Objective To explore the influence of biceps longus tendon sheath effusion on the treatment of ultrasound-guided intra-articular injections in patient with frozen shoulder. Methods 81 patients with clinically diagnosed frozen shoulders were divided into group A (with tendon sheath effusion of biceps brachii longus) and group B (without tendon sheath effusion of biceps brachii longus). All patients underwent ultrasound-guided intra-articular injections

and ultrasound examinations were performed to measure axillary recess capsule (ARC) thickness before and 2 weeks after the injection

and Constant-Murley shoulder score were evaluated. Results The ARC thickness was significantly reduced and the Constant-Murley scores were significantly increased in both groups after treatment (P <0.05). Compared with group B after the treatment

the Constant-Murley score of group A was significantly lower than that of group B

and the ARC thickness of group A was significantly higher than that of group B (P <0.05). Conclusion Tendon sheath effusion of biceps brachii longus can affect the efficacy of ultrasound-guided intra-articular injections for frozen shoulder. ARC thickness can be used as a reference index for evaluation of ultrasound-guided intra-articular injections for frozen shoulder.