Chronic tendon pain: no tendinitis, but high levels of glutamate and a vasculoneural ingrowth – implications for a new treatment?

Abstract

The etiology and pathogenesis of chronic tendon pain is unknown and treatment is notoriously difficult. Despite the fact that tendon biopsies have demonstrated an absence of inflammatory-cell infiltration, anti-inflammatory agents (nonsteroidal anti-inflammatory drugs and corticosteroidal injections) are commonly used. The authors have demonstrated that it is possible to use the microdialysis technique for in vivo investigations of human tendons and have found significantly higher concentrations of the neurotransmitter glutamate but not prostaglandin E2 in chronic painful tendinosis tendons compared with pain-free normal control tendons. The findings indicate that glutamate might be involved in chronic tendon pain and that there is no intratendinous prostaglandin E2-mediated inflammation during the chronic stage of these so-called tendinopathies. Using ultrasonography and color Doppler, and immunohistochemical analyses of biopsies, the authors have recently demonstrated a vasculoneural ingrowth in the chr...