Shoulder Anatomy and Biomechanics Quiz
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Questions and Answers

What is the primary function of the shoulder girdle muscles?

  • To support the weight of the upper extremity
  • To increase the range of motion with no compromise to stability
  • To stabilize the shoulder joint and maintain force-length relationships (correct)
  • To provide mobility to the shoulder joint

    • Which muscle is responsible for scapular protraction and upward rotation?

  • Serratus Anterior (correct)
  • Rhomboids
  • Pectoralis Minor
  • Levator Scapulae

    • What movement is facilitated by the trapezius muscle?

  • Shoulder horizontal adduction
  • Scapular elevation and upward rotation (correct)
  • Scapular downward rotation
  • Shoulder flexion

    • Which muscle primarily aids in the abduction of the humerus?

    <p>Supraspinatus</p> Signup and view all the answers

    Which of the following muscles stabilizes the sternoclavicular joint?

    <p>Subclavius</p> Signup and view all the answers

    What is the role of the biceps brachii in shoulder joint movement?

    <p>Flexion and adduction of the shoulder</p> Signup and view all the answers

    What movement does the rhomboids muscle primarily contribute to?

    <p>Downward rotation and retraction of the scapula</p> Signup and view all the answers

    Which actions are primarily associated with the pectoralis major?

    <p>Flexion, horizontal adduction, and internal rotation of the humerus</p> Signup and view all the answers

    Which muscle group is primarily responsible for shoulder extension and adduction?

    <p>Teres Major</p> Signup and view all the answers

    What type of joint motion does the sternoclavicular joint primarily allow?

    <p>Elevation and Depression</p> Signup and view all the answers

    What is the role of the serratus anterior muscle in scapular movements?

    <p>Protraction</p> Signup and view all the answers

    Which ligament is primarily responsible for maintaining the acromioclavicular joint?

    <p>Acromioclavicular Ligament</p> Signup and view all the answers

    Which movement corresponds to scapulothoracic upward rotation?

    <p>SC joint elevation and upward rotation at AC joint</p> Signup and view all the answers

    Which muscles are specifically categorized as internal rotators of the glenohumeral joint?

    <p>Teres Major and Pectoralis Major</p> Signup and view all the answers

    Which of the following muscles functions as an abductor of the arm?

    <p>Supraspinatus</p> Signup and view all the answers

    What is one function of the primary movements of the scapulothoracic articulation?

    <p>Enhance glenohumeral stability</p> Signup and view all the answers

    What are the primary internal forces that contribute to the dynamic stability of the glenohumeral joint?

    <p>Rotator cuff muscles and biceps</p> Signup and view all the answers

    During flexion of the glenohumeral joint, what is the expected gliding direction of the humeral head according to the convex-concave rule?

    <p>Forward and downward</p> Signup and view all the answers

    What is the consequence of capsular tightness on glenohumeral arthrokinematics?

    <p>Decreased range of motion during external rotation</p> Signup and view all the answers

    What role does the glenoid labrum serve in the stability of the glenohumeral joint?

    <p>It enhances articulation depth of the socket.</p> Signup and view all the answers

    Which movement pattern is essential to avoid primary impingement during arm elevation?

    <p>External rotation of the humerus</p> Signup and view all the answers

    What is classified as secondary impingement in the context of the glenohumeral joint?

    <p>Functional stenosis of the subacromial space</p> Signup and view all the answers

    What anatomical structures are considered static restraints to glenohumeral joint stability?

    <p>Bony structures and labrum</p> Signup and view all the answers

    What is the maximum degree of internal rotation expected at the glenohumeral joint?

    <p>80 degrees</p> Signup and view all the answers

    What is the ratio of glenohumeral motion to scapulothoracic motion during shoulder abduction?

    <p>2:1</p> Signup and view all the answers

    Which muscles are part of the rotator cuff that help stabilize the glenohumeral joint?

    <p>Supraspinatus and Subscapularis</p> Signup and view all the answers

    What role does the rotator cuff play during arm abduction?

    <p>It approximates the humerus to the scapula.</p> Signup and view all the answers

    What occurs during the initial 0-90 degrees of shoulder abduction in terms of scapulothoracic motion?

    <p>60 degrees of GH motion and 30 degrees of ST motion</p> Signup and view all the answers

    What is a consequence of poor scapular stabilization?

    <p>Inferior translation of the humeral head</p> Signup and view all the answers

    Which muscle assists the deltoid in abduction of the arm?

    <p>Supraspinatus</p> Signup and view all the answers

    What clinical implication is associated with the mid-phase of active abduction?

    <p>Impingement pain</p> Signup and view all the answers

    What happens to the relationship between the humerus and acromion during the scapulohumeral rhythm?

    <p>Simultaneous movement limits impingement.</p> Signup and view all the answers

    Study Notes

    Shoulder: Clinical Anatomy & Biomechanics

    • The shoulder complex comprises multiple joints: glenohumeral, acromioclavicular, sternoclavicular, scapulothoracic, and the subacromial space.
    • The glenohumeral joint is a ball-and-socket type joint.
    • The acromioclavicular joint is a gliding or planar joint.
    • The sternoclavicular joint connects the clavicle to the sternum and the first rib.

