The multifidus muscle is a deep, layered muscle of the back that plays a major role in spinal health. Dysfunction in this muscle is a frequent contributor to chronic low back discomfort. Because the multifidus provides specific support to the individual segments of the spine, its impairment can lead to mechanical instability and long-term pain. Understanding its function and common issues is an important step toward effective rehabilitation and lasting relief.
Understanding the Multifidus Muscle
The multifidus muscle is a collection of short, thick muscle bundles that run along the length of the spine, from the sacrum up to the neck. It is one of the deepest muscles of the back, lying close to the vertebral column and the facet joints. Its unique structure, where each bundle spans between two to five vertebral segments, gives it a localized and precise function.
The primary function of the multifidus is to provide segmental stability to the spine. It controls the movement of individual vertebrae, ensuring they remain properly aligned during activities like bending, twisting, and lifting. This deep muscle also has a high density of muscle spindles, giving it a significant role in proprioception, the body’s sense of its position and movement in space. Maintaining this localized control helps reduce wear on joint structures and protects the spine during daily activities.
Primary Causes of Pain and Dysfunction
Pain in the multifidus muscle often stems from two main mechanisms: acute injury or chronic dysfunction. An acute strain or sprain typically occurs from a sudden, uncontrolled movement, like incorrectly lifting a heavy object or a rapid twist. This overstretches the muscle fibers, causing immediate pain and swelling. This physical trauma causes a protective mechanism in the nervous system, leading to muscle guarding and spasm.
The more common and persistent issue is chronic dysfunction, which frequently involves muscle atrophy. Following an episode of low back pain or an injury, the multifidus muscle tends to “shut off” or weaken, often due to a reflex called arthrogenic muscle inhibition. This inhibition leads to a reduction in muscle size and strength, and in severe cases, the muscle tissue is replaced by fat, a process known as fatty infiltration.
Atrophy compromises the muscle’s ability to stabilize the individual spinal segments, leading to unwanted movement and subsequent mechanical pain. The resulting instability forces larger, superficial back muscles to compensate, but these muscles are not designed for precise segmental control. This perpetuates the cycle of pain and dysfunction. Dysfunction is also associated with a loss of motor control, meaning the brain struggles to activate the muscle correctly, even after the initial pain has resolved.
Treatment and Long-Term Rehabilitation Strategies
Treating multifidus muscle pain involves managing acute symptoms and implementing a targeted long-term rehabilitation plan. Acute pain management focuses on reducing inflammation and discomfort through conservative methods. These methods include short periods of relative rest, the application of ice or heat, and the temporary use of non-steroidal anti-inflammatory drugs (NSAIDs) to alleviate muscle spasm and pain.
Lasting relief relies on physical therapy aimed at restoring the muscle’s function and motor control. The goal is to retrain the deep, segmental stabilizing function of the multifidus, which does not automatically return to normal after an injury. Initial exercises focus on isolated activation, teaching the patient how to consciously engage the deep core muscles without recruiting the larger, compensating superficial muscles.
Specific stabilization exercises, often performed in a neutral spine position, are introduced to re-establish the brain-muscle connection. One common technique is the “abdominal draw-in,” where a person gently pulls their lower abdomen inward without tilting the pelvis, which helps to co-activate the multifidus alongside the transverse abdominis. This subtle movement aims to restore the precise, low-level contraction needed for segmental stability.
As control improves, the rehabilitation progresses to dynamic exercises that challenge the muscle’s ability to stabilize the spine during movement. Exercises like the Bird Dog, where opposite arm and leg are extended while maintaining a stable torso, are excellent for this purpose. The Superman exercise, performed by lifting the chest and legs slightly while lying face down, also targets the multifidus by engaging spinal extension.
Long-term strategies incorporate robust strengthening to build muscle resilience and prevent recurrence. This includes integrating the multifidus into functional, loaded movements like squats and deadlifts, but only after proper form and segmental control have been mastered. For individuals with chronic pain that resists traditional physical therapy, minimally invasive options like rehabilitative neurostimulation are sometimes used to directly stimulate the nerves controlling the multifidus.