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Elevation/Depression
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Protraction/Retraction
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Internal/external rotation
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Anterior/posterior tiping
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Static stabilization of the GH
• Due to incongruence of the GH articular surfaces, the bony surfaces
alone cannot maintain joint contact in dependent position (arm
hanging at the side).
• LOG pull the humeral head inferiorly it need an equal upward pull to
stabilize, such an upward pull is could be supplied by muscles such
as deltoid, supraspinatus, and long head of biceps but the EMG
shows these muscle are electrically silent, thus the stabilization in
this dependent position is passive, the superior capsule, SGHL, CH
ligament, are taut during relaxed dependent position. The resultant
pull of LOG and these structure create a force which compresses
the head in Glenoid fossa
• Healthy GH joint is seal by labrum and capsule, any translation
produces a negative pressure that resist the inferior translation. Any
tear in labrum thus results in
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Static stabilization of the GH
• Degree of Glenoid inclination also play a role in static stability ,
if there is upward inclination either structurally or by upward
scapular rotation will resist more inferior translation of the
humeral head.
• If the arm is loaded then the passive restraints are inadequate to
resist the translation then the supraspinatus is recruited
because the supraspinatus is attached on the capsular
structures, paralysis of the supraspinatus causes inferior
subluxation of the humeral head due to sustained forces which
causes the capsule to b e lax.
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Dynamic stabilization of GH
The deltoid and GH stabilization
• Generally deltoid is considered as prime mover for flexion and
abduction however the resultant action of the deltoid muscle is
used in stabilization of the GH joint during elevation
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The RC and GH stabilization
• The supraspinatus, infraspinatus, teres minor,
and subscapularis muscles compose the rotator
or musculotendinous cuff (also referred to by the
acronym SITS muscles)
• These muscles are the GH joint compressor
during elevation, these muscles and deltoid
muscle make force couple
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The supraspinatus and GH stabilization
• Unlike other RC muscles the suprspinatus has a superior
translatory component rather than inferior component
that’s why can,t offset the superior translation of the
deltiod. However the supraspinatus muscles rotatory
component is larger than that of other RC muscles
• The supraspinatus has a large moment arm that is
capable of independently producing abduction full range
of GH joint simultaneously stabilizing it
• Gravity also paly in stabilizing by offsetting the upward
pull of the supraspinatus and deltoid muscles
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The long head of bicep and GH
stabilization
• The long head of the biceps brachii runs superiorly from the anterior
shaft of the humerus through the bicipital groove between the
greater and lesser tubercles to attach to the supraglenoid tubercle
and superior labrum. It enters the GH joint capsule through an
opening between the supraspinatus and subscapularis muscles,
where it penetrates the capsule but not the synovium
• The long head of the biceps brachii, because of its position at the
superior capsule and its connections to structures of the rotator
interval capsule to be part of the reinforcing cuff of the GH jointThe
biceps muscle is capable of contributing to the force of flexion and
can, if the humerus is laterally rotated, contribute to the force of
abduction and anterior stabilization.
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Pairing of Pec Girdle and
Shoulder Joint Movements
Shoulder Jt
Shoulder Girdle
Abduction
Adduction
Flexion
Extension
Upward rotation
Downward rotation
Elevation / upward rotation
Depression / downward
rotation
Internal rotation
External rotation
Horizontal abduction
Horizontal adduction
Abduction
Adduction
Adduction
Abduction
(protraction)
(retraction)
(retraction)
(protraction)
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Orientation Muscles of the
Pectoral Girdle
• Muscles of the thorax that move the pectoral girdle
– Anterior thoracic muscles
– Posterior thoracic muscles
• Muscles of the thorax that move the humerus.
– Axial muscles that move the humerus
– Scapular muscles that move the humerus.
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Muscles of the Thorax Move the Pectoral
Girdle
Anterior thoracic muscles
Posterior thoracic muscles
• Subclavius
• Fiber of trapezius
• Pectoralis minor
• Levator scapulae
• Serratus anterior
• Rhomboid minor
• Rhomboid major
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Muscles of the Thorax that Move the
Humerus
Axial muscles
Scapular muscles
• Pectoralis major
• Fiber of deltoid
• Latissumus dorsi
• Rotator cuff
• Teres major
• Coracobrachalis
• Long & short head of
biceps
• Long head of triceps
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ORIGIN, INSERTION, ACTIONS AND
NERVE SUPPLY
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Subclavius Muscle
• Origin – 1st rib
• Insertion – lower surface of
clavicle
Subclavius
• Action
– Depression and move clavicle
anteriorly
– Helps stabilize pectoral girdle
• Nerve supply
– Subclavian nerve
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Pectoralis Minor
• Origin
– 2nd - 5th ribs, 3rd – 5th ribs or 2nd – 4th ribs.
