Useful Guide To Muscles of the Low Back – Anatomy 4 All!

Today we’ll cover muscles of the low back, in particular the ones I find most important in the clinical setting, including the erector spinae and the Quadratus Lumborum.

The muscles of the back are divided into three categories including superficial, intermediate, and deep¹. Today we’ll be focusing primarily on the deep muscles since they make up a majority of what we call the low back.

Section 1: Muscles of the Low Back Anatomy

Superficial Muscle Layer

Latissimus Dorsi

• Origin: Spinous processes of T7-L5, thoracolumbar fascia, iliac crest, and lower ribs.
  • Insertion: Intertubercular groove of the humerus.
  • Function: Extends, adducts, and medially rotates the arm; aids in trunk extension.

Intermediate Layer

Serratus Posterior Inferior

• Origin: Spinous processes of T11-L2.
• Insertion: Lower borders of ribs 9-12.
• Function: Assists in depressing ribs, stabilizing the thoracolumbar area.

Deep Muscle Layer (Intrinsic Muscles)

• Erector Spinae Group (Iliocostalis, Longissimus, Spinalis)
  • Origin and Insertion: Multiple vertebral attachments, spanning the sacrum to the skull.
  • Function: Extends and stabilizes the vertebral column.

Multifidus

• Origin: Sacrum, transverse processes of lumbar vertebrae.
• Insertion: Spinous processes of lumbar vertebrae, 2-4 segments above.
• Function: Stabilizes vertebrae, aids in extension and lateral rotation of the spine.

• Quadratus Lumborum
  • Origin: Iliac crest.
  • Insertion: 12th rib, transverse processes of L1-L4.
  • Function: Lateral flexion of the spine; assists in stabilizing the lumbar region.

Section 2: Functional Roles of Low Back Muscles

Spinal Stability and Core Support

The low back muscles play a major role in the motion of the axial skeleton.²

Mobility and Range of Motion

The low back is capable of combining movements, such as:

• Flexion and rotation
• Extension and lateral bending
• Lateral bending and rotation

These combined movements allow for a wide range of motion in the low back.

Load-Bearing and Shock Absorption

The lower back muscles are there to absorb and bear the load of the upper body.

Common Conditions Involving Low Back Muscles

According to the National Institute of Arthritis and Musculoskeletal and Skin Diseases, symptoms of back pain include the following:³

• Increasing pain with lifting and bending.
• Worsening pain when resting, sitting, or standing.
• Back pain that comes and goes.
• Stiffness in the morning when awakening and lessened back pain with activity.
• Pain that radiates away from the back into the buttocks, leg, or hip.
• Numbness or weakness in your legs or feet.

Muscle Strain and Sprain

Causes: Overuse, improper lifting, or sudden movements.

Symptoms: Pain, stiffness, limited mobility.

Degenerative Disc Disease

Breakdown of vertebrae over time due to effects wide raging.

Herniated Disc

Causes disc to compress or rupture. Can cause pinching of the nerves.

Assessment and Diagnostic Techniques

Physical Examination

Palpation of muscle groups, range of motion tests.

Evaluating muscle strength, endurance, and flexibility (such as Straight Leg Raise).

Surgical Considerations

Situations when surgery may be necessary for conditions like severe disc herniation. That should be discussed with a board certified surgeon for any medical advice or prognosis.

Section 3: Clinical Perspective on Low Back Muscles

Key Takeaway Summary

Understanding the muscles of the low back is essential for:

• Maintaining optimal posture and movement patterns
• Preventing lower back pain and injuries
• Enhancing athletic performance and functional ability

References

1. Modes RJ, Lafci Fahrioglu S. Anatomy, Back. [Updated 2023 Feb 27]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK539746/ ↩︎
2. Modes RJ, Lafci Fahrioglu S. Anatomy, Back. [Updated 2023 Feb 27]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK539746/” ↩︎
3. National Institute of Arthritis and Musculoskeletal and Skin Diseases. 2023. Back Pain. Retrieved October 16, 2024 from https://www.niams.nih.gov/health-topics/back-pain ↩︎

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