Kine305: Ch.12 Shoulder Girdle

Exam 2

Shoulder girdle consists of

Scapulothoracic joint, sternoclavicular joint, and acromioclavicular joint

Shoulder joint consists of

Glenohumeral joint

What are the joint actions

Elevation and depression

Protraction and retraction

Upward and downward rotation

Scapular tilt

Companion actions of the SG and SJ

Scapulohumeral rhythm

2:1 ratio - SJ ABD: SG UR

Promotes functional length-tension relationship

Landmarks of the scapula

Superior and inferior angle

Vertebral and axillary border

Spine

Coracoid process

Acromion process

Glenoid fossa

Landmarks of the clavicle

Sternal end (by the sternum), acromial end (by the acromion), body

Landmarks of the sternum

Manubrium, body, xiphoid process

Ligaments of sternoclavicular joint

Anterior and posterior sternoclavicular ligaments

Costoclavicular ligaments

Interclavicular ligaments

Ligaments of acromioclavicular joint

Superior and inferior acromioclavicular lligament

Coracoclavicular ligaments (conoid portion(medial) and trapezoid portion(lateral))

Coracoacromial ligament

Muscles of the scapulothoracic joint

Trapezius (upper, lower, middle)

Levator scapulae

Rhomboids

Serratus anterior

Pec minor

What is the common action of all 3 traps?

Upward rotation, middle trap does it less

Force couples

How these muscles work together

When 2 muscles generate force in different directions, opposite sides of the joint and that creates movement

Which muscles do retraction?

All traps and rhomboids

Which muscles do protraction?

Serratus anterior and pec minor

Which muscles do elevation?

Levator scapulae, upper trap, middle trap, rhomboids

Which muscles do depression?

Pec minor and lower trap

Which muscles do upper rotation?

SAULT —> Serratus anterior, upper and lower trap

Which muscles do downward rotation?

rhomboids, levator scapulae, pec minor

Which muscles do scapular tilt?

pec minor, ex. reaching into back pocket (sagittal plane)

Example of force coupling?

Upward rotation of the scap: lower trap is depressing and upward rotation, serratus anterior is protracting and upward rotation, and upper trap is elevating and upward rotation, So these forces are trying to create a VECTOR of upward rotation

Why is force coupling important?

Because if it didn’t upwardly rotate, then you would hit top of acromion each time and that would cause breakdown of rotator cuff, bony changes, etc.

This rotation keeps it open so you have room to do arthrokinematics, glides, rolls w/o impinging and pinching rotator cuff

Which muscles work together for downward rotation?

Pec minor, levator scapulae, and rhombiods

Crutches

Scapulas stabilized with hands bearing weight on handles which prevents scapula from depressing.

Pec minor pulls on rib cage

Lower trap pulls up on spine and pelvis

Elevates body, relative to scapula, allowing it to swing through crutches

Commonly seen injuries

arthritis, injuries related to football, clavicular fractions, injury to acromioclavicular(AC) and coracoclavicular(CC) ligaments, winging of scapular puts weakness of SA muscle