The acromion is the front edge of the shoulder blade or "roof" of the shoulder. It's the highest point of the shoulder blade and forms a bony arch over the rotator cuff and humeral head (top of arm bone).

The acromioclavicular joint is located at the tip of the shoulder where the acromion (shoulder blade) and collarbone (clavicle) come together.

In this procedure, a needle is inserted into a joint in order to remove fluid. Arthrocentesis is used for diagnosis as well as for treatment of shoulder problems.

In this procedure, medical dye is injected into the shoulder and an x-ray is taken of the area. This test is used in conjunction with an MRI to help identify a torn rotator cuff or labral tear.

Arthroscopic surgery is minimally invasive surgery. It uses a device called an arthroscope, a tiny, pen-shaped instrument that has a micro video camera attached to the end. The arthroscope is inserted through a small incision in the shoulder.

Arthrocentesis is the process of draining joint fluid. It involves inserting a needle under local anesthetic into the joint cavity and withdrawing fluid. The fluid is examined in the laboratory.