Serratus Posterior Inferior Muscle

Introduction

The serratus posterior inferior muscle is found in the back’s intermediate compartment. It is located in the lower part of the back, beneath the latissimus dorsi. It plays a role in respiration and stabilization of the lower thoracic and upper lumbar vertebrae.

Structure

The muscle is placed where the thoracic and lumbar spines meet. With an irregular quadrilateral shape, it is wider than the serratus posterior superior muscle and widely spaced apart from it.

A thin aponeurosis forms when the spinous processes of the top two or three lumbar vertebrae and the bottom two thoracic vertebrae meet.

It becomes fleshy, travels laterally and obliquely upward, then splits into four flat digitations. These go somewhat beyond the angles of the lowest four ribs’ inferior margins.

Origin

Spinous processes of T11 to L2 vertebrae.

Consists of muscle fibres that run superolaterally and originate from the lumbar and thoracis spines (typically T11-L3).

Insertion

Inferior borders of the 9th to 12th ribs (outer surfaces, near their angles).

Attaching to ribs 9 – 12.

Nerve Supply

Nerves T9-T12 intercostally.

Blood Supply

The posterior intercostal, subcostal, and upper lumbar arteries all contribute blood flow.

Innervation

Subcostal nerve (T12) and intercostal nerves (T9–T11).

Function

Depresses ribs 9 – 12. This rib movement may cause intake and forceful exhalation of air from the lungs.

Clinical Importance

Serratus posterior inferior muscle Pain

Serratus posterior inferior muscle discomfort is characterised by soreness or tenderness in the lower back and ribs, which can be severe. Numerous factors, including trauma or injury, poor posture, overuse, and muscular tension, may contribute to this discomfort, albeit they are quite uncommon.

Treatment for Serratus Posterior Inferior Muscle Pain:

• Rest and Steer Clear of Upsetting Activities
• Stretching and mild range-of-motion exercises with ice or heat therapy
• Manual therapy or massage
• Over-the-Counter Drugs for Pain
• Adjusting Posture and Making Ergonomic Adjustments
• Physical Therapy for Joint or Respiratory Conditions at Their Root

Serratus posterior inferior muscle Injury

The serratus posterior inferior muscle can sustain injuries that cause localised pain and discomfort in the lower back and ribcage area.These problems are uncommon, but can be caused by trauma, misuse, or poor biomechanics.

The superior and inferior serratus posterior muscles are often regarded as clinically irrelevant, despite the fact that their attachments suggest that they have a respiratory role. It’s interesting to note, though, that there is no evidence linking these muscles to breathing.

The concept that these muscles provide a respiratory function is contradicted by some electromyographic results. Furthermore, because of their association with myofascial pain problems, these muscles, especially the superior, may have greater clinical relevance than is typically thought.

Low Back Pain

It’s important to remember that this muscle supports the lower back by stabilising the four lower ribs and assisting in their descent and return, even if its primary role is proprioception.

The serratus posterior inferior functions in together with the quadratus lumborum, longissimus thoracis, and iloicostalis.

Trigger Point of Serratus Posterior Inferior

Trigger points in the serratus posterior inferior muscle can produce abnormal, localised discomfort that spreads throughout the muscle.

Usually, consumers describe this sensation as a persistent ache.

Deactivating more trigger points often doesn’t eliminate persistent discomfort.

Serratus posterior inferior stretch

Lift your forearms slightly over your wrists, reaching chest height.

Breathe deeply, then raise them gradually until your forehead touches the point where your arms cross.

Let out one last sigh and drop your arms.

Pause for a few seconds to recuperate, then repeat once or again.

Treatment

By training the serratus posterior inferior muscle, one may increase its strength, flexibility, and functionality. The following workouts target the serratus posterior inferior:

Deep Breathing Exercises:

Practice diaphragmatic breathing to engage the serratus posterior inferior during deep breathing. Concentrate on filling your lungs and expanding the lower section of your rib cage.

Thoracic Extension Stretch:

• Posture: Standing or Sitting
• Behind your back, shake hands.
• Raise your arms and slowly stretch them backward while maintaining your shoulder blades together.
• You should feel a little thoracic stretch after 15 to 30 seconds of holding the stretch.

Seated Forward Bend with Rotation:

• Sit down on the ground.
• Extending your legs
• With your right hand extended toward your left foot, bend forward at the hips.
• Moved your body to the left and placed your left arm behind you.
• After 15-30 seconds of stretching, switch sides.

Cat-Cow Stretch:

• Place yourself on your hands and knees
• As you raise your head and lower your belly into the Cow Pose, take a deep breath.
• Release the breath as you lower your chin into your chest and turn your back (Cat Pose).
• Repeat the process 10–15 times.

FAQs

References

• Serratus posterior inferior muscle – 2024 https://teachmeanatomy.info/encyclopaedia/s/serratus-posterior-inferior/
• Serratus posterior inferior muscle – 2023 https://mobilephysiotherapyclinic.net/serratus-posterior-inferior-muscle
• Serratus posterior inferior muscle – 2024 https://en.wikipedia.org/wiki/Serratus_posterior_inferior_muscle