Iliopsoas Part 1

​It's Muscle Monday again! This week is going to be part one in a two part post on the Iliopsoas muscle group. It's such an important group in the horse and there's so much to it, that one post will simply be way too long to try and delve into it all. Well, let's get to it!

L O C A T I O N:
The Iliopsoas muscle group is comprised of the Psoas Major and the Iliacus muscle.
PSOAS MAJOR:
Origin:
- Transverse processes of the lumbar vertebrae
- Ventral surface of the proximal ends (underside of the top) of the last two ribs.
Insertion:
- Lesser trochanter of the femur. It is here where it fuses with the Iliacus.
ILLICUS:
Origin:
- Sacroiliac surface of the ilium
- Wing of sacrum
- Sacroiliac ligament
- Psoas minor tendon
Insertion:
- Lesser trochanter of the femur. It is here where it fuses with the Psoas Major.

R O L E:
Both the Iliacus and Psoas Major that make up the Iliopsoas have the same muscular function.
- Hindlimb protraction
- Outward rotation of the hindlimb
- Hip joint flexion
- Stabilizer of vertebral column when the hindlimb is in a fixed position.
The Iliopsoas muscle group connects the trunk to the hindquarters, enabling hindlimb muscle engagement while maintaining correct posture. As is easily determined by noting the function of the Iliopsoas, correct and healthy function is required for efficient hindlimb protraction.

D Y S F U N C T I O N :
The Iliopsoas is particularly vulnerable to strain due to its anatomical positioning and function. Therefore, the likelihood of a force being applied beyond the muscles capabilities is increased.
Pre-disposing Factors to Injury:
- Inadequate warm-up
- Existence of a previous injury to the muscle or associated structures
- Fatigued muscles
- Loss of balance – ie. poor surfaces (This particularly places a lot of stress on the muscle insertion at the lesser trochanter of the femur.)
- Muscular tension/hypertonicity
- Head and neck in a deep and round position
- Serious fall
- Becoming cast

While the injury may have occurred in the Iliopsoas muscle group, a direct negative effect on the function of the Psoas Minor muscle may occur. Injury can occur on one or both sides.
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Next week we'll go more into pain symptoms, the link between the Iliopsoas and back pain, hormones, and diet and kidneys. See, there's quite a lot left to talk about with this muscle group! Until next week!