Transcript Kinesiology05_Shoulder_Complex1

SHOULDER COMPLEX
Dr. Michael P. Gillespie
ARTICULATIONS OF THE
SHOULDER
Four articulations of the shoulder exist involving
the sternum, clavicle, ribs, scapula and humerus.
 The series of joints of the shoulder complex allow
for extensive range of motion to the upper
extremity.
 This extensive range of motion allows us to reach
and manipulate objects.
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Dr. Michael P. Gillespie
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JOINTS OF THE SHOULDER
COMPLEX
Dr. Michael P. Gillespie
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MUSCLE INTERACTIONS
Muscles of the shoulder complex rarely act
isolation, but rather work in “teams” to produce
highly coordinated movements.
 These movements are expressed over multiple
joints.
 The coordinated actions of multiple muscles
allows for great versatility, control and range of
motion.
 Paralysis or weakness of any single muscle often
disrupts the entire kinematic sequencing of the
entire shoulder complex.
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Dr. Michael P. Gillespie
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OSTEOLOGY
Sternum
 Clavicle
 Scapula
 Proximal-to-Mid Humerus
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Dr. Michael P. Gillespie
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OSTEOLOGIC FEATURES OF THE
STERNUM
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Manubrium
Pair of oval-shaped clavicular facets, which articulate
with the clavicles.
 Costal facets – attachment for first two ribs.
 Jugular notch – superior aspect
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Dr. Michael P. Gillespie
Body
 Xiphoid Process
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STERNUM: ANTERIOR VIEW
Dr. Michael P. Gillespie
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OSTEOLOGIC FEATURES OF THE
CLAVICLE
Shaft
 Sternal end
 Costal facet
 Costal tuberosity
 Acromial end
 Acromial facet
 Conoid tubercle
 Trapezoid line
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CLAVICLE: SUPERIOR AND
INFERIOR SURFACES
Dr. Michael P. Gillespie
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OSTEOLOGIC FEATURES OF THE
SCAPULA
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Dr. Michael P. Gillespie
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Angles: Inferior, superior, and lateral
Medial or vertebral border
Lateral or axillary border
Superior border
Supraspinatous fossa
Infraspinatous fossa
Spine
Root of the spine
Acromion
Clavicular facet
Glenoid fossa
Supraglenoid and infraglenoid tubercles
Coracoid process
Subscapular fossa
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SCAPULA: POSTERIOR & ANTERIOR
VIEW
Dr. Michael P. Gillespie
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OSTEOLOGIC FEATURES OF THE
PROXIMAL-TO-MID HUMERUS
Head of the humerus
 Anatomic neck
 Lesser tubercle and crest
 Greater tubercle and crest
 Upper, middle, and lower facets on the greater
tubercle
 Intertubercular (bicipital) groove
 Deltoid tuberosity
 Radial (spiral) groove
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Dr. Michael P. Gillespie
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HUMERUS: ANTERIOR & SUPERIOR
VIEWS
Dr. Michael P. Gillespie
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FOUR JOINTS WITHIN THE
SHOULDER COMPLEX
Sternoclavicular
 Acromioclavicular
 Scapulothoracic
 Glenohumeral
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ARTHROLOGY OF THE SHOULDER
COMPLEX
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Dr. Michael P. Gillespie
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The most proximal articulation within the shoulder
complex is the sternoclavicular joint.
The clavicle functions as a mechanical strut holding
the scapula at a relatively fixed distance from the
trunk.
The acromioclavicular joint attaches the scapula to
the clavicle.
The anterior surface of the scapula rests against the
posterior-lateral surface of the thorax, forming the
scapulothoracic joint. This is not a true anatomic
joint. It is an interface between bones.
The scapula serves as a base of operation for the
glenohumeral joint. The glenohumeral joint is the
most distal and mobile link of the complex.
“Shoulder movement” describes the combined motions
at the glenohumeral and scapulothoracic joints.
