Foot drop. A foot drop is a common symptom of a bulging disc. It causes the muscles used to flex the ankle and toes to weaken. This symptom is a neuromuscular disorder that can cause pain and numbness. It affects the muscles and nerves, but is not a disease. A foot drop is usually a symptom of a condition in the lower back. A person with this condition tends to drag his or her front foot. He or she will try to compensate for the dragging by bending the knee to lift the foot higher than normal. A foot drop usually affects the muscle that is responsible for moving the ankle upward.