Shoulder Kinematics

Front 1

List the arthrology components of the ‘shoulder complex’ - specify joints
(functional & anatomical).

Back 1

Sternoclavicular-anatomical
Acromioclavicular-anatomical
Scapulothoracic-functional Is the point of contact between the anterior surface of the scapula and the posterior-lateral surface of the thorax.
Glenohumeral-anatomical

Front 2

What type of kinematic chain is involved between the scapulothoracic (ST),
sternoclavicular (SC), and acromioclavicular (AC) joints? Explain your answer.

Back 2

Closed kinematic chain, motion at one joint causes motion at another. Interdependent relationsips that the joints have together.

Front 3

List and demonstrate the 3 primary movements (osteokinematic motions) of the
scapulothoracic joint.

Back 3

Elevation-The scapula slides superiorly on the thorax, such as in shrugging the shoulders.
Depression-From an elevated position, the scapula slides inferiorly on the thorax.
Protraction-The medial border of the scapula slides anterior-laterally on the thorax away from the midline.
Retraction-The medial border of the scapula slides posterior-medially on the thorax toward the midline, such as occurs during the pinching of the shoulder blades together.
Upward Rotation-The inferior angle of the scapula rotates in a superior-lateral direction such that the glenoid foss faces upward.
Downward Rotation-The inferior angle of the scapula rotates in an inferior-medial direction such that the glenoid fossa faces downward.

Front 4

Motion at the SC joint involves motion of which bone?

Back 4

Clavicle

Front 5

Convex/concave rule of SC joint.

Back 5

Medial end of the clavicle is usually convex along its longitudinal diameter and concave along its transverse diameter. The clavicular facet on the sternum typically is reciprocally shaped, with a slightly concave longitudinal diameter and a slightly convex transverse diamter.

Front 6

List and demonstrate the osteokinematic motions, degrees of freedom, and
plane in which each motion takes place at the SC joint.

Back 6

Three degrees of freedom.
Elevation and depression
Protraction and retraction
Axial rotation of the clavicle.

Front 7

Identify location and direction of the joint axes for ELEVATION AND DEPRESSION at the SC joint.

Back 7

Occurs parallel to the frontal plane about an anterior-posterior axis of rotation. Occurs along the the SC joint's longitudinal diameter surface.

Front 8

Identify location and direction of the joint axes for PROTRACTION AND RETRACTION at the SC joint.

Back 8

Occur nearly parallel to the horizontal plane about a vertical axis of rotation.

Front 9

Identify location and direction of the joint axes for AXIAL rotation of the clavicle at the SC joint.

Back 9

3rd degree of freedom at the SC joint is a rotation of the clavicle about the bone's longitudinal axis. When the shoulder is abducted or flexed, a pointon the superior apect of the clavicle rotates posteriorly

Front 10

Describe SC joint arthrokinematics for each osteokinematic motion based on the
shape of the joint surfaces.
First Elevation and depression

Back 10

Along longitudinal diameter surface. Elevation of the clavicle occurs as the convex surface of its head rolls superiorly and simultaneously slides inferiorly on the concavity of the sternum. Depression of the clavicle occurs by action of its head rolling inferiorly and sliding superiorly.

Front 11

Describe SC joint arthrokinematics for each osteokinematic motion based on the
shape of the joint surfaces.
Protraction and Retraction

Back 11

Occurs along the SC joint's transverse diameter. Retraction occurs as the concave articular surface of the clavicle rolls and slider posteriorly on the convex surface of the sternum. Protraction are similar to retraction, except that they occur in an anterior direction.

Front 12

Describe SC joint arthrokinematics for each osteokinematic motion based on the
shape of the joint surfaces.
Axial (longitudinal) Rotation of the Clavicle

Back 12

The arthrokinematics of clavicular rotation involve a spin of the head of the clavicle abou the lateral surface of the articular disc.

Front 13

Motion at the AC joint involves motion of which bone?

Back 13

Scapula moving relative to a stable clavicle not relative to thoracic.

Front 14

List the osteokinematic motions, degrees of freedom, and plane in which each motion takes place at the AC joint.

Back 14

3 degrees of freedom
Upward and downward rotation
Horizontal plane rotational adjustments
Sagittal plane rotational adjustments

Front 15

Upward and Downward Rotation Location and joint axes

Back 15

Frontal plane
Axes-anterior/posterior
Upward rotation "swings upwardly and outwardly" The motion contributes an extensive component of overall upward rotation at the scapulothoracic joint. Downward roation at the AC joint returns the scapula back to its anatomic position, motion mechanically associated with shoulder adduction or extension.

Front 16

Horizontal plane rotational adjustments (Medial/lateral tilt)
Location and joint axes

Back 16

Horizontal plane
Axes-Vertical
Causes the medial border of the scapula to pivot away and toward the outer surface of the thorax.

