Tennis elbow, extensor carpi radialis brevis (ECRB) tendinosis, is a condition with unknown etiology and pathogenesis, known to be difficult to treat. The pain mechanisms have not been fully clarified, but involvement of a neurogenic inflammation mediated via the neuropeptide Substance-P (SP), has been suggested. In this investigation, grey-scale ultrasonography (US) and colour Doppler (CD) was used to examine the common extensor origin in 17 patients with the diagnose Tennis elbow in altogether 22 elbows, and in 11 controls with 22 pain-free elbows. In 21/22 elbows with chronic pain from the extensor origin, but only in 2/22 pain-free elbows, vascularity was demonstrated in the extensor origin. After US and CD-guided injection of a local anaesthetic, targeting the area with vessels, the patients were pain-free during extensor-loading activity. The area with vascularity found in the extensor origin seems to be related to pain. Most likely, the findings correspond with the vasculo-neural in growth that has been demonstrated in the chronic painful Achilles tendon, and possibly have implications for treatment.