For managing symptoms of adhesive capsulitis (AC), corticosteroid injection is typically conducted under the guidance of ultrasound via posterior glenohumeral recess (PGHR). It has been reported that pathologies such as inflammation and edema are most commonly observed in the coracohumeral ligament (CHL) and anterior and inferior joint capsules. We compared the therapeutic effects of corticosteroid injection into the CHL and inferior glenohumeral capsule (IGHC) with those of corticosteroid injection into PGHR in patients with AC.One hundred twenty consecutive patients with AC were included in this study and randomly allocated to either the CHL + IGHC group (n = 60) or the PGHR group (n = 60). Patients in both groups received 3 injections at 2 week intervals. After the first injection, if the patient's shoulder pain showed satisfactory improvement, further injections were not administered. The therapeutic effect was measured at 2 and 4 months after the first injection. Pain intensity was evaluated using the visual analog scale (VAS). Additionally, the passive range of motion (ROM) of the shoulder joint (abduction, external rotation, and internal rotation) was measured.VAS scores and ROM of abduction, external rotation, and internal rotation improved at follow-up evaluation in both groups (P < 0.05) (CHL and IGHC: VAS, pre-treatment = 6.5 ± 0.5, 2 months = 2.1 ± 0.8, 4 months = 1.4 ± 0.6; ROM-abduction, pre-treatment = 131.3° ± 16.4°, 2 months = 162.4° ± 8.2°, 4 months = 176.2° ± 5.6°; ROM-external rotation, pre-treatment = 31.6° ± 16.9°, 2 months = 67.2° ± 11.1°, 4 months = 81.3° ± 12.1°, ROM-internal rotation, pre-treatment = 6.2 ± 2.2, 2 months = 4.0 ± 2.2, 4 months = 2.7 ± 1.2; PGHR: VAS, pre-treatment = 6.5 ± 0.5°, 2 months = 3.9 ± 1.1, 4 months = 2.1 ± 1.1; ROM-abduction, pre-treatment = 132.1° ± 9.5°, 2 months = 145.5° ± 11.7°, 4 months = 167.4° ± 11.2°; ROM-external rotation, pre-treatment = 32.4° ± 13.4°, 2 months = 49.3° ± 13.2°, 4 months = 72.7° ± 18.0°, ROM-internal rotation, pre-treatment = 6.3 ± 1.4, 2 months = 5.4 ± 0.8, 4 months = 3.6 ± 1.0). However, the improvements were greater in patients who received corticosteroid injection into the CHL and IGHC compared to that into the PGHR at 2 and 4 months after the initiation of the treatment (P < 0.05).Long-term therapeutic outcomes were not investigated, and the therapeutic effect of corticosteroid injection into the CHL and IGHC was not compared with placebo injection.Corticosteroid injection into the CHL and IGHC might be a better treatment alternative for patients with AC.