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Questions and Answers
Which muscle is responsible for scapular downward rotation, depression, and protraction?
Which muscle is responsible for scapular downward rotation, depression, and protraction?
What is the primary function of the shoulder girdle concerning stability?
What is the primary function of the shoulder girdle concerning stability?
Which joint is stabilized by the Subclavius muscle?
Which joint is stabilized by the Subclavius muscle?
What type of motion does the Serratus Anterior muscle facilitate?
What type of motion does the Serratus Anterior muscle facilitate?
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How does the shoulder complex support the upper extremity during movement?
How does the shoulder complex support the upper extremity during movement?
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Which muscle is primarily responsible for the abduction of the humerus?
Which muscle is primarily responsible for the abduction of the humerus?
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The action of elevation and upward rotation of the scapula is primarily controlled by which muscle?
The action of elevation and upward rotation of the scapula is primarily controlled by which muscle?
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Which function is NOT associated with the shoulder girdle's mobility?
Which function is NOT associated with the shoulder girdle's mobility?
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Which muscle is primarily responsible for shoulder extension, adduction, and medial rotation?
Which muscle is primarily responsible for shoulder extension, adduction, and medial rotation?
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What type of motion do the upper and lower trapezius muscles primarily perform?
What type of motion do the upper and lower trapezius muscles primarily perform?
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Which muscles act as external rotators of the glenohumeral joint?
Which muscles act as external rotators of the glenohumeral joint?
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What is the maximum degree of elevation for the sternoclavicular joint?
What is the maximum degree of elevation for the sternoclavicular joint?
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Which ligament is NOT associated with the acromioclavicular joint?
Which ligament is NOT associated with the acromioclavicular joint?
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What type of movement characterizes the scapulothoracic elevation?
What type of movement characterizes the scapulothoracic elevation?
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What is the primary role of the scapulothoracic articulation?
What is the primary role of the scapulothoracic articulation?
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Which motion is NOT a primary function of the serratus anterior muscle?
Which motion is NOT a primary function of the serratus anterior muscle?
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What is the primary role of the rotator cuff muscles during humeral movement?
What is the primary role of the rotator cuff muscles during humeral movement?
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What is the scapulohumeral rhythm during shoulder abduction?
What is the scapulohumeral rhythm during shoulder abduction?
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What occurs during the 90-180 degrees of shoulder abduction regarding the scapulothoracic (ST) joint?
What occurs during the 90-180 degrees of shoulder abduction regarding the scapulothoracic (ST) joint?
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What is a potential consequence of poor scapular stabilization?
What is a potential consequence of poor scapular stabilization?
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During the early phase of active abduction, what is a common clinical implication experienced?
During the early phase of active abduction, what is a common clinical implication experienced?
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What ensures optimal force production through a larger portion of the range of motion in the glenohumeral joint?
What ensures optimal force production through a larger portion of the range of motion in the glenohumeral joint?
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What is the function of the supraspinatus muscle during shoulder abduction?
What is the function of the supraspinatus muscle during shoulder abduction?
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What is a primary purpose of the force couples acting on the glenohumeral joint?
What is a primary purpose of the force couples acting on the glenohumeral joint?
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Which component of the Glenohumeral Joint is primarily responsible for dynamic stability?
Which component of the Glenohumeral Joint is primarily responsible for dynamic stability?
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What is the primary action that must occur to avoid impingement during arm elevation?
What is the primary action that must occur to avoid impingement during arm elevation?
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The Convex Concave Rule states that when the convex surface is stationary and the concave surface is moving, what happens to gliding?
The Convex Concave Rule states that when the convex surface is stationary and the concave surface is moving, what happens to gliding?
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Which of these ligaments contributes to the capsuloligamentous complex of the Glenohumeral Joint?
Which of these ligaments contributes to the capsuloligamentous complex of the Glenohumeral Joint?
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What degree of external rotation is typically achieved at the Glenohumeral Joint?
What degree of external rotation is typically achieved at the Glenohumeral Joint?
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What is identified as primary impingement related to the subacromial space?
What is identified as primary impingement related to the subacromial space?
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Which motion is NOT a normal function of the Glenohumeral Joint?
Which motion is NOT a normal function of the Glenohumeral Joint?
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What contributes to abnormal arthrokinematics at the Glenohumeral Joint?
What contributes to abnormal arthrokinematics at the Glenohumeral Joint?
