2. • Designed for Mobility
• Unstable joint, provides more mobility than
stability
• Shoulder complex itself is connected to the
axial skeleton via the sternum and rests on the
thorax, whose shape exerts some influence on
the function of the entire complex.
• Multiaxial ball-and-socket joint.
INTRODUCTION
3.
4.
5. Bones of the shoulder joint
• Scapula
• Clavicle
• Sternum
• Humerus
6.
7. 1. Supra humeral jt:
1. functional joint
2. formed by movement of
the head of the humerus
below the coracoacromial
arch.
3. the movement between
these two components
plays an important role in
shoulder function,
referred as suprahumeral
space and consider it a
component of the GH
joint rather than a
separate linkage
8. STERNOCLAVICULAR JOINT
• Articulation - Medial aspect of the clavicle
and the manubrium of the sternum and first
costal cartilage.
• Consists of two saddle-shaped surfaces.
• Plane synovial joint, and has a fibrocartilage
joint disk
• The ligamentous reinforcements of this joint
are very strong, often resulting a fracture of
the clavicle before a dislocation of the SC
Joint.
9.
10. •The superior portion of the medial
clavicle does not contact the
manubrium
•Serves as the attachment for the SC
joint disk and the interclavicular
ligament.
•Functions of fibrocartilage joint disk, or
meniscus,
•Increases congruence between joint
surfaces.
•Shock absorber and helps prevent
displacement forward.
11.
12. • ATTACHMENT OF DISK-
upper and posterior margin of the clavicle,
to the cartilage of the first rib,(prevent medial
displacement of the clavicle)
• This orientation divides the joint into separate
cavities.
• Greater movement occurs between the disk
and the clavicle than between the disk and
the manubrium
13. LIGAMENTS AND THEIR FUNCTIONS:-
1. Anterior SC Ligament
– Reinforce Capsule Anteriorly
– Limits Anterior Translation of Clavicle
– Checks Anterior Movement of Head of Clavicle.
2. POST. SC LIGAMENT-
– Reinforce Capsule Posteriorly
– Limits Posterior Translation of Clavicle
– Checks Posterior Movement of Head of Clavicle
14.
15. COSTOCLAVICULAR LIGAMENT-
– Limits Elevation of Pectoral Girdle ,
– Acts as Fulcrum for Elevation-Depression Protraction-Retraction
– Checks Clavicular Elevation and Superior Glide of Clavicle
4. INTERCLAVICULAR LIGAMENT-
– Strengthens Capsule Superiorly
– Resists Excessive Depression or Downward Glide of
Clavicle
16.
17. KINEMATICS
• OSTEOKINEMATICS : 3 Degree of freedom
Elevation & depression
Protraction & retraction
Axial rotation of clavicle
18. Elevation and Depression
• Parallel to frontal plane and AP axis.
• 0°-45°/0-10°
ARTHROKINEMATICS
Elevation-
– the convex surface of clavicle rolls on the concave
surface of manubrium, and simultaneously slides
inferiorly to maintain joint contact.
• DEPRESSION- The reverse actions happen when
the clavicle is depressed as head rolling inferiorly
and slide superiorly.
• Fully depressed clavicle elongates and stretches
interclavicular ligament and superior portion of
capsular ligament.
19.
20. Protraction and Retraction
• 0-15°-30 / 0-15°-30°
• Horizontal plane and vertical axis
RETRACTION
– the concave surface of the clavicle rolls and slides posteriorly on the convex surface
of sternum.
– It stretches anterior anterior bundle of costoclavicular ligament and anterior
capsular ligament.
– with retraction, the lateral clavicle rotates posteriorly.
PROTRACTION
– the lateral clavicle rotates anteriorly
– Protraction occurs in same but in anterior direction .
– The extremes of protraction occur during a forward reach.
– Tightness in posterior bundle of cc ligament post capsular ligament and scapular
retractor muscles limit extremes of clavicular protraction.
21.
22. Axial Rotation of the Clavicle
• occurs as a spin between the saddle shaped surfaces of the medial clavicle
and manubrio costal facet
• the clavicle rotates primarily in only one direction from its resting position.
• The clavicle rotates posteriorly from neutral, bringing the inferior surface
of the clavicle to face anteriorly.
• From its fully rotated position, the clavicle can rotate anteriorly again to
return to neutral.
