Shoulder joint complex

• Function of the shoulder

  • Positions the upper limb for functional activities
  • Prehensile (gripping & reaching) function
  • Requires a large range of motion in all directions
  • Achieved by having a complex of joints
  • Sacrifices stability for the sake of mobility
• Bones of the shoulder complex

  • Clavicle
  • Humerus
  • Scapula
• Joints of the shoulder complex

  • Glenohumeral Joint (anatomical joint) - Ball & socket
  • Sternoclavicular Joint (anatomical joint) - Saddle
  • Acromioclavicular Joint (anatomical joint) - Plane
  • Scapulothoracic Joint (physiological Joint)
  • Subacromial joint (physiological)
• Scapulothoracic joint

  Physiological joint between scapula & thorax with no joint capsule or ligaments, connected by muscles
• Scapulothoracic joint

  • The perimuscles hold the scapula to the thorax
  • Provide controlled stability and mobility
  • Provide a stable base for movements at the other joints of the shoulder complex
  • Contributes 40% of abduction of glenohumeral joint
• Glenohumeral joint

  • Ball and socket joint
  • Glenoid labrum
  • Capsules
  • Ligaments
  • Coraco-acromial arch
  • Subacromial space
• Acromioclavicular Joint

  • Plane synovial joint
  • Slack joint capsule
  • Acromioclavicular ligaments
  • Coracoclavicular ligaments
  • Joint compressed in abduction
  • Anterior and posterior glide in the joint during movements of the shoulder complex
• Sternoclavicular Joint

  • Sellar joint
  • Articulation between medial end of the clavicle and clavicular notch of the sternum
  • Articular disc
  • Capsule & anterior and posterior sternoclavicular ligaments
  • Movements: gliding -anterior/posterior/forwards/backwards, rotation
• Shoulder Movements

  • Flexion
  • Extension
  • Abduction
  • Medial/Internal Rotation
  • Lateral/External Rotation
  • Circumduction
• Scapulohumeral rhythm

  • In abduction all joints of the shoulder complex contribute
  • The glenohumeral and the scapulothoracic joints move roughly in the proportion of 2:1
  • For every 2 degree of glenohumeral abduction, scapulothoracic joint contributes 1 degree
  • The scapulathoracic joint contribute 60 degrees of the 180 degree of abduction
• Muscles for scapulothoracic movements

  • Rhomboids Major
  • Rhomboids Minor
  • Trapezius Upper fibers
  • Trapezius Middle
  • Trapezius Lower
  • Levator scapulae
  • Serratus anterior
  • Pectoralis minor
• Scapular force couples

  • Upward rotation: Upper trapezius, Lower trapezius, Serratus anterior
• Muscles for glenohumeral movements

  • Abduction: Supraspinatus (initial 15 degrees), Deltoid (15-180 degrees)
  • Adduction: Pectoralis major, Teres major, Latissimus dorsi
  • Flexion: Anterior Deltoid, Long head of biceps
  • Extension: Posterior deltoid, Long head of triceps, Latissimus dorsi
  • External / Lateral Rotation: Infraspinatus, Teres minor, Posterior deltoid
  • Medial Rotation: Subscapularis, Pectoralis major, Teres major, Latissimus dorsi, Anterior deltoid
• Rotator cuff muscles

  • Glenohumeral joint is inherently unstable
  • Dynamic stability is provided by muscles: Subscapularis, Supraspinatus, Infraspinatus, Teres minor
  • Tendons blend with the capsule