Anatomy and pathology of the achilles tendon: Tendonitis, tendinitis, or tendinopathy, which is it?
The Achilles tendon is a conjoined tendon composed of the two heads of the gastrocnemius and the soleus muscles. The microstructure of the Achilles tendon consists of collagen fibrils cross-linked in a manner to provide exceptional strength as the Achilles tendon must withstand considerable force. The plantaris muscle is absent in 10% of cadaver specimens and is thought to be primarily vestigial in nature. The blood supply of the Achilles tendon arises from the intrinsic vascular system at the myotendinous junction as well as from the extrinsic segmental vascular system. The gastrocnemius and soleus muscles are innervated from the first and second sacral roots through the tibial nerve. The Achilles tendon undergoes pathophysiologic processes similar to those that affect other tendinous structures, and the lexicon surrounding these processes is the subject of much confusion. Tendinosis refers to the histopathological diagnosis of intratendinous degeneration without clinical or histological signs of intratendinous inflammation, while tendinitis is identified as the histopathological diagnosis of inflammatory features within the tendon proper.
