Muscle knots in the Semispinalis Cervicis are usually found deep in the upper back and lower neck, just beside the spine. When these knots are irritated, they can refer pain upward into the neck and the back of the head, sometimes mimicking tension headaches or neck stiffness. It’s one of those muscles that can cause a lot of discomfort, especially after long hours of looking down at a screen or poor posture.