Shoulder Biomechanics

Question 1

Shoulder pain responsible for approximately __% of ALL musculoskeletal complaints

Answer 1

16

Question 2

The clavicle is deviated about __ degrees posterior to frontal plane

Answer 2

20

Question 3

The scapular is deviated __ degrees anterior to the frontal plane

Answer 3

35

Question 4

The humeral head is extroverted about __ degrees posterior to the medial-lateral axis at the elbow

Answer 4

30

Question 5

The medial end of the clavicle appears _____ in the longitudinal diameter and _____ in the transverse diameter.

Answer 5

Convex

Concave

Question 6

The articular surface of the manubrium at the SC joint appears _____ in the longitudinal diameter and _____ in the transverse diameter.

Answer 6

Concave

Convex

Question 7

How many degrees of freedom are at the SC joint?

Answer 7

3

Question 8

Describe the motions that occur at the SC joint and in what plane they occur

Answer 8

1) elevation and depression in frontal plane
2) protraction and retraction in horizontal plane
3) posterior clavicular rotation in sagittal plane

Question 9

During elevation of the clavicle there is a _____ roll and an ______ glide at the SC joint.

Answer 9

superior

inferior

Question 10

During depression of the clavicle there is a _____ roll and an ______ glide at the SC joint.

Answer 10

inferior

superior

Question 11

During clavicular retraction there is a _____ roll and an ______ glide at the SC joint.

Answer 11

posterior

posterior

Question 12

During clavicular protraction there is a _____ roll and an ______ glide at the SC joint.

Answer 12

anterior

anterior

Question 13

What type of joint is the AC joint?

Answer 13

planar

Question 14

What are the primary movements at the AC joint?

Answer 14

Upward and Downward Rotation

Question 15

What are the secondary movements at the AC joint?

Answer 15

• Internal and External Rotation in the horizontal plane

- Anterior and Posterior Tilt in the sagittal plane

Question 16

What movement occurs at the AC joint with scapulothoracic protraction?

Answer 16

Internal Rotation

Question 17

What movement occurs at the AC joint with scapulothoracic elevation?

Answer 17

Anterior tilt

Question 18

Scapulothoracic elevation involves a summation of ______ at the sternoclavicular joint and _____ at the acromioclavicular joint

Answer 18

elevation

downward rotation

Question 19

Scapulothoracic depression involves a summation of ______ at the sternoclavicular joint and _____ at the acromioclavicular joint

Answer 19

depression

upward rotation

Question 20

Scapulothoracic protraction involves a summation of ______ at the sternoclavicular joint and _____ at the acromioclavicular joint

Answer 20

protraction

slight horizontal plane adjustments

Question 21

Scapulothoracic retraction involves a summation of ______ at the sternoclavicular joint and _____ at the acromioclavicular joint

Answer 21

retraction

external rotation

Question 22

Scapulothoracic upward rotation involves a summation of ______ at the sternoclavicular joint and _____ at the acromioclavicular joint

Answer 22

elevation

upward rotation

Question 23

Scapulothoracic downward rotation involves a summation of ______ at the sternoclavicular joint and _____ at the acromioclavicular joint

Answer 23

depression

downward rotation

Question 24

During abduction what two movements are happening?

Answer 24

Elevation at SC Joint & Upward Rotation at AC Joint

Question 25

During abduction the SC joint is most active during the _____ phase whereas AC is most active in ____ phase

Answer 25

early | late

Question 26

3 functions of upward roation at the SC joint

Answer 26

1) Projects the glenoid fossa upward and anterior-laterally, providing structural base to maximize upward and lateral reach of upper limb 2) Preserves optimal length-tension relationship of abductor muscles of GH joint, such as middle deltoid and supraspinatus 3) Helps maintain volume within subacromial space

Question 27

The longitudinal diameter of the humeral head is __ times larger than the glenoid fossa. The transverse diameter of the humeral head is __ times larger than the glenoid fossa.

Answer 27

1. 9 | 2. 3

Question 28

Typically in what direction is GH joitn instability most common?

Answer 28

anteriorly or inferiorly

Question 29

What fills the subacromial space?

Answer 29

- supraspinatus muscle and its tendon | - subacromial bursa

Question 30

4 Ligaments of the GH joint capsule

Answer 30

1) SGHL 2) MGHL 3) IGHL 4) Coracohumeral Ligament

Question 31

What is the posterior band of the IGHL responsible for?

Answer 31

Resistance on the follow through | 90° of abduction and full internal rotation

Question 32

Why is the Glenoid Labrum SoVulnerable to Injury?

Answer 32

1) Superior part of glenoid labrum only loosely attached to adjacent glenoid rim 2) Approximately 50% of the long head of the biceps tendon directly attaches to the superior glenoid labrum

Question 33

The glenoid fossa has approximately a __ degree upward tilt relative to the medial border of the scapula

Answer 33

5

Question 34

What is the importance of this upward tilt at the glenoid fossa?

Answer 34

holds the humeral head in place

Question 35

What will occur if there is a loss of upward rotation posture of the scapula?

Answer 35

The humeral head may slide down vertically

Question 36

During shoulder abduction what way is the slide and what way is the roll?

Answer 36

Roll superiorly Slide inferiorly Convex on concave = roll and slide in opposite directions

Question 37

Without the concurrent inferior slide with the superior roll, what would happen?

Answer 37

The humeral head will impinge against the arch and block further abduction

Question 38

How many degrees would you be able to abduct if the humeral head did not slide inferiorly?

Answer 38

22 degrees

Question 39

During the full 180 degrees of shoulder abduction, __ degrees is attributed to scapulothoracic joint upward rotation whereas __ degrees is attributed to GH abduction

Answer 39

60 | 120

Question 40

For every 3° of shoulder abduction, _° occurs by GH joint abduction and _° occurs by scapulothoracic joint upward rotation

Answer 40

2 | 1