Joint · Shoulders

Scapulothoracic articulation

Where the shoulder blade glides across the back of the ribcage. This is not a true joint — there is no capsule, no joint cavity and no cartilage; the shoulder blade is suspended by muscle and slides on a plane of loose tissue. It is included as an articulation because functionally it behaves like one, and because roughly a third of the movement of raising your arm happens here rather than at the shoulder joint itself. When the shoulder blade does not rotate upward properly, the ball-and-socket joint above it runs out of room — which is the mechanical story behind a great deal of shoulder pain.