Scapular Dyskinesia

Typical movement of the scapula occurs in the sagital, coronal, and transverse planes. The primary movements consist of two translations: superior/inferior, and protraction/ retraction, as well as three rotations: upward/downward, internal/external, and anterior/posterior. Upward rotation is primary and posterior tilt secondary during normal overhead UE elevation with internal/external rotation being minimal until 100°. (43 Ludewig,49 McClure JOSPT)
Review of the normal ratio of glenohumeral (GH) to scapulothoracic (ST) motion analyzed by Doody et al (16) under three-dimensional analysis found that the ratio of GH to ST motion changes from 7.3: 1 in the first 30° of elevation to 0.78: 1 between 90 and 150°. Bagg and Forrest found a ratio of 4.4:1 during early phase, and 1.7:1 within 80 to 140° of shoulder elevation. (book(8)