BL-36 (Cheng Fu) Support

What does BL-36 Cheng Fu do?

BL-36 activates the channel, relaxes the sinews and alleviates pain; regulates the lower jiao and alleviates pain; and treats haemorrhoids. It sits in the crease under the buttock, at the top of the Bladder channel’s run down the back of the leg.

• Activates the channel, relaxes the sinews and alleviates pain — the channel action, and the everyday one
• Regulates the lower jiao and alleviates pain
• Treats haemorrhoids — a named condition stated as an action

The haemorrhoid action puts it in a specific group. Querying our own action records, seven points name haemorrhoids in the action field itself rather than leaving them to the indication list: BL-35, BL-36, BL-54, BL-57, BL-58, DU-01 and the extra point Er Bai. Five of the seven are Bladder-channel points running from the coccyx down the back of the leg, and BL-36 is the highest of that leg group. The classical account has the channel’s course through the anal region as the reason.

Why this point, and the two below it, are about the leg above all. BL-36, BL-37 Yin Men and BL-40 Wei Zhong lie in a straight line down the back of the thigh, and their recorded indications are dominated by pain, numbness, weakness and impaired movement of the lower limb. That is the territory of the sciatic nerve, which runs beneath them — a correspondence between the classical channel line and a named anatomical structure that is unusually direct, and it is stated here as a correspondence rather than a mechanism.

On the name. “Cheng Fu” means Support — cheng is to receive or bear, the same character as in BL-57 Cheng Shan (Support the Mountain) on the calf and ST-01 Cheng Qi (Container of Tears) under the eye. Here it reads as the point that bears the weight of the trunk, at the fold where the buttock meets the thigh.

Source: Sacred Lotus sources & references (channel, action and location records; every action record naming haemorrhoids counted, and the BL-37, BL-40, BL-57 and ST-01 records queried, against our own data), cross-referenced against multiple online sources.

What is BL-36 Cheng Fu used for?

BL-36 is used for pain in the lower back and buttock, for wasting, pain, numbness and impaired movement of the leg, and for constipation. Our own indication record is reproduced here in full.

• Pain in the lower back and gluteal region
• Muscular atrophy of the lower extremities
• Pain of the lower extremities
• Numbness of the lower extremities
• Motor impairment of the lower extremities
• Constipation

Five of the six describe one thing: the back of the leg. Pain, numbness, weakness and wasting from the buttock downward is the classic presentation of nerve involvement in this territory, and BL-36 sits directly over the sciatic nerve at the gluteal crease. Constipation is the outlier, and it belongs with the lower-jiao action and the anorectal grouping the channel carries here.

An honest note, and it is the most important passage on this page. Leg pain with numbness or weakness requires medical assessment. The combination in this indication list — back pain, buttock pain, and pain, numbness, weakness or wasting down the leg — describes possible nerve-root compression, and if it is accompanied by numbness in the saddle region, weakness in both legs, or any change in bladder or bowel control it is a MEDICAL EMERGENCY requiring immediate care. Progressive weakness or visible wasting of a limb likewise needs prompt assessment. This record documents classical use; nothing here should delay any of that.

How it is combined. With BL-37 Yin Men below on the thigh and BL-40 Wei Zhong behind the knee — the three lie on one line. With GB-30 Huan Tiao in the buttock, the classical point for this territory. With BL-23 Shen Shu and BL-25 Da Chang Shu on the low back. With BL-57 and DU-01 for the haemorrhoid indication. All held here.

Source: Sacred Lotus sources & references (indication and action records; the BL-23, BL-25, BL-37, BL-40, BL-57, DU-01 and GB-30 records queried from our own data), cross-referenced against multiple online sources.

Where is BL-36 Cheng Fu located?

BL-36 is in the middle of the crease under the buttock — the transverse gluteal crease — directly above BL-40 in the back of the knee.

