Topic:Applied anatomy including blood and nerve supply of upper and lower limbs and joints of shoulder, hip and knee.
Question: Describe the anatomy of shoulder joint and the muscles involved in its movement.
Click here for Reference Material-This material is informational alone and is not specifically prepared as an answer for any question. Readers may do their own research before finalising diagnoses according to the characteristics unique to each question. Readers should not proceed without cross-referencing with relevant textbooks as well as standard guidelines available.
The shoulder joint, also known as the glenohumeral joint, is a ball-and-socket joint that connects the upper arm (humerus) to the shoulder blade (scapula). It’s the most mobile joint in the body, allowing for a wide range of motion in the arm.
The shoulder joint is made up of the following structures:
- Glenoid cavity: This is a shallow socket on the lateral aspect of the scapula that articulates with the head of the humerus.
- Humeral head: This is the ball-shaped portion of the humerus that fits into the glenoid cavity.
- Glenoid labrum: This is a fibrocartilaginous rim that surrounds the glenoid cavity and deepens the socket, providing stability to the joint.
- Shoulder capsule: This is a fibrous sac that encloses the joint and provides stability.
- Rotator cuff: This is a group of four muscles (supraspinatus, infraspinatus, teres minor, and subscapularis) that surround the shoulder joint and help to stabilize and move the arm.
The muscles involved in shoulder movement can be divided into two groups: the rotator cuff muscles and the deltoid muscle.
- Rotator cuff muscles:
a. Supraspinatus: This muscle originates on the supraspinous fossa of the scapula and inserts on the greater tubercle of the humerus. It’s responsible for initiating abduction (raising the arm out to the side) of the arm.
b. Infraspinatus: This muscle originates on the infraspinous fossa of the scapula and inserts on the greater tubercle of the humerus. It’s responsible for external rotation (rotating the arm outward) of the arm.
c. Teres minor: This muscle originates on the lateral border of the scapula and inserts on the greater tubercle of the humerus. It assists the infraspinatus in external rotation of the arm.
d. Subscapularis: This muscle originates on the subscapular fossa of the scapula and inserts on the lesser tubercle of the humerus. It’s responsible for internal rotation (rotating the arm inward) of the arm.
- Deltoid muscle: This muscle originates on the lateral third of the clavicle, the acromion process of the scapula, and the spine of the scapula, and inserts on the deltoid tuberosity of the humerus. It’s responsible for abduction of the arm.
