The Glenohumeral Joint

• Larger range of mobility than the hip joint but less stability

  Joint classification

  • Synovial ball and socket joint
• Axis of movement:

  3 degrees of movement (3 axes)
• Articular Surfaces:

  • Hemispherical head of humerus

  • Glenoid fossa of the scapula

  • Covered with hyaline cartilage
• Head of humerus

  • Covered with hyaline cartilage

  • Faces medially, superiorly (approx. 135 from shaft) and posteriorly (approx. 30 from frontal plane)
• Glenoid Fossa:

  Articulates with head of humerus

  Situated on lateral aspect of scapula and faces antero-laterally

  Pear-shaped and covered with hyaline cartilage

  Poor congruency of articular surfaces

  1:4 size ratio (glenoid fossa: humeral head)
• Glenoid Labrum:

  Glenoid fossa further deepened by glenoid labrum

  Made of fibrocartilage

  Triangular in cross-section

  Attached to articular margins of glenoid fossa
• Joint Capsule:

  A cylindrical sleeve that passes from glenoid fossa to humerus

  Lax structure especially inferiorly to accommodate the head of humerus during movement, therefore not a stabiliser of the joint
• Synovial Membrane:

  Lines inside of capsule

  Extends through capsule anteriorly to form subscapular bursa

  Extends through capsule posteriorly to form infraspinatus bursa

  Long head of biceps also sheathed in synovial membrane
• Subacromial (Deltoid) Bursa:

  Noncommunicating bursa

  Separates coracoacromial arch and deltoid muscle from superolateral aspect of shoulder joint
• Three glenohumeral ligaments:

  Thickenings in the anterior capsule

  All provide anterior stability to GH joint

  Superior glenohumeral ligament:

  • O: Upper part glenoid labrum

  • I: Runs laterally to upper surface lesser tubercle
• Glenohumeral Ligaments

  Middle glenohumeral ligament:

  • O: Below the superior glenohumeral ligament

  • I: Anterior aspect lesser tubercle below subscapularis insertion
• Glenohumeral Ligaments

  Inferior glenohumeral ligament:

  • O: Glenoid fossa

  • I: Anteroinferior part of anatomical neck of humerus
• Three accessory ligaments:

  Coracohumeral ligament

  • O: Lateral border of coracoid process, divides at intertubercular groove

  • I: Two tubercles of humeral head

  • A: Thought to provide stability as the arm hangs to prevent downward displacement of the humerus
• Three accessory ligaments:

  Coracoacromial Ligament

  • Strong triangular ligament

  • O: Coracoid process

  • I: Acromion process

  • A: Creates fibro-osseous coracoacromial arch with coracoid and acromion processes

  • Helps prevent superior displacement of humerus

  • Helps dissipate forces transmitted upwards through humerus
• Three accessory ligaments:

  Transverse humeral ligament

  O: Greater tubercle

  I: Lesser tubercle at upper end of bicipital groove

  Bridges gap between the two tubercles on humerous

  A: Holds long head biceps in place
• Glenohumeral flexion:

  • ROM: 180 (60 of this made possible by lateral rotation of scapula)
  • Spin & inferior glide (necessary for full flexion to occur)
  • Limited by: tension in the extensor muscles and posterior capsule
• Glenohumeral extension:

  • ROM: 90 (last 20 made possible by movement of scapula)
  • Spin
  • Limited by: contact of the greater tubercle of the humerus with the coracoacromial arch, anterior capsule, glenohumeral ligaments and shoulder flexors
• Glenohumeral abduction:

  • ROM: 180 (60 of this made possible by lateral rotation of scapula)
  • Superior roll, inferior glide
  • Limited by: contact between greater tubercle and coracoacromial arch and tension in rotator cuff muscles and shoulder adductors
  • (Last 60 of abduction is accompanied by glenohumeral lateral rotation to reduce contact between greater tubercle and coracoacromial arch)
• Glenohumeral adduction:

  • ROM: approx. 30 possible as arm crosses in front of body (accompanied by scapular protraction)
  • Inferior roll, superior glide
  • Limited by: contact with trunk
• Glenohumeral lateral rotation:

  Longitudinal axis through the humerus

  ROM: 80

  Posterior roll, anterior glide (when arm by side)

  Spin (when arm at 90 abduction)

  Limited by: tension in medial rotators and anterior capsule
• Glenohumeral medial rotation:

  • ROM: 100 - 110 (when the forearm is taken behind trunk)
  • Anterior roll, posterior glide (when arm by side)
  • Spin (when arm at 90 abduction)
  • Limited by: tension in lateral rotators and the posterior capsule
• Summary of Glenohumeral (GH) joint:

  GH joint is inherently unstable due to:

  •Incongruency of joint surfaces

  •Poor size ratio of articular surfaces

  •Lax capsule

  •Weak ligaments

  Stability of the GH joint is improved by:

  •Glenoid labrum

  •Long head of biceps tendon

  •Rotator cuff muscles and larger overlying muscles