The Glenohumeral (GH) Joint

Overview

• Also known as the shoulder joint.
• GH joint contributes to shoulder Range of Motion (ROM) but it's a combination of the shoulder girdle and the joint.

Anatomy

• Formed by the humeral head and the scapula.
• Joint space is "glenoid fossa".
• Allows three degrees of freedom:
  • Flexion/Extension
  • Abduction/Adduction
  • External/Internal rotation
  • Horizontal abduction/adduction

Stability

• Relies heavily on muscles, ligaments, and capsules.
  • Ligaments: Coracohumeral ligament, Glenohumeral ligament (Superior, Middle, Inferior)
  • Capsules
  • Bursa: Sac of soft tissue providing cushioning
    • Subacromial bursae: Beneath the acromion
    • Subcoracoid bursa: Beneath the coracoid process

Common Issues

• Shoulder is prone to injury
• Immobilization can lead to conditions like frozen shoulder
• Overuse and friction can damage both bursa and ligaments

Shoulder Movement & Contributing Muscles

• General Approach:
  • Importance of knowing the location, origin, and insertion of muscles

Abduction

• Primary Muscles: Middle deltoid, supraspinatus, biceps long head (in external rotation)
• Sequence: Supraspinatus initiates, biceps long head assists, deltoid dominates after initial 15-20 degrees

Adduction

• Primary Muscles: Pectoralis major, teres major, latissimus dorsi
• Views: Teres major and latissimus dorsi from back; pectoralis major from the front

Flexion

• Primary Muscles: Anterior deltoid, pectoralis major, coracobrachialis, biceps long head
• Contribution: Anterior deltoid is the main mover; pectoralis major and coracobrachialis assist

Extension

• Primary Muscles: Posterior deltoid, teres major, latissimus dorsi
• Function: Brings humeral bone backward

External Rotation

• Primary Muscles: Infraspinatus, teres minor, posterior deltoid (assists)
• Attachment: Lateral side of the humeral bone

Internal Rotation

• Primary Muscles: Subscapularis, pectoralis major, teres major, latissimus dorsi, anterior deltoid

Learning Tips

• Understand muscle location, origin, and insertion to comprehend their function