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Chapter 5- Shoulder Joint Kinesiology

-Shoulder

Joint is attached to the axial skeleton by the scapula at its attachment to the

clavicle at the SC joint.

-when there is humerus movement, it is usually accompanied by scapular movement

Shoulder jt. Actions

Shoulder jt.

Agonists

Shoulder girdle

actions

Shoulder girdle

agonists

Abduction

Supraspinatus,

deltoid,upper pec major

Upward

rotation/

elevation

Serratus

Anterior, middle/lower traps,

Levator

scapulae, rhomboids

Adduction

Lats,

teres major,

lower

pec major

Downward

rotation

Pec

minor, rhomboids

Flexion

Anterior

deltoid,

Upper

pec major, coracobrachialis

Elevation/

Upward

rotation

Levator

scapulae,

Serratus

anterior, upper/middle traps,

Rhomboids

Extension

Lats,

teres major,

Lower

pec major,

Posterior

deltoid

Depression/

Downward

rotation

Pec

minor

Lower

traps

Internal

Rotation

Lats,

teres major,

Pec

major, subscapularis

Protraction

(abduction)

Serratus

anterior,

Pec

minor

External

Rotation

Infraspinatus,

teres minor

Retraction

(adduction)

Middle/lower

traps,

Rhomboids

Horizontal

Abduction

Middle/posterior

deltoid, infraspinatus, teres minor

Retraction

(adduction)

Middle/lower

traps,

Rhomboids

Horizontal

Adduction

Pec

major, anterior deltoid,coracobrachialis

Protraction

(abduction)

Serratus

anterior,

Pec

minor

Diagonal

Abduction

Posterior

deltoid, infraspinatus, teres minor

Retraction/

Upward

rotation/ elevation

Traps,

rhomboids,

Serratus

anterior,

Levator

scapulae

Diagonal

Adduction

Pec

major, anterior deltoid, coracobrachialis

Protraction/

downward

rotation/ depression

Serratus

anterior,

Pec

minor

-because

shoulder joint does so many motions in all different planes, it has a big

amount of laxity which is the main reason for instability problems such as

rotator cuff impingement, subluxations, and dislocations.

-The more mobile a joint is, the less stability it has and vise versa

-scapula, clavicle and humerus serve as an attachment point for many muscles in

the should joint.

-Scapula Key

Landmarks Humerus

Key Landmarks

*supraspinatus fossa *Head

*infraspinatus fossa *Greater

Tubercle

*subscapular fossa(ANT.) *Lesser Tubercle

*spine *Intertubercular

groove

*glenoid fossa *Deltoid

Tuberosity

*coracoid process *Anatomical

Neck

*acromion process *Surgical

Neck

*inferior angle

Glenohumeral Joint

-multiaxial

ball and socket joint(enarthrodial). Joint capsule is needed, located around

glenoid fossa of the scapula and the anatomical neck of the humerus. Inner jt. Capsule

is synovial fluid and the outer jt. Capsule is fibrous.

-Joint stability is enhanced slightly by glenoid labrum, a cartilaginous ring

that surrounds the glenoid fossa just inside its periphery. Further stabilized

by its glenohumeral ligaments anteriorly and posteriorly.

-Anterior Glenohumeral ligaments

become taut(stretched) during external rotation, extension, abduction, and

horizontal abduction.

-Posterior glenohumeral ligaments

become taut(stretched) during interal rotation, flexion, and horizontal

adduction

-Inferior glenohumeral ligament has

become more of an importance of stability within the anterior and posterior GH

ligaments.

-Due to the wide range of motion involved in the glenohumeral joint, the

ligaments are quite lax until the extreme ranges of motion are reached.

(FOOSE). Ligaments kick in to prevent injury!

-Coracohumeral ligament- attaches

from lateral side of coracoids process and spans the joint anteriorly to the

medial side of the greater tubercle. Strengthens upper portion of the joint.

-Determining the EXACT range of each movement is difficult due to the accessory

motion at the shoulder girdle.