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PRIMARY MOVEMENTS OF THE
SCAPULOTHORACIC JOINT
Elevation
 Depression
 Protraction
 Retraction
 Upward Rotation
 Downward Rotation
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Dr. Michael P. Gillespie
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ELEVATION & DEPRESSION OF THE
SCAPULOTHORACIC JOINT
Dr. Michael P. Gillespie
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PROTRACTION & RETRACTION OF
THE SCAPULOTHORACIC JOINT
Dr. Michael P. Gillespie
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UPWARD ROTATION & DOWNWARD
ROTATION OF THE SCAPULOTHORACIC
JOINT
Dr. Michael P. Gillespie
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STERNOCLAVICULAR JOINT:
GENERAL FEATURES
The SC joint functions as the basilar joint of the
entire upper extremity and links the
appendicular skeleton to the axial skeleton.
 The joint must be firmly attached, yet allow
considerable range of movement.
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Dr. Michael P. Gillespie
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TISSUES THAT STABILIZE THE
STERNOCLAVICULAR JOINT
Anterior and posterior sternoclavicular ligaments
 Interclavicular ligament
 Costoclavicular ligament
 Articular disc
 Sternocleidomastoid, sternothyroid, sternohyoid,
and subclavius muscles
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Dr. Michael P. Gillespie
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KINEMATICS OF THE
STERNOCLAVICULAR JOINT
Osteokinematics of the SC joint involve rotation
in all three degrees of freedom.
 Elevation & Depression
 Protraction & Retraction
 Axial (Longitudinal) Rotation of the Clavicle
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Dr. Michael P. Gillespie
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OSTEOKINEMATICS OF THE
STERNOCLAVICULAR JOINT
Dr. Michael P. Gillespie
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ACROMIOCLAVICULAR JOINT:
GENERAL FEATURES
The AC joint is the articulation between the
lateral end of the clavicle and the acromion of the
scapula.
 An articular disc is present in most AC joints.
 The joint has an articular capsule and significant
ligament support.
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Dr. Michael P. Gillespie
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TISSUES THAT STABILIZE THE
ACROMIOCLAVICULAR JOINT
Superior and inferior acromioclavicular joint
ligaments
 Costoclavicular ligament
 Articular disc (when present)
 Deltoid and upper trapezius muscles
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Dr. Michael P. Gillespie
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KINEMATICS OF THE
ACROMIOCLAVICULAR JOINT
The motions of the AC joint are described by the
movement of the scapula relative to the lateral
end of the clavicle.
 Upward & Downward Rotation
 Horizontal & Sagittal Plane “Rotational
Adjustments” at the AC joint
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Dr. Michael P. Gillespie
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OSTEOKINEMATICS OF THE
ACROMIOCLAVICULAR JOINT
Dr. Michael P. Gillespie
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OSTEOKINEMATICS OF THE
ACROMIOCLAVICULAR JOINT
Dr. Michael P. Gillespie
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ACROMIOCLAVICULAR JOINT
DISLOCATION
The AC joint is
inherently susceptible
to dislocation due to
the sloped nature of
the articulation and
the high probability of
receiving large
shearing forces.
 Falling and striking
the tip of the shoulder
abruptly against the
ground would produce
such a shearing force.
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Dr. Michael P. Gillespie
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SCAPULOTHORACIC JOINT
The scapulothroacic Joint is not a true joint, but
rather a point of contact between the anterior
surface of the scapula and the posterior-lateral
wall of the thorax.
 The two surfaces do not make direct contact.
They are separated by muscles such as the
subscapularis, serratus anterior, and erector
spinae.
 An audible click during scapular movements may
indicate abnormal contact within the
articulation.
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Dr. Michael P. Gillespie
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KINEMATICS OF THE
SCAPULOTHORACIC JOINT
The movements at the scapulothoracic joint are a
result of cooperation between the SC and the AC
joints.
