Fig. 1.

The enthesis organ of the adult Achilles tendon. The enthesis itself is characterised by an enthesis fibrocartilage (EF) which is most prominent in the superior part of the attachment. In addition, there is a sesamoid fibrocartilage (SF) in the deep surface of the tendon, immediately adjacent to the enthesis, and a corresponding periosteal fibrocartilage (PF) on the opposing surface of the superior tuberosity (ST) of the calcaneus. The tendon (T) and bone are separated by the retrocalcaneal bursa (RB) into which protrudes the tip of Kager's fat pad (KP). Note that the heel fat pad (HP) extends upwards from the sole of the foot to the posterior part of the Achilles tendon. Arrows, fibrous septa of the fat pad. Masson's trichrome. Scale bar: 2 mm.