Which structure protects the rotator cuff tendons from friction against the acromion?

The subacromial bursa is a fluid-filled sac located beneath the acromion and above the rotator cuff tendons. Its primary function is to reduce friction between the rotator cuff tendons and the acromion during arm movements, particularly during overhead activities. By providing a cushioning effect, the subacromial bursa helps to prevent wear and tear on the tendons, which can lead to impingement syndrome or rotator cuff injuries. This protective role is essential for maintaining the smooth function of the shoulder joint and ensuring that the tendons can glide effectively without being pinched by surrounding structures.