Shoulder Arthrology Flashcards
What is the articulation of the sternoclavicular (SC) joint?
Clavicle is like a strut holding the scapula
The acromioclavicular (AC) joint attaches the _____ to _____.
Scapula; Clavicle
What is considered to not be a true joint?
The scapulothoracic joint
What describes an interface between bones where movements are linked to the movements at the SC and AC joints?
The Scapulothoracic joint
In the scapulothoracic joint what provides the base for the GH joint?
The position of the scapula
What is the most distal and mobile portion of the whole shoulder complex?
The glenohumeral joint
What decreases the effectiveness of the entire UE?
Weakness, painful or unstable links
Elevation is what kind of movement?
Superior slide
Depression is what kind of movement?
Inferior slide
Protraction is what kind of movement?
Medial border slides anterior and lateral
Retraction is what kind of movement?
Posterior and Medial
Upward rotation is what kind of movement?
- Inferior angle rotates superior and lateral direction
- Glenoid fossa faces upwards (UE elevation)
What makes up the sternoclavicular joint?
- Medial end of the clavicle
- Clavicular facet on the sternum
- Superior border of the cartilage of the first rib
What links the axial and appendicular skeleton?
The basilar joint of the UE
What joint has extensive periarticular tissue?
Sternoclavicular
What kind of joint is the SC joint?
Irregular saddle shape
What is the arthrokinematic movement of the SC joint?
Convex on Concave (with the sternal facet reciprocally shaped)
The longitudinal diameters of the SC joint extend roughly in the _____ plane between the superior and inferior points of the articular surfaces.
Frontal
The transverse diameters of the SC joint extend roughly in the _____ plane between the anterior and posterior points of the articular surfaces.
Transverse
What helps to reinforce the capsule at the SC joint?
The anterior and posterior SC ligaments
Where is the interclavicular ligament located?
Between the two clavicles
Where is the costoclavicular ligament located?
Between the clavicle and the costal cartilage of the rib below
What percentage of people have an articular disc at the SC joint?
50%
What muscles are associated with the SC joint?
- SCM
- Sternothyroid
- Sternohyoid
- Subclavius
How many degrees of freedom does the SC joint have and what are they?
- 3 degrees of freedom
- Sagittal
- Frontal
- Horizontal
What motions does the SC joint produce?
- Elevation/ Depression
- Protraction/ Retraction
- Rotation
What is the goal of the SC joint?
To place the scapula in the optimal position for the head of the humerus
If you move the GH joint you will ultimately move what other joint in combination?
SC joint
The clavicle will rotate in how many degrees of freedom with UE elevation?
All 3
What plane is elevation and depression in at the SC joint?
Generally parallel to the frontal plane
What is the axis of elevation and depression at the SC joint?
Near anterior-posterior
How many degrees of elevation and depression does the SC joint get?
- 35 to 45 degrees of elevation
- 10 degrees of depression
What are the arthrokinematics of elevation of the clavicle at the SC joint?
- Convex surface rolls superiorly and slides inferiorly
- Costoclavicular ligament will stretch and limit motion
What are the arthrokinematics of depression of the clavicle at the SC joint?
- Convex surface rolls inferiorly and slides superiorly
- Interclavicular ligament and superior portion of the capsule will stretch
The arthrokinematics of elevation and depression at the SC joint occur along what diameter?
Longitudinal
What plane is protraction and retraction in at the SC joint?
Occurs nearly parallel to the horizontal plane
What is the axis of protraction and retraction at the SC joint?
Vertical
How many degrees of protraction and retraction does the SC joint get?
15-30 degrees in each direction
The arthrokinematics of protraction and retraction at the SC joint occur along what diameter?
Transverse
What are the arthrokinematics of retraction of the clavicle at the SC joint?
- Concave surface of clavicle rolls and slides posteriorly on convex surface of sternum
- Stretches anterior costoclavicular ligament and anterior capsule
What are the arthrokinematics of protraction of the clavicle at the SC joint?
- Occurs in an anterior direction
- Stretches posterior costoclavicular ligament and posterior capsule
- Involves reaching forward
Axial (longitudinal) rotation of the clavicle at the SC joint is done at the bones _____ axis?
Longitudinal
When someone elevates their UE how much does the clavicle posteriorly rotate?
20-35 degrees
(as the UE returns the clavicle returns)
When talking about axial rotation of the clavicle the spin of its sternal end is relative to what?
The lateral surface of the articular disc
Axial rotation of the clavicle can not be preformed when the arm is in what position?
Resting at the side
Axial rotation of the clavicle is linked with the overall kinematic motions of what?
