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Questions and Answers
What is the primary function of the coracoacromial ligament?
Which of the following ligaments is NOT considered part of the glenohumeral joint complex?
What role do bursae play in the shoulder joint?
During shoulder abduction, what can occur due to the proximity of structures involved?
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Which bursa facilitates the movement of the tendon of the subscapularis over the scapula?
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What is a common consequence of rotator cuff injuries?
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Which tendon is particularly vulnerable due to its avascular nature?
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What structure is primarily responsible for stability in the shoulder joint?
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What results from dislocation of the glenohumeral joint?
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Which clinical sign indicates an axillary nerve injury?
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What type of joint is the shoulder joint classified as?
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What contributes to the instability of the glenohumeral joint?
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Which structure deepens the glenoid cavity to enhance stability?
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Which ligaments provide reinforcement to the shoulder joint capsule?
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What is the function of the subscapular bursa in the shoulder joint?
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Where does the tendon of the long head of biceps brachii arise from?
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What is the characteristic of the fibrous capsule of the shoulder joint?
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What role does the subacromial bursa play in shoulder movement?
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Which muscles are primarily involved in shoulder abduction?
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What condition is indicated by pain during arm abduction between 50-130 degrees?
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What arteries supply blood to the glenohumeral joint?
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Which nerves provide innervation to the glenohumeral joint?
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What is a common consequence of rotator cuff problems?
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Which muscle is NOT involved in the flexion of the shoulder joint?
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What anatomical structure is vulnerable during an intramuscular injection?
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During which shoulder movement does the trapezius muscle primarily support scapular rotation?
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Which of the following muscles is the primary initiator of shoulder abduction?
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Study Notes
Shoulder Joint Anatomy
- The shoulder joint (glenohumeral joint) is a ball-and-socket synovial joint formed between the glenoid cavity of the scapula and the head of the humerus.
- The joint is stabilized by a fibrous capsule, ligaments, and the rotator cuff muscles.
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Capsule:
- Attached to the glenoid labrum, scapula, and the anatomical head of the humerus.
- Thickened by three glenohumeral ligaments anteriorly and a coracohumeral ligament superiorly.
- Contains two openings:
- One for communication with the subscapular bursa, which facilitates the movement of the subscapularis tendon.
- Another for the passage of the long head of the biceps brachii tendon.
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Ligaments:
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Intracapsular:
- Superior, middle, and inferior glenohumeral ligaments: Reinforce the capsule anteriorly.
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Extracapsular:
- Coracoacromial ligament: Links the acromion and coracoid process.
- Coracohumeral ligament: Passes from the base of the coracoid process to the anterior part of the greater tubercle of the humerus.
- Transverse humeral ligament: Holds the tendon of the long head of the biceps in place during shoulder movement.
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Intracapsular:
The Coracoacromial Arch
- A strong osseoligamentous structure that provides a smooth under-surface for the acromion, coracoacromial ligament, and coracoid process.
- Overlies the humeral head and prevents superior displacement of the humerus.
- Separated from the supraspinatus tendon by the subacromial bursa.
- Contains: subacromial bursa, rotator cuff tendons, tendon of the long head of the biceps.
- Risk of soft tissue impingement between the head of the humerus and the acromion during abduction.
Bursae around the Glenohumeral Joint
- Subscapular bursa: Facilitates the movement of the tendon of the subscapularis over the scapula.
- Subacromial bursa: Facilitates the movement of the supraspinatus tendon under the coracoacromial arch and the deltoid muscle over the shoulder joint and the greater tubercle of the humerus.
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Inflammation of bursae: Can lead to:
- Subacromial bursitis: Pain on abduction of the arm between 50-130 degrees.
Movements of the Glenohumeral Joint
- Flexion: Pectoralis major, anterior fibers of deltoid, coracobrachialis, and biceps brachii.
- Extension: Latissimus dorsi and the posterior fibers of the deltoid.
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Abduction:
- Supraspinatus (initiator up to 15-20 degrees).
- Central deltoid fibers (20-90 degrees).
- Rotation of the scapula by trapezius and serratus anterior (above 90 degrees).
Neurovascular Supply of the Glenohumeral Joint
- Blood supply: Anterior and posterior circumflex humeral arteries, suprascapular artery.
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Innervation: Suprascapular, axillary, and lateral pectoral nerves.
- All from brachial plexus roots C5 and C6.
- Upper brachial plexus injuries can affect shoulder movement.
Clinical Application
- Axillary nerve and circumflex artery: Vulnerable during intramuscular injections and shoulder dislocation.
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Rotator cuff problems:
- Tendons rubbing under the coracoacromial arch can cause irritation and inflammation.
- Can lead to subacromial bursitis, supraspinatus tendonitis, rotator cuff injury, degeneration or rupture of tendons.
- Causes of rotator cuff injuries: Overuse, degenerative changes in tendons (older people), avascularity of the supraspinatus tendon, anatomical variation.
- Rotator cuff problems result in: Painful arc/impingement syndrome (pain on abduction of the arm between 70-120 degrees).
Stability of the Glenohumeral Joint
- Provided by:
- Rotator cuff tendons (anteriorly, posteriorly, superiorly).
- Glenohumeral intracapsular ligaments (anteriorly, inferiorly).
- Coracohumeral ligament (superiorly).
- Coracoacromial arch (superiorly).
- Glenoid labrum deepening of the glenoid cavity.
- Splinting effect of the long head of biceps above and the long head of triceps below.
Glenohumeral Joint Dislocation
- Most common type: Inferior dislocation, clinically defined as anterior dislocation due to the humeral head locating anteriorly.
- Mechanism: Pectoralis major pulling the arm anteriorly.
- Complications: Capsule and rotator cuff tendon tears.
- Recurrent dislocation: Can occur if tears heal poorly.
Axillary Nerve Injury
- Can be injured during dislocation due to its proximity to the inferior part of the joint capsule.
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Signs:
- Deltoid muscle paralysis with loss of abduction.
- Loss of sensation in a small area of skin over the central part of the deltoid ("regimental badge area").
Adhesive Capsulitis (Frozen Shoulder)
- Cause: Adhesive fibrosis and scarring between the inflamed capsule, rotator cuff, subacromial bursa, and deltoid.
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Symptoms:
- Difficulty abducting the arm.
- Lack of movement in the glenohumeral joint.
- Pain when elevating the shoulder.
- Causes: Dislocation, rotator cuff tears, calcific supraspinatus tendonitis, bicipital tendonitis.
Glenoid Labrum Tears
- Common in: Athletes and individuals with shoulder instability and partial dislocation.
- Symptoms: Pain, popping/snapping feeling.
Osteoarthritis of the Glenohumeral Joint
- Relatively uncommon: Cause of shoulder complaints.
- Cause: Degenerative changes of articular cartilage.
- Often secondary to: Trauma (dislocation, humeral head fracture, large rotator cuff tears).
- Primary osteoarthritis: More common in women and those over 60.
- Symptoms: Similar to frozen shoulder, with pain predominating.
- Diagnosis: X-rays.
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Description
Test your knowledge about the anatomy of the shoulder joint, specifically the glenohumeral joint. This quiz covers the structure, ligaments, and functions of the shoulder joint. Brush up on your understanding of the fibrous capsule, the rotator cuff muscles, and the various ligaments that stabilize this crucial joint.
