm2). Fiber lengths clustered into long (pectineus - 10.38 cm and gluteus minimus - 10.30 cm), moderate (obturator internus - 8.77 cm and externus - 8.04 cm), or short (inferior gemellus - 5.64 and superior gemellus - 4.85). There were no significant differences among muscles in pennation angle which were all nearly zero. When the gemelli and obturators were considered as a single functional unit, their collective PCSA (10.00 cm2) exceeded that of gluteus minimus as a substantial force-producing group. Conclusions: The key findings are that these muscles have relatively small individual PCSAs, short fiber lengths, and low pennation angles. The large collective PCSA and short fiber lengths of the gemelli and obturators suggest that they primarily play a stabilizing role rather than a joint rotating role.

Original languageEnglish (US)
Article number611
JournalBMC Musculoskeletal Disorders
Issue number1
StatePublished - Dec 20 2019


  • Architecture
  • Biomechanics
  • Fiber length
  • Hip
  • Joint
  • Muscle
  • Rotators
  • Stability

ASJC Scopus subject areas

  • Rheumatology
  • Orthopedics and Sports Medicine


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