• Insertion
– Coracoid process of scapula
• Action
– Abduction scapula and rotates it downward
– Elevate the ribs during forced inhalation.
• Nerve supply
– Medial pectoral nerve
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Pectoralis Minor
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Serratus Anterior
• Origin – Superior 8 or 9 ribs
• Insertion – vertebral border and
inferior angle of scapula
• Action
– Abduction and rotates the
scapula upward
– Elevate ribs when scapula
stabilized.
– Also known as “boxer’s
muscles”
• Nerve supply
– Long thoracic nerve
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Fiber of Trapezius
• Consists 3 fibers
• Superior or upper fiber,
middle fiber and inferior or
lower fiber.
• Important for move the
scapula.
• Nerve supply - accessory
nerve and cervical spinal
nerve.
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Upper / Superior
Fiber of Trapezius
• Origin – medial one third of
the superior nuchal line,
external occipital
protuberance and ligamentum
nuchae.
• Insertion – posterior border of
the lateral one third of the
clavicle.
• Action – scapular elevation
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Middle Fiber of Trapezius
• Origin – spinous process
of T1 – T5
• Insertion – medial border
of the acromion process
of scapula, and superior
border of the spine of the
scapula.
• Action – scapular
adduction.
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Lower / Inferior Fiber of Trapezius
• Origin – spinous
process of T6-T12
• Insertion – spine of the
scapula
• Action scapular
depression and
adduction
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Levator Scapulae
• Origin – transverse process of
Superior four or five cervical
vertebrae.
• Insertion – superior vertebral
border of scapula
• Action – Elevates scapula and
rotates it downward.
• Nerve supply – dorsal
scapular nerve and cervical
spinal nerve
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Rhomboid Major
• Origin – Spine of 2nd to 5th
thoracic vertebrae
• Insertion – vertebral border
of scapula inferior to spine of
scapula
• Action – elevates and
adducts scapula and rotate it
downward; stabilize scapula
• Nerve – dorsal scapular
nerve
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Rhomboid Minor
• Origin – Spine of 7th cervical
and 1st thoracic vertebrae.
• Insertion – Vertebrae border
of scapula superior to spine
• Action – elevates and adducts
scapula and rotate it
downward; stabilize scapula
• Nerve – dorsal scapular nerve
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Clavicle origin of
Pectoralis Major
• Origin – medial half of anterior
clavicle
• Insertion – greater tubercle and
intertubercular sulcus of
humerus
• Action – Flexion, adduction and
medial rotation arm at shoulder
joint.
• Nerve supply
– Medial and lateral pectoral
nerve
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Sternal origin of Pectoralis Major
• Origin – anterior surface of
sternum, costal cartilage of
2nd -6th ribs.
• Insertion – greater tubercle
and intertubercular sulcus of
humerus
• Action – extend arm at
shoulder joint.
• Nerve supply
– Medial and lateral pectoral
nerve
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Latissimus Dorsi
• Origin – Spines of inferior 6 thoracic vertebrae
(T6-T12), lumbar vertebrae (L1-L5), crest of
sacrum and illiac crest of hip bone and inferior
four ribs.
• Insertion – Intertubecular sulcus of humerus
• Action
– Extends, adduction and medial rotation arm at
shoulder joint.
• Nerve supply - Thoracodorsal nerve
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Latissimus Dorsi
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Fiber of Deltoid
• Consists 3 fibers
• Anterior, middle and
posterior fibers.
• Responsible for
movements of the humerus
at GH joint
• Nerve supply – axillary
nerve.
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Anterior Fiber of Deltoid
• Origin – anterior border of
the lateral one third of the
clavicle
• Insertion – deltoid
tuberosity
• Action – flexion and
middle rotation arm at GH
joint.
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Middle fiber of Deltoid
• Origin – lateral border and
superior surface of the
acromion process of the
scapula
• Insertion – deltoid
tuberosity
• Action – abduction arm at
GH joint
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Posterior Fiber of Deltoid
• Origin – inferior lip of the
crest of the spine of the
scapula
• Insertion – deltoid
tuberosity
• Action – extension and
lateral rotation arm at GH
joint.
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Rotator Cuff Muscles
• Consists 4 muscles
• S – Supraspinatus
• I – Infraspinatus
• T – teres minor
• S – Subscapularis
• Group of muscles that stabilize GH joint.
