“Exploring the Shoulder Complex: Learning the Anatomy of
Shoulder Joint”
The Shoulder complex consist of four joints: sternoclavicular, acromioclavicular,
scapulothoracic and, glenohumeral joint.
The shoulder joint (glenohumeral joint) is a synovial ball and socket joint that joint upper limbs
to the trunk, shoulder joint is the most mobile joint in the human body however also an unstable
joint that is more prone to dislocation and injuries. (Snell, 2010)
Bones:
The articulation of three bones
formed shoulder joint:
Humerus: (upper arm bone)
the head of humerus fits into
glenoid cavity of scapula
Scapula: (shoulder blade)
provides the glenoid cavity for
articulation with the humerus.
Clavicle: (collarbone)
stabilizes the shoulder joint by
connecting it to the sternum
and scapula. (Grey, 2021)
(figure 1)
Figure 1 Bones, articulation and, ligaments of shoulder joint, Netter Atlas
Human Anatomy 8th edition
, Articulating Surfaces
Glenoid Cavity (Scapula) – A shallow, concave structure that holds the humeral head.
Humeral Head – A large, rounded structure that fits into the glenoid cavity. (Grey, 2021)
Glenoid Labrum–A fibrocartilaginous rim that deepens the glenoid cavity and increases stability
(figure 1)
Ligaments:
Ligaments provide passive stability to the shoulder joint:
Capsular Ligaments:
Glenohumeral Ligaments (Superior, Middle, Inferior) – Strengthen the anterior capsule.
Coracohumeral Ligament – Extends from the coracoid process to the humerus, preventing
downward displacement.
Extracapsular Ligaments:
Coracoacromial Ligament – Forms an arch over the humeral head, preventing superior
displacement.
Acromioclavicular Ligament – Connects the acromion to the clavicle.
Coracoclavicular Ligament – Anchors the clavicle to the coracoid process (trapezoid & conoid
parts) (Keith L. Moore, 2018) (figure 1).
Muscles:
The shoulder joint is stabilized and moved by muscles, particularly the rotator cuff muscles
(Keith L. Moore, 2018).
Rotator Cuff Muscles (SITS)
These muscles surround the joint and provide stability and movement:
Supraspinatus – Initiates abduction (0-15°).
Infraspinatus – External rotation of the arm.
Teres Minor – Assists with external rotation.
Subscapularis – Internal rotation of the arm. (figure 2)
Muscles with their actions: (figure 3) (Hislop, 2007)
Muscle Action
Coracobracialis and Anterior Deltoid Flexion – Forward movement
Latissimus dorsi, Posterior deltoid Extension – Backward movement
Supraspinatus, Deltoid Abduction – Moving away from the body
Pectoralis major, Latissimus dorsi Adduction – Moving toward the body
Subscapularis, Pectoralis major Internal Rotation – Rotating inward
Infraspinatus, Teres minor External Rotation – Rotating outward
Circumduction – Combination of all movements Circumduction – Combination of all movements
in a circular motion in a circular motion.
Posterior Deltoid Horizontal Abduction
Pectoralis Major Horizontal Adduction
Shoulder Joint”
The Shoulder complex consist of four joints: sternoclavicular, acromioclavicular,
scapulothoracic and, glenohumeral joint.
The shoulder joint (glenohumeral joint) is a synovial ball and socket joint that joint upper limbs
to the trunk, shoulder joint is the most mobile joint in the human body however also an unstable
joint that is more prone to dislocation and injuries. (Snell, 2010)
Bones:
The articulation of three bones
formed shoulder joint:
Humerus: (upper arm bone)
the head of humerus fits into
glenoid cavity of scapula
Scapula: (shoulder blade)
provides the glenoid cavity for
articulation with the humerus.
Clavicle: (collarbone)
stabilizes the shoulder joint by
connecting it to the sternum
and scapula. (Grey, 2021)
(figure 1)
Figure 1 Bones, articulation and, ligaments of shoulder joint, Netter Atlas
Human Anatomy 8th edition
, Articulating Surfaces
Glenoid Cavity (Scapula) – A shallow, concave structure that holds the humeral head.
Humeral Head – A large, rounded structure that fits into the glenoid cavity. (Grey, 2021)
Glenoid Labrum–A fibrocartilaginous rim that deepens the glenoid cavity and increases stability
(figure 1)
Ligaments:
Ligaments provide passive stability to the shoulder joint:
Capsular Ligaments:
Glenohumeral Ligaments (Superior, Middle, Inferior) – Strengthen the anterior capsule.
Coracohumeral Ligament – Extends from the coracoid process to the humerus, preventing
downward displacement.
Extracapsular Ligaments:
Coracoacromial Ligament – Forms an arch over the humeral head, preventing superior
displacement.
Acromioclavicular Ligament – Connects the acromion to the clavicle.
Coracoclavicular Ligament – Anchors the clavicle to the coracoid process (trapezoid & conoid
parts) (Keith L. Moore, 2018) (figure 1).
Muscles:
The shoulder joint is stabilized and moved by muscles, particularly the rotator cuff muscles
(Keith L. Moore, 2018).
Rotator Cuff Muscles (SITS)
These muscles surround the joint and provide stability and movement:
Supraspinatus – Initiates abduction (0-15°).
Infraspinatus – External rotation of the arm.
Teres Minor – Assists with external rotation.
Subscapularis – Internal rotation of the arm. (figure 2)
Muscles with their actions: (figure 3) (Hislop, 2007)
Muscle Action
Coracobracialis and Anterior Deltoid Flexion – Forward movement
Latissimus dorsi, Posterior deltoid Extension – Backward movement
Supraspinatus, Deltoid Abduction – Moving away from the body
Pectoralis major, Latissimus dorsi Adduction – Moving toward the body
Subscapularis, Pectoralis major Internal Rotation – Rotating inward
Infraspinatus, Teres minor External Rotation – Rotating outward
Circumduction – Combination of all movements Circumduction – Combination of all movements
in a circular motion in a circular motion.
Posterior Deltoid Horizontal Abduction
Pectoralis Major Horizontal Adduction
