The purpose of this study is to determine whether radio-frequency (RF)-based plasma micro-tenotomy has a positive effective for the treatment of shoulder impingement syndrome with cuff tendinosis. Eighty patients with impingement syndrome and cuff tendinosis that treated arthroscopic were enrolled in the study. Patients were randomly assigned to receive either arthroscopic subacromial decompression alone (ASD group, n=40) or arthroscopic subacromial decompression combined with RF-based plasma micro-tenotomy (RF group, n=40). Clinical outcome data including VAS(Visual Analogue Scale) pain score, Shoulder range of motion (ROM), ASES(American Shoulder And Elbow Surgeons) score, UCLA(University of California, Los Angeles) score, Constant-Murley score and SST(Simple Shoulder Test) score were recorded preoperatively and at postoperative 3-week, 6-week, 3-month, 6-month and 1-year.

Inclusion Criteria:

1. a skeletally mature patient who agreed to participate in the study
2. shoulder impingement syndrome was diagnosed by one senior surgeon (CYJ) and without any sign of rotator cuff tear both on pre-operative MRI or intra-operative arthroscopic view
3. supraspinatous tendinosis was confirmed on preoperative MRI
4. the symptoms were not relieved by a standardized conservative treatment regime
5. patient underwent standard arthroscopic subacromial decompression surgery.

Exclusion Criteria:

1. any concomitant partial or full-thickness rotator cuff tear verified both on pre-operative MRI or intra-operative finding
2. concomitant biceps lesions or internal impingement
3. any history of surgical treatment on the same shoulder.