Final answer:
The closed packed position of the GH joint is when the humeral head is fully engaged in the shallow socket of the glenoid cavity, providing maximum stability to the joint. It is achieved when the arm is in abduction and external rotation.
Step-by-step explanation:
The closed packed position of the GH (glenohumeral) joint is when the humeral head is fully engaged in the shallow socket of the glenoid cavity, providing maximum stability to the joint. In this position, the articular surfaces of the humerus and the glenoid cavity are in close contact. The closed packed position of the GH joint is reached when the arm is in abduction and external rotation, such as when throwing a ball.