Biomechanics Final Exam

at what degree is the glenoid fossa oriented in the frontal plane?

30 degrees

in which directions is the humeral head oriented and rotated?

medially/superiorly, rotated 30 degrees

what is the angle of inclination of the humeral head in the frontal plane?

130-150 degrees

motion at which two joints produces motion at the ST joint? (scapulothoracic)

SC and AC joint

what structure in the sternoclavicular joint functions as a shock absorber while enhancing the stability of the joint?

fibrocartilage disc

what is normal ROM of elevation in the frontal plane for SC joint kinematics?

45-48 degrees

what is normal ROM of depression in the frontal plane for SC joint kinematics?

10 degrees

what is normal ROM of protraction in the horizontal plane for SC joint kinematics?

15-20 degrees

what is normal ROM of depression in the horizontal plane for SC joint kinematics?

30 degrees

what is normal ROM of posterior rotation in the for SC joint kinematics?

50 degrees

is which direction does roll and slide happen during elevation and depression in the SC joint?

opposite

is which direction does roll and slide happen during protraction and retraction in the SC joint?

same

during AC joint kinematics, what two motions occur with upward rotation and at what degree?

30 degrees, shoulder flexion and abduction

during AC joint kinematics, what two motions occur with downward rotation and at what degree?

17 degrees, shoulder extension and adduction

in AC joint kinematics, how does the scapula anteriorly tilt?

acromion anterior, inferior angle posterior

in AC joint kinematics, how does the scapula posteriorly tilt?

acromion posterior, inferior angle anterior

what is total ROM of anterior/posterior tilting at the AC joint?

20-40 degrees

how do the glenoid and medial scapular border move during internal rotation at the AC joint?

glenoid - anterior and medial medial scapular border - away from the thorax

how do the glenoid and medial scapular border move during external rotation at the AC joint?

glenoid - posterior and lateral medial scapular border - towards the thorax

what is resting position of the ST joint when it is anteriorly tilted

10-15 degrees

what is resting position of the ST joint when it is upwardly rotated

5-10 degrees from the vertical plane

what is resting position of the ST joint when it is medially rotated

35-45 degrees from horizontal plane

what are the combined motions of the ST joint kinematics?

AC joint + SC joint

what is normal ROM of ST joint for upward rotation

50-60 degrees

what is internal rotation of the ST joint?

vertebral border of the scapula moves posteriorly

what is external rotation of the ST joint?

vertebral border of the scapula moves anteriorly

ligaments of the GH joint provide what kind of stability?

static

rotator cuff muscles provide what kind of stability for the GH joint

dynamic

GH joint capsule provides _______ but provides minimal ______

mobility, stability

superior GH ligaments limits what kind of translation in resting position?

A/P and inferior

middle GH ligaments limits what kind of translation in resting position?

A/P translation in 0-60 degrees abduction

middle GH ligaments limits what kind of translation in resting position?

A/P translation in 90 degrees abduction or more

what is contained in the coracoacromial arch?

subacromial bursa, rotator cuff tendons, long head of biceps, joint capsule

what is subacromial impingement (subacromial pain syndrome)

anatomical or functional factors that decrease the subacromial space causing pain

in context of the glenoid and humerus, which surface is convex. Which is concave?

glenoid = concave, humerus = convex

if the glenoid is concave and the humerus is convex, in which direction does roll and slide happen?

opposite

when does maximum abduction occur in the GH joint?

during external rotation

what is normal ROM of GH abduction?

0-120 degrees

what is scaption? What is normal ROM?

30-45 degrees in the frontal plane

during internal rotation, which way does the humeral head roll and slide?

anterior, posterior

during external rotation, which way does the humeral head roll and slide?

posterior, anterior

would an impairment/dysfunction in the clavicle affect the scapula and humerus?

yes, one part of the chain can affect the whole complex

what is scapulohumeral rhythm?

relationship between the movement of the humerus and scapula during overhead elevation of the arm

scapular movement doesn’t occur after the first _____ degrees of GH abduction or _____ degrees of GH flexion

30, 60

what is the ratio of humerus to scapular movement?

