American Orthopaedic Society for Sports Medicine

Chronic tendinopathy, like medial and lateral epicondylitis and patellar and Achilles tendinopathy, is a well-known painful orthopaedic disease. The characteristic pathologic characteristics of all these tendinosis conditions are linked to microrupture of the tendon,4,5 granulation tissue,9 and degenerative changes.13,15 Nonsteroidal anti-inflammatory medication, physical therapy, steroid injections, and orthoses are symptomatic treatment for these and various other orthopaedic conditions, while arthroscopic or open surgery is reserved for patients with insufficient response to less invasive procedures. Neovessels and accompanying free nerve endings have been observed in tendinosis tissue using Protein Gene Product 9.5 immunohistochemistry.2 Furthermore, the ten-don insertion, which is supplied with substance P (SP) and calcitonin gene-related peptide (CGRP) innervation, has been implicated in the origins of tennis elbow.11 The rat model of Achilles tendinosis showed an increased number of nerve filaments and increased immunoreactivity for SP and CGRP.12 Neuropeptides SP and CGRP are not only involved in transmitting nociceptive information to the spinal cord, but also in peripheral effects, including microvascular leakage and local edema formation.21 Pathological nerve ingrowth may have been involved in the origin of tendinosis.11 On th