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Study Notes
Shoulder: Clinical Anatomy & Biomechanics
- The shoulder complex comprises multiple joints
- Glenohumeral joint, acromioclavicular joint, sternoclavicular joint, scapulothoracic articulation, and subacromial space are included.
Shoulder Complex
- These joints facilitate a wide range of upper extremity movements
- The glenohumeral joint, acromioclavicular joint, and sternoclavicular joint facilitate specific movements
- The scapulothoracic articulation, which is not a true joint, supports movement.
- The subacromial space is a crucial area for shoulder function.
Anatomical Orientation of the Shoulder Complex
- The scapula's position relative to the humerus is critical for movement.
- Scapular plane inclination, retroversion, and angles are important factors to consider. Values are given for reference.
Stability Functions of Shoulder Girdle
- The shoulder girdle provides a stable base for shoulder muscles to generate force.
- Shoulder girdle muscles, acting as stabilizers, maintain appropriate force-length relationships.
- The shoulder girdle ensures maximum congruence at the shoulder joint.
Mobility Functions of Shoulder Girdle
- The shoulder girdle provides the largest range of motion (ROM) of any complex in the body.
- The scapulohumeral rhythm improves ROM with less compromise to stability (4 joints vs. 1 joint).
- Shoulder girdle movements position the glenohumeral joint (GHJ) optimally for upper extremity movements.
Shoulder Girdle Motion
- Elevation and depression: upward and downward movement of the shoulders.
- Protraction and retraction: forward and backward movement of the shoulders.
- Upward and downward rotation: movement of the scapulae.
Shoulder Joint Muscles
- Pectoralis major: flexion, horizontal adduction, internal rotation of the humerus
- Deltoid: majority of shoulder movements, e.g., internal rotation, abduction, hyperextension, flexion, and horizontal adduction
- Coracobrachialis: forward movements of the humerus
- Subscapularis: internal rotation of the humerus and stabilizes glenohumeral joint
- Biceps brachii: flexion and adduction, horizontal adduction
- Supraspinatus: abduction of the humerus
- Infraspinatus: external rotation, horizontal abduction, stabilizes the humerus during flexion
- Teres minor: external rotation, horizontal abduction, stabilizes the humerus during flexion
- Latissimus dorsi: extension and adduction of the arm.
- Teres major: shoulder extension, adduction, medial rotation
- Triceps brachii: adduction, extension, hyperextension of the humerus
Scapulothoracic Muscles
- Elevators (upper trapezius, levator scapulae, rhomboids): move the scapula upward
- Depressors (lower trapezius, pectoralis minor): move the scapula downward
- Protractors (serratus anterior, pectoralis minor): move the scapula forward
- Retractors (mid & lower trapezius, rhomboids, levator scapulae): move the scapula backward
- Upward rotators (serratus anterior, upper trapezius): rotate the scapula upward
- Downward rotators (rhomboids, pectoralis minor, levator scapulae): rotate the scapula downward
Glenohumeral Joint Muscles
- Abductors (deltoid, supraspinatus): move the humerus away from the body
- Adductors (pectoralis major, latissimus dorsi, teres major): move the humerus towards the body
- Internal rotators (pectoralis major, subscapularis, anterior deltoid, latissimus dorsi, teres major): rotate the humerus inward.
- External rotators (infraspinatus, teres minor, posterior deltoid): rotate the humerus outward
- Flexors (biceps brachii, coracobrachialis, anterior deltoid): bend the arm at the shoulder.
- Extensors (triceps brachii, posterior deltoid, latissimus dorsi, teres major): straighten the arm at the shoulder.
Specific Joints Structure and Function
Sternoclavicular Joint
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Clavicle, sternum, first rib, sternoclavicular ligaments, costoclavicular ligament, articular disc, muscular attachments
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The sternoclavicular joint allows for elevation, depression, protraction, retraction, and axial rotation.
Acromioclavicular Joint
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Gliding or planar joint, articular disc, acromioclavicular ligament, coracoclavicular ligament.
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Upward and downward rotation, horizontal and sagittal plane adjustments.
Coracoclavicular Ligaments
- Conoid ligament and trapezoid ligament are part of the coracoclavicular ligaments
- They maintain the acromioclavicular joint and support the scapula.
Scapulothoracic Articulation
- Not a true joint, providing movement base for the humerus.
- Scapulothoracic motion is the sum of the acromioclavicular and sternoclavicular motions
Primary Movements of the Scapulothoracic Articulation
- Elevation and depression
- Retraction and protraction
- Upward and downward rotation
Scapulothoracic Elevation
- Scapulothoracic elevation is a combination of sternoclavicular joint (SCJ) elevation + downward rotation at the acromioclavicular joint (ACJ).