2:1

scapulohumeral rhythm ensures what?

the humerus remains centered on the glenoid

to complete full shoulder elevation, what motion needs to occur to clear the greater tubercle from the acromion?

external rotation

Does frontal plane elevation or scapula plane elevation require more external rotation?

frontal plane elevation

what is the role of the shoulder stabilizers?

orient the scapula and keep it against the thorax, orient the humeral head in the glenoid fossa, originate on the spine, ribs, and cranium, insert on the scap and clavicle.

what is the role of the shoulder mobilizers?

move the humerus, originate on the scap and clavicle, insert on the humerus or forearm

which muscles are scapulothoracic elevators?

upper trapezius, levator scapulae, rhomboids

which muscles are scapulothoracic depressors

lower trapezius, latissimus dorsi, pectoralis major

which muscles are scapulothoracic protractors

serratus anterior and pectoralis minor

which muscles are scapulothoracic retractors?

middle trapezius, rhomboids, lower trapezius

scapulothoracic muscles: what is the upward rotation force couple

serratus anterior, upper trapezius, lower trapezius

scapulothoracic muscles: what is the downward rotation force couple

levator scapulae, pectoralis major, rhomboids

what kind of stabilizer is the rotator cuff?

dynamic

which dynamic stabilizer of the rotator cuff attaches to the greater tubercle of the humerus, contributes to superior roll in arthrokinematics, and produces slight amount of external rotation?

supraspinatus

which dynamic stabilizers of the rotator cuff contribute inferior force to oppose superior roll, externally rotates the humerus to clear the greater tubercle from the acromion, and counters the superior force of the deltoid?

infraspinatus and teres minor

which dynamic stabilizer exerts inferior glide to oppose superior roll, counters the superior force of the deltoid, and provides internal rotation and anterior stability?

subscapularis

Which dynamic stabilizer assists inferior translation of the humeral head during humeral elevation?

long head of biceps and triceps

what are the glenohumeral primary movers

deltoid, lats, teres major, pec major, and coracobrachialis

what is the action of the latissimus dorsi?

shoulder extension, adduction, and internal rotation

what two muscles assist the lats?

teres major and long head of the triceps

which muscles has two heads that can function independently from one another? what are those two actions?

pec major, clavicular head assists with shoulder flexion and sternocostal head extends the shoulder from a fully flexed position

a weak serratus anterior would create a functional deficit in the shoulder complex causing what issue in the shoulder?

shoulder impingement

if upper trap is strong and lower trap is weak, which way will the scapula be pulled/rotated? What issue will this cause?

superior/upwardly rotate, shoulder impingement

which muscle is tight if you have limited upward scapular rotation and posterior tilt? What issue would this cause?

pec major, subacromial impingement

what two functional causes would cause shoulder impingement that are related to muscle imbalances?

rotator cuff insufficiency and scapulothoracic muscle weakness

In the sternoclavicular joint, which surface is convex?

medial calvicle

How many degrees is the glenoid oriented off the frontal plane?

30

True or False: AC joint motion can occur independently of SC joint motion

false

In SC joint protraction, the clavicle rolls anteriorly on the sternum and glides…

anteriorly

The goal of all shoulder joint kinematics is…

to keep the humerus centered on the glenoid during UE movement

What motion describes anterior motion of the acromion and posterior motion of the inferior angle of the scapula?

anterior tilt

True or False: some scapulothoracic kinematics describe the same motions as acromioclavicular kinematics

true

What is the ratio of humerus to scapular movement in scapulohumeral rhythm

2:1

What motions are required by the SC and AC joints for normal shoulder elevation?

AC upward rotation and SC posterior rotation

What motion at the GH joint is required to clear the greater tubercle from the acromion during elevation?

external rotation

What describes the GH arthokinematics observed during GH abduction?

superior roll, inferior glide

A muscle that originates on the spine and inserts on the scapula is most likely to be a:…

stabilizer

Which of these is NOT a scapular depressor?

levator scapulae

True or False: Diagonal fibers in the rhomboid and lower trap oppose each other.

true

what muscle opposes the force of the pec minor?

lower trapezius

Upward rotation of the scapula requires a force couple between what three muscles?

serratus anterior, lower trapezius, upper trapezius

What direction is the arthrokinematics motion supplied by the supraspinatus during arm elevation

superior roll

True or False: The infraspinatus and teres minor counter the force supplied by the deltoid muscle during arm elevation

true

Infraspinatus, teres minor, ad subscapularis supply what arthrokinematic motion during GH elevation

inferior slide

What is the goal of the rotator cuff?

the keep the humeral head centered on the glenoid during shoulder motion

What joints are in the “loose” hinge joint capsule of the elbow?

humeroradial, humeroulnar, proximal radioulnar

Which elbow ligament resists varus forces?

RCL

True or False: A hard end-feel in elbow extension is abnormal

false

In elbow extension, what direction does the radius slide on the humerus?

posterior

What is the normal average measurement of carrying angle

15 degrees

A carrying angle greater than the expected normal value s referred to as what?

cubital valgus

True or False: In supination and pronation, the roll and slide of the radius on the ulnar occur in the same direction

true

In the radiocarpal joint, which surface is concave?

the radius

What measurements are part of the functional position of the wrist?

20 degrees wrist extension and 10 degrees ulnar deviation

The keystone of the proximal transverse arch is the…

capitate