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

Hakan Alfredson and Lars Ohberg

The aetiology and patogenesis to chronic tendon pain is unknown, and treatment is known to be difficult. Despite that tendon biopsies have shown an absence of inflammatory cell infiltration, anti-inflammatory agents (NSAID´S, corticosteroidal injections) are commonly used. We have demonstrated that it is possible to use microdialysis technique for in vivo investigations of human tendons, and found significantly higher concentrations of the neurotransmitter glutamate, but not Prostaglandin E2 (PGE2), in chronic painful tendinosis (Achilles-, patellar-, ECRB-) tendons, compared to pain-free normal control tendons. The findings indicate that glutamate might be involved in chronic tendon pain, and that there is no PGE2-mediated inflammation in the chronic stage of these so-called tendinopathies. Using ultrasonography (US)+colour Doppler (CD), and immunhistochemical analyses of biopsies, we have recently demonstrated a vasculo/neural(SP- and CGRP-nerves) ingrowth in the chronic painful tendinosis tendon, but not in the pain-free normal tendon. A specially designed treatment, using US- and CD-guided injections of the sclerosing agent Polidocanol, targeting the neovessels outside the tendon, has in pilot studies been shown to cure the tendon pain in the majority of patients. A recent randomised double-blind study, verified the importance of injecting the sclerosing substance Polidocanol.