Muscle knots in the Serratus Posterior Inferior are typically located in the lower back, just below the lower ribs and slightly to the side of the spine. These muscle knots usually cause localized pain that stays around the muscle itself, often described as a nagging ache or sharp spasm, especially noticeable during deep breathing, twisting, or reaching overhead. You may sometimes mistake this pain for kidney issues or general back strain, and it can be tricky to find relief due to the muscle’s deep location beneath the Latissumus Dorsi.