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Questions and Answers
Accessory motions at the AC joint limit the mobility between the scapula and thorax.
Accessory motions at the AC joint limit the mobility between the scapula and thorax.
False
Proximal stabilizers of the shoulder complex originate on the scapula and clavicle.
Proximal stabilizers of the shoulder complex originate on the scapula and clavicle.
False
The deltoid and biceps brachii are classified as distal mobilizers.
The deltoid and biceps brachii are classified as distal mobilizers.
True
Optimal function of the shoulder complex does not require coordination between proximal stabilizers and distal mobilizers.
Optimal function of the shoulder complex does not require coordination between proximal stabilizers and distal mobilizers.
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Muscles like trapezius and serratus anterior are examples of distal mobilizers.
Muscles like trapezius and serratus anterior are examples of distal mobilizers.
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The superior portion of the medial clavicle makes contact with the manubrium.
The superior portion of the medial clavicle makes contact with the manubrium.
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The disc associated with the sternoclavicular joint primarily functions to enhance joint congruence.
The disc associated with the sternoclavicular joint primarily functions to enhance joint congruence.
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The sternoclavicular joint is primarily maintained by passive support from the fibrous capsule.
The sternoclavicular joint is primarily maintained by passive support from the fibrous capsule.
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The costoclavicular ligament has two segments with fibers directed laterally and medially.
The costoclavicular ligament has two segments with fibers directed laterally and medially.
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Flexibility of the sternoclavicular ligaments allows for free movement of the clavicle in all directions.
Flexibility of the sternoclavicular ligaments allows for free movement of the clavicle in all directions.
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The medial articular surface of the clavicle may override the shallow manubrial facet due to diagonal attachments.
The medial articular surface of the clavicle may override the shallow manubrial facet due to diagonal attachments.
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The strong fibrous capsule surrounding the sternoclavicular joint provides sole support to the joint.
The strong fibrous capsule surrounding the sternoclavicular joint provides sole support to the joint.
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The inferior gliding of the medial clavicle occurs with clavicular elevation when ligament limits are reached.
The inferior gliding of the medial clavicle occurs with clavicular elevation when ligament limits are reached.
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The lower trapezius primarily elevates the scapula.
The lower trapezius primarily elevates the scapula.
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Pectoralis minor depresses the shoulder girdle and rotates it laterally.
Pectoralis minor depresses the shoulder girdle and rotates it laterally.
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The serratus anterior is responsible for abducting the scapula.
The serratus anterior is responsible for abducting the scapula.
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The middle trapezius is the least effective muscle for retracting the scapula.
The middle trapezius is the least effective muscle for retracting the scapula.
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Latissimus dorsi directly depresses the shoulder girdle by acting on the scapula.
Latissimus dorsi directly depresses the shoulder girdle by acting on the scapula.
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The subclavius muscle fixes the clavicle to the second rib.
The subclavius muscle fixes the clavicle to the second rib.
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The lower part of the serratus anterior tilts the scapula inferiorly by pulling its inferior angle laterally.
The lower part of the serratus anterior tilts the scapula inferiorly by pulling its inferior angle laterally.
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Rhomboids act synergistically with the middle trapezius for scapular retraction.
Rhomboids act synergistically with the middle trapezius for scapular retraction.
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The broad ligament provides substantial anterior restraint to the GH joint primarily when the joint is in a position of 45–90° of abduction.
The broad ligament provides substantial anterior restraint to the GH joint primarily when the joint is in a position of 45–90° of abduction.
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The middle GH ligament effectively limits the extremes of internal rotation.
The middle GH ligament effectively limits the extremes of internal rotation.
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The line of gravity creates an upward force on the humerus.
The line of gravity creates an upward force on the humerus.
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In a healthy GH joint, there is positive intra-articular pressure.
In a healthy GH joint, there is positive intra-articular pressure.
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The inferior glenohumeral ligament attaches distally to the anterior-inferior and posterior-inferior margins of the anatomical neck of the humerus.
The inferior glenohumeral ligament attaches distally to the anterior-inferior and posterior-inferior margins of the anatomical neck of the humerus.
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The deltoid muscle contributes to the stability of the GH joint when extreme vertical loads are applied.
The deltoid muscle contributes to the stability of the GH joint when extreme vertical loads are applied.
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The axillary pouch becomes most taut at about 45 degrees of GH joint abduction.
The axillary pouch becomes most taut at about 45 degrees of GH joint abduction.
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The anterior band of the GH ligament is the weakest part of the entire capsule.
The anterior band of the GH ligament is the weakest part of the entire capsule.
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The GH joint has two degrees of freedom allowing it to rotate in two planes.
The GH joint has two degrees of freedom allowing it to rotate in two planes.
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The supraspinatus muscle assists in static stabilization of the arm when passive forces are inadequate.
The supraspinatus muscle assists in static stabilization of the arm when passive forces are inadequate.