Front 17

Sagittal plane rotational adjustments (Anterior/posterior tilt)
Location and joint axes

Back 17

Sagittal plane
Axes-Medial/ lateral
Causes the inferior angle to tilt or pivot away or toward the outer surface of the thorax.

Front 18

How might the coracoclavicular ligaments effect motion at the AC joint? (esp
frontal plane motion)

Back 18

Makes it more stable
Upward and downward rotation. Resist the upward rotation. Some say there are only 2 degree because of the ligaments.

Front 19

In light of class discussion, what is the primary function of the AC joint with
regard to the ST joint?

Back 19

To allow the scapula additional range of motion or rotations on the thoracic.

Front 20

Scapulothoracic Joint location

Back 20

A point of contact between the anterior surface of the scapula and the posterior-lateral wall of the thorax.

Front 21

Discuss the relationship between ST joint motion and SC/AC joint motion.

Back 21

Movement that occur between the scapula and the thorax are a result of a cooperation between the SC and the AC joint.

Front 22

Discuss the relationship between SC/AC joint motions and ST joint
elevation/depression.

Back 22

Elevation-the clavicle elevates about the SC joint. Downward roation of the scapula at the AC joint.
Depression-depress clavicle at SC joint, no rotation.

Front 23

Discuss the relationship between SC/AC joint motion and ST joint
protraction/retraction.

Back 23

Protraction-SC joint protracts clavicle, AC joint medial tilt (around rib cage)
Retraction-SC joint retracts clavicle, and AC joint lateral tilt.

Front 24

What is the ultimate function of scapular motion?(3 functions will be given in
class - not in text)

Back 24

1. Orient glenoid as scapula moves
2. Add range of motion to arm elevation
3. To provide a stable base for the humerus
Scapula can move under the humerus and provide a base for the humerus to sit when arm is elevated.

Front 25

What does it mean for the glenohumeral (GH) joint to have an ‘interdependent
relationship’ with the ST joint? (Or what ‘connection’ is there that leads to this
‘interdependent relationship? Answer not in text but what do you think?)

Back 25

If you move GH joint, ST joint movers. Scapula at glenoid moves at humerus.

Front 26

Generally, what is the orientation of the glenoid fossa (in a neutral position)?

Back 26

Anterior-laterally in the scapular plane. Upwardly rotated slightly

Front 27

Generally, what is the orientation of the humeral head ( in a neutral position)?

Back 27

Medially-superiorly and posterior slightly.

Front 28

Name the components responsible for static stability of the GHJ in normal
standing with arms at the sides.

Back 28

Coracohumeral ligament
labrum
Oriented upward
Gravity

Front 29

List and demonstrate the osteokinematic motions, degrees of freedom, and
planes in which motion takes place at the GH joint.

Back 29

Flexion/Extension-Sagittal
Add/Abduction-frontal
Internal/External-transverse
Three degrees

Front 30

Describe the arthrokinematics of the GH joint during arm elevation.

Back 30

Convex moving on concave
Roll-superior
Slide-inferior
Strict sagittal plane-true spin, one point on one point.

Front 31

Given normal arthrokinematics of the GH joint, what actually happens to the
‘humeral head’ during arm elevation? ( That is, which direction does the head
actually move?)

Back 31

Roll and cocurrent slide to prevent impingement. Center goes up

Front 32

Generally, how many total range of motion degrees are available at the
shoulder? Breakdown the number of degrees of arm elevation
(ABduction/Flexion) at the shoulder generally found at the scapulothoracic (ST)
joint and at the glenohumeral (GH) joint.

Back 32

For every 3 degrees of shoulder abduction, 2 degrees occurs by GH joint abduction and 1 degree occurs by scapulothoracic joint upward rotation.

180-abduction, 120 GH abduction and 60 scapulothoracic upward rotation

Front 33

What is scapulohumeral rhythm?

Back 33

For every 3 degrees of shoulder adbuction, 2 degrees occurs by GH joint abduction, and 1 degree occurs by scapulothoracic joint upward rotation. 180 shoulder abduction, 120 GH, 60 scapulothoracic.

Front 34

How many degrees does the ST joint contribute to arm elevation? How many
degrees does the GH joint contribute? What is the overall ratio of GH to ST joint
motion?

Back 34

2:1 120 degrees GH, 60 degrees ST.

Front 35

Abduction/adduction at the GH joint?
Plane, axis, arthokinematics?

Back 35

Frontal plane
anterior-posterior axis of rotation
Roll-and-slide along joint's longitudinal diameter

Front 36

Internal/external rotation?
Plane, axis, arthokinematics?

