Subacromial injection is a useful procedure to counteract shoulder impingement syndrome. With the aid of high‐resolution ultrasound, the needle can be introduced precisely into the subacromial/subdeltoid bursa located between the acromion above and the supraspinatus tendon below. The standardized method allows the injectate to distribute along the subdeltoid bursa, further reliving pain from subacromial/subdeltoid impingement. In a substantial part of shoulder pain patients, it is common to accompany pain along the bicipital groove, which the biceps long head tendon courses through. The biceps long head tendon is attached to the superior labrum of the glenoid cavity and acts as the second important structure to prevent upward migration of the humeral head, following the supraspinatus tendon. Overuse injury of the biceps tendon is a likely cause of anterior shoulder pain. Concomitant administration of medication into the subacromial bursa and biceps tendon sheath is theoretically more effective than injection to the subacromial bursa only because the formal procedure targets two vulnerable structures in shoulder impingement syndrome at once. Regarding the standard ultrasound‐guided subacromial injection. Therefore, we will conduct a randomized controlled trial investigating the effectiveness of standard subacromial injection in comparison with a novel approach simultaneously injecting the subacromial bursa and biceps tendon sheath.