• when arm is flexed or abducted a point on superior aspect of clavicle
rotates posteriorly 40-50 degree.
• CLOSED PACK POSITION :- Full posterior rotation
23.
24. ACROMIOCLAVICULAR JOINT
• Plane synovial joint
• ARTICULATION-
– between the small concave facet of acromion process
of the scapula and
– the convex lateral end of the clavicle.
• allows limited motions in all three planes.
• Function:-
– is to allow additional ROM
– Allow adjustments of the scapula
– Allows transmission of forces from upper extremity
to clavicle.
• Close-packed position humerus abducted to 90 degrees.
27. Capsule & Ligaments
• Joint Capsule:
– The AC Joint has a thin capsule lined with
synovium
– capsule is weak and is strengthened by capsular
ligaments both inferiorly and superiorly
– reinforced by deltoid and trapezius
– joint is unstable without its ligament.
29. LIGAMENTS
Acromio-
clavicular
Coracoclav
icular
1. Superior acromioclavicular ligaments
2. Inferior acromioclavicular ligaments
function:-
serves to reinforce the joint capsule
Both these ligaments attach to the undersurface of the clavicle
resist small rotary and translatory forces at the AC joint, restraint of
larger displacements
30. coracoclavicular ligaments
– Additional stability to joint
– Both portions also limit rotation of the scapula
– Divided into two parts
Conoid Ligament
is the fan shaped
– It is located more medially than the Trapezoid Ligament.
– Extends vertically from base of coracoid process to conoid tubercle of
clavicle.
Trapezoid Ligament
– superolateral portion of the Coracoclavicular Ligament
– quadrilateral in shape.
– horizontal in orientation.
– From superior surface of coracoid process to trapezoid line on the
clavicle
31.
32.
33. kinematics
• The articular facets of the AC joint are small,
afford limited motion.
• and have a wide range of individual
differences
• Permits subtle and slight movement of scapula.
• Slight movt of AC joint are physiologically
important providing the maximum extent of
mobility at ST Joint.
34. MOTIONS IN AC JOINT
• 3 MOTION
EXTERNAL/INTERNAL ROTATION
ANTERIOR/POSTERIOR TIPPING
UPWARDS/DOWNWARD ROTATION
35. Internal and external rotation
• vertical axis
• can best be visualized as bringing the glenoid
fossa of the scapula anteromedially and
posterolaterally
• These motions occur to maintain contact of
the scapula with the horizontal curvature of
the thorax as the clavicle protracts and
retracts, sliding the scapula around the thorax
in scapular protraction and retraction
36.
37. Anterior/Posterior tipping
• Oblique “A-P” axis
• tipping will result in the acromion tipping forward and the
inferior angle tipping backward
• Posterior tipping will rotate the acromion backward and the
inferior angle forward.
• As the scapula moves upward or downward on the rib cage in
elevation or depression, the scapula must adjust its position
to maintain full contact with the vertical curvature of the rib.
38. • Elevation of the scapula on the thorax, such as
occurs with a shoulder shrug, can result in
anterior tipping
• During normal flexion or abduction of the
arm, the scapula posteriorly tips on the thorax
as the scapula is upwardly rotating
• ROM - 30-40 degree
40. Upward and downward rotation
• Upward rotation of scapula occurs tilts the scapula upward
and outward in relation to lateral edge of clavicle.
• When the arm is raised over head in flexion
• Glenoid fossa as refrence.
• Downward rotation is associated with return back of scapula
to its anatomical position associated with extension.
• The amount of available passive motion into
upward/downward rotation at the AC joint is limited by the
attachment of the coracoclavicular ligament.
• 30 degree and downward rotation is 17 degree
• Complete upward rotation at AC joint is closed pack position.
41.
42.
43.
44. Scapulothoracic Joint
• Not true joint
• Union :- fibrous, cartilaginous
• Articulating surfaces :
– anterior scapula and
– Posterolateral thoracic wall.
• Depends on AC jt and SC joint
• Any movement of the scapula on the thorax
must result in movement at either the AC
joint, the SC joint, or both;
• the functional ST joint is part of a true
closed chain with the AC and SC joints and
the thorax
45. Resting Position of scapula
• 6 cm or 2 inches from mid line or lateral to
spine between 2nd to 7th rib
• internally rotated 30 to 45 from the coronal
plane
• tipped anteriorly 10 to 20 from frontal plane
• upwardly rotated 10 to 20 from sagittal plane
46.
