anatomyEXPERT - Supraspinatus

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Supraspinatus

Other Terms: Supraspinatus muscle, Musculus supraspinatus, Muscle supra-épineux

Muscle parts

None

Latin name

Musculus supraspinatus

Latin muscle parts

None

Group

Shoulder joint muscle – rotator cuff

Etymology

The English name for this muscle is the muscle above the spine. The term supra is Latin meaning “above or over” and spinatus comes from the Latin spina meaning “thorn.” Spina was originally used to describe any thorn-like or pointed projection, like the spinous processes of the vertebrae. This term was then transferred to the dorsal ridge formed by the individual spinous projections of the vertebrae. On the scapula it forms a dorsal ridge of bone.

Origin

Supraspinous fossa of the scapula and overlying supraspinous fascia.

Insertion

Superior most aspect of the greater tubercle of the humerus.

Action

Abduction of the humerus – the supraspinatus appears to be more prominent in the early stages of abduction than does the deltoid. Both muscles, however, show a progressive increase in activity from 0 to 90 degrees of abduction. At 90 degrees they reach their maximal activity and maintain this level between 90 and 180 degrees of shoulder abduction. They are not responsible for the movement between 90 and 180 degrees rather, this range of motion results from upward rotation of the scapula. During this latter phase they are actively resisting the gravitational load on the arm.Stabilizes the shoulder joint – as one of the rotator cuff muscles, the supraspinatus plays a critical role in stabilizing the shallow shoulder joint. This muscle, along with the superior part of the joint capsule and horizontal fibers of the posterior deltoid, stabilizes the shoulder joint from subluxation or downward dislocation of the vertically hanging arm during normal posture.