The incidence of frozen shoulder (FS) as a complication of simple arthroscopic shoulder surgery has yet to be defined. A single-surgeon case series of patients undergoing arthroscopic subacromial decompression (ASD) or ASD with arthroscopic acromioclavicular joint (ACJ) excision was analysed to establish FS rate, this cohort was then compared to a matched group of primary FS patients. Retrospective analysis of 200 consecutive cases was undertaken. All procedures listed, performed and reviewed by the senior author. 96 underwent ASD and 104 underwent ASD and ACJ excision. 6-months follow-up minimum. Incidence of frozen shoulder was 5.21% (ASD) and 5.71% (ASD+ACJ excision). Mean age was 52.3 years (95% CI: 47.4 to 57.2) of the patients that developed FS, compared to 57.2 years (95% CI: 55.2 to 59.2) in the patients who did not and 52 years (95% CI: 50.7 to 53.3) in the primary FS cohort (n=136). 9.1% of post-operative FS were diabetic compared to 17.1% of primary FS. 63.6% were female in the post-operative FS group, 47.1% in the primary FS group. Our results suggest that the risk of FS following simple arthroscopic procedures is 5%, with no increased risk if the ACJ is also excised. This cohort has the same average age as a primary FS. There is a trend toward female sex and diabetes does not increase the risk