What is the arthokinematic action of the humeral head on the glenoid fossa during humeral abduction?

During humeral abduction, the humeral head exhibits a specific arthrokinematic action relative to the glenoid fossa. As the arm is lifted away from the body, the humeral head rolls superiorly within the glenoid cavity. This superior roll allows the arm to move into abduction without impingement.

Simultaneously, there is an inferior glide of the humeral head. This inferior glide is crucial because it facilitates a smooth movement of the shoulder joint by allowing the joint structures to accommodate the movement and prevent compression or impingement of the rotator cuff tendons. If there weren't this inferior glide, the humeral head could collide with the acromion, leading to pain and restricted motion.

Overall, the combination of the superior roll and inferior glide optimally positions the humeral head, allowing for efficient and functional abduction of the arm.