BL40 (Weizhong / Middle of the Crook) Acupuncture Point Guide
Practitioner Guide from The Acupuncture Supply Co.
Professional acupuncture supplies and practical clinical resources for qualified practitioners in Ireland and across Europe.
BL40, known as Weizhong (“Middle of the Crook”), is located in the centre of the popliteal crease. This guide summarises the standard location, traditional functions, common combinations, anatomy and essential safety considerations.
This is a professional reference for appropriately trained practitioners. It is not a self-treatment guide and does not replace accredited anatomical and clinical training.
BL40 Weizhong quick reference
| Point name | BL40 — Weizhong (“Middle of the Crook”) |
|---|---|
| Channel | Bladder channel |
| Classification | He-Sea and Earth point of the Bladder channel; traditional Command point of the lumbar region and back |
| Region | Centre of the popliteal crease |
| Laterality | Bilateral |
| Core landmark | At the midpoint of the popliteal crease, between the tendons of biceps femoris and semitendinosus. |
Location of BL40 Weizhong
At the midpoint of the popliteal crease, between the tendons of biceps femoris and semitendinosus.
Use proportional B-cun measurement together with palpation and individual anatomy. A fixed centimetre measurement is not a substitute for anatomical location.
Traditional functions of BL40
- Benefits the lumbar region and back.
- Relaxes the sinews and benefits the knee.
- Clears Heat and cools Blood in traditional theory.
- Clears Summer Heat in traditional practice.
These descriptions belong to traditional acupuncture theory. They are not claims that BL40 has been proven to diagnose, prevent or treat disease.
Traditional clinical applications
- Lumbar or back pain after appropriate assessment.
- Knee stiffness or posterior-leg symptoms where local treatment is suitable.
- Heat or skin patterns described traditionally as involving the Blood.
Point selection should follow a complete assessment, differential diagnosis, informed consent and an individualised treatment plan.
Common point combinations
- BL40 + BL23: traditionally used for lumbar and Kidney-related patterns.
- BL40 + GB34: considered where sinew or knee dysfunction is prominent.
- BL40 + GV14: used in selected traditional strategies to clear Heat.
These are traditional examples rather than fixed prescriptions.
Anatomy and practitioner notes
The tibial nerve and popliteal vessels lie deep in the fossa. Tendon and crease landmarks must be palpated carefully, and the knee position should allow the crease to be seen without compressing the fossa.
Needling and essential safety
Avoid deep perpendicular insertion towards the popliteal neurovascular bundle. Do not needle through varicosities, a Baker’s cyst, swelling, infection or recent injury. Suspected deep-vein thrombosis, acute calf swelling, neurological deficit or significant trauma requires urgent medical assessment.
Use sterile, single-use needles, appropriate skin preparation and a technique suited to the patient’s anatomy, health, medicines and treatment position. Stop and reassess if unexpected sharp, electrical or strongly radiating sensation occurs.
Frequently asked questions
Where is BL40 Weizhong?
At the midpoint of the popliteal crease, between the tendons of biceps femoris and semitendinosus.
What does Weizhong mean?
Weizhong is commonly translated as “Middle of the Crook”. The English rendering helps explain the traditional name but does not replace the anatomical landmark.
Can patients use this guide for self-needling?
No. This resource is written for qualified practitioners and does not replace supervised anatomical and clinical training.
Continue exploring Project Lotus
Visit our Acupuncture Point Guides, or read the BL23 Shenshu Guide and GB34 Yanglingquan Guide.
Practitioners can also browse our professional acupuncture needles and the wider Practitioner Guides library.
Professional disclaimer: This article is provided for qualified acupuncture and healthcare practitioners for general educational purposes. Traditional actions and applications describe established acupuncture theory and are not claims of proven clinical efficacy. It is not medical advice, does not replace accredited training and should not be used as a universal treatment protocol. Practitioners remain responsible for assessment, consent, safe technique, infection control, record keeping, referral and compliance with professional and legal obligations.
Reference standards and safety reading:
World Health Organization. WHO Standard Acupuncture Point Locations in the Western Pacific Region.
World Health Organization. Guidelines on Basic Training and Safety in Acupuncture.
Master Tung’s Acupuncture / eLotus CORE. BL40 Weizhong reference page.
