The Shoulder Anatomy
Introduction
 Very complicated region
 Numerous and varied structures
○ Bones, tendons, muscles,
nerves, ligaments, bursae, etc.
 Highly maneuverable
○ 16,000 positions differentiated
in 1˚ increments
 Combination of
articulations
 Can be debilitating due to inability to
properly use hand(s)
 Injuries from:
○ Direct force/trauma
○ Secondary forces transmitted
proximally
○ Overuse – predisposition
w/overhead movements
 Connection of axial skeleton to upper extremity
 Only at
Stability vs. mobility
 The shoulder is inherently unstable
 Poor bony stability due to shallow
articulation
 Stability is gained
by the capsule,
ligaments, & labrum; and
by the
deltoid and rotator cuff muscles.
 As you give up
you gain
Skeletal anatomy
Humerus (proximal)
 Landmarks
 Head
 Greater tubercle (ant. lat.)
 Lesser tubercle (ant. med.)

(between tubercles)
 Anatomical neck (proximal to tubes)
 Surgical neck (distal to tubes)
 Diaphysis

Tuberosity
Scapula
 Located between Ribs 2-7
 No direct bony or ligamentous attachments
 Articulates with
&

Held against torso by muscle
attachment & atmospheric pressure
 Functions as both a
 Glenoid is oriented about 30-45° anterior to the
coronal plane of the body
 “
”
Notes
Places Rotator Cuff muscles at optimal
length-tension relationship
Scapular landmarks
 Body – anterior view = (a)
 Subscapular fossa
 Medial (vertebral) border
 Lateral (axillary) border
 Superior Border
 Glenoid fossa
 Acromion process
 Corocoid process
 Superior angle
 Inferior angle
 Body – posterior view = (b)
 Supraspinous fossa
 Infraspinous fossa
 Greater Scapular Notch
 Spine of scapula
 Acromion process
 scapular landmarks
 Body (lateral view)
 Glenoid fossa (cavity)
 Supraspinous fossa
 Acromion process
 Corocoid process
 scapular landmarks
 Body – largest portion of scapula
 Rotator cuff attachments  Separated by borders & angles
 Spine of scapula
 Separates
/
fossae
 Extends to form the acromion
 Corocoid process – fingerlike projection towards
anterior
 Glenoid fossa
 Articulates with
– smaller than head
 Superior and inferior tubercles
 Surrounded by
Clavicle
 “Collarbone”
 Slender,
bone
articulating w/ sternum & scapula
 Helps maintain alignment of scapula
 Anchors
to axial
skeleton
 Medial 2/3 – more cylindrical
 Lateral 1/3 – more flat
 Structural Weakness?
 Change of direction/shape

The Shoulder Anatomy
Articular anatomy
Articulations
 The shoulder is comprised of
distinct joints
 Sternoclavicular joint
 Acromioclavicular joint
 Glenohumeral joint
 Scapulothoracic joint
Sternoclavicular joint (SC)
 Articulation of
(breastbone)
and clavicle at the midline of the body
 Anchored by four separate ligaments
Acromioclavicular joint (AC)
 Articulation of
and clavicle
 Three degrees of movement
○ Elevation/depression
○ Protraction/retraction
○ Rotation
 Stabilized by three ligaments
○ Acromioclavicular ligament
○ Conoid ligament
○ Trapezoid ligament
Glenohumeral joint (GH)
 True shoulder joint
 Three degrees of freedom
○ Flexion/extension
○ ABD/ADD
○
 Combined movements to form
○ Horizontal flexion/extension
○ Circumduction
○ Elevation
 Supported by numerous ligaments that help to
form the joint capsule
 Superior GH ligament
 Middle GH ligament
 Inferior GH ligament
 Coracohumeral ligament (coracoid
process)
 Coracoacromial ligament*
 GH joint ligaments
GH articular anatomy
 Joint capsule allows for ~
of movement
 >1cm = laxity
 The humerus is oriented at the glenoid at a 30o
angle of rotation (____version)
 < 30o =
 > 30o =
Notes
Scapulothoracic joint (ST)
 Not a
– no bony articulations
 Three degrees of movement
○ Elevation/depression
○ Protraction/retraction
○ Upward/downward rotation
 Most important joint for shoulder mechanics
 Starting point in the chain of motion

Scapulohumeral rhythm
 The scapula and humerus move at differing
degrees during ABD
 Humerus moves first 30o
 Scapula & humerus move at 1:2 ratio for
next 60o
 Scapula & humerus move at 1:1 ratio
past 90o ABD
Muscular anatomy
ST vs. GH muscles
 Scapulothoracic muscles move the
on the
skeleton
 Direct vs. indirect based on attachments
 Glenohumeral muscles move the
on the
Scapulothoracic muscles
 Trapezius
 Superior, Middle, Inferior
 Levator scapulae
 Rhomboids
 Major, Minor
 Latissimus dorsi
 Serratus anterior
 Pectoralis major
 Pectoralis minor
Glenohumeral muscles
 Deltoid
 Anterior, Middle, Posterior
 Triceps brachii

 Teres major
 Coracobrachialis
Rotator cuff muscles
 Supraspinatus
 Infraspinatus
 Teres minor
 Subscapularis
The Shoulder Anatomy
 Functions
 Holds head of humerus in
 Rotation of humerus on long axis (IR/ER)
 Protects shoulder joint via common
musculotendinous sheath
 Stabilizes shoulder joint in every
direction EXCEPT
 Rotator Cuff Problems
 Rupture of rotator cuff muscles
 Calcification of tendons
 Humeral subluxation or dislocation
○ Superiorly: stabilized by
supraspinatus & coracoacromial
arch
○ Posteriorly: stabilized by
infraspinatus & teres minor
○ Anteriorly: stabilized by
subscapularis
○ Inferiorly:
Other anatomy
Bursae
 Subdeltoid bursa
 Under deltoid muscle
 Subacromial bursa
 Under
 Protects supraspinatus tendon
 Subcorocoid bursa
 Under coracoid process
 Protects subscapularis tendon
 Subscapular bursa
 Under neck of scapula
 Protects
tendon
Neurological anatomy
 Nerves C5, C6, C7, C8, and T1 comprise the
brachial plexus
 Branch off to create nerves in the UE
○ C5 – musculocutaneus n.
○ C6 – radial n.
○ C7 – median n.
○ C8 & T1 – ulnar n.
Notes
 The brachial plexus (network)
 Exits from the cervical spine (neck)
 Enters the upper extremity between
○ Clavicle
○
muscle
Vascular anatomy
 Subclavian Artery
 Becomes axillary artery
 Axillary Artery
 Becomes brachial artery