 Elevation & Depression
 Protraction & Retraction
 Upward & Downward Rotation
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Dr. Michael P. Gillespie
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SCAPULOTHORACIC ELEVATION
Dr. Michael P. Gillespie
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SCAPULOTHORACIC PROTRACTION
Dr. Michael P. Gillespie
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SCAPULOTHORACIC UPWARD
ROTATION
Dr. Michael P. Gillespie
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FUNCTIONAL IMPORTANCE OF
UPWARD ROTATION
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The upwardly rotated scapula projects the glenoid fossa
upward and anterior-laterally, providing a structural base
to maximize upward and lateral reach.
 The upwardly rotated scapula preserves the optimal
length-tension relationship of the abductor muscles of the
glenohumeral joint (middle deltoid & supraspinatous).
 The upwardly rotated scapula helps maintain the volume
within the subacromial space. A reduced subacromial
space can lead to painful and damaging impingement of
the supraspinatus tendon and subacromial bursa).
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Dr. Michael P. Gillespie
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Many functional activities require us to raise the arm
fully overhead.
The upward rotation of the scapula accounts for
nearly 1/3 of the 180 degrees of shoulder abduction or
flexion.
Functions
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GLENOHUMERAL JOINT: GENERAL
FEATURES
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Dr. Michael P. Gillespie
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The GH joint is the articulation formed between the
large convex head of the humerus and the shallow
concavity of the glenoid fossa.
It operates in conjunction with the moving scapula to
produce an extensive range of motion of the shoulder.
In anatomic position, the articular surface of the
glenoid fossa is directed anterior-laterally in the
scapular plane.
In anatomic position, the humeral head is directed
medially and superiorly, as well as posteriorly.
This orientation places the head of the humerus
directly against the face of the glenoid fossa.
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GLENOHUMERAL JOINT: ANTERIOR
VIEW
Dr. Michael P. Gillespie
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“LOOSE FIT” OF THE
GLENOHUMERAL JOINT &
INSTABILITY
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Several features of the glenohumeral joint contribute to a
design that favors mobility at the expense of stability.
The articular surface of the glenoid fossa covers only about 1/3
of the articular surface of the humeral head.
 The longitudinal diameter of the humeral head is about 1.9
times larger than the longitudinal diamter of the glenoid
fossa.
 The transverse diameter of the humeral head is about 2.3
times larger than the opposing transverse diameter of the
glenoid fossa.
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The surrounding muscles and ligaments maintain the
mechanical integrity of the joint.
A condition of excessive laxity or “joint play” associated
with large translations of the proximal humerus relative to
the glenoid is often referred to as shoulder instability.
Subluxation – incomplete separation of articular surfaces
often followed by spontaneous realignment
 Dislocation – complete separation of articular surfaces without
spontaneous realignment
Dr. Michael P. Gillespie
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“LOOSE FIT” IN GLENOHUMERAL
JOINT
Dr. Michael P. Gillespie
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GLENOHUMERAL JOINT STABILITY
A combination of passive and active mechanisms
achieve GH joint stability.
 Active mechanisms
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Passive mechanisms
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Forces other than activated muscle
1. restraint provided by capsule, ligaments, glenoid labrum,
and tendons
 2. mechanical support predicated on scapulothoracic
posture
 3. negative intracapsular pressure
Dr. Michael P. Gillespie
Forces produced by muscle
 Embracing nature of the rotator cuff
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ROTATOR CUFF MUSCLES & LONG
HEAD OF BICEPS BRACHII
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Dr. Michael P. Gillespie
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The glenohumeral joint receives significant structural
reinforcement from the four rotator cuff muscles.
The subscapularis is the thickest of these muscles and
lies just anterior to the scapula.
The supraspinatus, infraspinatus, and teres minor lie
superior and posterior to the capsule.
These four muscles form a cuff that protects and
actively stabilizes the GH joint, especially during
dynamic activities.
The belly of these muscles lies close to the joint.
The tendons of these muscle blend into the capsule.
The tendon of the long head of the biceps reinforces
the rotator interval (between supraspinatus and
subscapularis).
