How to find

To locate the popliteal crease, ask the patient to flex their knee slightly and palpate for the knee joint space. By flexing the knee against resistance, the tendon of the biceps femoris muscle will become more pronounced and visible. Locate BL-38 1 cun superior to the knee joint on the medial border of the tendon. BL 39 (Outside of the Crook) is located 1 cun distal to BL-38 on the level of the popliteal crease.


On the latero-dorsal aspect of the knee, 1 cun superior and lateral to the centre of the popliteal crease (BL 40 (Middle of the Crook)), medial to the biceps femoris muscle, or 1 cun proximal to BL 39 (Outside of the Crook).


  • Relaxes the muscles and tendons
  • Opens the channel and luo vessels
  • Clears Heat (from the Small Intestine)