BL-37 (Yin Men) Gate of Abundance

What does BL-37 Yin Men do?

BL-37 activates the channel and alleviates pain, and benefits the lumbar spine — the shortest action record of any point on the back of the leg, and entirely musculoskeletal.

• Activates the channel and alleviates pain
• Benefits the lumbar spine

Note what it does not carry. Its neighbour above, BL-36 Cheng Fu, records a lower-jiao action and an explicit haemorrhoid action; BL-40 Wei Zhong below records considerably more. BL-37 records neither — no organ action, no anorectal action, nothing outside the channel and the spine. It is the purest channel-and-pain point of the three, and this library states that rather than importing its neighbours’ range.

A point on the thigh that benefits the lumbar spine. That is the distal logic the Bladder channel is built on: the channel runs the whole length of the back and down the leg, so a point midway down the thigh reaches the low back along it. Our BL-40 record carries the classical status of this territory for the back, and BL-37 sits on the same line.

On the name. “Yin Men” means Gate of Abundance — men is a gate, the same character as in DU-04 Ming Men (Gate of Life) and BL-47 Hun Men (Hun Gate). Take care not to read the yin here as the yin of yin–yang: it is a different character, and the Bladder channel is a yang channel. Names on this channel are a recurring source of misreading — our BL-07 and BL-08 records document two others.

Source: Sacred Lotus sources & references (channel, action, location and translation records; the BL-07, BL-08, BL-36, BL-40, BL-47 and DU-04 records queried and compared against our own data), cross-referenced against multiple online sources.

What is BL-37 Yin Men used for?

BL-37 is used for pain in the lower back and thigh, for wasting, pain, numbness and impaired movement of the leg, and for hemiplegia. Our own indication record is reproduced here in full.

• Pain in the lower back and thigh
• Muscular atrophy of the lower extremities
• Pain of the lower extremities
• Numbness of the lower extremities
• Motor impairment of the lower extremities
• Hemiplegia

The whole list is one territory, and hemiplegia is the entry that reaches beyond it. Back, thigh and leg — pain, numbness, weakness, wasting — is the sciatic distribution the point sits over. Hemiplegia, paralysis of one side of the body, appears here as it does on several limb points in the classical literature, and it does not appear on BL-36 above.

An honest note, and it is the most important passage on this page. Hemiplegia — weakness or paralysis down one side — is most often the consequence of a stroke, and STROKE IS A MEDICAL EMERGENCY. Sudden weakness or numbness on one side, facial droop, difficulty speaking or sudden visual loss requires emergency medical care immediately; treatment given quickly changes outcomes and delay causes permanent harm. This record documents a classical indication in a historical system; it makes no claim that acupuncture treats stroke or its consequences, and nothing on this page should ever delay emergency care. Leg pain with numbness or weakness requires assessment, and back pain with saddle numbness, weakness in both legs or any change in bladder or bowel control is likewise an emergency.

How it is combined. With BL-36 Cheng Fu above and BL-40 Wei Zhong below — the three points of this line. With GB-30 Huan Tiao in the buttock and GB-34 Yang Ling Quan, the influential point for the sinews, on the lower leg. With BL-23 Shen Shu and BL-25 Da Chang Shu on the low back. All held here.

Source: Sacred Lotus sources & references (indication record; the BL-23, BL-25, BL-36, BL-40, GB-30 and GB-34 records queried and compared from our own data), cross-referenced against multiple online sources.

Where is BL-37 Yin Men located?

BL-37 is on the back of the thigh, in the groove between the hamstring muscles, six cun below BL-36 and eight cun above BL-40.

• In the depression between the hamstring muscles, on the midline of the back of the thigh
• 6 cun distal to BL-36 Cheng Fu at the gluteal crease
• 8 cun proximal to BL-40 Wei Zhong in the back of the knee

Our own record gives this point twice over, and the two agree. That is worth pausing on. Most points on a limb are given as a single measurement from one landmark, so an error in that measurement has nothing to check it against. BL-37 is given from both ends of the thigh — and 6 plus 8 is 14, which is exactly the standard proportional measure from the gluteal crease to the back of the knee. The two figures are internally consistent with the proportional system they belong to, and a reader can verify that without leaving these pages. Where our data checks itself, this library says so.

The groove between the hamstrings is a real landmark, and it becomes clearer when the knee is bent against resistance. Unlike the counting chains on the back, this point needs no vertebral count at all.

A practical note. The back of the thigh is a private region of the body, and treatment here calls for the same standards of consent, draping and professional conduct that apply anywhere on the buttock or thigh.

