The Shoulder JointThe Shoulder Joint(Glenohumeral Joint)(Glenohumeral Joint)

What bones make up the shoulder joint?

Clavicle Scapula Humerus

Joint involved

The shoulder joint is made up of theglenohumeral joint. This is an enarthrodial,or multiaxial, ball and socket joint. It is very mobile, but sacrifices stability.

The Shoulder JointThe Shoulder JointMany variable movements occur at the shoulder.Movement of the humerus usually involvesmovement 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

Internal Rotation External Rotation

Horizontal adduction

The Shoulder JointThe Shoulder JointTo study the 9 muscles of the shoulder joint,we will break them into intrinsic and extrinsicgroups. The intrinsic group originate on theclavicle and scapula.

What are the 7 intrinsic muscles of the shoulderjoint?

Supraspinatus Infraspinatus Subscapularis

Teres minor Coracobrachialis Deltoid

Teres major

The Shoulder JointThe Shoulder JointWhat are the two extrinsic muscles of theshoulder joint?

Latissimus dorsi Pectoralis major

Intrinsic muscles of the shoulder joint

The first group of intrinsic muscles are the SITSmuscles. The band of tendons of these fourmuscles compose the rotator cuff of the shoulderjoint. The functions of the SITS muscles includerotation of the humerus, and to provide stability, especially against subluxation.

Rotator CuffRotator Cuff

SupraspinatusSupraspinatus

The Shoulder JointThe Shoulder JointA. 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 JointThe Shoulder JointTesting 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.

InfraspinatusInfraspinatus

The Shoulder JointThe Shoulder JointB. 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 externalrotator of SITS muscles

Extension of humerus

Horizontal abduction

The Shoulder JointThe Shoulder JointExercises involving the infraspinatus

Chinning, dips, rope climbing. Any exercisein 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. Patientlays prone with arm hanging. Fixate the scapulaand have them rotate up against resistance.

Teres MinorTeres Minor

The Shoulder JointThe Shoulder JointC. 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 JointThe Shoulder JointExercises 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 testfor external rotation with scapula stabilized.

SubscapularisSubscapularis

The Shoulder JointThe Shoulder JointD. 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 JointThe Shoulder JointExercises 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 internalrotation against resistance.

Testing the subscapularis

Similar to other muscles, have the patient layprone, and internally rotate against resistance.

DeltoidDeltoid

Shoulder Joint MusclesShoulder Joint MusclesAdditional 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 MusclesShoulder Joint MusclesWhat 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 MusclesShoulder Joint MusclesExercises 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

CoracobrachialisCoracobrachialis(not brachialis)(not brachialis)

Shoulder Joint MusclesShoulder Joint MusclesB. Coracobrachialis muscle - This muscle is named for its origin and insertion.

What actions does the coracobrachialis perform?Adduction

Horizontal Adduction

Flexion

Exercises to strengthen would include:

Bench press Lat pullsSupine flies

Not particularly strong, most functional in Horizontal Adduction

Teres MajorTeres Major

Shoulder Joint MusclesShoulder Joint MusclesC. 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 MusclesShoulder Joint MusclesExercises to strengthen the teres major muscle

Rope climbing Lat pulls

Internal rotation against resistance

As with the coracobrachialis, this muscle is notvery powerful on its own.

Shoulder Joint MusclesShoulder 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 DorsiLatissimus Dorsi

Shoulder Joint MusclesShoulder Joint Muscles

What are some activities involving or strengthening the Latissimus dorsi?

Lat pull downs Chinning Rope climbing

Dips Rowing Pull over

Pectoralis MajorPectoralis Major

Shoulder Joint MusclesShoulder Joint MusclesE. 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):Upper fibers (clavicular head): internal rotation,horizontal adduction, some flexion, some abduction

Lower fibers (sternal head):Lower fibers (sternal head): internal rotation, horizontal adduction, extension, some adduction

Shoulder Joint MusclesShoulder Joint MusclesExercises or activities involving the pectoralismajor?

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 MusclesShoulder 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 InjuriesShoulder 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 InjuriesShoulder 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.