Anatomy Links: What is the Iliocapsularis Muscle?

 

An informal poll of our colleagues has concluded that no-one knew that the iliocapsularis muscle existed until two days ago… This got us thinking about other muscles of the hip that insert into the joint capsule, and their role in hip function and movement dysfunction.

Let’s dive in.  

 

Key Points: Iliocapsularis
  • The iliocapsularis is a constant muscle. ie., found in all human specimens!
  • Origin = Inferior border of the anterior inferior iliac spine + antereomedial joint capsule.
  • Insertion = Distal to the lesser trochanter.
  • Runs anterolaterally to posteromedially.
  • Lies under rectus femoris and lateral to iliacus (sometimes blends with iliacus).
  • Contraction pulls the hip joint capsule zona orbicularis superomedially -> stabilizing the hip anteriorly. 

  • Hypertrophy of the iliocapsularis is seen in patients with hip dysplasia, particularly helping to stabilize the femoral head when there is a deficient acetabulum.
  • Iliocapsularis limits synovial impingement between the acetabulum and head/neck of femur, due to tensioning of the hip capsule in flexion.
  • Iliocapsularis shows greater EMG activity in hip ranges > 90 degrees.
  • Iliocapsulais shows greater EMG activity with hip abduction and external rotation.


Iliocapsularis - Babst, et al. (2010)       

 

Anatomy Review: Muscular Attachments to the Hip Capsule
  • Reflected head of rectus femoris contributes to the anterosuperior hip capsule at the acetabular rim.
  • Contraction of rectus femoris, or high resting tone, will draw the hip capsule anteroinferiorly.
  • Balanced by contraction of iliocapsularis and gluteus minimus.
  • Gluteus minimus contributes to the lateral hip capsule, proximal to its insertion onto the greater trochanter.
  • Contraction of gluteus minimus, or high resting tone, will draw the hip capsule superomedially.

Deep capsular attachments of gluteus minimus, conjoint, and obturator externus tendons - Cooper et al, 2010.

  • Oburator externus contributes to the posteroinferior hip capsule near the posterior acetabular rim.
  • Contraction of the obturator externus, or high resting tone, will draw the hip capsule posteromedially.  
  • Conjoint tendon of obturator internus and the gemelli contributes to the posterosuperior aspect of the hip capsule.
  • Contraction of the conjoint tendon, or high resting tone of the obturator internus and/or gemelli, will draw the hip capsule medially.

 

Clinically: Pilates in Practice
  • Clients with anatomical and/or functional anterior hip impingement need to balance deep hip flexion and posterior hip support: seat the hip into hip flexion. Scooter; Eve’s lunge; sleeper; standing leg press.

                                          

  • Clients with hip dysplasia/a history of hip dysplasia need to strengthen hip flexion. Reverse knee stretches; resisted Bird-Dog.
  • Gluteus minimus abducts hip through slight hip extension, hip neutral, and slight hip flexion; align appropriately. Side lying leg series (mat/reformer/trapeze table).

  • Deep lateral rotators work with improved proprioceptive/joint load. Rotator discs.
  • Consider capsular attachments for labral issues, and other intra-articular hip pathologies too. Cue for support around the circumference of the hip.

 

 1. Babst, D., Steppacher, S., Ganz, R., Siebenrock, K., & Tannast, M. (2010). The Iliocapsularis Muscle: An Important Stabilizer in the Dysplastic Hip. Clinical Orthopaedics And Related Research®, 469(6), 1728-1734. doi: 10.1007/s11999-010-1705-x

2. Cooper, H., Walters, B., & Rodriguez, J. (2015). Anatomy of the hip capsule and pericapsular structures: A cadaveric study. Clinical Anatomy, 28(5), 665-671. doi: 10.1002/ca.22539

3. Sato, T., Sato, N., & Sato, K. (2016). Review of the Iliocapsularis Muscle and its Clinical Relevance. Anatomy & Physiology, 6(5). doi: 10.4172/2161-0940.1000237

4. Lawrenson, P., Grimaldi, A., Crossley, K., Hodges, P., Vicenzino, B., & Semciw, A. (2017). Iliocapsularis: Technical application of fine-wire electromyography, and direction specific action during maximum voluntary isometric contractions. Gait & Posture, 54, 300-303. doi: 10.1016/j.gaitpost.2017.03.027

5. <a href='https://www.freepik.com/free-photos-vectors/people'>People photo created by kjpargeter - www.freepik.com</a>

 

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