Supraspinatus

backMusculus supraspinatus

The supraspinatus sits in the shallow groove above the ridge on the back of your shoulder blade and passes over the top of the shoulder joint. It starts the movement of lifting your arm out to the side.

The supraspinatus fills the hollow above the horizontal ridge on the back of the shoulder blade, then runs outward, passes under the bony roof at the top of the shoulder, and attaches to the very top of the arm bone. It is the only one of the four cuff muscles that crosses over the top of the joint rather than around the front or back of it.

That position gives it a specific job. When your arm is hanging at your side, the deltoid pulls almost straight up the arm bone and is poorly placed to start the lift; the supraspinatus, pulling from above and inward, is well placed. This is usually taught as the supraspinatus initiating the first fifteen degrees of the movement and then handing over to the deltoid, and that is a useful picture of the leverage. It is not a picture of the activity: measurements of the muscles working show the deltoid and the supraspinatus firing together through the whole range rather than taking turns. The fifteen degrees describes where each one has the better angle, not where each one is switched on.

It is also the cuff muscle most talked about, because the space it passes through is narrow — a tunnel between the top of the arm bone and the bony roof above it. That anatomy is why it comes up so often in discussions of shoulder problems. What that means for any individual is a question for a professional.

Its other job runs all the time: pulling the head of the arm bone down into the socket so that the deltoid's upward pull does not simply drag it upward. The deltoid and the supraspinatus working against each other is what keeps the joint centred while the arm rises.

Training notes

Scaption is the one movement that trains it directly. Raise the arms to shoulder height in the plane roughly thirty degrees forward of straight out to the side, thumbs up. That plane matches the way the shoulder blade sits on the ribcage, and it puts the load along the supraspinatus rather than across it.

The empty-can version of this — the same raise with the thumbs turned down — is widely taught and worth a note of caution: it increases the muscle's share of the work by rotating the arm into a position many people find uncomfortable at the top. The thumbs-up version trains the same muscle and asks less of the joint.

Every overhead press and lateral raise involves the supraspinatus, since it works through every abduction and stabilises all of them, but neither trains it through a meaningful range of its own. That is why it goes untrained in programs that are otherwise thorough about the shoulder.

Anatomy

Origin
  • Supraspinous fossa of the scapula
Insertion
  • Superior facet of the greater tubercle of the humerus
Actions
  • Abducts the arm, with its best leverage through roughly the first fifteen degrees
  • Compresses the head of the humerus into the socket throughout arm movement
Innervation
Suprascapular nerve (C5–C6)

Exercises

Antagonists

Synergists