Right Shoulder Atlas

Belly-sleep view. Start on supraspinatus, then try Belly sleep — arm overhead, head on the shoulder.

Educational only

Live reading

Supraspinatus tendon

The top of the rotator cuff. It runs from the supraspinous fossa, under the acromion, onto the greater tubercle. Arm-overhead plus the weight of a head on that shoulder crowds this tendon in the subacromial space — the usual address for ‘it hurts when I sleep like that’. Right now: 42° flexion, 28° abduction, external 12°. The arm is not overhead, so the subacromial tunnel is relatively open. Open the Belly sleep preset to see the pinch pose.

Why it hurts to sleep like that

Under the roof. The subacromial tunnel is not crowded. Open Belly sleep to put the arm overhead.

Point of the shoulder. The AC joint sits right where a head would rest on the point of the shoulder. That load is compression from above, not arm angle.

Load these poses

Educational anatomy only — not a diagnosis, not medical advice. Belly-sleep with the arm overhead crowds the supraspinatus under the acromion and parks the head on the AC joint. Bones are BodyParts3D 4.0 adult-male right shoulder girdle (CC BY 4.0, Database Center for Life Science).

Flexion / overhead42° flex

At sideOverhead

Abduction28° abduction

AdductedOut to side

Rotation12° external

InternalExternal

Drag to orbit · scroll to zoom · two-finger drag to pan. Belly sleep puts the cuff under the acromial roof and the AC joint under a resting head.