The importance of the iliopsoas muscle in horses

The importance of the iliopsoas muscle in horses

The psoas muscle is often referred to as the iliopsoas. This is because three muscles: psoas major, psoas minor, and iliacus, all converge into one tendinous insertion. It is therefore difficult to define which of the three muscles is over- or under working, or is damaged, and so we tend to look at all 3 together.

What is the iliopsoas muscle?

As mentioned above, the iliopsoas is made up of 3 different muscles:

  • Psoas major & minor- running from the transverse processes of the lumbar vertebrae and the ventral aspect of the last 2 ribs, and attaching to the lesser trochanter of the femur.
  • Iliacus- running from the iliac crest of the pelvis to the lesser trochanter of the femur.

What does the iliopsoas muscle do?

The iliopsoas muscle is a non-weightbearing muscle but has some important functions, particularly in relation to hindquarter engagement. Its main functions are:

  • Hip flexion (and therefore protraction of the hindlimb)
  • Stabilisation of the lumbar vertebral column
  • Lateral rotation (outward) of the hindlimb

So, it’s easy to see how this group of muscles is important for hindquarter function, stability of the horses posture during movement, and engagement. Do to these functions, the iliopsoas is essential in pretty much all equestrian disciplines!

What causes injury?

As with all muscles, any number of factors can cause injury to the iliopsoas. Falls & slips, working regularly in poor posture, muscle fatigue, loss of balance due to uneven surfaces, or injury/fatigue to any of the surrounding muscles which then causes the iliopsoas to compensate.

How can I tell if its injured?

This is a tricky one because the iliopsoas is a deep muscle and cannot be palpated from the exterior of the horse. The only way to palpate this muscle is via an internal procedure which must only be done by a vet. However, there are signs and symptoms that indicate injury:

  • Inability to track up
  • Difficulty picking up a certain canter lead or maintaining canter
  • Reluctance to engage the hindquarters, particularly in movements that require a lot of collection
  • Pain/sensitivity over the lumbar area
  • Lameness
  • Over time a dip between the lumbar and sacral vertebrae may appear, and the pelvis may rotate
  • Uneven musculature over the hindquarters

What can I do if my horse has injured the iliopsoas?

As with everything, prevention is better than cure! Ensuring an adequate warm up and cool down, doing short bursts of more intense work that requires collection with plenty of breaks in between, riding on good surfaces, ensuring good hoof balance, not pushing the horse past the point of fatigue, and ensuring you are balanced in your position.

If you do suspect your horse has injured their iliopsoas, your vet or bodyworker can help develop a rehabilitation plan with you. Whilst its not possible to directly massage the iliopsoas muscle due to its deep location, it is beneficial to work the surrounding tissues as this can have a secondary effect on the iliopsoas muscle to aid in its relaxation.