S2_L2: Kinesiology of the Shoulder Complex

Question 1

TRUE OR FALSE: The muscle that is parallel to the movement is the one that is most activated. It’s always about the line or plane of movement to muscle fiber.

Answer 1

True

Question 2

TRUE OR FALSE: Elevation of the arm is always in relation to the trunk unless stated otherwise.

Answer 2

True

Note: As long as the trunk does not participate in the motion, the degree of elevation of arm from vertical and elevation of arm relative to the trunk will be the same.

Question 3

TRUE OR FALSE: The scapulohumeral rhythm is a combination of concomitant glenohumeral and scapulothoracic motion. It varies among individuals and external constraints, but in reality, there is no definitive scapulohumeral rhythm.

Answer 3

True

Question 4

It is the only muscle capable of producing simultaneous scapular upward rotation (prime mover), posterior tilting, and external rotation, and has the largest moment arms of any of the scapulothoracic muscles.

Answer 4

Serratus anterior

Note: It is also the primary stabilizer of the inferior angle and medial border of the scapula.

Question 5

Paralysis of this muscle results to scapular winging

Answer 5

serratus anterior (boxer’s muscle)

Question 6

____ occurs to maintain the contact of the scapula with the contour of the rib cage and to orient the glenoid fossa.

Answer 6

Scapular tilting

Question 7

During normal flexion or abduction of the arm, the scapula ____ tilts on the thorax as the scapula is upwardly rotating.

Answer 7

posteriorly

Question 8

TRUE OR FALSE: The orientation of the glenoid fossa is important for maintaining congruency with the humeral head; maximizing function of glenohumeral muscles, capsule and ligaments; maximizing stability of the glenohumeral joint; and maximizing available motion of the arm.

Answer 8

True

Question 9

TRUE OR FALSE: Elevation of the scapula in the thorax (e.g., shoulder shrug) can result in anterior tilting or tipping of the scapula.

Answer 9

True

Question 10

The greatest shear forces during humeral elevation typically occur between ___ degrees of elevation.

Answer 10

30-40

Question 11

Painful arc of motion between ___ degrees of elevation (flexion & abduction) may indicate the rotator cuff or biceps as the primary source of pain.

Answer 11

60-120

Note: Pain later in the range of motion may indicate acromioclavicular degeneration as the primary source of pain.

Question 12

TRUE OR FALSE: A force component parallel to the long bone has a stabilizing effect because the parallel component contributes to joint compression.

Answer 12

True

Question 13

Most frequently dislocated joint in the body

Answer 13

glenohumeral joint

Question 14

TRUE OR FALSE: Shoulder dislocations are usually anterior-inferior, but multi-directional.

Answer 14

True

Question 15

Most common because of the weakness of the rotator interval capsule, foramen of Weitbrecht, weak rotator cuff muscles, and tendency of humerus to shift anteriorly (anteversion of the scapula).
A. anterior shoulder dislocation
B. posterior shoulder dislocation
C. inferior shoulder dislocation

Answer 15

A. anterior shoulder dislocation

Question 16

Brought about by the pull of gravity, and weak supraspinatus, deltoids, rotator interval capsule support, and area on the superior aspect.
A. anterior shoulder dislocation
B. posterior shoulder dislocation
C. inferior shoulder dislocation

Answer 16

C. inferior shoulder dislocation

Question 17

A potential space between the superior and middle glenohumeral ligaments; thus accounts for the weak capsular region and anterior dislocations.

Answer 17

Foramen of Weitbrecht

Question 18

Area between the middle and inferior glenohumeral ligaments that is not a common problematic area

Answer 18

Foramen of Rouviere

Question 19

Enumerate the components of the rotator interval capsule (RIC)

Answer 19

superior glenohumeral ligament, superior joint capsule, and coracohumeral ligament

Question 20

Most functional activities of the shoulder happen in this shoulder motion

Answer 20

scaption/scapular abduction

Question 21

This structure is the osteoligamentous vault over the humeral head that forms the subacromial space, suprahumeral space, or supraspinatus outlet.

Answer 21

Coracoacromial/Suprahumeral Arch

Note: It is 10mm in healthy subjects with an adducted arm, 5mm in arm elevation.