47. Motions at ST jt
• Elevation /depression
• Protraction /retraction
• Upward / downward rotation
• Internal/ external rotn
48. Scapulothoracic stability
•Provided by the structure that maintain
integrity of the linked ac and sc jt
•the muscles that attach to both thorax nd
sacapula
Functions of muscles attaching to
scapula:Contract to stabilize shoulder region
Facilitate movements of the upper extremity
through appropriate positioning of the
Glenohumeral joint.
49. Upward and downward rotation
• It is the principal motion of the scapula observed
during active elevation of the arm
• Produced by clavicular elevation and posterior rotation
at the SC joint and by rotations at the AC joint.
• Plays a significant role in increasing the range of
elevation of the arm
• 60 degree of upward rotation
• closed-chain relationship between the SC, AC, and ST
joints
50.
51. Elevation/Depression
• Scapular elevation and depression can be
isolated by shrugging the shoulder up and
depressing the shoulder downward
• Produced by
– elevation/depression of the clavicle at the SC joint
and
– requires subtle adjustments in anterior/posterior
tipping and internal/external rotation at the AC
joint to maintain the scapula in contact with the
thorax.
52.
53. PROTRACTION/RETRACTION
• Produced by
– protraction/retraction of the clavicle at the SC
joint, and
– by rotations at the AC joint to produce internal
rot & ant tipping.
54. Internal/external rotation
• Internal/external rotation of the scapula on the
thorax should normally accompany protraction/
retraction of the clavicle at the SC joint.
• Internal rotation of the scapula on thorax which
occurs only at the AC joint, will result in the
prominence of the vertebral border of scapula.
• WINGING OF SCAPULA-suggestive of impaired
neuromuscular control of ST muscles.
57. Glenohumeral Joint
• ball-and-socket synovial joint
• Most movable joint in the body
• Articulation - large head of the humerus and
the smaller or shallow glenoid foss
• subsequently susceptible to degenerative
changes, instability, and derangement.
58. Glenoid cavity
• Pear shaped
• Shallow
• Directed Laterally and Upward
• Only1/3rd of the humeral head comes in
contact with the glenoid cavity at any position.
• Glenoid Fossa is deepened by a fibro-
cartilaginous rim of Glenoid labrum.
59. Humerus
• The head faces medially, superiorly, and posteriorly
with regard to the shaft of the humerus and the
humeral condyles.
• Because of the internally rotated resting position of the
scapula on the thorax, retroversion of the humeral
head increases congruence of the GH joint.
• Reduced retroversion of humeral head (anteversion)-
increases ROM for internal rotation and decreases
ROM for external rotation and has a tendency to
produce anterior GH subluxation.
• Vice versa for increased retroversion of humeral head.
60. Articulating surface
• Articular surface
– humeral head is directed medially and superiorly and
posteriorly
• Humerus
– Head face medially, superiorly, and posteriorly with
regard to shaft of humerus and condyles.
– has natural retroversion
• This orientation places the head of humerus
directly into scapular plane and therefore directly
against face of glenoid fossa
61.
62.
63. Angle of inclination
• The head faces medially, superiorly, and posteriorly
with regard to the shaft of the humerus and the
humeral condyles.
• An axis through the humeral head and neck in relation
to a longitudinal axis through the shaft of the humerus
forms an angle of 130 to 150 in
the frontal plane.
• This is commonly known as the angle of inclination of
the humerus.
• Angle of inclination=130-150 degrees
• Angle of torsion=30 degrees posteriorly
64. ANGLE OF TORSION
• In the transverse plane, the axis through the humeral head and neck in
relation to the axis through the humeral condyles forms an angle
described as approximately 30 posteriorly.
• This angle is known as the angle of torsion.
• The normal posterior position of the humeral head with regard to the
humeral condyles may be termed posterior torsion, retrotorsion, or
retroversion of the humerus.
• Because of the internally rotated resting position of the scapula on the
thorax, retroversion of the humeral head increases congruence of the GH
joint by “turning” the humeral head back toward the glenoid fossa.
• Reduced retroversion results in a more anterior position of the humeral
head on the glenoid surface when the arm is in an anatomically neutral
position
• Humeral retroversion can result in increased range of external rotation of
the humerus and a reduced range of medial rotation that puts the
humeral head at risk for posterior subluxation at end range.
65.
