The subacromial bursa is a fluid-filled sac that cushions and lubricates the outer surface of the rotator cuff in the shoulder. This lubrication helps to reduce friction with movement.
The shoulder is a ball-and-socket joint with three main bones that are held together by muscles, tendons, ligaments, and the joint capsule. The rotator cuff is a group of tendons known as the supraspinatus, infraspinatus, subscapularis, and teres minor. These tendons help keep the upper arm bone securely placed, or seated, into the socket of the shoulder blade and allow the shoulder to move in various directions.
The subacromial bursa is located between the upper tendon of the rotator cuff (supraspinatus tendon) and the outer corner of the shoulder blade (acromion).
WebMD Medical Reference from Healthwise