Scapulothoracic Joint

Authors
Affiliations

Nathaniel Yomogida, B.S., SPT

Doctor of Physical Therapy

B.S. in Kinesiology

Chloë Kerstein, B.S., SPT

Doctor of Physical Therapy

B.A. in Neuroscience

Alignment

  • Vertebral border
    • Parallel to spine, 2-3 finger width (3’’) from the midline of the thorax
  • Between 2nd and 7th thoracic vertebrae
  • 30° ant to the frontal plane (scapular plane)
  • 10° ant tilt
  • 5-10° upward rotation

Primary movements

There are 6 primary movements of the scapulothoracic joint:

  1. Elevation
  2. Depression
  3. Protraction
  4. Retraction
  5. Upward rotation
  6. Downward rotation

Elevation

Elevation refers to when the scapula slides superiorly relative to the thorax1. Shruggint the shoulders is an example of scapular elevation1.

  • Includes elevation of clavicle at SC and downward rot of scap at AC

Depression

Depression of the scapulothoracic joint refers to when the scapula slides inferiorly relative to the thorax from an elevated position1.

  • Lats
  • Pec Minor
  • Lower trapezius

Protraction

Protraction refers to when the medial border of the scapula slides anterolaterally relative to the thorax1. This will result in movement of the medial border away from the spine. An example of protraction is when you are reaching forward as far as possible1.

Retraction

Scapular retraction refers to when the medial border of the scapula slides posteromedially relative to the thorax towards the midline1. This is exemplified when you “pinch” the shoulder blades together.

Upward Rotation

During scapular upward rotation, the inferior angle of the scapula rotates superiolaterally relative to the thorax1 This results in the glenoid fossa facing upwards1.

Upward rotation is a key component when raising the arm upward1.

60° upward rotation during arm elevation

Downward rotation

Downward rotation refers to when the inferior angle of the scapula rotates in an inferomedially direction1. Downward rotation is most obvious when lowering the scapula from an upwardly rotated position1.

Downward rotation is key component of lowering the arm down to one’s side1.

Other kinematics

Force couple

  • Serratus anterior (greatest mechanical advantage for UR)
  • Upper trap (Initiation and throughout)
  • Late phase: Lower trap

Anterior Tilt

Posterior Tilt

20° post tilt during arm elevation

Internal Rotation

<= 5° IR/ER

External Rotation

<= 5°

Stabilization

The Serratus Anterior (along with the rhomboids) serves to aid in scapular stability during arm elevation2

Superior View of the shoulder: You can see how the rhomboids and SA both actively stabilize the scapulothoracic joint by pulling the scapula towards the thoracic wall2

Superior View of the shoulder: You can see how the rhomboids and SA both actively stabilize the scapulothoracic joint by pulling the scapula towards the thoracic wall2

Stabilization

  • Middle trap (add / retract) which counteract the protraction force of the Serratus anterior, resulting in stabilization of the scapula

References

1.
Neumann DA, Kelly ER, Kiefer CL, Martens K, Grosz CM. Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation. 3rd ed. Elsevier; 2017.
2.
Dutton M. Dutton’s Orthopaedic Examination, Evaluation, and Intervention. 5th ed. McGraw Hill Education; 2020.

Citation

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