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ROTATOR CUFF MUSCLE SUPPORT
Dr. Michael P. Gillespie
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TISSUES THAT REINFORCE OR
DEEPEN THE GLENOHUMERAL
JOINT
Joint capsule and associated capsular ligaments
 Coracohumeral ligament
 Rotator cuff muscles (subscapularis,
supraspinatus, infraspinatus, and teres minor)
 Long head of biceps brachii
 Glenoid labrum
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Dr. Michael P. Gillespie
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KINEMATICS OF THE
GLENOHUMERAL JOINT
Movement occurs in all three degrees of freedom.
 Abduction & Adduction
 Flexion & Extension
 Internal & External Rotation
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Dr. Michael P. Gillespie
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OSTEOKINEMATICS OF THE
GLENOHUMERAL JOINT
Dr. Michael P. Gillespie
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GLENOID LABRUM: VULNERABLE
TO INJURY
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Dr. Michael P. Gillespie
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The rim of the glenoid fossa is encircled by a
fibrocartilage ring, or lip, known as the glenoid
labrum.
It deepens the concavity of the fossa and increases the
contact area with the humeral head to help stabilize
the joint.
The superior part of the glenoid labrum is only loosely
attached.
50% of the fibers of the tendon of the long head of the
biceps are direct extensions of the superior glenoid
labrum.
Large or repetitive forces within the biceps tendon
can detach the superior labrum (near its 12 o’clock
position).
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GLENOHUMERAL JOINT: ACTIVE
ABDUCTION
Dr. Michael P. Gillespie
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GLENOHUMERAL JOINT: FLEXION
Dr. Michael P. Gillespie
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KINEMATIC RELATIONSHIPS OF
THE GLENOHUMERAL JOINT
Plane of Motion /
Axis of Rotation
Arthrokinematics
Abduction &
adduction
Near frontal plane /
near anteriorposterior axis of
rotation
Roll and slide along
joint’s longitudinal
diameter
Internal & external
rotation
Horizontal plane /
vertical axis of
rotation
Roll and slide along
joint’s transverse
diameter
Flexion & Extension,
internal & external
rotation (in 90
degrees of abduction)
Near sagittal plane /
near medial-lateral
axis of rotation
Primarily a spin
between humeral
head and glenoid
fossa
Dr. Michael P. Gillespie
Osteokinematics
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SCAPULOHUMERAL RHYTHM
“Scapulohumeral rhythm” describes the
kinematic relationship between glenohumeral
abduction and scapulothoracic upward rotation.
 After about 30 degrees of abduction, the rhythm
is remarkably constant.
 For every 3 degrees of shoulder abduction, 2
degrees occur by GH joint abduction and 1 degree
occurs by scapulothoracic upward rotation.
 A full arc of 180 degrees of abduction is the result
of a simultaneous 120 degrees of GH joint
abduction and 60 degrees of scapulothoracic
upward rotation.
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Dr. Michael P. Gillespie
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SCAPULOHUMERAL RHYTHM
Dr. Michael P. Gillespie
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SHOULDER ABDUCTION IN THE
FRONTAL PLANE VERSUS THE
SCAPULAR PLANE
Shoulder abduction in the frontal plane is often
used as a representative motion to evaluate
overall shoulder function; however, this motion is
not very natural.
 Abducting the shoulder in the scapular plane
(about 35 degrees anterior to the frontal plane) is
a more natural movement and generally allows
greater elevation of the humerus than in the
frontal plane.
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Dr. Michael P. Gillespie
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ABDUCTION: FRONTAL VS.
