Multifidus Muscle Ultrasound in Chronic Low Back Pain: Emerging Insights in Pain Medicine

Chronic low back pain (CLBP) is one of the most common causes of disability worldwide and remains a major challenge for clinicians. While conventional imaging often focuses on discs, facet joints, and neural compression, growing evidence suggests that dysfunction of the lumbar multifidus muscle (LMM) plays a critical role in persistent spinal pain and instability.

Musculoskeletal ultrasound (MSK-US) has emerged as a valuable imaging modality for evaluating multifidus morphology and function in real time. It provides a dynamic assessment of muscle thickness, contraction, asymmetry, and fatty degeneration without radiation exposure.

The Lumbar Multifidus Muscle

The lumbar multifidus is a deep paraspinal muscle located adjacent to the vertebral laminae and spinous processes. It belongs to the transversospinalis muscle group and is essential for:

• Segmental spinal stabilization

• Intervertebral motion control

• Lumbar posture maintenance

• Neuromuscular coordination

Biomechanical studies suggest that the multifidus contributes significantly to maintaining spinal stability within the lumbar “neutral zone.”

Multifidus Dysfunction in Chronic Low Back Pain

Multiple studies have demonstrated strong associations between chronic low back pain and multifidus abnormalities, including:

• Muscle atrophy

• Reduced cross-sectional area

• Fatty infiltration

• Decreased contractility

• Side-to-side asymmetry

Importantly, these abnormalities may persist even after resolution of acute pain episodes, potentially contributing to recurrent low back pain.

A review by Freeman et al. highlighted that lumbar multifidus dysfunction is strongly associated with chronic low back pain and spinal instability.

Recent evidence also demonstrates correlations between non-specific chronic low back pain and multifidus fatty infiltration and altered muscle function.

Why Multifidus Muscle Ultrasound Is Important

Although MRI remains the gold standard for evaluating fatty degeneration and spinal pathology, ultrasound offers several practical advantages:

• Real-time dynamic imaging

• Bedside evaluation

• Cost-effectiveness

• No radiation exposure

• Functional muscle assessment

• Rehabilitation biofeedback capability

Ultrasound is particularly useful for repeated follow-up assessments during rehabilitation programs.

Ultrasound Anatomy of the Multifidus

The lumbar multifidus appears sonographically as a hypoechoic muscle containing internal echogenic fibrous septae.

Key sonoanatomical landmarks include:

• Spinous process

• Lamina

• Facet joint

• Thoracolumbar fascia

• Erector spinae muscles

A standardized interpretation guide has emphasized the importance of understanding superficial, lateral, and deep multifidus components to improve consistency in ultrasound assessment.

Common Multifidus Muscle Ultrasound Findings in CLBP

1. Multifidus Atrophy

Reduction in muscle thickness and cross-sectional area is commonly observed in patients with chronic low back pain.

Wallwork et al. demonstrated reduced multifidus size and impaired contraction in individuals with chronic low back pain compared to controls.

2. Fatty Infiltration

Chronic dysfunction may lead to replacement of muscle tissue with fat.

Ultrasound findings include:

• Increased echogenicity

• Loss of normal muscle architecture

• Reduced contractile appearance

Recent studies have shown strong agreement between ultrasound and MRI for assessing fatty atrophy at symptomatic lumbar levels.

3. Impaired Muscle Activation

Dynamic ultrasound assessment during functional tasks can reveal delayed or inadequate multifidus contraction.

Patients with CLBP often demonstrate:

• Reduced thickening during contraction

• Delayed recruitment

• Asymmetrical activation patterns

Rehabilitative ultrasound imaging studies have shown that individuals with low back pain exhibit decreased muscle thickening and asymmetry compared to healthy controls.

Reliability of Multifidus Ultrasound

Several studies have demonstrated good-to-excellent reliability of ultrasound measurements of lumbar multifidus thickness and cross-sectional area.

Koppenhaver et al. reported high intra- and inter-examiner reliability for rehabilitative ultrasound imaging of lumbar multifidus muscles in patients with low back pain.

More recent studies continue to support the reliability of ultrasound assessment in both static and dynamic conditions.

Role in Rehabilitation and Biofeedback

One of the greatest advantages of ultrasound is its application as a rehabilitation biofeedback tool.

Real-time ultrasound imaging enables patients to visualize multifidus contraction during:

• Motor control exercises

• Core stabilization training

• Segmental activation exercises

This improves neuromuscular awareness and exercise precision.

Research suggests that restoration of multifidus activation may play a key role in reducing recurrent low back pain episodes.

Clinical Applications in Pain Medicine

Ultrasound assessment of the multifidus is increasingly relevant in:

• Chronic low back pain evaluation

• Segmental instability assessment

• Motor control dysfunction analysis

• Image-guided pain interventions

• Regenerative medicine procedures

Understanding multifidus anatomy improves precision during:

• Medial branch blocks

• Facet interventions

• Trigger point injections

• Fascial plane injections

• Regenerative therapies

Emerging Regenerative and Restorative Therapies

Recent therapeutic strategies targeting multifidus dysfunction include:

• Motor control rehabilitation

• Restorative neurostimulation

• Platelet-rich plasma (PRP) injections

• Neuromuscular retraining

• Regenerative medicine approaches

Emerging evidence suggests that targeted restoration of multifidus function may improve outcomes in patients with chronic mechanical low back pain.

Limitations of Ultrasound

Despite its advantages, ultrasound has limitations:

• Operator dependency

• Variable image quality in obese patients

• Difficulty visualizing deeper structures in some individuals

• Need for standardized protocols and training

Proper operator expertise is essential for accurate interpretation and reproducibility.

Future Directions

Future developments in multifidus ultrasound may include:

• AI-assisted image analysis

• Quantitative muscle assessment

• Ultrasound elastography

• Three-dimensional ultrasound imaging

• Automated fatty infiltration grading

Recent research is exploring AI-driven tissue layer analysis and advanced ultrasound segmentation models for chronic low back pain evaluation.

Conclusion

Lumbar multifidus dysfunction is increasingly recognized as a major contributor to chronic low back pain. Ultrasound imaging provides a reliable, dynamic, and clinically practical method for assessing multifidus morphology and function.

Beyond diagnosis, rehabilitative ultrasound serves as a valuable biofeedback tool that may enhance motor control retraining and rehabilitation outcomes.

As pain medicine continues to evolve toward functional and regenerative approaches, multifidus ultrasound is likely to become an increasingly important component of comprehensive chronic low back pain management.

References

1. Freeman MD, Woodham MA, Woodham AW. The role of the lumbar multifidus in chronic low back pain. PM&R. 2010.

2. Wallwork TL et al. The effect of chronic low back pain on size and contraction of the lumbar multifidus muscle. Manual Therapy. 2009.

3. Teyhen D. Rehabilitative ultrasound imaging. Journal of Physiotherapy. 2011.

4. Koppenhaver SL et al. Reliability of rehabilitative ultrasound imaging of the transversus abdominis and lumbar multifidus muscles. Arch Phys Med Rehabil. 2009.

5. Soer R et al. A guide for standardized interpretation of lumbar multifidus ultrasonography. 2022.

6. Abd-Elsayed A et al. Lumbar Multifidus Dysfunction and Chronic Low Back Pain. Pain Physician. 2025.

7. Cheung WK et al. Role of Ultrasound in Low Back Pain: A Review. Ultrasound Med Biol. 2020.