The Shoulder Joint

By : Gan Quan Fu, PT, MSc. Human Anatomy (Batch 3)

Content• Introduction• Glenoid Cavity• Ligaments Surrounding the joint• Bursae in Relation to the Shoulder Joint• Muscles Acting on Shoulder Joint• Blood and Nerve Supply• Joint Movement• Close and Loose Pack Position• Applied Anatomy

Overview

Introduction• Enarthrodial or Ball-and-Socket joint• Bones Involve

o Large globular head of humeruso Glenoid cavity of scapula

• Protected against displacement by tendons and by atmospheric pressure.

• Ligaments around gleno-humeral joint; Limit the amount of joint movemento Capsularo Coracohumeralo Transverse Humeralo Glenoid Ligament

• Above protected by arched vault formed by:o Under surface of coracoid processo Under surface of acromion processo Coraco-acromial ligament

Glenoid Cavity• Pear Shape• 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.

ARTICULATING SURFACE

LIGAMENTS SURROUNDING the SHOULDER JOINT

Capsular Ligament• Encircles entire

glenohumeral joint.• Attached:

o Medially: Above to the circumference of glenoid cavity beyond the glenoid ligament

o Laterally: Below to anatomical neck of the humerus

• Thicker above and below.• Loose and lax

• Allow bone to be separated from each other more than an inch

Muscles Supporting Capsular Ligament

• Superiorly Supraspinatus

• Inferiorly Long Head of Triceps

• Posteriorly Tendons of Infraspinatus and Teres Minor

• Anteriorly Tendon of Subscapularis

Openings of Capsular Ligament

3 Openingso Anteriorly

• Below coracoid Process, connection between synovial membrane of the joint and a bursa beneath the tendon of subscapularis muscle.

• Between the 2 tuberosities, passage of the biceps long head.

o Posteriorly• Not constant, where a

communication exists between joint and a bursal sac belonging to Infraspinatus muscle.

Supplemental Bands of Capsular Ligament

• Strengthen capsular ligament in the interior of the joint.

• Flood’s Ligamentso Situated on inner side of joint o Passes from inner edge of glenoid cavity o Attached to lower part of lesser tuberosity of humerus.

• Schlemm’s Ligaments o Situated at lower part of the jointo Passes from under edge of glenoid cavityo Attached to under part of neck of humerus

• Glenohumeral Ligamentso Situated at upper part of the joints, projects into its interior (can only be

seen when capsule is open). Attached above apex of glenoid cavity close to root of coracoid process, attached below lesser tuberosity of humerus (Forms inner boundary of upper part of bicipital groove)

Glenohumeral Ligaments

• 3 fibrous bands derived from thickening of the anterior part of fibrous capsule.

• All 3 Converge upward and medially blend with glenoid labrum:o SUPERIOR BAND :

attached to the upper end of lesser tubercle

o MIDDLE BAND : attached to lower part of lesser tubercle

o INFERIOR BAND : lower part of anatomical neck of humerus.

CORACO-HUMERAL

LIGAMENT• Broad Thick Band• Strengthens Upper

part of Capsular Ligament

• Attachmentso Arises from outer border of

coracoid processo Blended with tendon of

supraspinatus muscles

• United to capsule in greater part of its extend.

TRANSVERSE HUMERAL

LIGAMENT

• Broad band of fibrous tissues

• Connects the two lips of the upper part of intertubercular sulcus and acts as a retinaculum to keep the long tendon of biceps in position.

GLENOID LABRUM• Fibro-cartilage rim

attached around margin of glenoid cavity.

• Triangular on section• Thickest portion at

circumference of cavity, free edge is sharp and thin

• Continuous above with long head of biceps

• Deepens cavity for articulation and protects edges of bone

• Lined by synovial membrane

SYNOVIAL MEMBRANE

• Reflected from margin of glenoid cavity over fibro-cartilaginous rim surrounding it.

• Over internal surface of capsular ligaments.

• Covers lower part and sides of anatomical neck of humerus.

BURSAE in RELATION to the

SHOULDER JOINT

BURSAE IN RELATION TO THE SHOULDER JOINT

1) SUBSCAPULAR BURSA

2) INFRASPINATUS BURSA

3) SUBACROMIAL BURSA (SUBDELTOID)

4) SUBCORACOID BURSA

BURSA• SUBSCAPULAR BURSAIntervenes between the tendon of subscapularis and fibrous capsule. Communicates with the joint cavity through oval gap between superior and middle glenohumeral ligaments.

