Bursitis is the irritation or inflammation of the bursa, which is a sac filled with lubrication fluid and is located between tissues such as bone, muscle, tendons, and skin that decreases rubbing, friction, and irritation to occur. Bursitis is most often caused by repetitive, minor impact on the area. It also can be caused by a sudden, more serious injury. While bursitis could be caused by an injury, it also can be caused by age. As tendons age they are able to tolerate stress less, are less elastic, and are easier to tear.
As for symptoms, the most common one of bursitis is pain. The pain may build up gradually or be sudden and severe, especially if calcium deposits are present. Frozen shoulder can also be a result from the immobility and pain associated with shoulder bursitis.