Muscle knots in the Flexor Hallucis Longus are typically located deep in the lower leg along the back of the fibula and can refer pain down through the inside of the ankle and into the bottom of the big toe. This pain often feels like a dull ache or burning sensation and may radiate into the ball of the foot, especially during activities like walking, running, or standing on tiptoe. People sometimes mistake it for gout or plantar fasciitis.