An anatomical discovery challenges our understanding of the iliopsoas complex and may offer new insights into hip stability, movement and anterior hip pain.

Anatomists at Tulane University have identified a previously undescribed muscular attachment deep within the pelvis, revealing that the familiar iliopsoas complex may be more anatomically variable than previously recognised.

Published in Clinical Anatomy in July 2026, the study describes a structure called the iliac attachment of the psoas major, found in approximately 28% of the 200 cadaveric pelvic sides examined.

For manual therapists, physiotherapists and movement practitioners, the finding is a reminder that human anatomy is not always as uniform as textbooks suggest.

What Exactly Was Discovered?

The iliopsoas is one of the body’s principal hip flexors, formed primarily by the psoas major and iliacus muscles. It plays important roles in hip flexion, postural control and trunk stability.

During routine cadaveric dissection, researchers discovered an additional muscular structure lying deep beneath the iliacus muscle.

Unlike the iliacus, which joins the iliopsoas complex to attach to the femur, this newly described structure originates from the inner surface of the ilium, near the arcuate line of the pelvis, and merges directly into the posterior surface of the psoas major.

The attachment was approximately 8.3 cm long and 1.1 cm wide on average. It was separated from the overlying iliacus by a distinct fascial layer, sometimes containing adipose tissue.

This fascial separation, together with its consistent attachment to the psoas major, led the researchers to classify it as a distinct accessory muscular attachment rather than simply another portion of the iliacus.

More Common Than Expected

The researchers examined 200 pelvic sides from 100 donated human cadavers and identified the structure in 28% of sides.

It appeared more frequently on the right side than the left, although left-sided attachments tended to be slightly larger. Some individuals had the attachment on both sides, while others had it on only one.

Interestingly, the researchers found no significant relationship between the presence of the attachment and age or sex.

This suggests that the structure is an anatomical variation rather than a newly developed muscle or an abnormality.

Could It Help Stabilise the Psoas?

The muscle’s position offers intriguing possibilities.

It runs close to the iliopubic eminence and the iliopectineal bursa, where the iliopsoas passes across the anterior pelvis towards the hip.

Researchers suggest that the additional attachment may help stabilise the psoas major as it moves across this region, potentially influencing tendon movement and friction against adjacent structures.

Its relationship with the iliopectineal bursa is particularly interesting because this fluid-filled structure helps reduce friction around the iliopsoas.

However, these proposed functions remain hypothetical. The researchers did not conduct biomechanical experiments or muscle activation studies to establish what the attachment actually does during movement.

Why Does This Matter for Therapists?

The discovery may eventually contribute to our understanding of several clinical presentations involving the anterior hip.

Anterior hip and groin pain: The iliopsoas complex is frequently implicated in discomfort around the front of the hip. An additional muscular attachment could potentially influence regional mechanics, although no direct relationship with pain has yet been demonstrated.

Snapping hip syndrome: Internal snapping hip occurs when the iliopsoas tendon moves across structures within the anterior hip, sometimes producing an audible or palpable snapping sensation. The newly identified attachment lies close to this region and may be relevant to how these tissues interact.

Fascial anatomy: The presence of a distinct fascial plane between the accessory attachment and iliacus demonstrates the anatomical complexity of the deep pelvic region. For therapists interested in myofascial relationships, it provides another example of how muscles and connective tissues are organised into interconnected but distinguishable structures.

Individual variation: Perhaps the most immediate clinical lesson is that not every patient has exactly the same musculoskeletal anatomy. Variations in muscular attachments may contribute to differences in movement mechanics, although their clinical significance must be established through further research.

Importantly, the study does not demonstrate that this attachment causes hip pain, requires treatment or can be specifically identified through palpation. Nor does it establish any new manual therapy technique.

Anatomy Is Still Being Discovered

One of the most remarkable aspects of this research is that the discovery began with two students noticing something unusual during a routine anatomy dissection.

Their observation led to a systematic investigation under the guidance of Professor R. Shane Tubbs, demonstrating the continuing importance of cadaveric research.

Despite centuries of anatomical study, previously unrecognised structures and variations can still be identified.

For therapists, this discovery reinforces an important principle: anatomical knowledge continues to evolve, and clinical explanations should remain open to new evidence.

The iliac attachment of the psoas major may eventually help researchers better understand hip mechanics, tendon irritation and certain causes of anterior hip discomfort.

For now, its most important contribution is to expand our understanding of the complex anatomy of the iliopsoas region.

The takeaway for therapists: The discovery does not change current treatment recommendations, but it reminds us that the body is more variable and anatomically intricate than simplified illustrations suggest. Understanding these variations may eventually improve assessment, diagnosis and treatment of hip-related conditions.

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Reference: Roy, D. A., Bruce, C. T., et al. (2026). Iliac Attachment of the Psoas Major Muscle: Anatomical Study of a Novel Muscle Attachment. Clinical Anatomy. https://doi.org/10.1002/ca.70193