Muscle knots in the Rectus Abdominis are typically located along the front of the abdomen or what we know as the “six-pack” muscles. These tmuscle knots can refer pain to the lower and upper abdomen, mid and lower back, and even mimic symptoms like heartburn, indigestion, menstrual cramps, or urinary discomfort. The pain referral pattern in the mid and lower back are a horizontal pattern. You may feel a deep ache or tightness that worsens with core exercises, prolonged sitting, or emotional stress.