Ultrasonography has become an investigation of choice in the management of shoulder pain. The objective of this study was to determine whether the efficacy of subacromial-subdeltoid bursa injection correlated with the ultrasound findings.

We prospectively recruited patients who were seen between November 2012 and November 2013 for subacromial pain and whose rotator cuff was either intact or showed a full-thickness tear less than 1cm in length. A standardised physical examination of the shoulder was followed immediately by static and dynamic ultrasonography, intra-bursal injection of lidocaine, and a repetition of the same physical examination. Recorded ultrasonography features were the appearance of the bursa, shape of the coraco-acromial ligament, and bursal deformation induced by passage under the coraco-acromial ligament during dynamic imaging. A response to the injection was defined as greater than 75% improvements in at least three of the physical examination parameters.

We included 39 patients with a mean age of 56.7years. Ultrasonography showed abnormalities of the bursa in 30 patients, including 1 with an intra-bursal effusion, 10 with thickening, and 19 with both. Deformation of the bursa under the coraco-acromial ligament was noted in 26 patients. The proportions of patients with bursal effusion and with bursal thickening were similar in the 20 responders and 19 non-responders. Neither were any significant differences found for coraco-acromial ligament shape or bursal deformation under the ligament.

No correlation was found between ultrasonography findings and the efficacy of a local anaesthetic injection into the subacromial bursa. These findings suggest that ultrasound abnormalities may constitute mere physiological changes, in keeping with earlier studies in asymptomatic individuals. Thus, subacromial impingement may be currently overdiagnosed.