In a man lifting up suitcase, posterior dislocation of glenohumeral joint is prevented by:

Ans. (c) CoracobrachialisRef: Maheshwari 5th ed. / 88* Glenohumeral joint is the most important joint of shoulder complex.* It is a synovial ball and socket articulation between the head of the humerus and glenoid cavity of scapula.* Movements at this joint includes flexion, extension, abduction, adduction, medial rotation, lateral rotation and circumduction.* Posterior dislocation of glenohumeral (shoulder) joint would be prevented by the muscle which originate posteriorly and inserted anteriorly.# For Example: Corachobrachialis muscle originate from Coracoid process of scapula and inserted at Medial aspect of shaft of humerus.* The net vector of pull of this muscle would be anteriorly, opposing the posterior dislocation of shoulder joint.Origin & Insertions of Muscles Around Shoulder Joint:MuscleOriginInsertionDeltoidAnt. Fibres- Lateral l/3rd of anterior border of clavicleMiddle Fibres- Lateral border of acromionPosterior Fibres- Lower lip of crest of spineDeltoid Tuberosity of humerusCoracobra- chialisCoracoid process of scapulaMedial aspect of shaft of humerusLatissimus dorsiPosterior l/3rd of iliac crest, lumbar fascia, spine of lower 6 thoracic vertebrae, lower 4 ribs inferior angle of scapulaFloor of bicipital grooveBicepsLong head: supra glenoid tubercle of scapulaShort head: coracoids process of scapulaTuberosity of radiusThe classical clinical feature of posterior dislocation of shoulder is- arm is held in medial rotation and is locked in that position, and an examiner can not externally rotate it.