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Psoas major and its controversial rotational action.
A D Skyrme1, D J Cahill, H P Marsh
1Department of Anatomy, U.M.D.S., London, United Kingdom.
Clinical Anatomy (New York, N.Y.)
|July 9, 1999
Summary
The psoas major muscle primarily flexes the hip. Its rotational action on the femur depends on the hip
Area of Science:
- Anatomy
- Biomechanics
- Kinesiology
Background:
- The psoas major muscle's role as a primary hip flexor is established.
- Its function as a medial or lateral rotator of the femur remains debated.
Purpose of the Study:
- To investigate the rotational actions of the psoas major muscle on the femur.
- To determine the influence of hip joint position on psoas major muscle function.
Main Methods:
- Dissection of psoas and iliacus muscles in six cadaveric specimens.
- Assessment of psoas major muscle action by applying traction along its long axis.
- Visual estimation of femoral rotation in degrees with and without the hip joint capsule.
Main Results:
- In the anatomical position, psoas major traction caused hip flexion without rotation.
- Hip abduction during traction resulted in flexion, adduction, and lateral rotation.
- Hip adduction during traction produced only flexion; maximal flexion caused adduction.
- Results were consistent with and without the hip joint capsule.
Conclusions:
- Psoas major muscle's rotational action is position-dependent.
- It acts as a lateral rotator in hip abduction and does not rotate in adduction.
- These findings clarify the complex biomechanics of the psoas major muscle.