Shoulder [gleno-humeral joint]

Question 1

What forms the gleno-humeral joint?

Answer 1

• the articulation of the head of the humerus with the glenoid cavity of the scapula

Question 2

The lack of stability at the GH joint is demonstrated by what 4 factors?

Answer 2

1. lack of ossous support [large head of humerus does not fit well in the small glenoid fossa]
2. lack of ligamentous support [only 2 main ligaments, 1 ant and 1 post]
3. lack of muscular support [muscles are positioned ant, superior, and post to the joint–> also muscles attach lower on the humerus]
4. structure of the joint capsule [taught in the superior capsule, but loose inferiorly]

Question 3

What are the main 6 structures of the GH joint?

Answer 3

1. Glenoid labrum
2. Bursae
3. Capsule
4. Coracromial arch
5. Glenohumeral ligament
6. Coracoacromial ligament

Question 4

What are the movements at the GH joint?

Answer 4

• flex/extension
• Add/Abduction
• IR/ER
• Horizontal abduction/adduction
• Diagonal add/abduction

Question 5

What is the function of the Glenoid labrum?

Answer 5

• The structure surrounds the glenoid fossa enchanching the curvature and increases amount of contact
• it is synovium lined cartilage

Question 6

What are the 2 types of bursaes in the shoulder? And what is their main function?

Answer 6

1. Subacromial
2. Subdeltoid

Main function is to allow for smooth gliding of lower structires on upper structures without friction.

Question 7

How big is the joint capsule and why is it important?

Answer 7

• 2x the size of the humeral head (allows for 1inch of distraction from glenoid fossa)
• the loose capsule is taught superiorly and slack inferiorly

Question 8

How does the size of the GH joint capsule affect movement?

Answer 8

• The GH capusule surrounds the entire joint
• It is larger than the humeral head to allow movement of the g-h head away from the glenoid fossa (distarction more than 1”)
• It is taught superiorly and loose inferiorly (most muscles insert inferiorly on the humerus)

Question 9

What 3 structures makes up the coracromial arch? What is its purpose?

Answer 9

Its purpose is to protect the humeral head and the muscles, tendons, and bursae from direct trauma
* helps prevent superior dislocation (when you put your hand out when you fall)

Formed by:
1. coracoid process
2. acromion
3. coracoacromial ligament

Question 10

What is the GH ligament, and what is it’s purpose of each band?

Answer 10

The GH ligamnet tightens and provides a “check” to many humeral motions. It is made up of 3 bands that look like a Z on the anterior capsule

• All bands get tight on lateral rotation
• Middle and inferior bands become tight duing abduction

Question 11

Describe the coracohumeral ligament. What is its O and A? Describe the bands and what they do?

Answer 11

The coracohumeral ligament provides passive support of the upper extermity when the arm is in the dependent position.
* O: coracoid process
* A: greater tubercle of the humerus

The anterior and posterior band, both checking lateral rotation
* anterior band is tight during humeral extension
* Posterior band is tight duing humeral flexion

Question 12

Overview: what are the muscles of the GH?
- 4 anterior
- 2 superior/lateral
- 5 posterior

Answer 12

Anterior:
* pectoralis major
* anterior deltoid
* coracobrachialis
* subscapularis

Superior/lateral
* middle deltoid
* supraspinatus

Posterior:
* posterior deltoid
* latissimus dorsi
* teres major
* infraspinatus
* teres minor

Question 13

Describe the pectoralis major, its 2 heads, and it action

Answer 13

the strength of both heads combine to produce foreful contractions that bring the arm against the front and side of chest. Due to its anterior midline origin, It counters the strong posterior pull of the lat dorsi and mainatins possition of humerus.

Clavicular head: humeral flexion
Sternal head: humeral extension

Overall:
- humeral adduction
- horizontal adduction
- humeral IR

Question 14

Describe the anterior deltoid and actions

Answer 14

• humeral flexion
• humeral horizontal adduction
• humeral internal rotation

the fusiform (spindle) shape of muscle allows humerus to move through full ROM as it goes through flexion, horizontal adduction, and IR

Question 15

Describe the coracobrachialis and its actions

Answer 15

This is a secondary muscle to more powerful muscles of the gh-joint, it provides stability keep the humeral head in the glenoid cavity
* humeral horizontal adduction
* humeral flexion
* humeral adduction
* humeral IR

