The Shoulder

• Unstable - the glenoid labrum and rotator cuff muscles aid in stability of the shoulder
• Glenohumeral joint - the articulation of the humerus with the scapula; the cavity is very shallow (not as deep as the acetabulum) and therefore is not very stable
• Multiaxial, synovial, ball-and-socket joint
• Most mobile joint in the body, which allows: flexion, extension, AD-duction, AB-duction, circumduction, external/internal rotation, and horizontal AD-duction and AB-duction

• Humeral head articulates with the glenoid cavity
• Humeral neck barely visible
• Greater tuberosity (laterally)
• Lesser tuberosity (medially)
• Intertubercle groove - the biceps brachii long head tendon runs in this groove
• Transverse humeral ligament holds the biceps brachii tendon in the intertubercle groove
• Deltoid tuberosity - location of the insertion of the 3 bellies of the deltoid muscle
• Epiphyseal plate (growth plate) of the humerus is the last to close; this is important because many young people play baseball/softball and like to throw "junk" pitches, which can set them up for injury

• 17 muscles attach
• Glenoid cavity - circular and concave in shape
• Coracoid process - located inferior to the clavicle
• Scapular spine
• Acromion process
• Superior/inferior angle
• Medial border - located closer to vertebrae
• Axillary (lateral) border - located further from the vertebrae
• Superior border
• 4 Fossas (in which many muscles lie): glenoid, subscapular, infraspinous, and supraspinous

• 2 parts: sternal and acromial
• S-shaped long bone
• Most commonly broken at the midclavicular point (spot at which the bone curves and changes shape)

* Young people less than 15 years old are likely to break their clavicle if they fall on outstretched arms*

• The articulation between the humerus and the scapula
• Stabilized by the capsular ligament, which is located around the joint and is twice the size of the humeral head (contributes to looseness due to big size); capsular ligament attaches to the rim of the glenoid fossa
• The joint holds synovial fluid and is very loose
• The glenoid labrum deepens the socket of the shoulder and is often torn with dislocations

• The articulation between the thoracic ribs to the scapula
• Contains no ligaments because movement is needed
• This joint supplies the rhythm of the shoulder: for every 3 degrees of shoulder AB-duction, there is 1 degree of scapular rotation

• The articulation of the acromion process with the acromial end of the clavicle
• Stabilized by 3 ligaments total: acromioclavicular ligament and two coracoclavicular ligaments (trapezoid and conoid, which run from the coracoid process to the clavicle)
• Trapezoid ligament - Anterior, longer, and lateral
• Conoid - More medial, shorter
• 2nd most commonly injured joint of the upper extremity after the glenohumeral joint
• This joint is injured in a shoulder dislocation

• The articulation of the sternum and the sternal end of the clavicle
• Cartilaginous joint (contains an articular disc)
• Stabilized by 2 ligaments
• Anterior sternoclavicular ligament
• Posterior sternoclavicular ligament (on internal surface)

Origin: T6 - T12, last 3 - 4 ribs, and the posterior iliac crest

Insertion: Intertubercle groove

Action: Extension, AD-duction, and internal rotation

• *Tendon goes anterior to intertubercle groove*
• *Exercises: lat pull downs, shoulder AD-duction*

Origin: Anterior - Outer 1/3 of the clavicle (lateral aspect), Middle - Border of acromion, Posterior - Scapular spine

Insertion: Deltoid tuberosity

Action: Anterior - Shoulder flexion, Middle - Shoulder AB-duction, Posterior - Shoulder extension

• *Exercises: Anterior - Front raises, Middle - Side raises, upright rows, Posterior - Cable, bent-over rows*
• *The middle deltoid is the smallest of the three*

Origin: Inner (medial) 1/2 of clavicle, ribs, and sternum

Insertion: Intertubercle groove

Action: Shoulder horizontal AD-duction, shoulder internal rotation, and some shoulder flexion

• *Exercises: Bench press, push-ups*
• *Bench press form is important. The press should stop at 90 degrees to prevent badly injuring the tendon and to ensure you're pushing back from where the muscle is most contracted. In addition, if you go past 90 degrees, you are relaxing in order to generate force for pushing it back up, which is cheating.*

Strain

When shoulder is raised above 90 degrees, the humeral head will hit the acromion and cause impingement of the subacromial space and lead to injury. This is often how baseball pitchers get shoulder problems.

