Shoulder Joint Muscles - Definitions and Miscellaneous Information

Muscles responsible for extension of the shoulder: (7)

1. *Latissimus dorsi 2.* posterior deltoid 3. tricep brachii long head 4. teres major 5. pectoralis major sternal fibers 6. infraspinatus 7. teres minor.

Muscles responsible internal rotation of the shoulder (4)

1. *pectoralis major cf & sf 2. *anterior deltoid 3. subscapularis 4. latissimus dorsi

Muscles responsible for adduction of the shoulder (8)

1.*latissimus dorsi 2.*pectoralis major sf 3. anterior deltoid below 90 degrees fo abduction 4.posterior deltoid below 90 degrees of abduction 5. pectoralis major cf below 90 degrees of abduction 6. coracobrachalis 7. teres major 8. biceps brachii short head

Muscles responsible for adduction of the shoulder (3)

1.*pectoralis major cf & sf 2.*anterior deltoid 3. coracobrachalis

Muscles responsible for flexion of the glenoid humeral joint (shoulder) (4)

1.*pectoralis major clavicular fibers 2. *anterior deltoid 3. biceps brachii short head 4. coracobrachalis.

Muscles responsible for horizontal abduction of the shoulder (3)

1.*posterior deltoid 2.*infraspinatus 3. teres minor.

Muscles responsible for external rotation of the shoulder (3 )

1.*posterior deltoid 2.*infraspinatus 3. teres minor.

1st Degree Separated Shoulder

1st degree - partial tear of the A-C Ligaments

2nd Degree Separated Shoulder

2nd degree - complete tear of the A-C Ligaments and a partial tear of the Coracoclavicular Ligament;

3rd Degree Separated Shoulder

3rd degree - complete tear of the A-C ligaments and a complete tear of the Coracoclavicular Ligament.

Separated Shoulder (definition)

A Separated Shoulder is defined as tears of the ligaments that stabilize the A-C joint.

Most common mechanism of injury for luxation, subluxation, and separated shoulder

A fall on an out stretched arm/hand or a fall on the acromion process are the most common injury mechanisms for a luxation, subluxation & separated shoulder.

Luxation (definition)

A luxation of the shoulder is defined as a complete dislocation of the shoulder where the head of the humerus is completely forced out of the glenoid fossa and remains out.

Subluxation (definition)

A subluxation of the shoulder is defined as a partial dislocation of the shoulder where the head of the humerus is briefly partially forced out of glenoid fossa but returns to the original position.

Four muscles that compose the rotator cuff

Anterior - Subscapularis, Posterior - Supraspinatus, Infraspinatus, Teres Minor

Impingement syndrome

Impingement syndrome is defined as superior movement of the humeral head into the subacromial space and trapping and squeezing the three structures (supraspinatus tendon, biceps brachii longhead tendon & subacromial bursae) that are located within the subacromial space against the acromial arch (acromion process and coracoacromial ligament) and causing trauma to these structures. Any movement of shoulder abduction above 90 degrees can cause impingement syndrome. This is why it is important to strengthen humeral head depressers, the rotator cuff & the biceps brachii longhead.

Muscles responsible for humeral movement, joint stability, & depression of the head of the humerus (11)

Pectoralis Major, Coracobrachalis, Subscapularis, Biceps Brachii, Infraspinatus, Teres Minor, Deltoid, Supraspinatus, Latissimus Dorsi, Teres Major & Triceps Brachii.

Empty can test

The empty can test is utilized to detect a weak supraspinatus. To administer the test, the subjects arms should be placed in full internal rotation with about 30 degrees of elbow flexion (as if emptying a can of water. This position isolates the supraspinatus by rotating its insertion, the superior aspect of the greater tubercle of the humerus, to a more superior position which neutralizes the deltoid except the posterior aspect of the deltoid. The examiner should then push several times on the superior aspect of the hand. A weak supraspinatus will not be able to resist the pushes.

Second most often injured rotator cuff muscles (2)

The infraspinatus & teres minor are the second most often injured rotator cuff muscles due to the fact that they must eccentrically contract in order to decelerate the humerus during the follow through phase of throwing.

Responsibility of Rotator Cuff

The rotator cuff is responsible for stabilization and centering of the humeral head within the glenoid fossa and depressing the humeral head as it moves past 90 degrees of abduction in order to inhibit the humeral head from entering into the subacromial space and impinging the 3 structures located there (supraspinatus tendon, biceps brachii long head tendon & subacromial bursae).

Most often injured rotator cuff muscle

The supraspinatus is the most often injured rotator cuff due to the fact that the supraspinatus tendon runs through the subacromial space to its insertion, therefore can become impinged.

Impinge (definition)

To impinge is defined as to be forced upon or against something. Syndrome (L. - running together) is defined as a number of symptoms occurring together to characterize a specific disease.