66. Periarticular connective tissue
• Surrounded by fibrous capsule
• Capsule attaches along the rim of glenoid fossa and
extends to the anatomic neck of humerus
• Synovial membrane lines the intra capsular portion
• Glenoid Labrum composed of: fibrocartilage rim &
Joint capsule
Tendon of long head of biceps brachii
Glenohumeral ligaments
Rotator Cuff Muscles
67.
68.
69. GLENOID LABRUM
• Enhance the depth or curvature of the fossa by
50%.
• It is a redundant fold of dense fibrous connective
tissue with little fibrocartilage.
• It is attached to glenohumeral ligament and long
head of biceps brachii.
• GH CAPSULE & LIGAMENTS
– GH Capsule laxity is required for large excursions of
shoulder joint.
– But capsule gives less stability alone and its work has
to be reinforced by GH ligaments.
70. GH LIGAMENT AND CAPSULE
• The capsule is reinforced by the superior, middle, and
inferior GH ligaments, as well as by the coracohumeral
ligament a thin area of capsule between the superior
and the middle GH ligaments
• known as the foramen of Weitbrecht) is a particular
point of weakness in the capsule.
• Although the capsule is reinforced anteriorly by the
subscapularis tendon, the foramen of Weitbrecht is a
common site of extrusion of the humeral head with
anterior dislocation of the joint.
71.
72.
73. superior GH ligament
– passes from the superior glenoid labrum to the
upper neck of the humerus deep to the
coracohumeral ligament.
– Limits ant and inferior translation in arm at 0
degrees of abduction
Middle GH ligament
– runs obliquely from the superior anterior labrum
to the anterior aspect of the proximal humerus
below the superior GH ligament attachment
– This ligament blends with the anterior capsule.
– Limits anterior translation at arm 45 degrees
abduction Middle GH Lig
74. INFERIOR GH LIGAMENT
– 3 portions and has been termed the inferior GH ligament complex (IGHLC)
– Components are the anterior, posterior bands and the axillary pouch in between.
– IGHLC plays the major role in stabilization.
– With abduction, the axillary pouch slack is taken up, and the IGHLC resists inferior
humeral head translations.
– With subsequent humeral external rotation from an abducted position the anterior
band of the IGHLC fans out to provide anterior stability and resistance to anterior
humeral translation.
– With humeral abduction and medial rotation the posterior band of the IGHLC fans out
and provides posterior stability and resistance to posterior humeral translation
– In all positions of humeral abduction, the capsule and GH ligaments tighten with
rotation of the humerus, producing tension and consequently increasing GH stabilization
– Limits posterior translation with arm 45 degrees abd+ IR - Posterior band of IGHLC
75. Coracohumeral ligament
• originates from the base of the coracoid process and
may be defined as having two bands
• The first inserts into the edge of the supraspinatus and
onto the greater tubercle, where it joins the superior
GH ligament; the other band inserts into the
subscapularis and lesser tubercle.
• The two bands form a tunnel through which the
tendon of the long head of the biceps brachii passes.
• resisting humeral external rotation with the arm
adducted
76. • The rotator interval
capsule is made up of
the superior GH
capsule, superior GH
ligament, and
coracohumeral
ligament.
• Together, these
structures bridge the
gap between the
supraspinatus and
subscapularis muscle
tendons
77. Coracoacromial arch
coracoacromial (or suprahumeral) ARCH
– Formed by the coracoid process
– the acromion
– coracoacromial ligament
• That spans the two bony projections
• arch prevents the head of humerus from dislocating
superiorly,
• because an unopposed upward translatory force on the
humerus would cause the head of the humerus to hit the
coracoacromial arch
• protects the structures beneath it from direct trauma from
above
• Fun as a roof of GH joint
78. subacromial space, or area between the
humeral head and coracoacromial arch, is also
referred to as the suprahumeral space or
supraspinatus outlet.
• Radiographically, this space has been
quantified by measuring a superior-to-inferior
acromiohumeral interval.
• During elevation of the arm, this space
decreases
81. Bursae
• subacromial
• subdeltoid bursae
• These bursae separate the supraspinatus tendon and
head of the humerus from the acromion, coracoid
process, coracoacromial ligament, and deltoid
muscle.
• The bursae may be separate but are commonly
continuous with each other.
• Collectively, the two are known as the subacromial
bursa.
