The shoulder blade
Scapula · scapula
A flat triangular bone on your upper back that anchors the arm and lets it move freely.
What it does
The shoulder blade is a flat, triangular bone that floats on the back of your ribcage, held mainly by muscles rather than joints. It provides the shallow socket for the humerus and a platform for seventeen muscles. As you lift your arm overhead, the scapula rotates and slides to keep the socket under the arm.
Surprising fact
The scapula is attached to the rest of the skeleton by a single small joint with the collarbone; everything else holding it in place is muscle.
Why it matters
Because muscles do most of the holding, weak or tired back muscles let the shoulder blade drift, which can contribute to shoulder and neck pain. "Winging" of the shoulder blade is a classic sign that one of those muscles isn't working.
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Open in the 3D atlas · Suggest a correction · Not medical advice.
3D models: Z-Anatomy & BodyParts3D (CC BY-SA 4.0 / 2.1 JP). Card text CC BY 4.0.