The Shoulder Joint
(Glenohumeral Joint)
What bones make up the shoulder joint?
Clavicle Scapula Humerus
Joint involved
The shoulder joint is made up of the
glenohumeral joint. This is an enarthrodial,
or multiaxial, ball and socket joint. It is
very mobile, but sacrifices stability.
The Shoulder Joint
Many variable movements occur at the shoulder.
Movement of the humerus usually involves
movement at the shoulder girdle, known as
“scapulohumeral rhythm.”
What are the 8 movements that occur at the
shoulder joint?
Abduction Adduction Flexion Extension
Horizontal abduction Horizontal adduction
Internal Rotation External Rotation
Shoulder Girdle Movements
Shoulder Girdle Shoulder Joint
What shoulder joint
(glenohumeral) Protraction Horizontal
motions occur Adduction
with each Retraction Horizontal
shoulder girdle Abduction
(scapular) Upward Rotation Abduction
motion? Downward Adduction
Rotation
Elevation Shoulder shrug
Depression Shoulder
depression
The Shoulder Joint
To study the 9 muscles of the shoulder joint,
we will break them into intrinsic and extrinsic
groups. The intrinsic group originate on the
clavicle and scapula.
What are the 7 intrinsic muscles of the shoulder
joint?
Supraspinatus Infraspinatus Subscapularis
Teres minor Coracobrachialis Deltoid
Teres major
The Shoulder Joint
What are the two extrinsic muscles of the
shoulder joint?
Latissimus dorsi Pectoralis major
Intrinsic muscles of the shoulder joint
The first group of intrinsic muscles are the SITS
muscles. The band of tendons of these four
muscles compose the rotator cuff of the shoulder
joint. The functions of the SITS muscles include
rotation of the humerus, and to provide stability,
especially against subluxation.
Rotator Cuff
Supraspinatus
The Shoulder Joint
A. Supraspinatus muscle - This muscle is most
superior of the rotator cuff. It pulls the head
of the humerus into the glenoid fossa to
initiate abduction and provide an effective
angle of pull for the deltoid. It helps reinforce
the shoulder joint.
Actions - assist abduction, stabilize head of
humerus
The Shoulder Joint
Testing the supraspinatus for injury
1. Resisting against abduction - if the patient has
trouble abducting the arm against resistance
and tries to substitute the scapular muscles, it
can indicate supraspinatus damage.
2. Drop arm test - if the patient can not slowly
lower the arm from an abducted position, it
can indicate supraspinatus injury.
Infraspinatus
The Shoulder Joint
B. Infraspinatus muscle - located just inferior to
the supraspinatus, it also helps reinforce the
shoulder capsule and stabilize the humerus
during abduction.
Actions of the infraspinatus
External rotation - most powerful external
rotator of SITS muscles
Extension of humerus
Horizontal abduction
The Shoulder Joint
Exercises involving the infraspinatus
Chinning, dips, rope climbing. Any exercise
in which the arms are pulled down forcefully.
Works in conjunction with teres major and
latissimus dorsi.
Testing of the infraspinatus muscle
External rotation against resistance. Patient
lays prone with arm hanging. Fixate the scapula
and have them rotate up against resistance.
Teres Minor
The Shoulder Joint
C. Teres minor - Inferior to the infraspinatus,
this muscle also reinforces the shoulder
capsule and helps stabilize the head of the
humerus during abduction.
Actions of the teres minor
External rotation Horizontal abduction
Extension
The Shoulder Joint
Exercises to strengthen the teres minor
Same as infraspinatus - chinning, rope climbing,
dips, any movement in which arms go down
forcefully.
Testing the teres minor
Same test as for infraspinatus, prone test
for external rotation with scapula stabilized.
Subscapularis
The Shoulder Joint
D. Subscapularis - the final muscle in the four
“rotator cuff” muscles. As with the others,
helps stabilize shoulder capsule. This is the
only rotator cuff muscle to originate on the
anterior surface of the scapula.
Actions of the subscapularis
Internal rotation - main action
Adduction
Extension - from flexed position
The Shoulder Joint
Exercises involving the subscapularis
As with infraspinatus and teres minor, it is
involved in chinning, dips and rope climbing.
