Transcript ESS 303 -- Biomechanics

ESS 303 – Biomechanics
Shoulder Joint
The Scapula (Right)
Humerus (Right)
Anterior View
Posterior View
The Shoulder Joint
Shallow ball-and-socket
Socket: Glenoid fossa of the shoulder blade
Ball: ½ the spherical head of the humerus
No more than ½ of the head is in the socket
at any given time
Bony stability is weak
In fact – the head may move up to 2-3 cm
away from the glenoid fossa
Stability
Keeping the humoral head in contact
with the glenoid fossa
Passive: Glenoid Labrum
Circles around the outside of the glenoid
cavity
Increases depth of concavity
Active: Rotator cuff
Rotator Cuff
Muscles tense to stabilize the humoral
head against the glenoid fossa
Helps prevent the head from rotating out of
the fossa
Allows the deltoid to contribute to abduction
4 muscles: supraspinatus, subscapularis,
infraspinatus, and teres minor
Rotator Cuff Injuries: Common
Types: Tendonitis, bursitis, strain or tear
Who: Baseball pitchers & anyone who
puts heavy demands on their shoulders
Most treated with simple care and
exercise
Causes: age (>40), poor posture,
breaking a fall with your arm, heavy
lifting (especially overhead), repetitive
stress, others
Rotator Cuff Injuries: Common
Rotator Cuff Injuries: Common
 Self treatment:
 Stop the activity – for a few days or until pain stops
 Ice and heat
 Medications
 Exercises
 Medical treatment
 Severe or long-lasting (> 1 week) pain, immobile,
etc
 Medications, surgery, etc
Dislocation & Subluxation
Movements & Major Muscles
Flexion: pectoralis major (clavicular),
anterior deltoid & coracobrcahialis
Extension: pectoralis major (sternal),
latissimus dorsi & teres major
Abduction: middle deltoid &
supraspinatus
Adduction: pectoralis major (sternal),
latissimus dorsi & teres major
Movements & Major Muscles
 Horizontal (Transverse) Abduction: middle and
posterior deltoids, infraspinatus & teres minor
 Horizontal (Transverse) Adduction: pectoralis
major, anterior deltoid, coracobrachialis
 Medial Rotation: pectoralis major, latissimus dorsi,
teres major & subscapularis
 Lateral Rotation: teres minor, infraspinatus &
posterior deltoid
 Other movements are exaggerations or
combinations of above: Hyperextension,
Hyperabduction, Hyperadduction &
Circumduction