BL40 Weizhong

Reviewed by · Licensed Acupuncturist & TCM Physician · Last reviewed June 2026

BL40 (Weizhong, “Weizhong”) is the He-Sea Point point of the Bladder Meridian. It is located at the midpoint of the transverse popliteal crease, in the depression between the tendons of biceps femoris and semitendinosus. The point is best located with the knee slightly flexed. It benefits the lumbar spine and knees, clears heat and cools the blood, dispels blood stasis, resolves dampness, and alleviates pain.

Location

At the midpoint of the transverse popliteal crease, in the depression between the tendons of biceps femoris and semitendinosus. The point is best located with the knee slightly flexed.

Needling

Perpendicular insertion 1.0 to 1.5 cun, or prick the popliteal vein to cause bleeding. Avoid deep insertion to prevent injury to the popliteal artery and nerve.

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TCM functions

Benefits the lumbar spine and knees, clears heat and cools the blood, dispels blood stasis, resolves dampness, and alleviates pain..

Indications

Lumbar pain, lumbar pain radiating up the spine to the head, heavy and painful conditions of the lumbar region and legs, chronic stubborn rashes, genital twitching, urinary incontinence, difficult urination, tight sinews, epilepsy with opisthotonos, heat illness with lack of sweating, hot feet with reversal, inability to bend or extend the knee, lower abdominal fullness, urinary retention, hemorrhoids, pain in the perineal region, leprosy with loss of eyebrows, fever, lumbar and spinal pain, lower back heaviness and inability to lift the body, wind-damp impediment (Bi syndrome), pain in the hip joint, heat in the four limbs during febrile disease, bladder diseases, lower back pain like it is broken, inability to bend the hip, popliteal fossa feeling knotted, calf feeling like it's being torn apart, pain in the neck, back, lumbar, sacrum, popliteal fossa, calf, and foot, urinary retention with lower abdominal distention, pain in the knee and big toe, lumbar and spinal pain with a heavy, sinking sensation..

He-Sea PointLower He-Sea Point of the BladderCommand Point

Clinical notes

Weizhong is a primary point for acute and chronic lumbar pain, sciatica, and knee disorders, famously summarized by the saying 'for lumbar and back problems, seek Weizhong.' The classical texts emphasize bloodletting this point, especially for heat conditions, chronic skin diseases, and severe pain along the Bladder channel. Its function as the Bladder's Lower He-Sea point also makes it effective for urinary disorders like retention and incontinence.

On the Bladder channel

BL40 is one of 67 points on the Bladder Meridian. Nearby points:

Frequently asked questions

Where is BL40 located?

BL40 (Weizhong) is located at the midpoint of the transverse popliteal crease, in the depression between the tendons of biceps femoris and semitendinosus. The point is best located with the knee slightly flexed.

What is BL40 used for?

BL40 benefits the lumbar spine and knees, clears heat and cools the blood, dispels blood stasis, resolves dampness, and alleviates pain. Common clinical indications include lumbar pain, lumbar pain radiating up the spine to the head, heavy and painful conditions of the lumbar region and legs, chronic stubborn rashes, genital twitching, urinary incontinence, difficult urination, tight sinews, epilepsy with opisthotonos, heat illness with lack of sweating, hot feet with reversal, inability to bend or extend the knee, lower abdominal fullness, urinary retention, hemorrhoids, pain in the perineal region, leprosy with loss of eyebrows, fever, lumbar and spinal pain, lower back heaviness and inability to lift the body, wind-damp impediment (Bi syndrome), pain in the hip joint, heat in the four limbs during febrile disease, bladder diseases, lower back pain like it is broken, inability to bend the hip, popliteal fossa feeling knotted, calf feeling like it's being torn apart, pain in the neck, back, lumbar, sacrum, popliteal fossa, calf, and foot, urinary retention with lower abdominal distention, pain in the knee and big toe, lumbar and spinal pain with a heavy, sinking sensation.

How is BL40 needled?

Perpendicular insertion 1.0 to 1.5 cun, or prick the popliteal vein to cause bleeding. Avoid deep insertion to prevent injury to the popliteal artery and nerve. Caution: The Zhen Jiu Ju Ying warns: 'Puncturing the large vessel in the center can cause a person to collapse and lose color.' This refers to the popliteal artery.

Which meridian is BL40 on?

BL40 is a point on the Bladder Meridian (Zú Tài Yáng Páng Guāng Jīng).

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⚠️ This page is for general education and is not medical advice. Acupuncture is a traditional practice; evidence varies by condition and study quality, and individual results differ. It does not replace diagnosis or treatment by a licensed professional. Always consult a qualified acupuncturist or physician.