The Pectoralis Minor. Permission Joseph E. Muscolino. The Muscular System Manual - The Skeletal Muscles of the Human Body, 4th ed. (Elsevier, 2017).

Six Causes of Shoulder Impingement Syndrome – Part 2

For scapular upward rotation to occur, scapular downward rotator musculature must lengthen. If scapular downward rotation muscles are tight, they might not be flexible enough to allow for scapular upward rotation, thereby causing shoulder impingement syndrome to occur.