ROTATOR MUSCLES. WHAT IT IS? - Rotator muscles are paired muscles that are located in the girdle area of the upper limb. Their function is to extend and internally rotate the body, as well as flex the arm at the level of the elbow joint. The muscle tissue from which the rotator muscles are formed is located within the belt; the biceps and humerus form muscle bundles. - All muscles in the rotators are divided into two groups. The former provide extension and abduction in the shoulder joint, the latter lead to flexion in the elbow joint and abduction in the wrist joint. In addition, they support the back, acting as a stabilizer.