Shoulder joint

The shoulder joint (art. humeri) is formed by the glenoid cavity of the scapula and the head of the humerus. The articular surface of the head is spherical, almost 3 times larger than the flat surface of the glenoid cavity of the scapula. The glenoid cavity is supplemented at the edges by a cartilaginous glenoid lip (labrum glenoidale), which increases the congruence of the articular surfaces and the capacity of the glenoid fossa. The joint capsule is attached to the outer side of the glenoid lip, as well as to the anatomical neck of the humerus. The capsule of the shoulder joint is thin, weakly stretched, free. From above, the joint capsule is strengthened by the only coracohumeral ligament in this joint (lig. coracohumerale), which begins at the base of the coracoid process of the scapula and is attached to the upper part of the anatomical neck of the humerus. Fibers of the tendons of nearby muscles (subscapularis, etc.) are also woven into the capsule. The synovial membrane of the joint capsule forms two protrusions. One of them is the intertubercular synovial sheath (vagina synovialis intertubercularis) which, like a case, surrounds the tendon of the long head of the biceps brachii muscle, passing through the joint cavity. The second protrusion is the subscapularis muscle subtendinous bursa (bursa subtendinea m. subscapularis) located at the base of the coracoid process, under the tendon of this muscle.

The shape of the articular surfaces of the shoulder joint is spherical. It has a large amplitude of movement around three axes, which is facilitated by a free joint capsule, a large difference in the size of the articulating surfaces, and the absence of strong ligaments. Flexion and extension are performed around the frontal axis. The total range of these movements is approximately 120°. Relative to the sagittal axis, abduction (to the horizontal level) and adduction of the arm are performed. The range of movement is up to 100°. Relative to the vertical axis, outward (supination) and inward (pronation) rotations are possible with a total volume of up to 135°. Circular movements (circumductiio) are also performed in the shoulder joint. The movement of the upper limb above the horizontal level is performed in the chest and in the clavicular joint when raising the scapula together with the free upper limb.

The radiograph of the shoulder joint clearly shows the head of the humerus and the glenoid cavity of the scapula. The contours of the lower medial part of the head overlap the glenoid cavity of the scapula. The X-ray gap in the image looks like an arcuate strip.

Shoulder movement in the shoulder joint: flexion - extension (around the frontal axis) - within 120°; abduction - adduction (around the sagittal axis) - 70-80°; rotation around the longitudinal axis - 135°.

Abduct the shoulder: deltoid muscle, supraspinatus muscle.

Adduct the shoulder: pectoralis major, latissimus dorsi, subscapularis, infraspinatus.

Flex the shoulder: deltoid muscle (anterior bundles), pectoralis major muscle, biceps brachii, coracobrachialis muscle.

Extend the shoulder: deltoid muscle (posterior bundles), triceps brachii (long head), latissimus dorsi, teres major, infraspinatus.

Rotate the shoulder inward: deltoid muscle (anterior bundles), pectoralis major muscle, latissimus dorsi muscle, teres major muscle, subscapularis muscle.

Rotate the shoulder outward: deltoid muscle (posterior bundles), teres major muscle, infraspinatus muscle.

[ 1 ], [ 2 ], [ 3 ], [ 4 ]