90-95 degrees of Abduction

0 degrees of adduction, 75

degrees anterior to trunk

**first 30 degrees is PURE GLENOHUMERAL

(after 30, scapular rotation occurs)

40-60 degrees of extension

90-100 degrees of flexion

70-90 degrees of interal(70)

& external (90) rotation

45 degrees of horizontal

abduction

135 degrees of horizontal

adduction

**2:1 RATIO- FOR EVERY 2 DEGREES OF

GLENOHUMERAL MOTION, THERE IS 1 DEGREE OF SCAPULA MOTION**

Glenohumeral

Movement – Arthrokinematic Motion

During ABDUCTION:

-Roll, Glide and Spin

-Convex/ Concave Rule

-Convex structure moves OPPOSITE the

concave

-Concave structure moves SAME to the convex

Example: in shoulder abduction, the deltoid is the actual abductor doing the

motion but the supraspinatus, subscapularis, infraspinatus and teres minor

accompany it to help maintain the head of the humerus in the glenoid fossa.

-Glenohumeral

joint is frequently injured due to its anatomical design

-shallowness of glenoid fossa

-laxity of ligamentous

structures

-lack of strength &

endurance in muscles

-anterior/anteroinferior GH

sublaxations & dislocations (COMMON)

-posterior dislocations-

(RARE)

-posterior instability

problems- (COMMON)

-Rotator Cuff is most commonly injured

-included in rotator cuff is

subscapularis,supraspinatus,infraspinatus & teres minor

-attachment of rotator cuff is the

front, top & rear of humeral head

-rotator cuff point of insertion

enables humeral rotation

-cuff is vital in maintaining

humeral head in correct approx. within glenoid fossa while the

more powerful muscles move humerus

through its wider ROM

-GH joint is

paired with shoulder girdle to accomplish total shoulder ROM

-170-180 of TOTAL abduction

includes:

-approx. 60 degrees of scapula

upward rotation

-25 degrees of scapula

elevation

-95 degrees of GH abduction

-Scapulohumeral rhythm

-for every 2 degrees of glenohumeral motion,

there is 1 degree of scapula motion.

-Acromioclavicular

Seperation

-1st degree separation:

mild (stretched ligament)

-2nd degree separation:

ruptured (AC torn, CA stretched)

-3rd degree separation:

complete tear to both ligaments

-Adhesive Capsulitis (frozen shoulder)

-inflammation of the joint capsule

-common for women over 40 y.o. and

takes about a year to resolve itself

-Middle Deltoid “inch worm effect”

-without the “inchworm effect” the

middle deltoid would run out of contractile power

as it neared 90 degrees of abduction

-upward rotation of scapula causes

origin of deltoid to move away from insertion of humerus,

when this occurs, it allows middle

deltoid to finish motion.

Muscles of

the Shoulder Joint:

-Nerve Innervations:

-Lateral Pectoral Nerve

C5-C7 Pectoralis Major (Clavicular Head)

-Medial Pectoral Nerve

C8-T1 Pectoralis Major (Sternal Head)

-Thoracodorsal Nerve

C6-C8 Latissimus Dorsi

-Axillary Nerve C5-C6 Deltoid, Teres Minor

-Upper Subscapular Nerve

C5-C6 Subscapularis

-Lower Subscapular Nerve

C5-C6 Subscapularis, Teres Major

-Suprascapula C5-C6 Supraspinatus, Infraspinatus

-Musculotaneous C5-C7

Coracobrachialis

-Agonist Actions:

-GH Flexion Anterior

Deltoid, Upper Pectoralis Major

-GH Extension Teres

Major, Latissimus Dorsi, Lower Pectoralis Major

-GH Abduction Deltoid,

Supraspinatus, Upper Pectoralis Major

-GH Adduction(lat. Pull) Latissimus

Dorsi, Teres Major, Lower Pectoralis Major

-GH Int. Rotation Latissimus

Dorsi, Teres Major, Supscapularis, Pectoralis Major

-GH Ext. Rotation Infraspinatus,

Teres Minor

-GH Hor. ABD Posterior/Middle

Deltoid, Infraspinatus, Teres Minor

-GH Hor. ADD Anterior Deltoid, Pectoralis Major,

Coracobrachialis

-GH Diag. ABD Posterior

Deltoid, Infraspinatus, Teres Minor, Triceps Brachii LH

-GH Diag. ADD ANT.

Deltoid, Coracobrachialis, Biceps SH, Pec.Major UP&LOW