With your arms at your sides, palms facing your body, bend your elbows 90 degrees. Keeping your elbows against your body swing your forearms away from your body. This is lateral rotation — also referred to as external rotation — and the normal range of motion for a healthy shoulder is 90 degrees.

Movement that brings the anterior surface of the limb toward the midline of the body is called medial (internal) rotation. Conversely, rotation of the limb so that the anterior surface moves away from the midline is lateral (external) rotation (see Figure 3).