Glenohumeral Joint Anatomy and Function

Introduction to Glenohumeral Joint

• It's the most mobile joint in the human body, making it highly unstable.
• Requires strong supportive tissues (ligaments, bursa) to maintain stability.

Scapula Structure

• Features a lateral angle and a shallow glenoid fossa.
• The head of the humerus articulates with the glenoid fossa.

Role of the Labrum

• The labrum is a specialized ligament fused to the edge of the glenoid fossa.
• It acts like a suction cup, enhancing articulation stability.
• Increases the depth of the socket and overall surface area for humeral articulation.
• Similar structure in the hip joint known as the acetabular labrum (located on the acetabulum of the pelvis).
• Importance in joint congruency and prevention of injuries like labral tears, which can lead to pain and mobility issues.

Articular Cartilage

• The head of the humerus is coated with articular (hyaline) cartilage, enabling smooth, frictionless movement.
• It provides shock absorption during arm movement.

Glenohumeral Joint Stability

• Stability provided by ligaments forming the glenohumeral joint capsule.
• Includes:
• Superior Glenohumeral Ligament (upper joint support)
• Middle Glenohumeral Ligament (mid-joint support)
• Inferior Glenohumeral Ligament (provides support wrapping around anterior to posterior)
• Coracohumeral Ligament (extends from the coracoid process to the humerus)
• These ligaments are watertight to contain synovial fluid, crucial for joint lubrication and nourishment.

Functions and Limitations of Ligaments

• Middle Glenohumeral Ligament: Limits external rotation (stretching occurs during lateral arm movement).
• Encouragement to think about specific movements that other ligaments limit.

Rotator Cuff Muscles

• Provides additional support to hold the humerus in the glenoid fossa.
• Most around scapula, inserting near the humerus.

Bursa in the Shoulder

• Bursa are fluid-filled sacs that protect tissues (e.g., between muscles and bones).
• Prevents friction and damage during movement (ex: deltoid muscle movement).
• Bursitis: Inflammation of bursa, can be caused by overuse (aseptic bursitis) or infection (septic bursitis).
• Treatment varies:
• Aseptically: rest, cooling/heating packs.
• Septically: anti-inflammatories, antibiotics.

Conclusion

• Overview of the tissues surrounding the glenohumeral joint highlights their importance in joint stability and injury prevention.
• Moving forward into muscles and their roles will build upon this foundational knowledge of arthrological features.