• Infraspinatus bursaCommunicates with the joint from behind

• Subacromial bursaLargest bursa of the body intervenes between supraspinatus and coraco-acromial arch. It does not communicate with the joint.It is of great value in the abduction of arm at the shoulder joint where is protects the supraspinatus tendon against friction with the acromion

MUSCLES ACTING on SHOULDER

JOINT

Muscles in Relation to the Joint

• Above Supraspinatus• Below Long head of

Triceps• Front Subscapularis• Behind Infraspinatus and

Teres Minor• Deltoid is placed most

externally and covers the articulation from its outer side, as well as in front and behind.

Blood and Nerve Supply to Shoulder

Joint

Blood and Nerve Supply

• Blood Supply1.Anterior circumflex

humeral vessels2.Posterior circumflex

humeral vessels3.Suprascapular vessels

• NERVE SUPPLY1) Axillary nerve2) Musculocutaneous

nerve3) Suprascapular Nerve4) Lateral pectoral nerve

Summary on Should Joint Anatomy

Movements of the Shoulder Joint

MOVEMENTS AT THE SHOULDER

JOINTS• Movement in every direction (Flexion, extension, abduction,

adduction, rotation, circumduction)• Highly mobile due to:

o Large size of head of humerus in comparison with the depth of glenoid cavity (Even when supplemented by glenoid ligament)

o Looseness of the capsule of the joint (Laxity of fibrous capsule)

o When movements of arm are arrested by contact of the bony surface Tension of corresponding fibers and muscles acting on accessory ligaments farther movements of scapula and accessory structures to the shoulder joint (acromio and sterno-clavicular joints).

• Spinal Cord regulating Shoulder movements (C5, C6, C7 & C8)o Flexion, Abduction, & lateral rotation (C5, C6,).o Extension, Adduction, & Medial rotation is (C6, C7, C8)

Osteo- & Arthrokinematics of Shoulder Joint

• Osteokinematicso Flexiono Extensiono Hyperextensiono Abductiono Adductiono Medial rotation (internal rotation)o Lateral rotation (external rotation)o Horizontal abductiono Horizontal adductiono Circumduction

• Concave-convex ruleo Convex humeral head moves within the concave glenoid fossao The Convex joint surface (Humeral Head) moves in a direction opposite

to the movement of the body segment (Humeral Shaft)

Flexion• Plane of Motion:

o Sagittal Plane

• Axis of Motion: o Transverse Axis through the center of the

humeral head

• Muscles Involved:o Pectoris majoro Anterior Fibres od Deltoido Coraco-brachialiso Biceps (When the foreare is flexed)

• Humeral head glides posterior laterally in the glenoid cavity

• Range of Motiono 0 – 90 degrees

Factors Limiting Shoulder Flexion

• Inferior Glenohumeral ligament• Tightness of posterior joint capsule

Extension• Plane of Motion:

o Sagittal Plane

• Axis of Motion: o Transverse Axis through the center of

the humeral head

• Muscles Involve:o Latissimus dorsio Teres majoro Posterior fibers of Deltoido Triceps (When forearm is extended)

• Humeral head glide anterior medially in glenoid cavity

• Range of Motiono 0 – 45 degrees or 60 degrees

Factors Limiting Shoulder Extension

• Superior and medial gleno-humeral ligament

Abduction• Plane of Motion:

o Frontal Plane

• Axis of Motion: o Sagittal axis through the center of the

humeral head

• Muscles Involve:o Deltoido Supraspinatus

• Humeral head glide inferiorly in glenoid cavity

• Range of Motiono Total : 0 – 165 degrees or 175 degreeso Full internal rotation of humerus: 0 – 60

degreeso Full external rotation of Humerus: 0 – 90

degrees

Factors Limiting Shoulder Abduction

• Inferior glenohumeral ligament • Tightness of the inferior joint capsule of the

glenoumeral joint

Adduction• Plane of Motion:

o Frontal Plane

• Axis of Motion: o Sagittal axis through the center of the

humeral head

• Muscles Involve:o Subscapulariso Pectoralis Majoro Latissimus dorsio Teres major

• Humeral head glide superiorly in glenoid cavity

• Factors Limiting:o Trunk

Internal Rotation• Plane of Motion:

o Transverse Plane

• Axis of Motion: o Vertical axis through the center of humeral

head

• Muscles Involve:o Subscapulariso Pectoralis Majoro Latissimus dorsio Teres major

• Humeral head glide posteriorlaterally in glenoid cavity

• Range of Motiono 0-70º as the arm at 90º of shoulder

abduction and 90º elbow flexiono If the elbow is extended, shoulder rotation

occurs simultaneously with forearm rotation.