• The subacromial bursa permits smooth gliding
between the humerus and supraspinatus tendon and
85. Abduction/ Adduction
• Defined as a rotation of humerus
• frontal plane and A-P axis
• Convex head of humerus rolling superiorly while simultaneously
sliding inferiorly
• Roll slide occur along or close to longitudinal diameter
• Adduction is similar
• As abduction proceeds the humeral heads unfolds and stretches
axillary pouch
• Excessive stiffness in axillary pouch can limit full abduction
• 120 degree
• Full shoulder abduction requires 60 degree of upward rotation
• For complete range of abduction to occur, there must be 35-40
degrees of lateral rotation, for the clearance of greater tubercle
under the Coracoacromial arch.
86.
87. Flexion / extension
• Rotation of humerus in sagittal plane
• About mediolateral axis
• Transverse Spinning of humeral head about fixed point on
glenoid face
• No roll slide is necessary
• There is some internal rotation movement is appreciated.
As the GH joint is flexed beyond 90 degree tension
coracohumeral ligament may produce small IR on humerus
• For full ROM scapular upward rotation is neccessary
• Extension stretches ant capsular ligament
• 120⁰ of flexion & about 50⁰ of extension.
88.
89. Internal and external rotation
• Defined as axial rotation of humerus
• horizontal plane and Vertical axis
• Range varies with position of the arm.
• With arm by the side internal & external rotation may
be limited to as little as 60⁰ of combined motion.
• With 90⁰ humeral abduction the range is 120⁰
• Arthrokinematics takes place in transverse diameter
• ER-- Humeral head rolls posteriorly and slide anteriorly
on fossa of glenoid
• IR – same but direction of roll and slide is reversed
90.
91. Importance of roll and slide at GH
• Completion of full range abduction.
• how a simultaneous roll and slide allow large
convex surface to roll over smaller concave
surface without running out of articular
surface
• Without inferior slide during abduction it will
create jamming or impingement of head
against coaracoacromial arch
92.
93. Abduction in frontal plane versus
scapular plane
• Functional movement
• Scapular plane
• This can be performed without the need of
external rotation
• Impingement is avoided because since in scapular
plane abduction places the apex of greater
tubercle under high point of CA arch
• It also allows the naturally retroverted humeral
head to fit more directly into glenoid fossa
94.
95. Scapulohumeral Rhythm
• Inman and colleagues in 1944
• GH joint flexion and abduction occurs simultaneously
with scapular upward rotation and this is referred to as
scapulohumeral rhythm
• For every 3 degree of movement 2 degree is done by GH
joint and 1 degree is done by ST joint.
• The ratio has considerable variation among individuals
but is commonly accepted to be 2:1 (2 of glenohumeral
motion to 1 of scapular rotation) overall motion.
• for scapular upward rotation -- the ST joint motion can
occur only through a combination of motions at the SC
and AC joints.
96. Early phase (0 to 90 degree )
– Assuming 2:1, 60 is done by GH and 30 is done by
ST and AC joint
– 20-25 degree of clavicular elevation at SC joint +
5-10 degree of upward rotation at AC joint
– Other subtle adjustments occurs
• Late phase ( 90- 180 degree)
– 60 done by GH and 30 degree ST
– Clavicular elevation at sc 5 degree + ac joint
upward rotn
– Clavicle rotates posteriorly 40 degree during late
phase
97.
98.
99.
100. • Static Stabilization of the GH Joint in
the Dependent Arm-
• UNLOADED ARM
– Passive tension in the rotator interval capsule
– air-tight capsule producing negative intraarticular pressure
– Ligaments
– Glenoid inclination-there is slight upward tilt of glenoid fossa
either due to anatomically or due to upward rotation of the
scapula.
▪ LOADED ARM
– Supraspinatus activity starts when the passive tension in
rotator interval capsule is insufficient as in loaded arm.
101. Dynamic stabilization
EFFECT OF DELTOID (ALONE) ON ABDUCTION
The Deltoid and Glenohumeral Stabilization
– deltoid muscle is a prime mover (along with the supraspinatus) for GH
abduction.
– The anterior deltoid - GH flexion.
– The action lines of the three segments of the deltoid acting together
coincide with the fibers of the middle deltoid
– The majority of the force of contraction of the deltoid causes the
humerus and humeral head to translate superiorly
– The deltoid cannot independently abduct (elevate) the arm.
