The muscles surrounding and attaching to the spine, called paraspinal muscles, are responsible for both moving and stabilizing the spine. These muscles function as spinal stabilizers, protecting the spine by helping to maintain its alignment and preventing excessive movement.
- Longissimus Dorsi:
- Location: The longissimus dorsi is the largest and most prominent of the paraspinal muscles, extending from the sacrum to the occiput, running along the entire length of the spine. It lies deep to the superficial muscles of the back.
- Attachments: This muscle attaches to the transverse processes of the vertebrae, as well as to the ribs and the pelvis.
- Function: The longissimus dorsi helps in extending and flexing the spine, maintaining posture, and facilitating lateral flexion. It also plays a role in stabilizing the spine during movement. This muscle is important for the horse’s ability to perform collected movements and maintain a balanced posture during various gaits.
- Iliocostalis:
- Location: The iliocostalis muscle is located lateral to the longissimus dorsi, running along the ribs and the lumbar spine.
- Attachments: It attaches to the angles of the ribs and the transverse processes of the lumbar vertebrae.
- Function: This muscle is primarily involved in stabilizing the spine and assisting in lateral flexion of the back. The iliocostalis also supports posture and helps maintain the ribcage during movement. It contributes to the horse’s ability to bend and flex its body, especially during lateral movements and turns.
- Multifidus:
- Location: The multifidus muscles are deep muscles that run along the vertebral column from the sacrum to the cervical spine. They are segmented, with short, overlapping fibers attaching to multiple vertebrae.
- Attachments: Multifidus muscles attach from the sacrum, ilium, and transverse processes of the vertebrae to the spinous processes of the vertebrae above them.
- Function: The multifidus muscles are key in stabilizing the spine, controlling finer movements, and assisting with both extension and rotation of the vertebral column. These muscles help maintain the alignment of the spine and prevent excessive movement that could lead to injury. In horses, the multifidus is essential for dynamic stability during movement, especially in complex maneuvers that require precise control of the spine.
- Spinalis:
- Location: The spinalis muscle is located closest to the vertebral column, running along the spinous processes of the thoracic and upper lumbar vertebrae.
- Attachments: It attaches to the spinous processes of the vertebrae, particularly in the thoracic region.
- Function: The spinalis muscle is involved in the extension of the spine, helping to straighten and support the back. It also contributes to the overall stability of the vertebral column. This muscle works in concert with the other paraspinal muscles to maintain the horse’s posture and facilitate smooth, coordinated movements along the length of the spine.
- Rotatores:
- Location: The rotatores muscles are small, deep muscles found between the transverse and spinous processes of adjacent vertebrae. They are part of the deepest layer of the paraspinal muscles and are most prominent in the thoracic region of the spine.
- Attachments: These muscles attach from the transverse process of one vertebra to the base of the spinous process of the vertebra above.
- Function: The rotatores assist in the rotation and stabilization of the spine. Although they are smaller and less segmented than the multifidus muscles, they play an important role in fine-tuning spinal movements and providing proprioceptive feedback. The rotatores contribute to the intricate control of vertebral positioning, which helps maintain spinal alignment and stability during dynamic movements.
The small size of these muscles enables the spine to make minute adjustments when bending, weight-bearing, and during rotational movements. Their activity increases during weight-bearing activities, such as when carrying a rider.
The paraspinal muscles are embedded in fascia that merge with or connect to the ligaments of the spine, which in turn are intimately connected to the thoracolumbar fascia. This interconnectedness provides support, mobility, and stability to the spine.
The paraspinal muscles can only perform their job correctly if the fascia surrounding them is mobile enough to allow them to function and receive full sensory input.
Spine health and functionality truly start with fascia, the largest sensory organ in the body. Before we see the issues, before the horse feels the “not-quite-right” or needs an adjustment, the fascia is already telling the story.
This concept applies to the horse’s entire body. Ensuring the health and mobility of fascia is key to maintaining overall equine well-being.
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