Back 36

Horizontal plane
Vertical axis of rotation
Roll-and-slide along joint's transverse diameter

Front 37

Flexion/extension and internal/external rotation (in 90 degrees of abduction)
Plane, axis, arthokinematics?

Back 37

Sagittal plane
Medial-lateral axis of rotation
Spin between humeral head and glenoid fossa.

Front 38

In the early phase of Abduction (or arm elevation), which muscles are driving this
initial 30 degrees of ST motion and at which anatomical joint(s) does this motion
primarily take place?

Back 38

Early phase: Shoulder Abduction to 90 degrees. 60 degrees of GH and 30 degrees of scapulothoracic upward. 20-25 degrees of clavicular elevation at the SC joint and 5 to 10 degrees of upward rotation at the AC joint. Upper trap and serratus anterior

Front 39

In the late phase of Abduction (or arm elevation), which muscles are driving this
additional 30 degrees of ST joint upward rotation and at which joints does the
motion occur? (Consider motion of the clavicle.)

Back 39

Late phase: Shoulder Abduction from 90 degrees to 180 degrees. 60 degrees of GH joint abduction and 30 degrees of scapulothoracic upward rotation. Clavicle elevates 5 degrees at the SC joint. The scapula, in contrast, upwardly rotates at the AC joint 20 to 25 degrees. Upper and lower trap, serratus anterior.

Front 40

Describe osteokinematic motions (of clavicle & scapula) that
occur.

Back 40

Frontal plane--Clavicle elevates, posteriorly rotate
Scapula-upward rotation, elevate , anterior and medial tilt
Axis of rotation goes up along spine of scapula.

Front 41

Define force couple (see p19) and give two examples of muscular force couples
at the shoulder, one at the ST joint and one at GHJ.

Back 41

Is formed when two or more muscles simultaneously produce forcces in different linear directions, although the torques act in the same rotary directions.
Supraspinatus and deltoid

Front 42

Explain what the frontal plane motion effect would be at the GHJ if the deltoid
muscle contracted alone & unopposed by any other force? (Based your
explanation on the breakdown of the deltoid resultant force vector into its
component forces.)

Back 42

More translation then rotation swing out

Front 43

How do the combined actions of the deltoid and the rotator cuff muscles produce
motion at the GH joint?

Back 43

Rotational components working together and translation components cancel each other out.

Front 44

What would be the effect at the GH joint if the supraspinatus muscle contracted
alone and unopposed? Explain how these effects are possible again based on
breakdown of resultant force vectors into component forces.

Back 44

More rotation because longer than the translational component

Front 45

What role does gravity play in working with the supraspinatus muscle during arm
elevation?

Back 45

Gravity is cancelled out.

Front 46

In what osteokinematic motions does the long head of the bicep contribute to
arm elevation and explain how the bicep does this? (Also, by what
mechanism(s) does the long head of biceps appear to provide stabilization to the
anterior GHJ?)

Back 46

Flexes the GH joint in the pure sagittal plane. Medial-lateral axis.
Passes in front of the axis and goes into the joint capsule. Bowstring mechanism. The line of pull has to get lateral.

Front 47

How is length-tension of the deltoid maintained throughout arm elevation?

Back 47

As the deltoid shortens, and gets too short the scapula upwardly rotates and adds length.

Front 48

For which plane of motion and osteokinematic motion of the arm is the function
of the trapezius most critical? Serrratus anterior? Clinical significance?

Back 48

Traps-Abduction/frontal
Serratus-Sagittal
Trapezius is more important in abduction and frontal plance because of the ways the fibers are orientated. When a muscle islying inthat plane, more motion in that plane. Clinical significance-wraps around rib cage.

Front 49

What is the role of the rhomboids during arm adduction & extension of the GHJ?

Back 49

Retraction and downward rotation, stabilizing muscles of scapula.

Front 50

Contrast the strength of internal vs external rotator muscles of the shoulder.
What accounts for the difference?

Back 50

Internal rotator muscles are stronger, because internal rotators produce more torque and have more muscle mass.

Front 51

What might be a potential problem with the difference in strength of the IRs and
ERs?

Back 51

External rotators weakness, instabilty. Slow down the internal rotators.

Front 52

What are the internal rotators?

Back 52

Subscapularis, anterior deltoid, pectoralis major, latissimus dorsi, and teres major.

Front 53

What are the external rotators?

Back 53

Infraspinatus, teres minor, posterior deltoid.

Front 54

What motion does the latissimus dorsi produce at the ST joint during open chain
activity vs closed kinematic chain activity?

Back 54

Closed chain for latissimu dorsi-wheelchair, pushing the body out of the wheelchair. Arm and scapula are fixed and body moving (pelvis and thorax) proximal to illac crest. Latissimus dorsi can provide pressure relief. Open chain, medially rotate, adduct, extension. Closed chain-downward rotation, depresses, retracts scapula.