The anatomic and functional effects of clavicle malunion, defined as 15 mm of shortening, were evaluated in 10 subjects. Bilateral shoulder computed tomography with 3-dimensional reconstructions was performed. A self-administered questionnaire was completed, and biomechanical testing of subjects was undertaken comparing strength and velocity of movement between shoulders. Mean shoulder scores and visual analog global assessments of shoulder function were significantly worse in the injured shoulder. Biomechanical assessment recorded a reduction in muscular strength for adduction, extension, and internal rotation of the humerus as well as a reduced peak abduction velocity in the injured shoulder (P < .05). Computed tomography assessment showed that clavicular shortening produced increased upward angulation of the clavicle at the sternoclavicular joint (P < .005) and increased anterior scapular version (P < .05). These changes in static anatomic relationships are possible mechanisms limiting shoulder function after short clavicle malunions. Consideration should be given to the prevention of shortening by open reduction and internal fixation, especially in the young, active age group.