– Another force or set of forces must be introduced to work
synergistically with the deltoid for the deltoid to work effectively.
102. muscles
stabilize the joint by the following five mechanisms?
(1) passive muscle tension from the bulk effect
of the muscle
(2) contraction causing compression of the articuIar
(3)Joint motion that secondarily tightens passive
ligamentous constraint
(4) barrier effect of the contracted muscle,
(5) redirection of the joint reaction force to the center of
the glenoid surface by coordination of muscle activity
103. labrum
• function is to increase the stability of the
humeral head on the glenoid socket by
increasing the depth of its cavity
• After removal of the labrum, the stability ratio
decreases by 20% on average
104. Scapular inclination
• Itoi et al , who demonstrated that the
shoulder was stabilized inferiorly by the
scapular inclination angle in the hanging arm
position.
105. The Rotator Cuff and Glenohumeral
Stabilization
– supraspinatus,
– infraspinatus,
– teres minor,
– subscapularis muscles
• compose the rotator or musculotendinous cuff (also referred to by the acronym SITS
muscles)
• These muscles are considered to be part of a “cuff” because the inserting tendons of each
muscle of the cuff blend with and reinforce the GH capsule.
• The action lines of the four segments of the rotator cuff (the superiorly located
supraspinatus, posteriorly located infraspinatus and teres minor, and the more anteriorly
located subscapularis muscles
• The infraspinatus, teres minor, and subscapularis muscles individually or together have a
similar line of pull.
106. The Supraspinatus and Glenohumeral
Stabilization
• Although the supraspinatus muscle is part of
the rotator cuff
• The supraspinatus has a superiorly directed
translatory component
• and can independently abduct the humerus.
•
107. The Long Head of the BicepsBrachii
and Glenohumeral Stabilization
• The long head of biceps may produce its effect by tightening the relatively
loose superior labrum and transmitting increased tension to the superior
and middle GH ligaments.
• 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, is
sometimes considered to be part of the reinforcing cuff of the GH joint.
• The 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.
• 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
108. ARTICULAR SURFACE
• As the humeral head rests on the fossa, gravity
acts on the humerus parallel to the shaft in a
downward direction (caudally directed
translatory force).
• This appears to require a vertical upward pull to
maintain equilibrium.
• Such a vertical force could be supplied by muscles
such as the deltoid, supraspinatus, or the long
heads of the biceps brachii and triceps brachii.
109. • Capsule has an airtight seal, which produces
negative intra-articular pressure.
• This pressure creates a relative vacuum that
resists inferior humeral translation caused by
the force of gravity
• When the available passive forces are
inadequate for static stabilization, as may
occur in the heavily loaded arm, activity of the
supraspinatus is recruited.
110. Elevators of ST joint
Upper trapezius
– provides postural support to girdle
– Upper traps attaching to the lateral end of clavicle
provides excellent leverage about SC joint
maintainence of posture
Levator scapulae
Rhomboids
111. PARALYSIS OF UPPER TRAPEZIUS
• Damage to spinal accessory nerve 11
• Markedly depressed, protracted and excessive
downward rotation
• Pull of gravity on arm
• Chronically depressed clavicle may result in superior
dislocation at SC joint
• As lateral is lowered the medial end is fprced upward
due to fulcrum action of underlying first rib
• Depressed shaft of clavicle eventually compress
subclavian vessels
112. In long term condition there will be inferior
subluxation of GH joint
With long term paralysis glenoid fossa loses its
upwardly rotated position allowing the
humerius to slide inferiorly.
113.
114.
115. Depressors of ST joint
• Lower traps
• Latissimus dorsi – depress the shoulder girdle
by pulling the humerus and scapula inferiorly
• Pectoralis minor
• Subclavius
119. Upward rotators of scapula
• Trapezius
• Serratus anterior
• Inserted into inferior angle and medial border of
scapula
• Plays important role in stabilizing the scapula to thorax
• Paralysis will cause winging of scapula
• The scapular winging is internal rotation of the scapula,
produced by the remaining muscles without the
stabilizing external rotation influence of the serratus.
• The serratus anterior muscle also has a large MA to
produce posterior tipping of the scapula.