Flexion and Abduction
What makes up the acromioclavicular joint?
- The lateral end of the clavicle
- The acromion of the scapula
The clavicular facet on the acromion faces what direction?
Medial and slightly superior
Are articular discs present in the AC joint?
Articular discs of varying forms present in most AC joints
What is the capsule at the AC joint reinforced by?
By the superior and inferior AC ligaments
What is the extrinsic stability for the AC joint?
Coracoclavicular ligament
The coracoclavicular ligament is made up of two parts that branch from the coracoid process to the clavicle, what are they?
- Trapezoid ligament
- Conoid ligament
How many degrees of freedom are found at the AC joint?
3 degrees of freedom
What is the primary motion of the AC joint?
Upward and downward rotation
What is the secondary motion of the AC joint?
Rotational adjustment motions - to fine tune the position of the scapula in the horizontal and sagittal planes
Upward rotation of the scapula at the AC swings _____ and _____ relative to the end of the clavicle.
Upward; Outward
How many degrees of upward rotation do we get at the AC joint?
Up to 30 degrees
Downward rotation of the scapula at the AC joint returns the scapula to what?
Anatomical position
What plane is downward rotation at the AC joint preformed in?
Frontal plane depicted - but really the scapular plane
Pivoting or twisting type motions of the scapula around the lateral end of the clavicle at the AC joint are considered what kind of motions?
Rotational adjustment
Rotational adjustment motions help to optimally align the scapula against what?
The thorax
The horizontal plane rotational adjustment motions of the AC joint sit on what axis and produce what movements?
- A vertical axis
- Medial border moves away and creates internal rotation of the glenoid fossa
The sagittal plane rotational adjustment motions of the AC joint sit on what axis and produce what movements?
- Medial-lateral axis
- Inferior angle pivots away and creates an anterior tilt or reverse a posterior tilt
What happens at the AC joint during protraction?
The AC joint internally rotates in the horizontal plane and helps align the anterior surface of the scapula with the thorax curved surface
Elevation or shrugging creates a _____ tilt.
Anterior
What joint is considered not to be a true joint?
Scapulothoracic joint
Why is the scapulothoracic joint not considered a true joint?
It does not have direct contact because it is separated by laters of muscles (the subscapularis, serratus anterior, and erector spinae)
The scapula is seated in between what ribs?
The 2nd and 7th ribs
Where is the medial border of the scapula located?
6 cm lateral to the spine
What degree of anterior tilt, upward rotation, and internal rotation is found at the scapulothoracic joint?
- 10 degrees of anterior tilt
- 5-10 degrees of upward rotation
- 30-40 degrees of internal rotation
UE ROM is largely dependent on what?
Scapular motion
Elevation and depression as a whole are combinations of what joints?
Composite SC and AC
Protraction and retraction is a summation of what motions?
Horizontal motions at both the SC and AC
For protraction and retraction movements what does each joint involved focus on?
- SC joint focuses on the protraction aspect
- AC joint focuses on the internal rotation
What supports/ stabilizes the head of the humerus during upward and downward rotation?
The glenoid fossa
Upward rotation is the summation of _____ elevation and SC/ scapular upward rotation.
Clavicular
What degrees of upward rotation do we get at the scapula?
60 degrees
What makes up the glenohumeral joint?
- Large convex head
- Shallow concavity (glenoid fossa)
The head of the humerus is positioned how?
Medially, superiorly, and posteriorly (normal retroversion)
How would you describe the fibrous capsule?
- Capsule that branches from the rim of the glenoid fossa to the anatomical neck of the humerus
- It is loose fitting, thin and expandable
- It allows for mobility, and is reinforced by external ligaments
In the anatomical position, is the inferior portion of the capsule slackened or taught?
Slackened - called the axillary pouch
What lines the inner wall of the GH joint?
Synovial membrane
There is an extension of the synovial membrane that lines the intracapsular portion of the tendon of the long head of the biceps and exits into the _____ _____.
Intertubercule groove
The head of the humerus and the glenoid fossa is line with what?
Articular cartilage
What amount of space is present in the GH joint?
A volume 2 times the size of the humeral head
What are the 3 primary stabilizers of the GH joint?
- A passive tension that is in the embedded ligaments
- Active forces that are produced by the local muscles (specifically the rotator cuff)
- Long head of the biceps tendon crosses superior over the head of the humerus to help stabilize too
The GH capsular ligaments are fibrous connective tissues made up of interlacing collagen fibers that limit what motion?
Extremes of rotation and translation
The superior ligament of the GH capsule resists what motions?
Exterior rotation and inferior and anterior translations of the humeral head
The middle ligament of the GH capsule does what?
