Shoulder Biomechanics Flashcards
Shoulder pain responsible for approximately __% of ALL musculoskeletal complaints
16
The clavicle is deviated about __ degrees posterior to frontal plane
20
The scapular is deviated __ degrees anterior to the frontal plane
35
The humeral head is extroverted about __ degrees posterior to the medial-lateral axis at the elbow
30
The medial end of the clavicle appears _____ in the longitudinal diameter and _____ in the transverse diameter.
Convex
Concave
The articular surface of the manubrium at the SC joint appears _____ in the longitudinal diameter and _____ in the transverse diameter.
Concave
Convex
How many degrees of freedom are at the SC joint?
3
Describe the motions that occur at the SC joint and in what plane they occur
1) elevation and depression in frontal plane
2) protraction and retraction in horizontal plane
3) posterior clavicular rotation in sagittal plane
During elevation of the clavicle there is a _____ roll and an ______ glide at the SC joint.
superior
inferior
During depression of the clavicle there is a _____ roll and an ______ glide at the SC joint.
inferior
superior
During clavicular retraction there is a _____ roll and an ______ glide at the SC joint.
posterior
posterior
During clavicular protraction there is a _____ roll and an ______ glide at the SC joint.
anterior
anterior
What type of joint is the AC joint?
planar
What are the primary movements at the AC joint?
Upward and Downward Rotation
What are the secondary movements at the AC joint?
- Internal and External Rotation in the horizontal plane
- Anterior and Posterior Tilt in the sagittal plane
What movement occurs at the AC joint with scapulothoracic protraction?
Internal Rotation
What movement occurs at the AC joint with scapulothoracic elevation?
Anterior tilt
Scapulothoracic elevation involves a summation of ______ at the sternoclavicular joint and _____ at the acromioclavicular joint
elevation
downward rotation
Scapulothoracic depression involves a summation of ______ at the sternoclavicular joint and _____ at the acromioclavicular joint
depression
upward rotation
Scapulothoracic protraction involves a summation of ______ at the sternoclavicular joint and _____ at the acromioclavicular joint
protraction
slight horizontal plane adjustments
Scapulothoracic retraction involves a summation of ______ at the sternoclavicular joint and _____ at the acromioclavicular joint
retraction
external rotation
Scapulothoracic upward rotation involves a summation of ______ at the sternoclavicular joint and _____ at the acromioclavicular joint
elevation
upward rotation
Scapulothoracic downward rotation involves a summation of ______ at the sternoclavicular joint and _____ at the acromioclavicular joint
depression
downward rotation
During abduction what two movements are happening?
Elevation at SC Joint & Upward Rotation at AC Joint
During abduction the SC joint is most active during the _____ phase whereas AC is most active in ____ phase
early
late
3 functions of upward roation at the SC joint
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
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.
- 9
2. 3
Typically in what direction is GH joitn instability most common?
anteriorly or inferiorly
What fills the subacromial space?
- supraspinatus muscle and its tendon
- subacromial bursa
4 Ligaments of the GH joint capsule
1) SGHL
2) MGHL
3) IGHL
4) Coracohumeral Ligament
What is the posterior band of the IGHL responsible for?
Resistance on the follow through
90° of abduction and full internal rotation
Why is the Glenoid Labrum SoVulnerable to Injury?
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
The glenoid fossa has approximately a __ degree upward tilt relative to the medial border of the scapula
5
What is the importance of this upward tilt at the glenoid fossa?
holds the humeral head in place
What will occur if there is a loss of upward rotation posture of the scapula?
The humeral head may slide down vertically
During shoulder abduction what way is the slide and what way is the roll?
Roll superiorly
Slide inferiorly
Convex on concave = roll and slide in opposite directions
Without the concurrent inferior slide with the superior roll, what would happen?
The humeral head will impinge against the arch and block further abduction
How many degrees would you be able to abduct if the humeral head did not slide inferiorly?
22 degrees
During the full 180 degrees of shoulder abduction, __ degrees is attributed to scapulothoracic joint upward rotation whereas __ degrees is attributed to GH abduction
60
120
For every 3° of shoulder abduction, _° occurs by GH joint abduction and _° occurs by scapulothoracic joint upward rotation
2
1
