Five Histologic Layers of the Supraspinatus and Infraspinatus Tendons1. Layer 1: Superficial LayerThickness: ~1 mmComposed of fibers from the coracohumeral ligament.2. Dense Parallel Tendon FibersThickness: 3–5 mmDensely packed parallel collagen fibers.Stronger than layer 3 by twofold.Prone to intrasubstance tears between this layer and layer 3.3. Deep Layer with Non-Uniform Collagen Orientation..