- Stabilizes most motions
- Resists anterior translation of the humeral head, especially in 45 to 90 degrees of abduction and extremes of external rotation
Where is the middle ligament of the GH capsule slackened?
In internal rotation (blends with the subscapularis)
The inferior GH ligament has 3 portions (bands), in what position are they taught in?
- All: Taught in 90 degrees of abduction
- Axillary: combined with anterior-posterior and inferior translations
- Anterior: and full external rotation; anterior translation of humeral head
- Posterior: and full internal rotation
What do the inferior bands of the GH capsule support?
- Hammock like so it supports the suspended humeral head
What do the inferior bands of the GH capsule resist?
Inferior and anterior-posterior translation
What is the strongest and thickest part of the GH capsule?
Anterior
Where does the coracohumeral ligament run?
From the coracoid process to the greater tubercle
What does the coracohumeral ligament blend with?
The superior capsule and supraspinatus tendon
Where is the coracohumeral ligament taught?
In anatomical position
What does the coracohumeral ligament resist?
Inferior translation of the humeral head and external rotation
What is being described when someone says: its is a significant structural support to the capsule, it blends with the capsule, the belly of the muscles are close to the joint, and it protects and is an active stabilizer.
The rotator cuff
Where does the subscapularis sit in reference to the capsule?
Anterior
Where do the supraspinatus, infraspinatus, and teres minor sit in reference to the capsule?
Superior and posterior
What is the thickest muscle in the rotator cuff?
Subscapularis
Where is the most common site for a dislocation?
Rotator cuff interval - inferior and supraspinatus/ subscapularis
What is the rotator cuff interval reinforced by?
- Long head of the biceps
- Coracohumeral ligament
- Superior and middle capsular ligaments
The long head of the biceps originates where?
- The supraglenoid tubercle and the labrum
- The intracapsular tendon crosses the humeral head
- Runs through the inter tubercle groove on the anterior humerus
What does the long head of the biceps resist?
Anterior translation of the humeral head
The glenoid labrum is a _____ ring.
fibrocartilaginous
The glenoid labrum gets _____ percent of its depth from its structures and is a stabilizer.
50%
What are the 5 tissues that reinforce or deepen the glenohumeral joint?
- Joint capsule/ GH capsular ligaments
- Coracohumeral ligaments
- Rotator cuff muscles (SITS)
- Long head of the biceps
- Glenoid labrum
The GH joint is like a …
Ball on an inclined surface
What provides ligamentous support for scapulothroacic posture?
Superior capsular structures: superior capsular ligament, coracohumeral ligament, and the tendon of the supraspinatus
When looking at a free body diagram, the force from the humerus into the GH joint labeled CF is what?
The compressive force
The coracoacromial arch is formed by what two structures?
- Coracoaromial ligament
- Acromion process
What is considered the “roof” of the GH joint?
The coracoacromial arch
The coracoacromial arch is _____ cm in adults at rest with their arms by their sides.
1 cm
The subacromial space is the space between the _____ and the _____ _____.
Arch; humeral head
What is within the subacromial space?
- Supraspinatus muscle
- Supraspinatus tendon
- Subacromial bursa
- Long head of the biceps
- Superior capsule
Where are bursa sacs typically placed around the GH joint?
Situated where significant frictional forces develop such as between tendons, capsules and bone, muscles and ligaments, and 2 adjacent muscles
- there are 2 superior to the humeral head
The subacromial bursa protects what muscle from what bone?
Protects the supraspinatus from the acromial bone
The subdeltoid bursa limits friction forces between what muscle and what bone?
Limits friction between the deltoid and the supraspinatus tendon and the humeral head
The shoulder has how many degrees of freedom?
3 degrees (flexion/extension, abduction/adduction, internal/ external rotation)
The shoulder also has a 4th motion, what is it?
Horizontal abduction/ adduction that starts at 90 degrees of abduction
Horizontal abductions sits on what axis?
Vertical axis
What is the anatomical position of the shoulder?
0 degrees
Rotation (abduction/adduction) of the humerus is done in what plane and on what axis?
- The frontal plane
- The anterior - posterior axis
During shoulder abduction when does the scapula start to upwardly rotate as well?
At 60 degrees
What is the arthrokinematic movement of humerus abduction?
The convex head of the humerus rolls superior and slides inferiorly along the longitudinal diameter of the glenoid fossa
* adduction is reverse
What tendon blends with the superior capsule?
Supraspinatus
Active contractions pull the capsule tight and prevent it from being punched between what two surfaces?
The humeral head and the undersurface of the acromion
At 90 degrees of abduction the humeral head stretches out the inferior capsular ligament (axillary pouch) which acts like a hammock and supports what?
