The exact etiology of Achilles tendinosis is unclear, but the main pathologic stimulus is an overuse injury of
multifactorial origin involving several intrinsic factors (foot misalignment, poor flexibility, joint laxity) and
extrinsic factors (activity level, type of activity, training technique, footwear, training environment). In general,
Achilles tendinosis most commonly develops when athletes abruptly increase their training activity.
As discussed above, microtears heal slowly due to limited vascular supply to the tendon and slow protein
regeneration. Hypoxia and ischemia-reperfusion injury, as well as exercise-induced hyperthermia, play a role
in the pathogenesis. Recurrent microtrauma occurring with continued training can lead to tendon
degeneration. Additionally, tendon that has been stretched repeatedly to >4% of its original length loses
elasticity, which supports the idea of overuse in the pathogenesis of the disease