Summary of the Anatomy of the Shoulder Joint (Lateral View)

In this lecture, we explored the anatomy of the shoulder joint with a focus on the lateral view. This included a detailed overview of the joint’s structure, the bones and features involved, the surrounding muscles, ligaments, and bursae, and the clinical implications of these anatomical features. We began with a general review of the shoulder joint, examining its components like the humerus and scapula, and moved into a more detailed look at the joint cavity, supporting ligaments, and the muscles that aid in the joint's movement and stability. Lastly, we discussed the bursae that help in reducing friction and associated clinical conditions.

The Shoulder Joint - Structure and Function

• Type: Ball-and-socket synovial joint.
• Range of Movement: Flexion, extension, abduction, adduction, medial and lateral rotation, circumduction.
• Main Bones: Humerus and scapula.
  • Humerus Features:
    • Articular surface: Head of humerus.
    • Lesser and greater tubercles; inter-tubercular groove.
    • Anatomical neck.
  • Scapula Features:
    • Glenoid cavity (articulates with humerus).
    • Supraglenoid and infraglenoid tubercles.
    • Acromion and coracoid processes.

Joint Cavity and Ligaments

• Glenoid Cavity/Fossa: Shallow, poorly supportive socket enhanced by the glenoid labrum increasing depth.
• Joint Capsule: Envelops humeral head, extends to the anatomical neck of the humerus, contains synovial fluid.
• Ligaments:
  • Coracohumeral Ligament: From coracoid process (posterior side) to humerus.
  • Glenohumeral Ligaments: Superior, middle, and inferior; enhance anterior stability, help prevent inferior displacement.
  • Coracoacromial Ligament: Forms a protective arch over the joint.

Muscles Impacting the Shoulder Joint

Rotator Cuff Muscles

• Supraspinatus: Superior stability, from supraspinous fossa to greater tubercle.
• Infraspinatus: Posterior stability, from infraspinous fossa to greater tubercle.
• Teres Minor: Also aids posterior stability, from lateral scapula border to greater tubercle.
• Subscapularis: Anterior stability, from subscapular fossa to lesser tubercle.

Other Relevant Muscles

• Teres Major: From lower scapula to inter-tubercular groove (medial lip), enhances lower joint stability.
• Triceps Brachii (Long Head): From infraglenoid tubercle to olecranon of ulna, spans the joint.
• Biceps Brachii (Long Head): From supraglenoid tubercle, travels within capsule to radial tuberosity.

Bursae of the Shoulder

• Subacromial and Subdeltoid Bursae: Reduces friction between acromion process and supraspinatus tendon.
• Subtendinous Bursa of Subscapularis: Reduces friction under the tendon of subscapularis; communicates with joint, infection implications.

Clinical Implications

• Subacromial Bursitis: Inflammation from overuse or trauma, commonly affects supraspinatus movements, leads to painful arc syndrome (pain between 60-120 degrees of arm abduction).

Recap

This comprehensive review of shoulder anatomy from a lateral perspective gives crucial insights into how the joint’s components work together for complex movements, how they are protected by ligaments and muscles, and potential areas for clinical issues such as bursitis.

Resources and Next Steps

Visit kenhub.com for more tutorials, quizzes, and anatomical imagery to reinforce your learning.