On the name. “Yin Men” — Gate of Abundance, the abundance being the thickness of the muscle it lies among. Positional.

Source: Sacred Lotus sources & references (location and translation records, retained unchanged; the BL-36 and BL-40 positions queried and the recorded distances summed and checked against the standard thigh proportion).

• A Manual of Acupuncture (p. 297): On the back of the thigh, in the depression between the hamstring muscles, 6 cun distal to Chengfu BL-36, and 8 cun proximal to Weizhong BL-40, on the line connecting Chengfu BL-36 and Weizhong BL-40.
• Chinese Acupuncture and Moxibustion (p. 183): 6 cun below Chengfu (BL-36) on the line joining Chengfu (BL-36) and Weizhong (BL-40).

How is BL-37 Yin Men needled?

Our own record states perpendicular insertion of 1.0–2.0 inches, with moxibustion applicable — the DEEPEST RECORDED RANGE OF ANY POINT IN THIS ENTIRE LIBRARY, confirmed by querying every recorded depth we hold — and the SCIATIC NERVE runs directly beneath. What follows is a neutral record of what the reference literature documents. It is not instruction, and this page does not teach technique.

• Angle and depth as recorded: perpendicular, 1.0–2.0 inches. For scale: 0.1 inch at the fingertip Jing-Well points, 0.3–0.5 inch at the thoracic back points, 0.8–1.2 inches at the sacral liao points, 1.0–1.5 inches at BL-36 above. The back of the thigh carries the thickest soft tissue of any point on this channel, and the recorded depths track that exactly.
• Moxibustion: recorded as applicable.
• Regional anatomy: biceps femoris lies laterally and semitendinosus and semimembranosus medially, with the groove between them overlying the point; the sciatic nerve descends the back of the thigh in that plane, directly beneath; the perforating branches of the profunda femoris artery cross the region, and the femur lies deep.

Hazard, stated proportionately and precisely. No body cavity, no pleura, no great vessel at the surface — none of the trunk hazards apply here. What is present is the largest nerve in the body, immediately beneath the recorded needle path, and the sensation of contacting it is distinctive and immediate. A recorded depth of up to two inches is not an invitation to depth; it is a measure of how much tissue lies above a structure that a reader should understand is there. The same relationship holds at BL-36 above.

What is not claimed. No study measuring a safe depth at BL-37 could be located, and none is borrowed. The paediatric CT study this library uses covers 23 points on the trunk and shoulder and does not reach the leg. No case report naming BL-37 was located, and none is asserted.

Source: Sacred Lotus sources & references (needling record, retained unchanged, and every recorded needling depth in our data queried and ranked, confirming BL-37 as the deepest; the point list of PMID 26922245 / PMC4769822 confirmed not to include BL-37), cross-referenced against multiple online sources; regional anatomy from standard anatomical description.

Is there research on BL-37, and what should a reader know?

No trial isolates BL-37. Where the point appears it is one component of a sciatica, low-back or post-stroke protocol, and a study that includes a point in a protocol is not evidence about that point.

Post-stroke rehabilitation is where a reader will most often meet this point, because of the hemiplegia indication — and it is the area where the gap between a classical indication and modern practice is widest. Nothing in this record should be read as suggesting that acupuncture treats stroke, and the emergency warning above is the operative statement on this page. Where trials exist they use multi-point protocols in a rehabilitation setting alongside conventional care, and none of that attaches to this point alone.

What this page can state with confidence. BL-37 has the deepest recorded needling range of any point in this library — 1.0–2.0 inches, and querying every recorded depth in our data returns no point reaching 2.0 inches other than this one — and the sciatic nerve lies directly beneath it. Its action record is the shortest of the three thigh points and entirely musculoskeletal — it carries none of BL-36’s lower-jiao or anorectal range. And our own two recorded distances, 6 cun below BL-36 and 8 cun above BL-40, sum to the standard 14-cun thigh measure, which means the record checks itself.

A note on searching for it. “BL 37”, “UB 37” and “Yinmen” searches return protocol trials and a large volume of unrelated material — Yinmen matches place names and personal names, and the syllable yin pulls in a great deal of yin–yang material that has nothing to do with this point, whose yin is a different character. Our library codes this channel BL- while some sources use UB-. Any claim attached to this point should be checked against what a study actually used.

Source: Sacred Lotus sources & references (action, indication, location and needling records; every recorded depth queried and ranked, and the BL-36 and BL-40 distances summed and checked, against our own data).