SCAPULAR
Dr. Michael P. Gillespie
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INNERVATION OF MUSCLES &
JOINTS OF THE SHOULDER
COMPLEX
Brachial Plexus
 Innervation of Muscle
 Innervation to the Joints
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Dr. Michael P. Gillespie
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BRACHIAL PLEXUS
Dr. Michael P. Gillespie
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NERVES THAT FLOW FROM THE
BRACHIAL PLEXUS AND
INNERVATE THE SHOULDER
Primary Nerve
Root(s)
Muscles Supplied
Axillary
C5, C6
Deltoid, teres mino
Thoracodorsal
(middle subscapular)
C6, C7, C8
Latissimus dorsi
Upper subscapular
C5, C6
Subscapularis (upper
fibers)
Lower subscapular
C5, C6
Subscapularis (lower
fibers), teres major
Lateral pectoral
C5, C6, C7
Pectoralis major and
occasionally
pectoralis minor
Dr. Michael P. Gillespie
Nerve
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NERVES THAT FLOW FROM THE
BRACHIAL PLEXUS AND
INNERVATE THE SHOULDER
Primary Nerve
Root(s)
Muscles Supplied
Medial pectoral
C8, T1
Pectoralis major
(sternocostal head),
pectoralis minor
Suprascapular
C5, C6
Supraspinatus,
infraspinatus
Subclavian
C5, C6
subclavius
Dorsal scapular
C5
Rhomboid major &
minor, levator
scapula*
Long thoracic
C5, C6, C7
Serratus anterior
* Also innervated by C3 & C4 nerve roots from cervical plexus
Dr. Michael P. Gillespie
Nerve
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PRIMARY MUSCLES ACTING AT THE
SCAPULOTHORACIC JOINT
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Elevators
Upper trapezius
 Levator scapulae
 Rhomboids
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Depressors
Lower trapezius
 Latissimus dorsi
 Pectoralis major
 Subclavius
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Dr. Michael P. Gillespie
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PRIMARY MUSCLES ACTING AT THE
SCAPULOTHORACIC JOINT
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Protractors
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Retractors
Middle trapezius
 Rhomboids
 Lower trapezius
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Dr. Michael P. Gillespie
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Serratus anterior
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PRIMARY MUSCLES ACTING AT THE
SCAPULOTHORACIC JOINT
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Upward Rotators
Serratus anterior
 Upper and lower trapezius
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Downward Rotators
Rhomboids
 Pectoralis minor
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Dr. Michael P. Gillespie
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ELEVATORS OF THE
SCAPULOTHORACIC JOINT
Dr. Michael P. Gillespie
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DEPRESSORS OF THE
SCAPULOTHORACIC JOINT
Dr. Michael P. Gillespie
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PROTRACTION OF THE
SCAPULOTHORACIC JOINT
Dr. Michael P. Gillespie
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RETRACTION OF THE
SCAPULOTHORACIC JOINT
Dr. Michael P. Gillespie
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MUSCLES PRIMARILY
RESPONSIBLE FOR ELEVATION OF
THE ARM
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Scapulothoracic Joint Muscles
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Anterior and middle deltoid
Supraspinatous
Coracobrachialis
Biceps (long head)
Dr. Michael P. Gillespie
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The term “elevation” of the arm describes the active
movement of bringing the arm overhead without
specifying the exact plane of motion.
Glenohumeral Joint Muscles
Serratus anterior
Trapezius
Rotator Cuff Muscles
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Supraspinatus
Infraspinatus
Teres minor
Subscapularis
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FUNCTION OF THE ROTATOR CUFF
MUSCLES IN ABDUCTION AT THE
GLENOHUMERAL JOINT
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Supraspinatus
Drives the superior roll of the humeral head
 Compress the humeral head firmly against the
glenoid fossa
 Creates a semirigid spacer above the humeral head,
restricting excessive superior translation of the
humerus
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Infraspinatus, Teres Minor, and Subscapularis
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Dr. Michael P. Gillespie
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Exert a depression force on the humeral head
Infraspinatus and Teres Minor
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Externally rotate the humerus
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SHOULDER ADDUCTION &
EXTENSION
Dr. Michael P. Gillespie
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SCAPULOTHORACIC DOWNWARD
ROTATION & GLENOHUMERAL
ADDUCTION
Dr. Michael P. Gillespie
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INTERNAL ROTATION OF THE
SHOULDER
Dr. Michael P. Gillespie
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SHOULDER INSTABILITY
Posttraumatic Instability
 Atraumatic Instability
 Acquired Shoulder Instability
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POSTTRAUMATIC INSTABILITY
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Dr. Michael P. Gillespie
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Posttraumatic instability is attributed to a specific event
involving a traumatic dislocation of the glenohumeral joint.
