060317 Shoulder posture
An ideal alignment will have the line of reference passing midway through the shoulder joint as it travels downward. The arm and shoulder position depends on where the scapulae and upper back positions are. In a normal, i.e. correct alignment, the scapulae will be lying flat against the upper back. This position is roughly located between the second and seventh thoracic vertebrae with about four inches separation. Even this separation depends on the size of the person.
Positions of the scapulae, other than that described, will negatively affect the position of the shoulder. This particular misalignment of the Glenohumeral joint will in many cases set the athlete up for an impending injury.