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Supraspinatus Muscle
• Origin – supraspinous fossa
of scapula
• Insertion – Greater tubercle
of humerus (anterior aspect)
• Action – initially abduction
(15 degrees) at shoulder
joint, stabilizing shoulder
joint
• Nerve supply Suprascapular nerve
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Infraspinatus Muscle
• Origin – Infraspinous fossa
of scapula
• Insertion – Greater tubercle
of humerus (posterior
aspect)
• Action – Laterally rotation
and adduction arm at
shoulder joint
• Nerve supply Suprascapular nerve
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Teres Minor
• Origin – Inferior lateral
border of scapula
• Insertion – Greater tubercle
of humerus (inferior aspect)
• Action – Laterally rotation,
extends and adduction arm
at shoulder joint
• Nerve supply – axillary
nerve
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Subscapularis Muscle
• Origin – subscapular
fossa of scapula
• Insertion – lesser tubercle
of humerus
• Action – Medial rotation
arm at shoulder joint
• Nerve supply – upper and
lower subscapular nerve
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Teres Major
• Origin – Inferior angle of
scapula
• Insertion – Intertubecular
sulcus of humerus
• Action
– Extends arm at
shoulder joint
– Assist in adduction and
medial rotation of arm
at shoulder joint.
• Nerve supply
– Lower subscapular
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Coracobrachialis
• Origin - Coracoid process of
scapula
• Insertion - Middle of medial
surface of shaft of humerus.
• Action - Flexion and adduction
arm at shoulder joint.
• Nerve supply Musculocutaneous nerve
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Biceps Brachii
• Consists 2 head
• Long head and short
head of biceps
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Short head of Biceps
• Origin – Coracoid process of
scapula
• Insertion – radial tuberosity of
radius
• Action – Flexion forearm at
elbow joint, flexion arm at GH
joint and supination at
radioulnar joint.
• Nerve supply Musculocutaneous nerve
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Long head of Biceps
• Origin – Tubercle above the
glenoid cavity of scapula
(supraglenoid tubercle)
• Insertion – Radial tuberosity of
radius
• Action – flexion forearm at
elbow joint, flexion arm at GH
joint and supination forearm at
radioulnar joint.
• Nerve supply Musculocutaneous nerve
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Long head of Triceps
• Origin – tubercle below to
glenoid cavity of scapula
(infraglenoid tubercle)
• Insertion – Olecranon of ulna
• Action - Extends forearm at
elbow joint , Extends arm at
shoulder joint
• Nerve supply - Radial nerve
Posterior View
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Sternomastoid / Cleidomastoid
•
Join together to form sternocleidomastoid
muscle
•
Origin
(i) Sternomastoid - upper part of the anterior
surface of the manubrium of sternum.
(ii) Cleidomastoid - superior border and anterior
surface of the medial third of the clavicle.
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Sternomastoid / Cleidomastoid
• Insertion – Mastoid process of
the mastoid portion of temporal
bone.
• Action - Acting together, flexes
the neck, raises the sternum and
assists in forced inspiration.
• Nerve supply – accessory nerve
(cranial nerve XI)
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Force Couples at
Scapulothoracic Joint
• Serratus anterior produces antero-lateral movement of the inferior
angle
• Upper trapezius pulls scapula medially
• Forces Couples for abduction
 0-90° Deltoid and supraspinatus
 90-150 ° Trapezius (Upper and Lower), Serratus anterior, deltoid
 150-180 ° As above plus contralateral spinal muscles
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Force Couple for Flexion
• 0-60° Anterior deltoid, coracobrachialis, pectoralis
major
• 60-120° Trapezius (upper & lower), serratus
anterior
• 120-180° Lower trapezius, serratus anterior,
contralateral spinal muscles
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Scapular Rotation
Phase 1
• Upper & lower portions of trapezius & serratus anterior
produce an upward rotatory force on the scapula
• Motion at the A-C joint prevented by the oracoclavicular
ligament
• Rotation of the scapula occurs as elevation of the
clavicle occurs at the S-C joint
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Phase 1
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Scapular Rotation
Phase 2
• Further motion at the S-C joint is prevented by the costoclavicular
ligament
• Continued upward rotation of the scapula pulls on the costoclavicular ligament causing posterior rotation of the clavicle
• Posterior rotation of the clavicle allows further rotation of the scapula
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Phase 2
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Scapular Rotation
Necessary to:
• Enhance glenohumeral stability
• Elevate acromion to avoid impingement
• Maintain effective length tension relationship of
scapulohumeral muscles
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