The vast majority of traumatic dislocations occur in the
anterior direction, typically related to a fall or forceful
collision.
The pathomechanics of an anterior dislocation often involve
the motion or position of extreme external rotation in an
abducted position.
The force then drives the humeral head off the anterior
aspect of the glenoid fossa.
This dislocation often injures the rotator cuff muscles,
middle and inferior GH ligaments, and anterior-inferior
rim of the glenoid labrum (Bankart lesions).
Posttraumatic dislocations frequently lead to future
recurrences.
Posttraumatic instability does NOT respond well to
conservative care and often requires surgery.
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ATRAUMATIC INSTABILITY
These individuals tend to display generalized and
excessive ligamentous laxity throughout the
body, often described as being congenital.
 This type of instability is usually not associated
with a traumatic event.
 The instability can be unidirectional or
multidirectional, and bilateral.
 Atraumatic instability tends to respond favorably
to conservative therapy involving strengthening
and coordination exercises.
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Dr. Michael P. Gillespie
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ACQUIRED SHOULDER INSTABILITY
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Dr. Michael P. Gillespie
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The pathogenics of acquired shoulder instability are
related to overstretching and subsequent
microtrauma of the capsular ligaments within the GH
joint.
This condition is associated with repetitive, highvelocity shoulder motions that involve extreme
external rotation and abduction.
These motions are common in throwing sports,
swimming, tennis, and volleyball.
The anterior bands of the inferior GH ligament and to
a lesser extent the middle GH ligament are
vulnerable to plastic deformation.
This tissue deformation leads to increased laxity.
This can contribute to other conditions such as rotator
cuff syndrome and internal impingement syndrome.
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SUPRASPINATUS VULNERABILITY
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Dr. Michael P. Gillespie
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The supraspinatus is one of the most used muscles of
the entire shoulder complex.
It assists the deltoid during abduction.
It provides dynamic and static stability to the GH
joint.
It is subjected to large internal forces even during
routine activities.
The muscle exhibits a 1:20 mechanical advantage
over a load in the hand, implying that the muscle
must exert a force 20 times greater than the weight of
the load.
This can lead to tears of the muscle as it inserts into
the capsule and greater tubercle of the humerus.
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SHOULDER IMPINGEMENT
SYNDROME
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Dr. Michael P. Gillespie
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Subacromial shoulder impingement syndrome is
among the most common painful disorders of the
shoulder.
It is caused by repeated an unnatural compression of
the tissues within the subacromial space.
The tissues affected are the supraspinatus tendon,
the tendon of the long head of the biceps brachii, the
superior capsule, and the subacromial bursa.
These tissues become compressed between the
humeral head and the coracoacromial arch.
This impingement can be a very important factor in
rotator cuff syndrome.
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DIRECT OR INDIRECT CAUSES OF
SHOULDER IMPINGEMENT
SYNDROME
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Dr. Michael P. Gillespie
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Abnormal kinematics at the glenohumeral and
scapulothoracic joints.
“Slouched” posture that affects the alignment of the
scapulothoracic joint.
Fatigue, weakness, poor control, or tightness of the muscles
that govern motions at the GH or scapulothoracic joints.
Inflammation and swelling of tissues within and around
the subacromial space.
Excessive wear and subsequent degenration of the tendons
of the rotator cuff muscles.
Instability of the GH joint.
Adhesions within the inferior GH joint capsule.
Excessive tightness in the posterior capsule of the GH joint
(and associated anterior migration of the humeral head
towards the lower margin of the coracoacromial arch).
Abnormal shape of the acromion or coracoacromial arch.
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