Shoulder Part 1

Question 1

List the arthrology components of the ‘shoulder complex’–specifically joints (functional and anatomical)

Answer 1

Sternoclavicular–Sternum and clavicle. Keeps clavicle a constant distance away from thorax.
Acromioclavicular–acromion and clavicle.
Scapulothoracic–scapula and thoracic cage… Mechanically linked to the movements of the SC and AC joints.
Glenohumeral–Glenoid fossa and head of humerus.

Question 2

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

Answer 2

A closed kinematic chain, because if one joint moves, all joints move. There is a little bit of motion where the glenohumeral joint may move as an open kinematic chain, but it is impossible for the scapula to move without the other two joints moving.

Question 3

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

Answer 3

Elevation/Depression
Protraction/Retraction
Upward/Downward Rotation

Question 4

Motion at the SC joint involves motion of which bone?

Answer 4

Clavicle.

Question 5

What is the function of the SC joint?

Answer 5

SC joint functions as the basilar joint of the entire upper extremity. Binds the appendicular skeleton to the axial skeleton.

Question 6

How many degrees of freedom does the SC Joint have?
What are they?
What plane of motion do they operate in?
What is their ROM?

Answer 6

3 degrees of freedom.
Elevation/Depression–Frontal plane. 45 degrees elev. 10 degrees depression.
Protraction/Retraction–Horizontal plane. (Vertical axis) 15-30 degrees.
Rotation–Longitudinal medial/lateral axis rotates in the sagittal plane. Posterior rotation of 20-35 degrees.

Question 7

Identify location and direction of the joint axes for each motion at the SC joint.

Answer 7

Sternoclavicular joint.
Elevation/Depression–Anterior/Posterior on clavicle
Protraction/Retraction–Verticle (superior/inferior) on Clavicular facet of Manubrium.
Rotation–Longitudinally medial/laterally through clavicle.

Question 8

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

Answer 8

Elevation/Depression–Roll up, Glide down.
Protraction/Retraction–Roll and slide anteriorly.
Rotation–Spin

Question 9

Motion at the AC joint involves motion of which bone?

Answer 9

The acromion.

Question 10

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

Answer 10

3 Degrees of freedom–Gliding joint.
Upward/Downward Rotation–30 degrees. Frontal plane.
Rotational Adjustment Motions– to optimally align the scapula against the thorax. and add to total ROM.
Horizontal plane adjustments–
Internal and External Rotation. Medial border of scapula moves away and toward scapula. Direction defined by the orientation of the glenoid fossa.
Sagittal plane adjustments–
Anterior/Posterior Tilting–Ant. the scapular body and glenoid face down. Post. up.

Question 11

Identify location and direction of the joint axes for each motion at the AC joint.

Answer 11

Upward/Downward Rotation–Anterior/Posterior
Internal/External Rotation–Superior/Inferior
Anterior/Posterior Tilting–Longitudinally from Medial/Lateral.

Question 12

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

Answer 12

The coracoclavicular ligaments would restrict the ability of the clavicle to separate vertically from the scapula. Thus, the scapula would follow the clavicle when the clavicle moves superiorly.

Question 13

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

Answer 13

The primary funtion is to allow the scapula to rotate in 3 dimension so that the Scapula rotates and that the glenoid is positioned underneath the humerus. Upper extremity motion is increased and the scapula remains congruent with the humerus giving it a stable base.

***gives the scapula more motion.

Question 14

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

Answer 14

ST and SC–if one moves, the other moves. All three joints generally move in tandem.

Question 15

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

Answer 15

In pure elevation, the sc joint (clavicle) elevates. The AC joint (acromion) rotates downward and the sc joint will elevate and downward rotate.

Question 16

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

Answer 16

In protraction, the SC and AC joints summate rotations as the scapula follows the path of the clavicle. ??Each joint can rotate independently of the other and compensate for the other when there is a deficiency.???

AS the scapula moves forward in protraction, the SC joint protracts. At AC joint there is medial rotation.

Retration of scapula, retraction of SC of clavicle. The AC joint is a lateral rotation…as much as can take place….

Question 17

What is the ultimate function of scapular motion? (3 actual functions)

Answer 17

1. Orient the glenoid for optimal contact with the humeral head.
2. Add range to elevation of the human arm.
3. Provide a stable base for the humerus.

Elevation of the arm is to get the hand over the head.

Question 18

What does it mean for the glenohumeral joint to have an interdependent relationship with the ST joint? (Or what conncection is there that leads to this interdependent relationship?

Answer 18

The glenoid fossa’s attachment to the scapula demonstrates interdependence because the glenohumeral range of motion would only go so far without the support of the glenoid fossa holding the the weight and changing the angle of the articulation as the scapula rotates in order for the arm to rotate superiorly and elevate.

Question 19

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

Answer 19

The glenoid fossa is oriented 4 degrees superior relative to the horizontal axis of the body of the scapula.
In a neutral position, the scapula is is normally positioned against the posterior-lateral surface of the thorax, with the glenoid fossa faceing about 35 degrees anterior to the frontal plane…scapular plane.

Question 20

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

Answer 20

Retroversion…aligns the humeral head within the scapular plane for articulation with the glenoid fossa. The head faces medially and superiorly, forming as approximate 135 degree angle of inclination to the humeral shaft. The head is rotated posteriorly about 30 degrees within the horizontal plane.

Question 21

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

Answer 21

Active mechanisms–Forces produced by muscles. (rotator cuff)
Passive mechanisms–1. Restraint provided by capsule, ligaments, glenoid labrum, and tendons; 2. mechinal support caused by scapulothoracic posture; 3. negative intracapsular pressure.

Question 22

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

Answer 22

3 degrees of freedom.
Flexion/extension in Sagittal plane–spin.
Abduction/adduction in frontal plane–roll and glide in opposite directions.
Internal/external rotation in horizontal/transverse plane–roll and glide in opposite directions

Question 23

Describe the arthrokinematics of he GHJ joint during arm elevation.

Answer 23

Roll is up and slide is down.

Question 24

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

Answer 24

The humeral head moves upward a few millimeters. The slide allows enough correction to offset most upward movement. The humeral head also naturally rotates externally. This allows the greater tubercle of the head to pass posterior to the acromion and avoid jamming the subacromial space.

Question 25

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

Answer 25

180 total degrees .

GHJ = 120 degrees
ST = 60 degrees

Question 26

What is the overall ratio of glenohumeral to ST joint ROM?

Answer 26

2:1 ratio

Question 27

What is scapulohumeral rhythm?

Answer 27

The scapulohumeral rhythm is the synchronization of movement of the scapula and humerus as the arm is elevated above the head.

Question 28

Describe the early phase of shoulder abduction kinematics.

Answer 28

0-90 degrees with 60 degrees from GHJ and 30 degrees from ST joint; the 30 degrees from the ST joint comes primarily from SC joint clavicular elevation and little from AC joint upward rotation of scapula.

Question 29

Describe the late phase of shoulder abduction kinetics.

Answer 29

90-180 degrees with 60 degrees from GHJ and 30 degrees from the st joint; the 30 degrees from the ST joint comes primarily from AC joint upward rotation of the scapula and little from SC joint elevation; NOTE – clavicle posteriorly rotates in late phase to allow for AC joint upward rotation.