Understanding adaption to load is essential for prevention and treatment of tendinopathy/tendinosis. Cytokine release in response to load is one mechanism involved in mechanotransduction. The cytokine tumor necrosis factor alpha (TNF-a) is implicated in tendinosis and can induce apoptotic effects via tumor necrosis factor receptor 1 (TNFR1). The complete absence of information concerning the TNF-a system in Achilles tendon is a limitation as mid-portion Achilles tendinosis is very frequent. To examine expression patterns of TNF-a and its two receptors (TNFR1 and TNFR2) in human Achilles tendinosis and control tissue and to biochemically confirm the presence of TNF-a in tendinosis tissue.