Final answer:
The subscapularis is the rotator cuff muscle located on the anterior side of the scapula, medially rotating the arm and stabilizing the shoulder joint.
Step-by-step explanation:
The rotator cuff muscle located on the anterior side of the scapula is the subscapularis. This muscle is responsible for medially rotating the arm and, along with the other three rotator cuff muscles, plays a critical role in stabilizing the shoulder joint. The subscapularis arises from the anterior surface of the scapula and attaches to the lesser tubercle of the humerus, effectively contributing to the dynamic ligament system that holds the head of the humerus in the glenoid cavity of the scapula.