BackgroundSteroid injection after percutaneous irrigation of calcific deposits is a common method for the treatment of rotator cuff calcific tendinitis (RCCT). However, steroids may prevent calcification resorption and cause potentially irreversible damage to tendons. Recent studies have confirmed the positive effects of ozone injection in shoulder tendinopathies, but no RCCTs have been reported. Thus, our study aims to evaluate the non-inferiority of ozone versus steroid injection.MethodsThis is a prospective, randomized, parallel control and non-inferiority trial. A total of 100 patients with unilateral symptomatic RCCT will be enrolled and randomized in a 1:1 ratio to two groups: ultrasound-guided injection with ozone or corticosteroid. The primary outcome is the numeric rating scale for pain (NRS) at 1 week and 3 months following the procedure. Secondary outcomes include a multi-dimensional evaluation of shoulder disability and quality of life improvement, the degree of calcification absorption after treatment, and the number of multiple treatments.DiscussionThe results of this study will provide short-term and long-term evidence for the effectiveness of ozone treatment in RCCT in relieving pain or improving shoulder function.Trial registrationChinese Clinical Trial Registry ChiCTR2200063469. Registered on 7 September 2022.