The head of the humerus
Where will you find the most (7.5 mm) acromiohumeral distance? (chart in words)
When shoulder abduction is at 20 degrees
Where will you find the least (2.6 mm) acromiohumeral distance? (chart in words)
When shoulder abduction is at 85 degrees
Where will you find the middle amount (5 mm) of acromiohumeral distance? (chart in words)
When shoulder abduction is at 150 degrees
At a low degree (about 20-35 degrees) of abduction what is closest to the undersurface of the acromion?
The humeral head
At a medium degree (about 35-70 degrees) of abduction what is closest to the undersurface of the acromion?
Distal attachment of the supraspinatus
At a high degree (about 70-160 degrees) of abduction what is closest to the undersurface of the acromion?
Proximal shaft of the humerus
At what degree is the supraspinatus usually compressed?
35-70 degrees
What is adhesive capsulitis?
Excessive thickening or stiffness in the inferior capsular ligament
What does adhesive capsulitis limit?
Limits inferior slide of the humeral head
The superior roll in adhesive capsulitis leads to what?
- Jamming of the humeral head against the coracoacromial arch
- There is only 22 degrees before this without any slide
What is impingement syndrome?
An unnatural and repeated compression or abrasion that may damage the suprasinatus tendon, subacromial bursa, long head of the biceps tendon, or the superior parts of the capsule
Over time repeated compression may lead to what?
Impingement syndrome
Flexion is rotation of the humerus in what plane and on what axis?
- The sagittal plane
- The medial-lateral axis
What are the arthrokinematics of shoulder flexion?
Spinning motion of the humeral head in the fossa
During shoulder flexion are most of the surrounding capsular structures taut or slackened?
Taut
In extremes of flexion tension in the posterior capsule may cause a slight _____ translation of the humerus.
Anterior
How many degrees of GH flexion do we get and then how much do we get when we add the scapula in?
- 120 degrees of GH flexion
- 180 degrees includes the scapula
How much active and passive extension do we get at the shoulder?
- 65 degrees of active extension
- 80 degrees of passive extension
Extension causes a slight _____ tilt of the scapula and stretch of capsular ligaments
Anterior
Axial rotation of the humerus (IR and ER) is done in what plane and along what axis?
- The horizontal plane
- The longitudinal axis
In neutral where do we sit when it comes to IR and ER?
- 75-85 degrees of internal rotation
- 60-70 degrees of external rotation
What are the arthrokinematics of internal and external rotation?
- Occurs over a transverse diameter
- Roll posterior, slide anterior for external rotation
- Roll anterior and slide posterior for internal rotation
At what degree of abduction is external rotation primarily spinning?
90 degrees
How many kinematic principles are there for shoulder abduction?
Six - motion is not at a specific joint but at the whole complex
The first kinematic principle is scapulohumeral rhythm, what does this mean?
- There is a generalized 2:1 ratio of scapulohumeral rhythm so for every 3 degrees of abduction you get 2 degrees of GH joint and 1 degree of ST upward rotation
- You have active shoulder abduction of about 180 degrees that occurs as a result of simultaneous 120 degrees of GH joint and 60 degrees of scapulothoracic upward rotation
The second kinematic principle is SC and AC joint movement during full abduction, what does this mean?
The 60 degrees of upward rotation of the scapula during full shoulder abduction is the result of a simultaneous elevation at the sternoclavicular (SC) joint combined with upward rotation at the acromioclavicular (AC) joint
The third kinematic principle is also SC and AC joint movement during full abduction, what does this mean?
- The clavicle retracts at the SC joint during shoulder abduction
- The clavicle is horizontal about 20 degrees posterior to the frontal plane to start
- During abduction the clavicle retracts another 15-20 degrees
- The clavicle does more in the frontal plane than the scapula or flexion
What is the fourth kinematic principle?
- The upwardly rotating scapula posteriorly tilts and less consistently externally rotates slightly during full shoulder abduction
- At rest it is anteriorly tilted 10 degrees and internally rotated 30-40 degrees
- With abduction it posteriorly tilts 20 degrees
What is the fifth kinematic principle?
- The clavicle posteriorly rotates around its own axis during shoulder abduction
- 20-35 degrees during full abduction
- This is the most predominant motion of the clavicle with abduction
- Those with subacromial impingement showed reduced rotation
What is the sixth kinematic motion?
- The GH joint externally rotates during shoulder abduction
- Allows the greater tubercle on the humerus to pass posterior to the acromion
- Strict frontal plane has more than scaption
- 25-50 degree range; majority occurring before 70-80 degrees of abduction
