Bladder Meridian
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BL-40
Earth-Tu
Sea-He Point
Ma Dan Yang Heavenly Star
Safety Warnings
- Dangerous point - requires extra caution
- Deep needling contraindicated - shallow insertion only
- Moxibustion contraindicated
Needle Depth
0.5–1.5 cun
Needle Angle
90° (Perpendicular)
Body Area
Knee
Location
At the midpoint of the popliteal crease, between the tendons of biceps femoris and semitendinosus muscle.
Main Actions
- Cools the blood
- Clears Summer-Heat
- Removes obstructions from the channel and eases lower back pain
- Benefits the Bladder
Indications
Commentary
Weizhong is an important point with various functions.
First of all, it clears Heat and cools Blood, so that it is widely used for skin diseases due to Heat in the Blood.
It clears Summer-Heat. Therefore it treats Heat stroke that causes vomiting, diarrhoea, fever, delirium, headache, irritability and red skin rashes during summer time.
It also clears Damp-Heat from the Bladder, so as to treat various unitary symptoms such as burning urination.
It also removes obstructions from the Channel, so that it is able to relax the sinews and benefit the lower back. In fact, it is one of the most important distal point for any types of lower back pain, but it is more recommended for acute and Excess patterns. Due to BL-40's nature of cooling Blood, it is not recommended to be used for weak patients with severe Deficiency or Coldness symptoms. In these type of back pain cases, Kunlun BL-60 is more suitable.
As for the location of the lower back pain, BL-40 is more recommended if the ache is either bilateral or unilateral instead of being on the spine. Other typical manifestations are sciatica, lower back stiffness and knee pain.
Classical Sources
Ling Shu (Spiritual Pivot): "委中，腘中央，為合，委而取之" - 'Weizhong is in the center of the popliteal fossa, it is the He-Sea point; bend [the knee] to access it.'
Su Wen (Cì Yāo Tòng Lùn): Describes using bloodletting at the popliteal region combined with Kidney channel points for treating lumbar pain with heat and dyspnea.
Zhēn Jiǔ Dà Chéng (Great Compendium of Acupuncture and Moxibustion): Refers to BL-40 as 'Blood Cleft' (血郄), emphasizing its role as an important bloodletting point for Blood stasis conditions.
Si Zong Xue Ge (Song of the Four Command Points): "腰背委中求" - 'For disorders of the waist and back, seek Weizhong.'
How to Locate
First flex the knee slightly in order to reveal the popliteal crease, where Weizhong BL-40 is located at the center.
Caution
The popliteal artery, popliteal vein, and tibial nerve lie directly beneath this point. Avoid deep insertion and always palpate for the arterial pulse before needling. Angle the needle slightly if needed to avoid vessels. When bloodletting, only prick superficial veins visible at the surface. Patients with varicose veins in this area require extra caution. In patients with kidney deficiency patterns causing chronic low back pain, bloodletting is not recommended as it may further weaken the constitution.
Needle Angle
90° (Perpendicular)
Depth Category
Medium
Standard Depth
0.5–1.5 cun
Needling Directions
Vertically 0.5–1.5 cun. Caution: Popliteal nerve, artery and vein lie deep to this point.
Expected Deqi Sensation
Soreness, distention, and heaviness locally in the popliteal fossa. Deqi sensation often radiates down to the calf along the Bladder channel pathway, or may radiate upward toward the lumbar region. Electric or tingling sensation may occur if the tibial nerve is stimulated (deeper needling).
Moxibustion
Contraindicated
Duration: N/A (Moxibustion generally contraindicated at this point)
Cupping
Particularly Recommended
Bloodletting
Particularly Recommended
Gua Sha
Questionable
Five Element & Transporting Classification
Five Phase
Earth-Tu
Transporting Type
Sea-He Point
Mother-Child Role
Child (Reducing)
Special Point Classifications
Ma Dan Yang Heavenly Star
Organ & Tissue Associations
Lower He-Sea Point for:
Bladder
Command Point
Commands region:
Back
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