BL39 Outside of the Crook

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

BL39 (Weiyang, “Outside of the Crook”) is the Lower He-Sea point of the Bladder Meridian. It is located on the posterior aspect of the knee, lateral to BL40 (Weizhong), on the medial border of the biceps femoris tendon. It relaxes sinews, invigorates channels, alleviates pain, benefits the bladder.

Location

On the posterior aspect of the knee, lateral to BL40 (Weizhong), on the medial border of the biceps femoris tendon.

Needling

Perpendicular insertion 1.0-2.0 cun.

TCM functions

Relaxes sinews, invigorates channels, alleviates pain, benefits the bladder.

Indications

Low back pain, stiffness of the hip, spasm of the gastrocnemius, retention of urine.

Lower He-Sea

Clinical notes

As the Lower He-Sea point of the Sanjiao (Triple Burner), Weiyang is important for regulating the water passages and treating disorders of the lower burner, especially urinary retention or difficulty. It also excels at relaxing sinews and invigorating channels in the popliteal region, making it useful for knee pain, sciatica, and stiffness in the lower back and leg. Its Lower He-Sea category links it to the Sanjiao's role in fluid metabolism.

On the Bladder channel

BL39 is one of 67 points on the Bladder Meridian. Nearby points:

Frequently asked questions

Where is BL39 located?

BL39 (Weiyang) is located on the posterior aspect of the knee, lateral to BL40 (Weizhong), on the medial border of the biceps femoris tendon.

What is BL39 used for?

BL39 relaxes sinews, invigorates channels, alleviates pain, benefits the bladder. Common clinical indications include low back pain, stiffness of the hip, spasm of the gastrocnemius, retention of urine.

How is BL39 needled?

Perpendicular insertion 1.0-2.0 cun.

Which meridian is BL39 on?

BL39 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.