6.1 Shoulder Complex

Question 1

What are the four joints of the shoulder complex?

Answer 1

Sternoclavicular, acromioclavicular, scapulothoracic (functional), and glenohumeral joints.

Question 2

Which joint of the shoulder complex is not a true anatomical joint?

Answer 2

The scapulothoracic joint — it’s a functional articulation between the scapula and thoracic cage.

Question 3

What bones make up the shoulder complex?

Answer 3

Clavicle, scapula, and humerus.

Question 4

In what planes does the clavicle move?

Answer 4

All three planes: frontal (elevation/depression), transverse (protraction/retraction), sagittal (posterior rotation).

Question 5

During shoulder elevation, what happens to the clavicle?

Answer 5

It elevates and posteriorly rotates to position the scapula optimally.

Question 6

What are the motions of the scapula?

Answer 6

Elevation, depression, protraction (abduction), retraction (adduction), upward rotation, downward rotation, anterior tilt, and posterior tilt.

Question 7

What is the orientation of the humeral head?

Answer 7

Faces medially, posteriorly, and superiorly with 130–150° inclination and 30–40° retroversion.

Question 8

What structure deepens the glenoid fossa and adds stability?

Answer 8

The glenoid labrum.

Question 9

Why is the glenohumeral joint capsule loose?

Answer 9

To allow extensive mobility; its volume is twice the size of the humeral head.

Question 10

What are the open- and closed-packed positions of the glenohumeral joint?

Answer 10

Open-packed: 40–55° abduction, 30° horizontal adduction, neutral rotation. Closed-packed: full abduction and external rotation.

Question 11

What is scaption (scapular plane abduction)?

Answer 11

Arm elevation in a plane ~30–45° anterior to the frontal plane; optimal for rotator cuff efficiency and capsular alignment.

Question 12

Describe the arthrokinematics of glenohumeral abduction.

Answer 12

Convex humeral head rolls superiorly and glides inferiorly on the concave glenoid.

Question 13

Describe the arthrokinematics of shoulder external rotation.

Answer 13

Humeral head rolls posteriorly and glides anteriorly.

Question 14

Describe the arthrokinematics of shoulder internal rotation.

Answer 14

Humeral head rolls anteriorly and glides posteriorly.

Question 15

What type of joint is the sternoclavicular (SC) joint?

Answer 15

A saddle-type synovial joint with three degrees of freedom.

Question 16

During clavicular elevation at the SC joint, which way does the clavicle roll and glide?

Answer 16

Rolls superiorly and glides inferiorly (convex on concave).

Question 17

During clavicular protraction, what are the arthrokinematics?

Answer 17

Rolls and glides anteriorly (concave on convex).

Question 18

What type of joint is the acromioclavicular (AC) joint?

Answer 18

A planar synovial joint that allows gliding and rotational adjustments of the scapula.

Question 19

What is scapulohumeral rhythm?

Answer 19

A coordinated 2:1 ratio of glenohumeral to scapulothoracic movement during arm elevation (120° GH + 60° scapular upward rotation = 180° total).

Question 20

Why is scapulohumeral rhythm important?

Answer 20

It ensures smooth motion, optimal muscle length-tension, and prevents impingement during arm elevation.

Question 21

During full arm elevation, scapula should

Answer 21

External rotation, upward rotation, posterior tilt