Factors Limiting Internal Rotation

• Posterior Capsule

External Rotation• Plane of Motion:

o Transverse Plane

• Axis of Motion: o Vertical axis through the center of

humeral head

• Muscles Involve:o Infraspinatuso Teres Minor

• Humeral head glide anteriomedially in glenoid cavity

• Range of Motiono 0-90º as the arm at 90º of shoulder

abduction and 90º elbow flexiono If the elbow is extended, shoulder

rotation occurs simultaneously with forearm rotation.

Factors Limiting External Rotation

• Coracohumeral ligament• 3 glenohumeral ligaments

Circumduction• A combination of flexion, abduction, extension,

and adduction or in the reversed sequenceo glenohumeral flexion abduction extension adductiono glenohumeral extension abduction flexion adduction

Close and Loose Packed Position

• Close Packed positiono Position where the articular

surfaces of joint are in maximal congruency status, resulting in greatest mechanical stability.

o Most ligament and capsule surrounding joint are taut.

o 90° of glenohumeral abduction and full external rotation

• Loose Packed positiono Position where the articular

surface of joint are in minimal congruency status.

o Supporting structures are most lax.

o 55° of semi-abduction and 30° of horizontal adduction

APPLIED ANATOMY

Dislocation• Humeral head is hold in place by

the Rotator cuff (S,I,T,S) Muscles.

• Humeral Head separated from scapula at glenohumeral joint.

• Commonly downward dislocation because Rotator Cuff protects joints in all direction except inferiorly.

• Hemiparesis/Hemiplegia patients prone to dislocate their shoulder their Rotator cuff muscles are weak to hold the shoulder joint in place.

Adhesive Capsulitis• Frozen Shoulder• Pain and Stiffness in the

Shoulder• Shoulder capsule thickens

and becomes tight. Stiff bands of tissue — called adhesions — develop. In many cases, there is less synovial fluid in the joint.

• Unable to move your shoulder - either on your own or with the help of someone else.

Stages of Adhesive Capsulitis

• It develops in three stages:o Freezing (Pain worsens, shoulder loses range of

motion. Typically lasts from 6 weeks to 9 months.)

o Frozen (Painful symptoms may actually improve during this stage, but the stiffness remains. During the 4 to 6 months of the "frozen" stage, daily activities may be very difficult.)

o Thawing (Shoulder motion slowly improves. Complete return to normal or close to normal strength and motion. Typically takes from 6 months to 2 years.)

SLAP LESION• Injury to the labrum of the

shoulder.• SLAP = Superior Labrum

Anterior and Posterior. • In a SLAP injury, the superior

part of the labrum is injured. This top area is also where the biceps tendon attaches to the labrum.

• SLAP tear occurs both in front (anterior) and back (posterior) of this attachment point.

• The biceps tendon can be involved in the injury as well.

Bankart Lesion• Tear of the labrum and

attached joint capsule along the anterior inferior quadrant of the Glenoid ligament/Inferior glenohumeral ligament.

• Associated with shoulder dislocation.

• Bony Bankart is when some of the glenoid bone is broken off with the anterior inferior labrum (Shoulder joint more unstable than Bankart Tear)

Shoulder Bursitis• Inflammation of shoulder

Bursa• Commonly Subacromion

Bursao Usually related to shoulder

impingement of Subacromion Bursa between rotator cuff tendon and acromion

• Subdeltoid bursa less commonly inflammed

• Commonly co-exists with rotator cuff tears or tendonitis

Surgical Intervention

• Front of the shoulder joint is commonly approached for surgical intervention

• Aspiration needle maybe introduced through deltopectoral triangle (closer to deltoid)

References• Gray, H. (2012) Gray’s Anatomy; The classic

Anatomical Handbook for Doctors, Students and Artist, 15th edn. London; Bounty Books.

• Saladin, K. S. (2007) Anatomy and Physiology: The Unity of Form and Function. 4th edn. New York; McGraw-Hill.