120. Elevation of arm
• That abduct or flex the humerus at GH joint
• Scapular msl that upaward rotate
• Protraction at ST joint
• Rotator cuff
• Deltoid
• Supraspinatus
• Coracobrachialis
• Biceps
• ST – SA, trapezius
121. Integrated movement during elevation
Upward Rotators of the Scapula
– The motions of the scapula are primarily produced by a balance of the forces between
the trapezius and serratus anterior muscles through their attachments on the clavicle
and the scapula.
TRAPEZIUS WITH SERRATUS Anterior-forms a force couple for scapular upward
rotation
INITIATION Of scapular rotation- upper trap + middle traps
AT THE END RANGE= Lower traps
• DELTOID
• Scapular plane abduction- anterior and middle deltoid
• Posterior deltoid has smaller MA and thus less effective in frontal plane abduction.
• Maintenance of appropriate length-tension relationship of deltoid is dependent on
scapular position/movement and stabilization.
• For example: when scapula cannot rotate, there is more shortening of deltoid and
thus loss of tension, which causes elevation to upto 90 degrees only.
122. Supraspinatus
• Primary function is to produce abduction with
deltoid muscle.
• It has a fairly constant MA throughout the
range of motion of abduction
• secondary function: acts as a ‘steerer’ of
humeral head and helps to maintain stability
of dependent arm.
123. • INFRASPINATUS, TERES MINOR AND
SUBSCAPULARIS
• These muscle function gradually increases from- 0-115 degrees of elevation after
which (115-180 degrees) it dropped.
• In the initial range of elevation, these muscles (infrasp and t.minor) work to pull
the humeral head down, and during the middle range, these muscles act to
externally rotate for clearing greater tubercle under coracoacromial arch.
• Subscapularis helps as internal rot when arm is at side and during initial range
With more abduction, its inter rot capacity decreases. Then it acts with other RC
muscles to promote stability by compression.
124. UPPER AND LOWER TRAPEZIUS + SERRATUS ANTERIOR
This force couple produces upward rotation of scapula.
When the trapezius is intact and the serratus anterior
muscle is paralyzed, active abduction of the arm can
occur through its full range, although it is weakened.
When the trapezius is paralyzed (even though the
serratus anterior muscle may be intact), active
abduction of the arm is both weakened and limited in
range to 75, with remaining range occurring exclusively
at the GH joint.
Without the trapezius (with or without the serratus
anterior muscle), the scapula rests in a downwardly
rotated position as a result of the unopposed effect of
gravity on the scapula.
125. Serratus anterior produces upward rotation, posterior
tipping and external rotation of scapula, which is
necessary for upward elevation of arm.
The serratus is the primary stabilizer of the inferior angle
and medial border of the scapula to the thorax.
How SA and trap work with deltoid???
The serratus anterior and trapezius muscles are prime
movers for upward rotation of the scapula.
These two muscles are also synergists for the deltoid
during abduction at the GH joint.
The trapezius and serratus anterior muscles, as upward
scapular rotators, prevent the undesired downward
rotatory movement of the scapula by the middle and
posterior deltoid segments that are attached to the
126. • scapula.
• The trapezius and serratus anterior muscles maintain an optimal length-tension relationship with
the deltoid and permit the deltoid to carry its heavier distal lever through full ROM.
Rhomboid
It works eccentrically to control upward rotation of the scapula produced by the trapezius and the
serratus anterior muscles.
It adducts the scapula with lower traps to offset the lateral translation component of the serratus
anterior muscle.
Depression involves the forceful downward movement of the arm in relation to the trunk.
• Latissimus Dorsi and Pectoral Muscle
• Function
– When the upper extremity is free to move in space, the latissimus dorsi muscle may produce adduction,
extension, or medial rotation of the humerus. Through its attachment to both the scapula and humerus, the
latissimus dorsi can also adduct and depress the scapula and shoulder complex.
– When the hand and/or forearm is fixed in weight- bearing, the latissimus dorsi muscle will pull its caudal
attachment on the pelvis toward its cephalad attachment on the scapula and humerus. This results in lifting
the body up as in a seated pushup.
• Pectoralis major muscle
• Clavicular portion
• Sternal portion
• Abdominal portion Flexion of shoulder Depression of shoulder Depressor function is assisted by
pectoralis minor
• Teres Major and Rhomboid Muscle Function In order for the teres major muscle to extend the
heavier humerus rather than upwardly rotate the lighter scapula, the synergy of the rhomboid
muscles is necessary to stabilize the scapula.
127.
128.
129.
130.
131.
132.
