小圆肌 (xiǎo yuán jī) is a small muscle located in the shoulder region, specifically beneath the 肩胛骨 (scapula). It plays a crucial role in the movement and stabilization of the 肩关节 (shoulder joint). This muscle helps in the rotation of the arm and assists in lifting the arm away from the body. The 小圆肌 is part of the 肩部肌肉群 (shoulder muscle group) and works alongside other muscles, such as the 大圆肌 (teres major) and 肩袖肌肉 (rotator cuff muscles). Strengthening this muscle can improve shoulder function and reduce the risk of injuries during physical activities.