The paucity of effective treatments in tendon disorders partially reflects lack of understanding of its pathogenesis.4 Historically considered a degenerative pathology and therefore termed ‘tendinosis’, research conducted during the last decade has revealed the presence of immune cells (mast cells, macrophages, T cells)5–12 and inflammatory cytokines (interleukin (IL)-6, IL-15, IL-17, IL-18, IL-33, tumour necrosis factor alpha (TNF-α))10 11 13 14 in tendinopathic tissues. The gene discussed is IL17A; the disease is disease of the tendon.