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The coracoacromial arch is formed by the acromion, the coracoid process, and the coracoacromial ligament.
The coracoacromial arch is formed by the acromion, the coracoid process, and the coracoacromial ligament.
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The subacromial space includes the long head of the triceps muscle.
The subacromial space includes the long head of the triceps muscle.
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The primary rotational movements at the GH joint include flexion, extension, and rotation, but not horizontal adduction.
The primary rotational movements at the GH joint include flexion, extension, and rotation, but not horizontal adduction.
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The greater the glenoid inclination, the more stability is provided against humeral inferior translation.
The greater the glenoid inclination, the more stability is provided against humeral inferior translation.
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Multiple separate bursae exist around the shoulder for cushioning and support.
Multiple separate bursae exist around the shoulder for cushioning and support.
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The rotator interval capsule includes the coracohumeral ligament.
The rotator interval capsule includes the coracohumeral ligament.
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Study Notes
Sternoclavicular Joint Stability - Disc
- The superior part of the medial clavicle does not contact the manubrium.
- The SC joint disk attaches to the posterosuperior clavicle, manubrium, first costal cartilage, and the fibrous capsule.
- The disk increases joint congruence and absorbs forces transmitted through the clavicle.
- It prevents the medial movement of the clavicle, ensuring the medial articular surface does not override the shallow manubrial facet.
Sternoclavicular Joint Stability - Capsule and Ligaments
- The sternoclavicular joint depends on three ligaments for support: sternoclavicular ligaments (anterior and posterior) and the costoclavicular ligament.
- The sternoclavicular ligaments reinforce the capsule and prevent anterior and posterior translation of the medial end of the clavicle.
- The strong costoclavicular ligament connects the clavicle and the first rib.
- The costoclavicular ligament prevents elevation of the lateral end of the clavicle and contributes to inferior gliding of the medial clavicle during clavicular elevation.
Muscle actions of the shoulder - Proximal Stabilizers
- These muscles originate on the spine, ribs, and cranium and insert on the scapula and clavicle.
- Examples include: trapezius and serratus anterior.
Muscle Actions of the Shoulder - Distal Mobilizers
- These muscles originate on the scapula and clavicle and insert on the humerus or forearm.
- Examples include: deltoid and biceps brachii.
Muscle Actions of the Shoulder Girdle - Depressors
- Posterior aspect: Lower trapezius and latissimus dorsi.
- Ventral aspect: Pectoralis minor and subclavius.
Muscle Actions of the Shoulder Girdle - Lateral Aspect - Protractors
- Serratus anterior: Upper part draws the scapula anteriorly and laterally, slightly elevates and superiorly rotates it.
- Serratus anterior: Lower part tilts the scapula superiorly by pulling its inferior angle laterally and causing the glenoid cavity to face superiorly.
Muscle Actions of the Shoulder Girdle - Lateral Aspect - Retractors
- Middle trapezius, rhomboids, and lower trapezius function as primary retractors of the scapula.
- The middle trapezius has the most optimal line of force for retraction.
The Inferior Glenohumeral Ligament
- It attaches to the anterior-inferior rim of the glenoid fossa and the labrum.
- It attaches to the anterior-inferior and posterior-inferior margins of the anatomic neck of the humerus.
- The axillary pouch and surrounding inferior capsular ligaments become taut at 90 degrees of abduction.
- It provides a cradling effect that resists inferior and anterior/posterior translations of the humerus.
- The anterior band is the strongest and provides the primary ligamentous restraint to anterior translation of the humeral head.
The Coracoacromial Arch
- It's formed by the coracoid process, acromion, and coracoacromial ligament.
- It forms the functional "roof" of the GH joint.
- The subacromial space contains the supraspinatus muscle and tendon, subacromial bursa, long head of the biceps, and part of the superior capsule.
- It prevents superior dislocation of the humeral head.
The Bursae
- Multiple bursae exist around the shoulder.
- The line of gravity creates a downward force on the humerus, and the passive tension in the rotator interval capsule creates a compressive force.
- A negative intra-articular pressure and glenoid inclination help provide static stability.
Static Stabilization of the GH Joint in Neutral Position
- The supraspinatus muscle helps maintain stability when passive forces are inadequate.
- The subscapularis may also provide some support through its connections to the rotator interval.
- Muscles with upward-directed translatory force, such as the deltoid, supraspinatus, and long heads of the biceps and triceps, assist in stability under extreme vertical load.
Mobility - Osteokinematics
- The GH joint rotates in all 3 planes with 3 degrees of freedom.
- The primary rotational movements are: flexion/extension, abduction/adduction, and internal/external rotation.
- A fourth motion is horizontal adduction/abduction.
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Description
This quiz explores the anatomy and stability of the sternoclavicular joint, focusing on its disc, capsule, and ligaments. Learn how these structures contribute to joint congruence and prevent excessive movement, ensuring the integrity of this vital joint within the shoulder region.
