Muscle knots in the Deltoid are often found in the front and back of the shoulder muscle, especially near the top of the shoulder and upper arm. These muscle knots can refer pain down the outer arm, back of the shoulder, and the front of the shoulder. It can sometimes mimicking symptoms of shoulder bursitis or even a rotator cuff issue. You may feel a dull ache or tenderness that makes lifting the arm or reaching overhead a bit uncomfortable.