Origin: Inferior angle of the scapula

Insertion: Intertubercle groove

Action: Shoulder AD-duction and some shoulder internal rotation

*Exercises: Horizontal raises (works out the middle deltoid while going up, but works the teres major while going back down*

*1 of 4 Rotator Cuff Muscles*

Origin: Supraspinous fossa

Insertion: Greater tuberosity of the humerus

Action: Shoulder AB-duction in 45 degree angle, shoulder horizontal AD-duction, and shoulder internal rotation

*Exercises: "Empty Can" exercise or "Full Can" exercise (especially if rotator cuff muscles are injured)*

*1 of 4 Rotator Cuff Muscles*

Origin: Infraspinous fossa

Insertion: Greater tuberosity of the humerus

Action: Shoulder external rotation

*Exercises: Cables, therabands (in open pack position)*

*1 of 4 Rotator Cuff Muscles*

Origin: Superior lateral border (superior to the teres major)

Insertion: Greater tuberosity

Action: Shoulder external rotation

*1 of 4 Rotator Cuff Muscles*

Origin: Subscapular fossa

Insertion: Lesser tuberosity of the humerus

Action: Shoulder internal rotation

*Consists of 4 intertwined parts*

• Trap. 1:
• Origin: Base of Skull
• Insertion: Clavicle
• Action: Elevate scapula

• Trap. 2:
• Origin: Cervical vertebrae (C1 - C7)
• Insertion: Acromion
• Action: Elevate scapula

• Trap. 3:
• Origin: Upper thoracic spine (T1 - T6)
• Insertion: Scapular spine
• Action: Scapular retraction

• Trap. 4:
• Origin: Lower thoracic spine (T7 - T12)
• Insertion: Inferior scapular spine
• Action: Scapular depression

*Exercises: Shoulder shrugs, upright rows (Trap. 1 & 2), Cable rows/ high rows (Trap. 3), dead lifts (Trap. 4)*

Origin: C1 - C4 transverse processes

Insertion: Superior medial border of the scapula

Action: Scapular elevation

*Exercises: Shoulder shrugs*

Origin: T2 - T5 spinous processes

Insertion: Medial inferior border of scapula

Action: Scapular retraction

*Exercises: Cable rows*

Origin: C7 - T1 spinous processes

Insertion: Medial superior scapular border

Action: Scapular retraction

• *Located superior to rhomboid major*
• *Exercises: Cable rows*

*The "wing" muscles with a finger-like appearance*

Origin: Ribs 1 - 8

Insertion: Medial border of the scapula

Action: Scapular protraction

• *Very difficult muscle to train; will not be visible without having very little body fat*
• *Exercises: Push-ups with a "plus", scapular punches*

Origin: Ribs 3 - 5

Insertion: Coracoid process

Action: Tilts/pulls scapula away from the thorax

*Difficult muscle to train*

• Neural complex that innervates the shoulder, arm, forearm, and hand
• Signs & Symptoms: Weakness, radiating pain, numbness, tingling (the more stretch that is experienced, the longer the effects/symptoms will last)
• Common Name: Stinger or Dead Arm (seen commonly in football players)
• Players cannot return to play until full range of motion and strength returns because it can predispose you to a bigger or worse injury

• 3 structures involved: Supraspinatus tendon, subacromial bursa, and the long head of the biceps brachii tendon
• Results in numbness and radiating pain in arm during overhead motions
• Most common sign: Athlete/individual cannot sleep on corresponding side