Xu M, et al. - This research intended to evaluate the intrarater reliability of acromiohumeral distance measurement and to evaluate the level of relationship between acromiohumeral distance measured by ultrasonography, and the degree of supraspinatus tendon tear, in individuals suffering from chronic shoulder pain. Researchers performed a cross-sectional, case-control study comprising a total of 59 individuals with a unilateral supraspinatus tendon tear. Researchers found excellent intrarater reliability for the ultrasound method of acromiohumeral distance measurement. Compared with joints with partial-thickness supraspinatus tendon tear and an intact supraspinatus tendon, the acromiohumeral distance of shoulders with full-thickness supraspinatus tendon tear was significantly smaller. A significant positive relationship was found between reduced acromiohumeral distance and the severity of a supraspinatus tendon tear.