Anatomy and Functional Dynamics of the Equine Thoracolumbar Spine

The area of your horse’s back between the withers and the loins is known as the thoracolumbar spine. It has a vital role in movement, posture, and performance. Whether your horse is doing dressage, jumping, eventing, or pleasure riding, this region must function efficiently to support both the rider and the forces during movement.

The thoracolumbar spine T11-L2

In this blog, we take a look at the structure of the thoracic and lumbar spine, its relationship to posture and strength, and the muscle groups that work behind the scenes to keep your horse moving well.

Anatomy: What’s in the Thoracolumbar Spine?

The thoracolumbar spine is junction between the thoracic spine (T1-T18) and the lumbar spine (L1-L6). The tall bony projections on top of the vertebrae, the dorsal spinous processes, form the outline of the back. The back of the saddle sits at the front of this region, and the saddle should not extend past the last thoracic vertebrae and rib. This region of the spine allows for a large range of movement in multiple planes of motion.

Key anatomical components:

• Vertebrae: provide the rigid structure to the spine, houses the spinal cord and provides exits for nerve roots that innervate the rest of the body, gives anchor points to key muscles involved with locomotion and stability,

• Intervertebral or Facet joints: Facilitate movement between each vertebra through a range of planes (flexion, extension, rotation)

• Ligaments: Including the supraspinous ligament, which runs along the top of the spine

• Muscles: Epaxials (along the top) and abdominal muscles (underneath) work together to stabilise the spine

  
  

Function: What Does This Part of the Spine Actually Do?

• Stabilises posture, provides the structure and form to the trunk and provides pathways for important nerves to relay information from brain to the trunk and limbs

• Acts as a bridge between the forelimbs and hindlimbs and helps transmit forces from the hind end,

• From a ridden perspective it supports the rider’s weight and allows for bend and flexion, which is a key part of movement under saddle.

When this area lacks strength or mobility, it can lead to compensation elsewhere, discomfort, or reduced performance.

Functional Anatomy: How the Spine Moves and Works

Working on the circle showcases the flexibility required through the thoracolumbar spine

While the thoracolumbar spine doesn’t have a large range of motion between each vertebra, its cumulative movement matters, especially when the horse is asked to carry a rider, collect, bend, or transition between gaits.

This region of the spine can move in:

1. Flexion and Extension: Mostly happens in the lumbar region and facilitates rounding the back and engagement the hindquarters (flexion). Extension occurs naturally during propulsion and jumping while the ability of the spine to flex allows for collection and carrying weight correctly under saddle

2. Lateral Bending: Involves side-to-side movement and is important for turning, circling, and bending around the leg. This can often be restricted when there’s stiffness, joint pain, or muscle imbalance.

3. Rotation: Lateral bending can't take place without rotation, so this is a subtle but important movment allowing one side of the spine to twist slightly compared to the other. This helps with balance and dynamic movement, especially in canter transitions or lateral work.

Together, these movements contribute to what’s known as spinal kinematics — the ability of the spine to coordinate movement through the trunk. While the movement at each segment is small, the combined flexibility and control determines overall range of motion, intern affecting movement and performance.

The Core-Spine Connection

Core strength is a foundational element of spinal health. The deep abdominal and back muscles — including the multifidus, transversus abdominis, and obliques — support the vertebrae and help stabilise the spine during movement.

The spine is not just supported by bones and ligaments — it depends heavily on muscular control, particularly from the deep stabilising muscles of the back and abdomen.

These include:

• Multifidus – provides segmental spinal stability

• Longissimus dorsi – helps with spinal extension

• Transversus abdominis – deep abdominal stabiliser

• Obliques and rectus abdominis – assist with flexion, posture, and trunk control

If these muscles are weak or inactive:

• The spine becomes less stable

• The horse may “hollow” through the back

• Compensatory movement patterns arise (e.g., overloading the forelimb or avoiding engagement)

Why This Matters in Practice

Poor spinal function or muscle imbalance can result in a loss of topline and a weak back and present with issues under saddle. This may include a reluctance to bend/collect, difficulty engaging the hindquarters and soreness under saddle.

Understanding these structures and how they work together, helps us better support spinal health. Regular chiropractic care in conjunction with a consistent activating warm up, strength programs, focused training and proprer saddle fit will all help to keep our spine and its associated structures functioning at their best.

The thoracolumbar spine is not just a passive structure — it’s dynamic, responsive, and integral to how your horse moves, performs, and feels. A well-functioning spine relies on good structure, strong stabilising muscles, and thoughtful conditioning.

When we understand this system better, we can better support our horses — both in training and in soundness.

Wondering about the health of your horse’s spine? Book a consultation to assess spinal function, posture, and overall comfort.

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