The Small Muscle Behind Big Back Problems: The Multifidus Muscle

The equine back is an intricate structure of bones, joints, and soft tissues that must work together in perfect harmony to allow for efficient, pain-free movement. At the core of this system lies one of the most important yet often overlooked muscles of the spine—the multifidus. This deep stabilizing muscle runs along both sides of the vertebral column, from the neck through the sacrum, and plays a critical role in maintaining spinal stability and postural control during movement.

The multifidus muscle helps stabilize the horse’s spine and support performance. When it weakens, back pain and poor movement often follow. Image courtesy of Kinetic Equine Medicine, serving equine athletes throughout Western Washington.

The Role of the Multifidus

The multifidus is sometimes referred to as the “core stabilizer” of the horse’s back. Unlike larger, more visible muscles that produce motion—such as the longissimus dorsi—the multifidus works behind the scenes to fine-tune and stabilize each vertebra during locomotion. It’s a postural muscle, designed for endurance rather than power. By providing small, precise contractions, it prevents excessive motion between spinal segments, protecting the joints, ligaments, and spinal cord from strain.

When the multifidus is strong and functioning properly, it supports proper alignment of the spine and allows the larger muscles of movement to work efficiently. A healthy multifidus contributes to the fluid, elastic, and balanced movement we associate with a sound, comfortable horse.

What Happens When It Weakens

Unfortunately, the multifidus is one of the first muscles to atrophy in the presence of back pain or even during periods of stall rest. Studies have shown that this atrophy occurs rapidly—often within days—and does not automatically reverse once the source of pain is removed. This means that even after a horse recovers from an episode of back soreness or lameness, the multifidus may remain weak and unable to provide proper stabilization.

When the multifidus loses its tone and function, the spine becomes less stable. The horse may begin to compensate by recruiting larger, superficial muscles such as the longissimus dorsi. While these muscles can help move the back, they are not designed for stabilization. Over time, this pattern of compensation creates increased strain on the vertebral joints and surrounding soft tissues. The result is a cycle of stiffness, poor performance, and eventually clinical back pain or chronic conditions such as kissing spine (overriding dorsal spinous processes).

Rebuilding the Multifidus

Because multifidus atrophy doesn’t resolve on its own, rehabilitation must include targeted exercises to restore its strength and coordination. Controlled, low-intensity movements such as raised pole work, dynamic mobilization exercises, in-hand stretches, and specific groundwork techniques have been shown to activate and rebuild this deep muscle. When integrated into a comprehensive rehabilitation or maintenance program, these exercises can help restore spinal stability and reduce the likelihood of recurring back pain.

Why It Matters

For performance horses especially, spinal stability is foundational. A weak or inactive multifidus not only affects movement quality but also predisposes the horse to compensatory lameness and long-term musculoskeletal problems. Recognizing and addressing multifidus dysfunction early—through proper assessment, treatment, and rehabilitation—can make the difference between a horse that struggles and one that thrives in its athletic career.