Question 16

Describe the subscapularis and its action

Answer 16

One of the rotator cuff muscles
* A: humeral internal rotation

Question 17

Describe the biceps brachii and its actions

Answer 17

Primarily a muscle of the elbow and forearm. At the GH joint it serves as a shunt muscle provding stability duing humeral flexion, and horizontal adduction
* A: humeral flexion and horizontal adduction

Question 18

Describe the action of the middle deltoid

Answer 18

The most powerful deltoid muscle provding** abduction** and contributes to force of anterior deltoid as it raises the arm. The line of pull of its fibers does not allow this muscle to effectivey initiate the movement of abduction when the arm is in the dependent or resting position

A: humeral abduction

Question 19

Describe the supraspinatus and its action

Answer 19

One of the rotator cuff muscles. Essential for normal abduction of humerus, its line of pull allows the humeral head to lift until the middle deltoid can take over
* A:** humeral abduction**

Question 20

Describe the posterior deltoid and its actions

Answer 20

The weakest deltoid muscle
Actions:
* humeral horizontal abduction
* extension and hyperextension
* ER

Question 21

Describe the latissimus dorsi and actions

Answer 21

Powerful muscle of the GJ joint that acts on the arm down to the body from any position. Its posterior midline origin counters the strong pull of the pec major

Actions:
* IR
* adduction
* hyperextension
* extension

Question 22

Describe the teres major and actions

Answer 22

The helper of the lat dorsi. It is active duing all movements involving forceable depression of the arm and works with lats to draw humerus down to the body

Actions:
* IR
* extension
* hyperextension
* adduction

Question 23

Describe the infraspinatus and teres minor and their action

Answer 23

They are rotator cuff muscles
* A: ER

Question 24

Describe the long head of the triceps and action

Answer 24

Primarily serves as a muscle of the elbow and forearm. AT the GH joint it serves as a shunt muscle providing stability duing humeral adduction, extension, and hyperextension

Question 25

What are the 4 rotator cuff muscles?

Answer 25

1. Supraspinatus
2. infraspinatus
3. teres minor
4. subscapularis

They are dynamic ligaments and are the only ones that have a direct attacthment on the humeral head. They contract to keep the humeral head congruent with the glenoid cavity

Question 26

What is scapulohumeral rhythm?

Answer 26

the pattern of concomitant, coordinated, and consistent pattern of movements occuring in the shoulder complex components (bones, joints, muscles)
* the shoulder complex, its bones, muscles, and joints act in a coordinated manner to provide the greatest ROM and versitality of movement to the UE.
**
2:1 ratio
Every 2 degrees of movement at the GH, there will be 1 degree of motion at the scapulothoracic joints

Question 27

Describe the axioscapula muscle attachments

Answer 27

The muscles that originate on the axial skeleton and insert on the scapula.
Their function of these muscles is to rotate and stabilize it; putting the glenoid cavity in the best position for the movement and positioning of the humeral head
* pec major
* serratus anterior
* trapezius
* levator scapula
* rhomboids

Question 28

Describe the scapulohumeral muscles

Answer 28

Those muscles that originate on the scapula and insert on the humerus. The function of these muscles is to rotate the humerus (primarily the head), while keeping the head of the humerus in alignment with and proximal to the glenoid cavity.
* deltoids
* supraspinatus
* infraspinatus
* teres minor
* teres majjor
* subscapularis
* coracobrachialis

Question 29

What are the different disorders of the shoulder complex?

Answer 29

• Bursitis
• Bicipital tendonitis
• Rotator cuff tears
• Shoulder disolocation
• Shoulder seperation: tearing and/or rupture of the acromioclavicular and coracoclavicular ligaments
• Frozen shoulder

Question 30

What is a frozen shoulder? And what is the progression/stages?

Answer 30

Frozen shoulder (adhesive capsulitis): the joint capsule enclosing the joints becomes thickened and tight and bands of scar tissue form(adhesions)
- stiffness and pain in shoulder with limitations in ROM

• Painful/Freezing stage: most painful stage, motion is restricted, but not comepleetly stiff, typcially 6-12 weeks. (may not fully notice lack of ROM bc still in functional limits
• Frozen stage: pain eases up, but stiffness gets worse, lasts 4-6 months
• Thawing stage: gradual, motion steadily improves over a length of time, can last over a year