Understanding the Horse's Back

With good back posture being key to a good performance as well as a happy healthy horse, understanding more about how the horse's back works should be high on the list for every rider, trainer and therapist as this information can help us to keep the horse's back healthy, strong and mobile.

Knowing the names of the bones of course help us to communicate with our vet and other team members that help to look after our horses. But in my mind it is having an understanding of the locations, shapes and function of the anatomical structures. And also the answer to the question - why. Why are the bones in that position? Why are they that shape? Why is there more movement in one part of the horse's body compared to another? Why are there strong muscles in that particular location?

When we begin to answer questions such as these, about our horse's back, it can help us to understand how we should be riding and training our horses. It can also help us to assess our individual horses. Knowing what is a normal range of movement, for example, is key to being able to recognise when things change with your own horse.

Back Anatomy

Technically the back just consists of the thoracic and lumbar sections of the spine. However the health, position and movement of the back is affected by the health, position and movement of the head and neck, the forelimbs, the pelvis, the hindlimbs and hoof balance. So in reality it is important to study the anatomy and relationships of the whole horse.

In the on-demand webinar, Understanding the horse's back, using anatomically painted horses and slow motion videos, this is something that's discussed. Packed with information, tips and exercises related to the anatomy, biomechanics, structure and function of the horse’s back, the webinar is divided into three main parts:-

1. Back Anatomy

2. Back Biomechanics

3. Back Posture

Learn more about the webinar Understanding the Horse's Back here: https://www.horsesinsideout.com/webinar-back1

The horse’s spine is a strong and complex structure consisting of the vertebrae supported by a myriad of ligaments and muscles.

The Thoracic Spine

This consists of 18 vertebrae each separated by a fibrocartilaginous intervertebral disc and locked together by articular processes. With very little movement between each joint it is a very rigid area. The rigidity of the horse’s spine is what allows us to ride our horses!

The spine runs lower than many people imagine due to the fact that each vertebral body is topped by a spinous process of up to 30 centimetres, the longest being the 4th and 5th thoracic vertebrae which create the withers. These then decrease in length towards the tail. They provide extensive areas for muscle and ligament attachment as well as acting as a fulcrum for movement particularly at the withers. The tops of the spinous processes can be felt as knobbly ‘bumps’ along the midline of the horse’s back.

18 pairs of ribs insert between neighbouring thoracic vertebrae via synovial joints before protruding horizontally to curve round the barrel of the horse. The first eight pairs, which house and protect the lungs, are known as true ribs. They join on to the sternum and allow the chest cavity to expand as the horse breathes. The other ten are known as false ribs and are attached to each other.

The Lumbar Spine

The absence of ribs in the lumbar region make this area appear weaker. The lumbar region transmits forces created at the hindquarters forward.

This is the loins region. Six lumbar vertebrae form a continuation of the thoracic spine. This complex area is characterised by the length and width of the transverse processes which project horizontally to provide points of attachment for large, strong ligaments and muscle groups. They also provide protection for the organs that lie below.

This area of the spine is often described in conjunction with the thoracic vertebrae as the thoracolumbar spine. The spinous processes projecting from the top of the lumbar vertebrae are a similar length to the last few thoracic vertebrae.

Ligaments of the Back

The main ligaments support the back rather like a series of cables in a suspension bridge. They are:-

The Supraspinous Ligament This lies on top of and attaches to each spinous process from the withers to the sacrum. As it moves away from the nuchal ligament it becomes more fibrous and more inelastic. When the back is flexed and lifted up, this puts the supraspinous ligament under traction. Its main function is to restrain the movements of the dorsal spines and keep the vertebrae in place thus giving the back support, strength and stability.

The Ventral Longitudinal Ligament

This attaches to the underside of the vertebral bodies, and is only present from the fifth thoracic vertebrae towards the tail. It is a relatively weak ligament that supports the thoracic, lumbar and sacral regions of the spine. This ligament is stretched when the back is hollowed.

The Interspinous Ligament

This ligament fills the gaps between the spinous processes and provides further support and stability to the vertebrae. The fibres are attached diagonally so as not to interfere with flexion and extension of the back.

Musculature of the back

The main muscles involved in stabilising the back are close to the spine and include the thoracis and lumborum sections of the multifidus muscle.

Further away from the vertebrae, the muscles become bulkier and more powerful. They are responsible for gymnastic movement, supporting the back and are involved in transferring movement created at the hind end forward. They can be split into two groups:

1. The main extensors of the back.

These are the erector spinae group consisting of the iliocostalis, longissimus dorsi and the spinalis thoracis muscles which run along the top of the vertebrae and either side of the spinous processes.

2. The main flexors of the back.

These include the abdominal muscles which consist of the internal and external abdominal oblique muscles, the transverse abdominal muscle and the rectus abdominae. These all work together to hold the abdomen in place, assist respiration, move the ribs and support the correct positioning of the vertebral column. These muscles need to be strong to assist the back in supporting the weight of the rider.

Summary

· The horse’s back consists of 18 thoracic and 6 lumbar vertebrae

· There is little movement between the vertebrae

· Strong ligaments support the back

· The muscles which extend the back are situated above the vertebral bodies and include the longissimus dorsi muscle

· Muscles which flex the back include the abdominal muscles

If you'd like to learn more about check out Gillian's webinar Understanding the Horse's Back here: https://www.horsesinsideout.com/webinar-back1