A specific exercise for this muscle is internal
rotation against resistance.
Testing the subscapularis
Similar to other muscles, have the patient lay
prone, and internally rotate against resistance.
Deltoid
Shoulder Joint Muscles
Additional Intrinsic Muscles
A. Deltoid Muscle - This muscle forms the rounded
muscle bulk of the shoulder joint. It is a strong
abductor, but cannot initiate that movement
because the angle of pull is parallel to the humerus
when the arm is by the side. Recall that the
supraspinatus initiates the movement.
The deltoid muscle is divided into three portions,
and hence is sometimes called “deltoids” muscle.
The three portions are anterior, middle, and posterior.
Shoulder Joint Muscles
What are the actions of the anterior deltoid?
Abduction Internal rotation
Horizontal adduction Flexion
What are the actions of the middle deltoid?
Abduction
What are the actions of the posterior deltoid?
Abduction External rotation
Horizontal abduction Extension
Shoulder Joint Muscles
Exercises to strengthen the deltoid muscle
Bench press Overhead press Front arm raise
Lateral arm raise Prone flies
Supine horizontally adducted dumbbell raises will
strengthen the anterior deltoid.
Prone horizontally abducted dumbbell raises will
strengthen the posterior deltoid
Coracobrachialis
(not brachialis)
Shoulder Joint Muscles
B. Coracobrachialis muscle - This muscle is named
for its origin and insertion.
What actions does the coracobrachialis perform?
Adduction Flexion
Horizontal Adduction
Exercises to strengthen would include:
Bench press Supine flies Lat pulls
Not particularly strong, most functional in
Horizontal Adduction
Teres Major
Shoulder Joint Muscles
C. Teres Major muscle - Together with the
infraspinatus and teres minor, it helps stabilize
the humerus during abduction. It is also known
as the latissimus dorsi’s little helper.
What are the actions of the teres major?
Adduction Internal Rotation Extension
Shoulder Joint Muscles
Exercises to strengthen the teres major muscle
Rope climbing Lat pulls
Internal rotation against resistance
As with the coracobrachialis, this muscle is not
very powerful on its own.
Shoulder Joint Muscles
D. Latissimus dorsi – latissimus means widest &
dorsi means back (Latin). Powerful in adduction,
extension and internal rotation of humerus.
Powerful contraction in chinning. Assisted in all
actions by teres major.
What are the actions of the latissimus dorsi?
Adduction Internal Rotation Extension
Horizontal abduction
Latissimus Dorsi
Shoulder Joint Muscles
What are some activities involving or strengthening
the Latissimus dorsi?
Lat pull downs Chinning Rope climbing
Dips Rowing Pull over
Pectoralis Major
Shoulder Joint Muscles
E. Pectoralis Major (pectus, breast bone) –
works closely with anterior deltoid.
It is divided into upper and lower sections.
Actions of Pectoralis Major
Upper fibers (clavicular head): internal rotation,
horizontal adduction, some flexion, some abduction
Lower fibers (sternal head): internal rotation,
horizontal adduction, extension, some adduction
Shoulder Joint Muscles
Exercises or activities involving the pectoralis
major?
Bench press Push ups Dumbell flies
Pull ups Incline press Decline press
Incline press muscles combine bench & overhead
presses.
Decline press made up of bench press & the dip.
Shoulder Joint Muscles
Biceps brachii (short and long heads)
originate on the scapula and insert on the
radius. It crosses two joints. Short head
assists flexion, adduction; Long assists with
abduction.
Triceps brachii (long head) originates on the
scapula just below the glenoid fossa. It
assists with shoulder extension and
adduction.
Shoulder Joint Injuries
Dislocation: the head of the humerus is
pushed out of the glenoid fossa. The
glenohumeral joint is the most commonly
dislocated joint in the body.
Rotator cuff damage: this is the most
common disorder of the shoulder. Supra-
spinatus is most commonly injured.
Shoulder Joint Injuries
Rotational injuries: tears of the labrum, the
rotator cuff muscles, and the biceps brachii
tendon among injuries resulting from repeated,
forceful rotation at shoulder. Tears of rotator
cuff attributed to extreme tension during
deceleration phase of throwlike motion.
Subscapular neuropathy: compression of
subscapular nerve.