Glenohumeral Joint

Question 1

Why does the GH joint have a poor bone congruency? And what anatomical structure helps improve this? What’s it’s other function?

Answer 1

• the head of the humerus is 3x as large as the glenoid fossa
• glenoid labrum improves congruency and decreases compressional stress by increasing SA

Question 2

Where does the GH joint capsule attach on the humerus? What are the GH joint capsule unique features?

Answer 2

• anatomical neck

- loose to provide movement, and even sags inferiorly at the axillary recess

Question 3

What is the weakest part of the GH joint capsule? What MOI can cause shoulder subluxation/luxation at these weak ligaments?

Answer 3

• inferior/anterior ligaments in axillary recess
• place arm in horizontal abduction and ER puts the weakest ligaments more anteriorly, then force on posterior surface pushes humeral head anteriorly to strain those weak ligaments

Question 4

What are the 3 ligaments of the GH joints?

Answer 4

• coracohumeral ligament
• coracoacromial ligament
• glenohumeral (sup, middle, inf)

Question 5

Where does the coracohumeral ligament run? What type of ligament is it? What movements does it limit?

Answer 5

• from coracoid process and 1 fiber goes to the greater and other fibers go to lesser tubercles, spanning the bicipital groove
• capsular ligament
• limits inferior translation and adduction

Question 6

Where does the coracoacromial ligament run? What type of ligament is it? What movements does it limit?

Answer 6

• from coracoid processs to acromium and forms roof of coracoacromial arch
• extrinsic ligament
• limits superior movement of humerus

Question 7

Where do the glenohumeral ligaments run? What type of ligaments are they? What movements do they each limit?

Answer 7

• thickening of joint capsule
• capsular ligament
• superior ligaments limit posterior translation, ER, and adduction
• middle ligaments limit ER
• inferior ligaments limit anterior translation, ER, and abduction

Question 8

What is unique about the GH synovium?

Answer 8

-it encompasses the biceps brachii long head tendon

Question 9

Describe the Scapulohumeral Rhythm in Abduction (ROM up to 180)

Answer 9

0-90 pure GH abduction
90-120 ER to clear greater tubercle (& prevent impingement at coracoacromial arch) and provides extra articular surface for motion (and continues abduction)
120-180 scapular upward-rotation

Question 10

What are the 3 scapulohumeral rhtyhms?

Answer 10

• GH flexes as the scapular posterior tilts and elevates
• GH horizontally abducts (& adducts) as the scapula retracts
• GH abducts/adducts as the scapula up/down rotates and elevates/depresses

Question 11

What is a dynamic ligament? Give the 4 dynamic ligaments?

Answer 11

• when a muscle acts uses isometrically to limit excessive ROM at a joint
• subscapularis, suprspinatus, infraspinatus, and teres minor

Question 12

Give examples of injuries to the supraspinatus or the bursa related to it (which lubricates and increases SA).

Answer 12

• subacromial bursitis when too much friction over a long period of time
• supraspinatus tendon can calcify in to mineralized fibrocartilage if too much compression/impingement from coracoacromial arch
• can avulse (tear the bone away)

Question 13

Give MOI for the infraspinatus.

Answer 13

-high acceleration of humerus in horizontal abduction and can’t control the deceleration, so infraspinatus torn