Scapulothoracic Upward Rotation
- This is a combination of SCJ elevation + upward rotation at the ACJ.
Scapular Rotation
- Enhances glenohumeral stability
- Elevates the acromion to prevent impingement
- Maintains effective length tension relationship of scapulohumeral muscles
Glenohumeral Joint
- Humeral head, Glenoid Fossa, Glenoid Labrum, Rotator Cuff Muscles (SITS), Capsuloligamentous complex, Coracohumeral Ligament, Long Head of Biceps, Subacromial Space
Glenohumeral Ligaments
- Superior glenohumeral ligament (SGHL)
- Middle glenohumeral ligament (MGHL)
- Inferior glenohumeral ligament (IGHL)
- Anterior band
- Posterior band
- Axillary pouch
Coracohumeral Ligament
- Anterior band
- Posterior band
Glenohumeral Joint Motions
- Flexion/Extension (120/45 degrees)
- Abduction/Adduction (120 degrees)
- Internal/External Rotations (80/70 degrees)
- Cannot be isolated from other shoulder girdle elements
Glenohumeral Joint Stability
- Static restraints: bony structures, labrum, capsuloligamentous structure, negative joint pressure
- Dynamic restraints: rotator cuff, biceps, proprioceptive receptors, neuromotor coordination
Kinematics and Biomechanics
Convex Concave Rules
- Convex stationary + concave moving = gliding in the same direction as angular motion
- Concave stationary + convex moving = gliding in the opposite direction of angular motion
Glenohumeral Joint Motions
- Normal arthrokinematics: combines rotation and translation to keep the humeral head centered on the glenoid
Glenohumeral Roll / Glide
- Describes the complex combined movements.
Glenohumeral Joint Motions (Abnormal)
- Abnormal arthrokinematics
- Capsular tightness
- Rotator cuff tears
Subacromial Space
- Clinical relevance: avoiding impingement during arm elevation.
- External rotation of humerus
- Upward rotation of the scapula to elevate acromion
Dynamic Stabilization Mechanisms
- Passive muscle tension
- Compressive forces from muscle contraction
- Joint motion that tightens passive structures
- Redirection of joint force toward center of GH joint
- Force-length relationships are variable due to multiple joints.
- Tension development in agonist frequently requires tension development in antagonist to prevent humeral head dislocation.
- Force couples involve two forces equal in magnitude but opposite in direction, important for maintaining stability
Force Couples Acting on Glenohumeral Joint
- Transverse plane: anterior vs. posterior rotator cuff muscles
- Coronal plane: deltoid vs. inferior rotator cuff
Force Couples Disruption
- Diagrams illustrate disruption of force couples (abnormal movements).
Rotator Cuff Muscles
- Supraspinatus, Infraspinatus, Teres Minor, Subscapularis
Rotator Cuff – Dynamic GH Stabilizer
- Illustrates how the rotator cuff muscles work together to maintain dynamic stability.
Rotator Cuff Function
- Approximates humerus to function
- Supraspinatus helps the deltoid with abduction
- Subscapularis, infraspinatus and teres minor depress humeral head
Scapulohumeral Rhythm
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Movement relationship between the humerus and scapula during arm raising movements.
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Ratio of 2:1 - for every 3 degrees of shoulder abduction, 2 degrees occur at GH joint and 1 at ST joint (SC & AC joint)
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Preserves length-tension relationships of the glenohumeral muscles
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Sustains force production through a larger portion of the range of motion
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Prevents impingement between the humerus and the acromion.
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Movement limits relative movement between the two bones
Scapulohumeral Rhythm Clinical Implications
- Rotator cuff pain early in abduction
- Impingement pain mid-abduction
- AC pain late in abduction
Effects of Poor Scapular Stabilization
- Poor resting scapular posture (protracted)
- Loss of upward tilt of scapula
- Loss of GH joint stability.
- Inferior humeral translation and internal rotation
- Rotator cuff ischemia, supraspinatus in particular
- Capsular laxity, poor dynamic stabilization
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Description
This quiz explores the various muscles associated with the shoulder girdle, their functions, and contributions to stability and movement. Delve into muscle anatomy, including the roles of the Serratus Anterior, Subclavius, and trapezius muscles. Test your knowledge on the mechanics of shoulder joint movements and their importance in upper extremity support.
