Subacromial space measured by ultrasound imaging in asymptomatic subjects and patients with subacromial shoulder pain: an inter-rater reliability study.

Inter-rater reliability varied largely from poor to good between two examiners with different US experience. Clinicians might use the US as additional tool for detecting the subacromial structures, but a structured training including also symptomatic subjects is suggested. Researchers may further investigate the OR in matched case-control studies, and an overall agreement phase is recommended before starting the inter-rater reliability phase.