Abstract:Objective To explore the application value of measuring axillary pouch thickness（APT）by musculoskeletal ultrasound in the diagnosis and evaluation of frozen shoulder. Methods A total of 168 patients with frozen shoulder who visited the Department of Ultrasound Medicine of Jiangsu Provincial Hospital of Chinese Medicine from January 2023 to January 2025 were selected. The APT was measured by musculoskeletal ultrasound imaging, and the Shoulder Pain and Disability Index（SPADI）was used to assess shoulder function. The differences of APT and SPADI scores in patients with frozen shoulder in different stages and severity were analyzed. Results A total of 168 frozen shoulder patients underwent musculoskeletal ultrasound examination. Patients were divided into three groups according to disease course：acute phase group（≤3 months, n=64）, chronic phase group（4-6 months, n=63）, and recovery phase group（>6months, n=41）.The APTs were（4.04±0.73）mm, （3.97±0.93）mm, and（3.40±0.63）mm, respectively, and the SPADI scores were 50.38±17.10, 49.60±19.91 and 42.61±19.95, respectively. There were statistically significant differences in APT among the three groups（F=9.213, P＜0.01）, but the difference in SPADI among the three groups was not statistically significant（P＞0.05）. Based on SPADI scores, the patients were categorized into four groups：mild disability group（0-30 points, 33 cases）, moderate disability group（31-60 points, 89 cases）, severe disability group（61-80points, 36 cases）, and very severe disability group（81-100 points, 10 cases）. The APTs of patients in the mild disability group, moderate disability group, severe disability group, and very severe disability group were（3.43±0.89）mm, （4.02±0.81）mm, （3.84±0.63）mm, and（3.93±1.00）mm, respectively, and the differences among four groups were statistically significant（F=4.356, P=0.006）, with the mild disability group having the smallest APT（P＜0.05）.Conclusion Musculoskeletal ultrasound is a rapid, inexpensive and non-invasive technique that can assist in the clinical diagnosis of frozen shoulder. APT is highest in the acute phase of frozen shoulder and lowest in patients with mild shoulder pain and disability, which can assist clinicians in diagnosing frozen shoulder.