Rotator Interval and Intra-articular Corticosteroid Injection for Frozen Shoulder

The purpose of this study is to compare ultrasound guided capsular corticosteroid injection into the rotator interval/anterior capsule and the GH joint with ultrasound guided corticosteroid injection into the GH joint only. Both methods will be compared with placebo injections. Primary outcome measure: pain reduction at week 6 Secondary outcome measures: improvement of function (SPADI, Life quality, ROM). 0-hypothesis: no difference between the methods. The investigators want to find out if the clinical effect of the combined capsular and intra-articular injections are better than placebo and better that intra-articular injections