Figure 1: Types of enthesis. A) Indirect fibrous bone-tendon interface. Tendon joins directly to the bone by collagen fibres inserting into the periostuem layer of the bone (Sharpey’s fibres). B) Direct fibrocartilaginous bone-tendon interface. Tendon transitions through fibrocartilage regions before reaching the bone. Collagen fibres become more disorganised and mineral content increases as the soft tissue reaches the bone.