Participants: adult patients (>20 year old) with shoulder impingement syndrome Inclusion criteria: shoulder pain>3 weeks; no contraindication for local injection; Visual analogue scale of pain>4 Participant number: at least 30 at each treatment arm Exclusion criteria: systemic rheumatologic disease, Ankylosing spondylitis, malignancy, major trauma or recent injections on the affected shoulder Study design: single center double blind randomized controlled trial Randomization method: block randomization (block size: 4), computerized random sequence generation, allocation concealment (+) Detail of the intervention