ObjectiveTo compare the efficacy of combination therapy (hydrodilatation and subdeltoid bursa injection with corticosteroid, mobilization, and physical therapy [PT]) with that of PT alone for treating frozen shoulder. DesignA prospective, 2-arm parallel, single-blinded, randomized controlled trial. SettingRehabilitation clinic of a private academic hospital. ParticipantsPatients (n=70) with frozen shoulder (freezing stage). InterventionsParticipants (n=35) in the combination group underwent hydrodilatation and subdeltoid bursa injection with corticosteroid twice, mobilization, and usual-care PT for 8 weeks; participants (n=35) in the PT group received only the usual-care PT for 8 weeks. Main Outcome MeasuresThe Shoulder Pain and Disability Index (SPADI) was the primary outcome measure. The secondary outcome measures were pain scores on a visual analog scale, range of motion (ROM), the Shoulder Disability Questionnaire (SDQ), quality of life (evaluated using the 36-item Short-Form Health Survey [SF-36]), and self-assessment of the treatment effect. ResultsCompared with the PT group, the combination group had significantly better pain (during activity), SPADI, SDQ, active and passive ROM, and self-assessment scores (all P<.001) as well as scores on some parts of the SF-36 (physical function and bodily pain, P<.05). Between-group differences were significant at the 1-, 2-, 4-, and 6-month follow-ups. ConclusionsA combination of hydrodilatation (with corticosteroid), bursal corticosteroid injection, and joint mobilization with PT was superior to PT alone for treating frozen shoulder, and the effects persisted for at least 6 months.