Question 22

Enumerate the contents of the subacromial space, the region between the suprahumeral/coracoacromial arch and humeral head

Answer 22

1. subacromial bursa
2. rotator cuff tendons
3. portion of tendon of the long head of the biceps brachii

Note: These structures are protected superiorly from direct trauma by the coracoacromial arch. Contact of the humeral head with the undersurface of the arch can cause painful impingement or mechanical abrasion of the structures within the subacromial space.

Question 23

These bursae are very important in the shoulder complex because they separate the supraspinatus tendon and humeral head from the acromion, coracoid process, coracoacromial ligament, and deltoid muscle.

Answer 23

Subacromial and subdeltoid bursae

Note: The bursae are commonly continuous with each other and are collectively known as subacromial bursa.

Question 24

TRUE OR FALSE: The subacromial bursa permits smooth gliding between the humerus and supraspinatus tendon and surrounding structures. Interruption or failure of this mechanism is a common cause of pain.

Answer 24

True

Question 25

TRUE OR FALSE: The subacromial space is considered as a component of the glenohumeral joint rather than a separate joint.

Answer 25

True

Note: The subacromial or suprahumeral joint (or space) is also described as a functional joint which is formed by movement of the head of humerus below the coracoacromial arch.

Question 26

This structure is a false joint formed by the coracoid process, acromion, coracoacromial ligament, and inferior surface of acromioclavicular joint. It acts as a physical barrier to superior translatory forces acting on the humeral head, preventing it from dislocating superiorly.

Answer 26

Coracoacromial/Suprahumeral Arch

Note: The coracoacromial ligament connects the acromion and coracoid process and creates the subacromial space below these structures.

Question 27

This condition occurs with a narrowed subacromial space. It occurs most commonly secondary to inflammation or degeneration of the supraspinatus tendon.

Answer 27

Subacromial bursitis

Question 28

TRUE OR FALSE: In shoulder impingement syndromes due to a narrowed subacromial space, the supraspinatus tendon (supraspinatus impingement syndrome), subacromial bursa, or long head of biceps are the ones usually impinged.

Answer 28

True

Note: There is no one single reason why people develop impingement syndromes, there are multiple factors involved. If the reason is anatomical, surgery is the solution.

Question 29

TRUE OR FALSE: Below 60º or above 120º in relation to the painful arc of shoulder motion, the supraspinatus tendon has yet to rotate past the overlying acromion or has already rotated past it, respectively. In these ranges, the pain is minimized or decreased.

Answer 29

True

Note: Beyond 120º, the space is less narrowed (opening further) because the scapula moves more superiorly with clavicular elevation, which is why there is no more pain/reduces the pain for the patient.

Question 30

Enumerate the 3 functional reasons for a narrowed subacromial space

Answer 30

1. Repetitive shoulder motion (Leads to inflammation, fibrosis, and thickening of soft tissues; e.g., throwers & swimmers)
2. Abnormal scapular mechanics (E.g., inadequate posterior tilting or upward rotation of the scapula)
3. Poor humeral mechanics (I.e., inadequate rolling or gliding movements, excessive superior or anterior translation of humeral head)

Question 31

Enumerate the 4 anatomical reasons for a narrowed subacromial space

Answer 31

1. Shape of acromion process (a curved or hooped shape causes narrowing compared to a flat shape)
2. Another object occupies the space (e.g., bony spurs or osteophytes)
3. Large coracoacromial ligament (congenital)
4. Disproportionately large humeral head

Question 32

This muscle is the prime mover of glenohumeral flexion

Answer 32

Anterior deltoid

Question 33

These muscles are the prime movers of glenohumeral abduction

Answer 33

deltoid and supraspinatus

Question 34

Most vulnerable rotator cuff muscle to tensile overload and chronic overuse because it is either passively stretched or actively contracting; it also participates in humeral elevation.

Answer 34

Supraspinatus

Question 35

It is the combination of scapular, clavicular, and humeral motion that occurs when the arm is raised either forward or to the side; including sagittal plane flexion, frontal plane abduction, and all the motions in between.

Answer 35

Elevation

Question 36

This movement is a combination of upward rotation of the scapula, external rotation of the shoulder, and posterior tilting of the scapula.

Answer 36

Abduction

Question 37

TRUE OR FALSE: Motion of the scapula on the thorax normally contributes about one-third of the total shoulder complex motion necessary for arm elevation, whereas the glenohumeral joint contributes about two-thirds of the total motion.

Answer 37

True

Question 38

TRUE OR FALSE: Any motions of the scapula will influence glenohumeral joint function.

Answer 38

True

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