The Shoulder Joint

Bones of the shoulder joint

• Scapula
• Glenoid Fossa Infraspinatus fossa
• Supraspinatus fossa Subscapular fossa
• Spine Coracoid process
• Acromion process
• Clavicle
• Humerus
• Greater tubercle Lesser tubercle
• Intertubercular goove Deltoid tuberosity
• Head of Humerus

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Shoulder Joint

• Bones:
• humerus
• scapula
• clavicle
• Articulation
• glenohumeral joint
• Glenoid fossa of the scapula (less curved)
• head of the humerus
• enarthrodial (ball and socket)

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Shoulder Girdle

Shoulder Joint

• Connective tissue
• glenoid labrum: cartilaginous ring, surrounds glenoid fossa
• increases contact area between head of humerus and glenoid fossa.
• increases joint stability
• Glenohumeral ligaments: reinforce the glenohumeral joint capsule
• superior, middle, inferior (anterior side of joint)
• coracohumeral ligament (superior)
• Muscles play a crucial role in maintaining glenohumeral joint stability.

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Movements of the Shoulder Joint

• Arm abduction, adduction about the shoulder
• Arm flexion, extension
• Arm hyperflexion, hyperextension
• Arm horizontal adduction (flexion)
• Arm horizontal abduction (extension)
• Arm external and internal rotation
• medial and lateral rotation
• Arm circumduction
• flexion, abduction, extension, hyperextension, adduction

Scapulohumeral rhythm

• Shoulder Joint
• abduction
• adduction
• flexion
• extension
• internal rotation
• external rotation
• horizontal abduction
• horizontal adduction

• Shoulder Girdle
• upward rotation
• downward rotation
• elevation/upward rot.
• Depression/downward rot.
• Abduction (protraction)
• adduction (retraction)
• adduction (retraction)
• abduction (protraction)

Understanding Scapula Movements

• Functions of movements:
• Stabilize scapula when shoulder complex is loaded/moving
• allows for different axes of rotation and lengths of muscles (which is related to force generating capability)
• Positioning scapula to facilitate movement of glenohumeral joint by changing orientation of glenoid fossa.

Muscles of the Shoulder Joint

• Organization
• anterior, posterior, superior, inferior
• rotator cuff muscles
• Origins and insertions
• Organization
• adductors, abductors, flexors, extensors …

Muscles of the Shoulder Joint

• Anterior
• pectoralis major
• coracobrachialis
• subscapularis
• biceps brachii

Muscles of the Shoulder Joint

• Posterior
• infraspinatus
• teres minor
• latissimus dorsi
• teres major
• triceps brachii, long head
• Superior
• deltoid
• supraspinatus

Rotator Cuff muscles

• Rotator Cuff: provides stability
• Supraspinatus
• infraspinatus
• teres minor
• subscapularis
• Note: there is an inherent lack of inferior stability of the shoulder joint.

Muscles of the Shoulder Joint

• Origin
• Insertion
• Actions
• Palpation

Deltoid Muscle�p119-121

• Origin:
• anterior fibers: anterior lateral third of the clavicle
• middle fibers: acromion process
• posterior fibers: inferior edge of the scapular spine
• Insertion:
• deltoid tuberosity on the lateral humerus

Deltoid Muscle�(deltoid: triangular)

• Action
• anterior: abduction, flexion, internal rotation, horizontal adduction
• middle: abduction
• posterior: abduction, outward rotation, extension, horizontal abduction

Coracobrachialis Muscle (p118)

• Origin
• coracoid process of the scapula
• Insertion
• Middle 1/3 of the medial surface of the humerus
• Action
• horizontal adduction, flexion, adduction

Supraspinatus Muscle (p126)

• Origin
• supraspinatus fossa
• Insertion
• Superiorly on the greater tubercle of the humerus
• Action
• abduction

Infraspinatus Muscle (p122)

• Origin
• infraspinatus fossa of the scapula
• Insertion
• Superior/lateral surface of the greater tubercle of the humerus
• Action
• outward rotation, horizontal abduction, adduction, abduction

Teres Minor Muscle (p128)�(teres: rounded)

• Origin
• Upper 2/3 of axillary border of the scapula
• Insertion
• Posterior surface of greater tubercle of the humerus
• Action
• Outward rotation, extension, adduction, horizontal abduction

Subscapularis Muscle (p125)

• Origin
• subscapular fossa
• Insertion
• lesser tubercle of the humerus
• Action
• inward rotation, extension

Teres Major Muscle (p127)

• Origin
• Lower 1/3 of the axillary border of the scapula/inferior angle of scapula
• Insertion
• crest of lesser tuberosity of humerus
• Action
• extension, adduction, inward rotation

Latissimus Dorsi Muscle (p123)�(latissimus: widest)

• Origin
• Spines of lower 6 thoracic and lumbar vertebrae
• Posterior surface of sacrum
• Posterior aspect of crest of illium
• Lower 3-4 ribs
• Inferior angle of scapula
• Insertion
• intertubercle groove of humerus
• Action
• extension, adduction, inward rotation, horizontal adduction

Pectoralis Major Muscle (p124)

• Origin
• upper fibers (clavicuolar head)
• medial half of anterior surface of clavicle
• lower fibers (sternal head)
• anterior surface of costal cartilage of first six ribs, adjacent portion of sternum
• Insertion
• Crest of the greater tuberosity of the humerus
• tendon “twists” such that lower fibers insert superior to upper fibers

Pectoralis Major Muscle

• Action
• horizontal adduction
• flexion
• inward rotation
• adduction

Summary of Muscles

• Deltoid (anterior, middle, posterior)
• Coracobrachialis
• Supraspinatus
• Infraspinatus
• Teres minor
• subscapularis
• teres major
• Latissimus dorsi*
• Pectoralis major * (upper and lower)
• *do not originate on the scapula

Summary: Shoulder Joint

• Bones: Humerus, Scapula (Glenoid Fossa)
• glenohumeral joint
• Muscles
• Rotator Cuff
• supraspinatus, infraspinatus, teres minor, subscapularis
• deltoid, coracobrachialis, teres major, latissimus dorsi, pectoralis major
• Stability is sacrificed for flexibility
• ligaments: glenoid labrum, Glenohumeral ligaments, coracohumeral

Summary of actions

• Flexors
• pectoralis major, anterior deltoid, coracobrachialis
• Extensors
• Posterior deltoid, latissimus dorsi, teres major, teres minor subscapularis
• Abductors
• Anterior and middle deltoid, supraspinatus
• Adductors
• latissimus dorsi, teres major, teres minor

Summary of Actions (cont)

• Inward rotators
• subscapularis, pectoralis major, latissimus dorsi, anterior deltoid
• Outward rotators
• Teres minor, infraspinatus, posterior deltoid