The subscapularis muscle is one of the rotator cuff muscles. It is located on the inside of the scapula, and can be difficult to access. This muscle functions to internally rotate the arm as well as to adduct the shoulder. It is also a stabilizer of the shoulder joint. When this muscle is overloaded or injured trigger points can form. These points will refer pain into the back of the shoulder and down the inside of the arm to the wrist. Trigger points in the subscapularis are often associated with a frozen shoulder.