Shoulder joint including the factors affecting the stability and the mobility of the shoulder joint

 1. Give an account of the shoulder joint including the factors affecting the stability and the mobility of the shoulder joint.

 It’s a multi-axial, ball and socket typed, synovial joint
 It’s an articulation between glenoid fossa with the head of humerus.
 Glenoid cavity is small and shallow. (head of humerus is four times that of the cavity)
 Has a strong but lax capsule, which is attached proximally to the margins of the glenoid labrum.
 Anteriorly it is attached to the anatomical neck of the humerus.   But medially the capsule extends further, inferiorly down to the surgical neck; superiorly it is deficient for passage of the long tendon of the biceps brachii.
 Capsule is lined with synovial membrane.
 And is reinforced by superior, inferior, middle Glenohumeral ligaments
 Coracoacromial ligament, transverse humeral ligament and glenoid labrum are the ligaments that surround the joint
 Bursae under Subscapularis and (sometimes) that under Infraspinatus communicate with the joint cavity.
 Subacromial bursa does not communicate with the joint cavity in the normal individual
 The stability of the joint is maintained mainly by Rotator cuff
 It is a musculotendinious cuff (made of muscles, tendons and ligaments)
 These muscles and ligaments are originating from scapula and inserted to the humerus.
 The rotator cuff muscles are Supraspinatus, Infraspinatus, Teres minor &Subscapularis
 Cuff is deficient inferiorly. So the joint is more likely to dislocate inferiorly)
 Coracoacromial arch present superiorly (The arm is less likely to dislocate superiorly)
 Glenoid labrum increases stability by increasing the depth of glenoid fossa
 Blood supply  Anterior circumflex humeral vessels  Posterior circumflex humeral vessels  Suprascapular vessels  Subscapular vessels
 Joint is innervated mainly by  Axillary nerve  Musculocutaneous nerve  Suprascapular nerve
 Wide range of movements (high mobility)  Flexion, extension, abduction, adduction, medial rotation, lateralrotation and circumduction.  The above movements are possible because the humeral head isdisproportionate to the glenoid cavity (Four times larger).  Because the capsule is strong but lax.
 Clinical – Shoulder dislocation (mostly inferior)