    Anatomical Orientation of the Shoulder Complex

    • The scapular plane is at a 35-degree angle from the sagittal plane.
    • The humerus has a 30-degree retroversion.
    • The clavicle is at a 20-degree angle from the scapular plane.

    Stability Functions of Shoulder Girdle

    • Provides a stable base for shoulder muscles to generate force.
    • Shoulder girdle muscles act as stabilizers.
    • Maintains proper force-length relationship.
    • Maintains maximal congruence of the shoulder joint.

    Mobility Functions of Shoulder Girdle

    • Allows for the largest range of motion (ROM) of any complex in the body.
    • Shoulder girdle increases ROM with less compromise of stability (scapulo-humeral rhythm) – 4 joints vs. 1 joint.
    • Facilitates upper extremity movements by positioning the glenohumeral joint favorably.

    Shoulder Girdle Motion

    • Elevation/Depression: Movement of the scapula up and down, respectively.
    • Protraction/Retraction (Abduction/Adduction): Movement of the scapula forward and backward, respectively.
    • Upward/Downward Rotation: Rotational movement of the scapula.
    • Upward/Downward Tilt: Tilting of the scapula.

    Muscular Considerations

    • The muscles that act on the shoulder girdle include the trapezius, levator scapulae, rhomboids, serratus anterior, and pectoralis minor.
    • The muscles that act on the shoulder joint include the deltoid, pectoralis major, coracobrachialis, subscapularis, biceps brachii, supraspinatus, infraspinatus, teres minor, latissimus dorsi, and teres major.

    Scapulothoracic Muscles

    • Elevators: upper trapezius, levator scapulae, rhomboids
    • Depressors: lower trapezius, pectoralis minor
    • Protractors: serratus anterior, pectoralis minor
    • Retractors: mid & lower trapezius, rhomboids, levator scapulae
    • Upward Rotators: serratus anterior, upper trapezius
    • Downward Rotators: rhomboids, pectoralis minor, levator scapulae

    Glenohumeral Joint Muscles

    • Abductors: deltoid, supraspinatus
    • Adductors: pectoralis major, latissimus dorsi, teres major
    • Internal Rotators: pectoralis major, subscapularis, anterior deltoid, latissimus dorsi, and teres major
    • External Rotators: infraspinatus, teres minor, posterior deltoid
    • Flexors: biceps brachii, coracobrachialis, anterior deltoid
    • Extensors: triceps brachii, posterior deltoid, latissimus dorsi, teres major

    Specific Joints Structure and Function

    • The sternoclavicular joint comprises the clavicle, sternum, and first rib, with various ligaments (sternoclavicular, costoclavicular, interclavicular) and an articular disc.
    • The acromioclavicular joint consists of the acromion, clavicle, and an articular disc, with acromioclavicular and coracoclavicular ligaments.
    • The scapulothoracic articulation lacks actual joint structure, being a dynamic interaction between the scapula and thoracic cage.

    Scapulothoracic Articulation Motion

    • Elevation/Depression: Movement of the scapula up and down.
    • Retraction/Protraction: Movement of the scapula forward and backward.
    • Upward/Downward Rotation: Rotation of the scapula.

    Glenohumeral Joint Components

    • Humeral head, glenoid fossa, glenoid labrum, rotator cuff muscles, capsuloligamentous complex, coracohumeral ligament, long head of biceps, and subacromial space.

    Glenohumeral Ligaments

    • Superior glenohumeral ligament (SGHL)
    • Middle glenohumeral ligament (MGHL)
    • Inferior glenohumeral ligament (IGHL) complex: anterior band, posterior band, axillary pouch

    Glenohumeral Joint Motion

    • Flexion/Extension: movement of the humerus forward and backward, respectively.
    • Abduction/Adduction: movement of the humerus away from and toward the body, respectively.
    • Internal/External Rotations: rotation of the humerus internally and externally.

    Glenohumeral Joint Stability

    • Static restraints: Bony structures, labrum, capsuloligamentous structure, and negative joint pressure.
    • Dynamic restraints: Rotator Cuff, Biceps, proprioceptive receptors, and neuromotor coordination

    Kinematics and Biomechanics

    • Convex-Concave Rules: Describe how bones move and interact in a joint during action. Convex-on-concave rule or concave-on-convex rule.
    • Normal Arthrokinematics: Rotation and translation keep the humeral head centered on the glenoid.

    Clinical Implications

    • Subacromial Space: Avoidance of impingement due to anatomical structure.
    • Dynamic Stability Mechanisms: Passive muscle tension during movement, compressive forces from muscle contraction, tightening of passive structures, and redirecting joint forces towards the center of the GH joint.
    • Force Couples: Forces generated by muscles for joint movement stability.
    • Rotator Cuff Dynamics: Role of the rotator cuff muscles in stabilizing the glenohumeral joint and in producing controlled motion of the humeral head.
    • Scapulohumeral Rhythm: Relationship and coordination of scapula and humerus movement in abduction.
    • Effects of Poor Scapular Stabilization: Factors and consequences of poor scapular mechanics.

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    Shoulder Biomechanics PDF

    Description

    Test your knowledge on the anatomy and biomechanics of the shoulder complex, including its joints, orientation, and functions. This quiz covers stability and mobility aspects essential for understanding shoulder dynamics in clinical practice.

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