Humeral Movement - Internal Rotation

Humeral Movement - Internal Rotation

Humoral movement refers to the motion of the humerus bone within its surrounding structures and is essential for proper arm function. One specific type of humeral movement is internal rotation, which involves turning the upper arm towards the body's midline. This movement occurs primarily when lifting objects towards the chest or raising the hand above shoulder level.

Anatomy and Mechanism The humerus is one of three bones that make up the human upper limb, with two articulating surfaces allowing it to move freely. During internal rotation at the glenohumeral joint between the humerus and scapula, both the head of the humerus and the glenoid cavity rotate together around a common center of rotation. The muscle most responsible for this movement is the teres major, which lies deep under the deltoid. Other muscles involved include the latissimus dorsi, anterior fibers of the pectoralis major, and posterior heads of biceps brachii.

Clinical Significance Internal rotation deficit can limit functional activities such as dressing, hygiene, and reaching backward behind the back. It is also associated with postural changes due to chronic abduction of the shoulder, resulting in decreased strength and performance in overhead tasks. Injuries like a torn rotator cuff or fracture may further impair internal rotation. However, restricted internal rotation typically results from muscular imbalances rather than damaged tissues. Adequate internal rotation is crucial for maintaining proper balance, stability, and flexibility at the shoulder during daily activities.

Explore the concept of humeral movement focusing on internal rotation of the upper arm towards the body's midline, crucial for various arm functions. Learn about the anatomy and mechanism behind this motion, including the key muscles involved. Discover the clinical significance of internal rotation deficit and its impact on daily activities and shoulder stability.