Sclerosing injections targeting neovascularisation have been demonstrated to give promising clinical results in patients with chronic painful Achilles tendinosis. In this study, fifteen elite or recreational athletes (12 men and three women) with the diagnosis patellar tendinosis/Jumper's knee in 15 patellar tendons were included. All the patients had a long duration of pain symptoms (mean = 23 months) from the patellar tendon, and ultra-sonography + colour doppler examination showed structural tendon changes with hypo-echoic areas and a neovascularisation, corresponding to the painful area. The patients were treated with ultrasound and colour doppler-guided injections of the sclerosing substance Polidocanol, targeting the area with neovascularisation. At follow-up (mean = 6 months) after a mean amount of three treatments, there was a good clinical result in 12/15 tendons. The patients were back to their previous (before injury) sport activity level, and the amount of pain recorded on a VAS-scale had decreased significantly (VAS from 81 to 10). Our findings indicate that treatment with sclerosing injections, targeting the area with neovessels in patellar tendinosis, has the potential to cure the pain in the tendons and also allow the patients to go back to full patellar-tendon loading activity.