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 Internal Rotation External Rotation Horizontal adduction

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 Intrinsic muscles of 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 Horizontal Adduction Flexion Exercises to strengthen would include: When arm is abducted above 90 degrees, assists with adduction. Assists with flexion. Floyd text suggests lat pulls for coracobrachialis – okay until arm reaches 90 degree elevation. Bench press Lat pulls Supine flies 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 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 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.