Shoulder Girdle Anatomy and Kinesiology

Bones of the Shoulder Girdle

Scapula and Clavicle (they move together as a unit).

Only Bony Link to Axial Skeleton

The clavicle's articulation with the sternum (Sternoclavicular joint).

Scapulothoracic Joint Definition

Not a true synovial joint; movement of the scapula on the rib cage.

Three Major Joints of the Shoulder Complex

Sternoclavicular (SC), Acromioclavicular (AC), and Glenohumeral joints.

Scapular Elevation

Upward or superior movement of the scapula.

Scapular Depression

Downward or inferior movement of the scapula.

Scapular Adduction (Retraction)

Movement of the scapula medially toward the spinal column.

Scapular Abduction (Protraction)

Movement of the scapula laterally away from the spinal column.

Scapular Upward Rotation

Turning glenoid fossa upward and moving inferior angle superiorly/laterally away from the spinal column

Scapular Downward Rotation

Returning inferior angle medially and inferiorly toward spinal column.

Scapular Anterior Tilt (Upward Tilt)

Superior border moves anteroinferiorly; inferior angle moves posterosuperiorly during hyperextension.

Scapular Posterior Tilt (Downward Tilt)

Superior border moves posteroinferiorly; inferior angle moves anterosuperiorly during hyperflexion.

Movements regarding shoulder girdle

- Stabilize scapula so the shoulder joint muscles will have a stable base from which to exert force for moving the humerus

- Contract to maintain scapula in a relatively static position during shoulder joint actions

- Contract to move shoulder girdle & to enhance movement of upper extremity when shoulder goes through extreme ranges of motion

General Characteristics of Shoulder Girdle Muscles

5 muscles primarily involved in shoulder girdle movements

• All originate on axial skeleton & insert on scapula and/or clavicle

• Do not attach to humerus & do not cause shoulder joint actions

• Essential in providing dynamic stability of the scapula so it can serve as a relative base of support for shoulder joint activities such as throwing, batting, & blocking

Five Primary Shoulder Girdle Muscles

Trapezius, Rhomboids, Levator Scapulae, Serratus Anterior, Pectoralis Minor.

Trapezius (Upper Fibers) — Origin & Insertion

Origin: superior nuchal line, external occipital

protuberance

Insertion: Lateral 1/3 of the clavicle

Trapezius (Middle Fibers) — Origin & Insertion

Origin: Spinous processes of the vertebra T1-T4

Insertion: Acromion of the scapula; Spine of the scapula

Trapezius (Lower Fibers) — Origin & Insertion

Origin: Spinous processes of the thoracic vertebrae

T4-T12

Insertion: Medial part of the spine of the scapula

Trapezius — Innervation

Accessory Nerve (Cranial Nerve XI).

Trapezius — Actions by Fiber Group

Upper: Elevation, head extension/rotation. Middle: Elevation, upward rotation, adduction. Lower: Depression, adduction, upward rotation.

Levator Scapulae — Origin, Insertion, Innervation

Origin: Posterior tubercles of transverse processes of C1-C4 vertebrae

Insertion: Medial border of scapula superior to root of scapular spine

• Innervation: Dorsal Scapular (C4, C5), and Cervical (C3, C4)

Levator Scapulae — Primary Action

Elevates the medial margin of the scapula.

Rhomboid Minor — Origin & Insertion

Origin: Nuchal ligament, spinous processes C7-T1. Insertion: Medial border near base of spine.

Rhomboid Major — Origin & Insertion

Origin: Spinous processes T2-T5.

Insertion: Medial border from spine to inferior angle.

Rhomboid Muscles — Innervation & Actions

Innervation: Dorsal Scapular (C4, C5).

Actions: Retraction (Adduction), Downward Rotation, Elevation.

Serratus Anterior — Origin & Insertion

Origin:

• Superior part: Ribs 1-2, Intercostal fascia

• Middle part: Ribs-3-6

• Inferior part: Ribs 7-8/9 (variably extends to rib 10

Insertion:

• Superior part: Anterior surface of superior angle of scapula

• Middle part: Anterior surface of medial border

scapula

• Inferior part: Anterior surface of inferior angle and medial border of scapula

Serratus Anterior — Innervation & Actions

Innervation: Long Thoracic Nerve.

Actions: Protraction (Abduction), Upward Rotation, Thoracic Wall Stabilization.

Scapular Winging Cause

Weakness or paralysis of Serratus Anterior / injury to Long Thoracic Nerve.

Pectoralis Minor — Origin, Insertion, Innervation

Origin: Costal cartilages ribs 3-5.

Insertion: Medial border and coracoid

process of scapula

Innervation: Medial and lateral pectoral

nerves (C5-T1)

Pectoralis Minor — Actions

Protraction (Abduction), Downward Rotation, Depression.

Subclavius — Origin, Insertion, Action

Origin: Costal cartilage rib 1. Insertion: Anteroinferior surface middle 1/3 clavicle.

Subclavius purpose

• Stabilization and protection of

sternoclavicular (SC) joint

• Depression

• Abduction

Scapula Protraction (Abduction) Agonists

Pectoralis Minor, Serratus Anterior.

Scapula Retraction (Adduction) Agonists

Middle Trapezius, Lower Trapezius, Rhomboids.

Scapula Upward Rotation Agonists

Middle Trapezius, Lower Trapezius, Serratus Anterior.

Scapula Downward Rotation Agonists

Pectoralis Minor, Rhomboids, Levator Scapulae.

Scapula Elevation Agonists

Levator Scapulae, Upper Trapezius, Middle Trapezius, Rhomboids.

Scapula Depression Agonists

Lower Trapezius, Pectoralis Minor, Serratus Anterior (inferior part).