LSU Health Rediscovers Anatomy to Correct “Common Knowledge” about Hip Muscles

November 8, 2021

LSU Health New Orleans anatomists and their colleagues have shown that centuries-old knowledge about the musculature that assists with human walking and running was correct after all. Though the information was known many years earlier, Henry Gray’s detailed studies of the human thigh in the 1858 Anatomy: Descriptive and Surgical identified the iliopsoas, the most powerful hip flexor, as two separate and distinct muscles. Somewhere along the line, though, that information was simplified and combined in most modern textbooks. Students have been being taught that the two muscles combine into a single tendon that inserts on a bony bump known as the lesser trochanter. Research led by Jayc Sedlmayr, PhD and Emma Schachner, PhD, both associate professors of cell biology and anatomy at LSU Health New Orleans School of Medicine, and their colleagues, found the early anatomists were right. These muscles do not join into a single tendon but attach to very different regions of the lesser trochanter in different ways. Their results are published online in The Anatomical Record, available here.

“We did 3D digital modeling comparing the “textbook” idea of the two muscles inserting as a common tendon and our finding of them inserting separately in different areas, and found it completely changes how each works in flexing the hip,” notes Dr. Sedlmayr. “The models show that they function independently due to the different attachment sites.”

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Adds Dr. Schachner, “Separate insertions. Separate innervations. Separate muscles. Their fibers interconnect but they have different moment arms in flexion than assumed before.”

Besides showing, contrary to previously published descriptions, that the iliacus tendon does not fuse with the psoas tendon, the research team also found that the pectineus, adductor brevis, and magnus muscles have insertions into the lesser trochanter, too. This research makes it clear that the lesser trochanter is more important than previously identified.

They conclude that understanding the real anatomy is key. They conclude that since these muscles can be injured during activities like walking, running, and falls, their rediscovery has important implications about how to correctly approach them clinically.

“These findings could also significantly affect our understanding of the evolution of human upright gait and bipedal locomotion,” concludes Sedlmayr.

Other members of the research team included Drs Karl T. Bates of the University of Liverpool, and Jonathan J. Wisco of the Boston University School of Medicine.

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