133. Horizontal Adduction and Abduction at
the Glenohumeral Joint
• HORIZONTAL ADDUCTION: Anterior to joint:
– Pectoralis major (both heads), anterior deltoid,
Coracobrachialis
– Assisted by short head of biceps brachii
• HORIZONTAL ABDUCTION: Posterior to joint:
– Middle and posterior deltoid, infraspinatus,
teres minor
– Assisted by teres major, Latissimus dorsi
134. • Shoulder joint has to bear most of the weight
amongst all other articulations of the shoulder
girdle
• Shoulder has to provide direct mechanical
support
• Large leverage
• More compressive forces on the shoulder joint
• Deltoid produces upward shear forces as
compared to rotator cuff which produces
downward shear forces.
Loads on the Shoulder
137. Loads on the Shoulder
• Arm segment moment arm:
–Perpendicular distance between weight
vector and shoulder
• Large torques from extended moment arms
countered by shoulder muscles
–Load reduced by half with maximal elbow
flexion
138.
139.
140.
141. Deltoid
• Deltoid: Anterior
• Origin Anterior surface of the lateral aspect of
the clavicle
• Insertion Deltoid tuberosity of the humerus
• Action Sh flexion, HADD, Sh IR, abd
• Innervation Axillary n
142. • Deltoid: Middle
– Origin Superior lateral surface of the acromion
– Insertion Deltoid tuberosity of the
humerus
– Action Sh ABD, Sh flexion
– Innervation Axillary n.
• Deltoid: Posterior
– Origin Spine of the scapula
– Insertion Deltoid tuberosity of the
humerus
– Action Sh extension, HABD, Sh
ER
– Innervation Axillary n
147. Pectoralis Major
Origin
Clavicular portion: anterior
margin of the medial portion
Of the clavicle
Sternal portion: lateral
margin of the manubrium
and body of the sternum and
cartilage of the first 6-7 ribs
Insertion
Crest of the greater tubercle of
the humerus
Action
Clavicular: Shoulder flexion, IR
and Horiz ADD
Sternal: Sh IR, Sh ADD, Sh
extension to anatomic position
Innervation
Clavicular: lateral pectoral n.
Sternal: lat & medial pectoral n.
148. Latissimus Dorsi
Origin
Thoracolumbar fascia,
spinous processes of lower
thoracic and lumbar
vertebrae, posterior iliac
crest, lower 4 ribs and
inferior angle of scapula
Insertion
Floor of intertubercular
groove of humerus
Action
Sh ADD, Sh extension, Sh IR,
scapular depression
Innervation Thoracodorsal n.
“tidbit”
Necessary for
“crutchwalking” and
transfers!
149. Teres
Major
Origin
Inferior angle of
the scapula
Insertion
Crest of the
lesser tubercle of
the
humerus
Action
Sh ADD, Sh
extension, Sh IR
Innervation Lower scapular n.
150. Supraspin
atus
Origin
Supraspinous fossa
of the scapula
Insertion
Greater tubercle of
the humerus
Action
Sh ABD, stabilization
of the GH, slight ER
Innervation Suprascapular n.
“Tidbit”
One of the rotator
cuff muscles
152. Teres Minor
Origin
Posterior
lateral
border of the
scapula near
the inferior
angle
Insertion
Greater
tubercle of the
humerus
(inferior to the
infraspinaus)
Action
Sh ER,
stabilization of
the GH joint
Innervation Axillary n
153. Subscapulari
s
Origin
Subscapular fossa
of the scapula
Insertion
Lesser tubercle of
the humerus
Action
Sh IR, stabilization
of the GH joint
Innervation
Upper and lower
subscapular n.
“tidbit”
One of the rotator
cuff muscles
155. Biceps Brachii
Origin
Long head:
supraglenoid tubercle
of
glenoid fossa
Short head: coracoid
process of the
scapula
Insertion
Radial tuberosity of the
radius
Action
Sh flexion, elbow
flexion, forearm
supination
Innervation Musculocutaneous n.
“tidbit”
The actions of the
biceps brachii are
“perfect” in
combination for
opening a
bottle of wine.“The
Corkscrew effect”
158. middle trap &
Rhomboids=scap retraction
Lower trap=scap retraction,
upward rotation and
depression
Pec minor=scap depression
Serratus anterior=scap
abduction and upward
rotation
Only attachment of
scapula to thorax is
through these muscles
