Shoulder is a complex joint. For shoulder flexion to get the arm overhead – 12 ribs and their vertebral attachments and 10 with sternal attachments, scapular motion through 3 dimensions (frontal plane, saggital plane, and transverse plane rotations), humeral rotation and alignment within the glenoid fossa, AC and SC joint motions or limitations, vertebral motion of at least the 12 thoracic vertebral segments, and finally local muscular issues – means to get your arms in the air to wave them like you just don’t care can take motion from 38 joints through 3 planes of action and muscular actions from at least 24 muscles that attach through the thoracic spine, scapula and humerus.
It’s tough for the scapulae to retract and depress if the person has rounded shoulder (i.e.rib cage is stuck in flexion.)
In terms of scapular motion, the shoulder blades have the ability to move through 3 planes due to their floating attachment to the body.
For rotation, the scapula rely on triangulation force application from 3 different muscle groups to create upward rotation and 3 different groups to produce downward rotation.
During upward rotation movements,To read more register