BL-40 - Middle of the Crook
委中 - Wěi zhōng
Point Region: Knee
BL-40 Weizhong, meaning 'Middle of the Crook,' is the most vital point on the entire Bladder meridian. As the He-Sea and Earth point, it is a master point for the entire back, from the lower back to the neck, as well as the legs and hips. It is the command point for the lumbar region and a master at clearing heat from the body.
Think of Weizhong as a central point of power for your entire back. It's the go-to point for all types of back pain, from acute spasms to chronic lower back stiffness. It's also a powerful point for clearing heat from the blood, which can manifest as skin conditions, fever, or a restless mind.
By commanding the lumbar region and clearing heat, BL-40 helps to restore a sense of ease and balance to the entire body. It's a point that reminds us that our ability to stand tall and move freely is rooted in a strong and unburdened back.
Location & How to Find
Anatomical Location: At the midpoint of the popliteal crease, between the tendons of biceps femoris and semitendinosus.
How to Locate:
- Bend your knee and locate the horizontal crease at the back of your knee
- Find the exact center point of this crease, between the two main tendons
- Gently press into the soft depression - this is BL-40

Primary Functions
Musculoskeletal System
- Relieves lower back and knee pain
- Treats sciatica and leg disorders
- Strengthens lumbar spine
- Reduces leg stiffness
Circulatory System
- Improves blood circulation in legs
- Treats varicose veins
- Reduces leg swelling
Urinary & Kidney System
- Supports kidney function
- Treats urinary disorders
Clinical Applications
Primary Indications
- Lumbar pain
- Hemiplegia
- Leg paralysis
- Hip stiffness
- Knee spasms
- Lower back disorders
Related Health Concerns
Common Conditions:
Related Acupoints
Select a point to learn about its location, primary functions, clinical applications, and protocols.
BL-40 Protocols
Acute Lower Back Pain Relief (3 minutes)
- Sit with legs extended or lie down comfortably
- Locate BL-40 (center of the popliteal crease, behind the knee)
- Press firmly with thumbs for 30 seconds on each leg
- Massage in circular motions for 1 minute to release tension
- Repeat pressure while breathing deeply to ease discomfort
Important Precautions
- Avoid needling large blood vessels
- Caution in bleeding disorders