Shoulder Muscles - Rotator Cuff

The rotator cuff muscles are an important muscle group that play a critical role in stabilizing the shoulder joint. The four muscles (supraspinatus, infraspinatus, teres minor, and subscapularis) have thick, fl at tendons of insertion that form a strong musculotendinous cuff around all but the inferior aspect of the glenohumeral joint. These tendons are intimately applied to the fi brous membrane of the joint capsule. Individually each muscle contributes little to the total range of motion of the humerus at the glenohumeral joint. However, they play a prominent role in stabilizing the joint and positioning and stabilizing the head of the humerus in the glenoid cavity. When the rotator cuff muscles are compromised by injury, the shoulder joint loses stability and becomes highly susceptible to dislocation.

12Spine of scapula

13Medial border of scapula

14Greater tubercle of humerus

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Deep dissection of the right shoulder muscles

Anterior view

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Deep dissection of the right shoulder muscles

Posterior view

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Deep dissection of the right shoulder muscles

Medial view

183

Shoulder Muscles - Prime Movers

The prime movers of the shoulder joint are the muscles that share a common attachment on the intertubercular groove (pectoralis major, teres major, and latissimus dorsi) and the deltoid muscle. These large muscles are superficial to the muscles of the rotator cuff and form extensive attachments on the pectoral girdle and axial skeleton. Inserting more distally on the humerus then the muscles of the rotator cuff, they have a better mechanical advantage and produce the major movements of the shoulder joint. The intertubercular groove muscles also form the anterior and posterior walls of the axilla. The large pectoralis major forms the anterior wall of the axilla, while the sheet-like latissimus dorsi and thick, round teres major form the posterior axillary wall.

10Teres minor

11Triceps brachii

21Brachialis

22Posterior scalene

23Middle scalene

24Anterior scalene

25Omohyoid

27Sternothyroid

28Thyrohyoid

29Sternocleidomastoid

30External oblique

32Clavicle

33Humerus

34Spine of scapula

35Thoracolumbar fascia

36Linea alba

37Common carotid artery

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Muscles of neck, shoulder, brachium, and back

Posterior view

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Muscles of neck, shoulder, brachium, and chest

Anteror view

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