Muscle knots in the Biceps Femoris are located in the back of the thigh, especially near the outer portion of the thigh. These muscle knots can refer pain to the crease of the buttock, posterior thigh, behind the knee, and even down into the lateral calf and ankle, often mimicking sciatica or IT band syndrome. You may feel deep aching or sharp pain during walking, sprinting, or sitting for long periods, and tightness may limit knee flexion or hip extension.