• In the centre of the transverse gluteal crease, in the depression between the hamstring muscles
• On a line directly superior to BL-40 Wei Zhong, which defines the vertical
• BL-37 Yin Men lies 6 cun below it on the same line

Two landmarks, and both are real. The gluteal crease is a visible fold, and BL-40 is at the midpoint of the crease behind the knee — so BL-36 is fixed by a horizontal feature and a vertical line, neither of which requires counting or proportional measurement. That is unusually secure for a point on the limb.

A measurement worth checking, because it confirms itself. Our own records place BL-37 six cun below BL-36 and eight cun above BL-40. Those sum to fourteen cun from the gluteal crease to the back of the knee — which is exactly the standard proportional measure for the back of the thigh. Our two recorded distances are internally consistent with the proportional system they belong to, and a reader can verify that without leaving these pages.

A practical note. The gluteal crease is a private region of the body. Treatment here calls for the same standards of consent, draping and professional conduct that apply anywhere on the buttock or thigh. This record describes a location in a reference work.

On the name. “Cheng Fu” — Support. Positional and descriptive: the fold that bears the trunk.

Source: Sacred Lotus sources & references (location and translation records, retained unchanged; the BL-37 and BL-40 positions queried and their recorded distances summed and checked against the standard thigh proportion).

• A Manual of Acupuncture (p. 296): Just below the buttock, on a line directly superior to Weizhong BL-40, in the centre of the transverse gluteal crease in a depression between the hamstring muscles.
• Chinese Acupuncture and Moxibustion (p. 183): On the posterior side of the thigh, at the midpoint of the inferior gluteal crease.

How is BL-36 Cheng Fu needled?

Our own record states perpendicular insertion of 1.0–1.5 inches, with moxibustion applicable — among the deepest recorded ranges on this channel — and the structure that governs the point is the SCIATIC NERVE, which passes directly beneath the gluteal crease. 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, 1.0–1.5 inches. Compare 0.3–0.5 inch at the thoracic back points and 0.8–1.2 inches at the sacral liao points. The buttock and posterior thigh carry the thickest soft tissue on the body, which is why the recorded depths here are the largest in this stretch.
• Moxibustion: recorded as applicable.
• Regional anatomy: gluteus maximus lies above the crease and the hamstring group below it; the sciatic nerve passes deep to gluteus maximus and descends the back of the thigh close to the midline, lying beneath this point; the inferior gluteal vessels and the posterior cutaneous nerve of the thigh accompany it, and the ischial tuberosity lies medially above.

Hazard, stated proportionately and precisely. There is no body cavity here, no pleura and no great vessel — the recorded hazards of the trunk do not apply. What is present is the largest nerve in the body, directly beneath, and the sensation of contacting it is distinctive and immediate. That is the reason the recorded depth has a stated top rather than being open-ended, and it is why this point is not comparable to a shallow back point despite both being “on the Bladder channel”.

What is not claimed. No study measuring a safe depth at BL-36 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 buttock or leg. No case report naming BL-36 was located, and none is asserted.

Source: Sacred Lotus sources & references (needling record, retained unchanged, and the recorded depths at the thoracic, sacral and thigh points compared; the point list of PMID 26922245 / PMC4769822 confirmed not to include BL-36), cross-referenced against multiple online sources; regional anatomy from standard anatomical description.

Is there research on BL-36, and what should a reader know?

No trial isolates BL-36. Where the point appears it is one component of a sciatica or low-back protocol, and a study that includes a point in a protocol is not evidence about that point.

Sciatica protocols are where a reader will meet this point, almost always alongside GB-30 Huan Tiao, BL-40 Wei Zhong and BL-23 Shen Shu. Evidence about a protocol is not evidence about a point within it, and none of that literature is claimed here.

What this page can state with confidence. BL-36 sits in the centre of the gluteal crease on a vertical line above BL-40 — two real landmarks, no counting required. Its recorded depth of 1.0–1.5 inches is among the deepest on the channel, and the sciatic nerve lies directly beneath it, which is the fact that governs the point. Five of its six recorded indications describe the back of the leg. And our own recorded distances check out internally: BL-36 to BL-37 is 6 cun and BL-37 to BL-40 is 8 cun, summing to the standard 14-cun thigh measure.

A note on searching for it. “BL 36”, “UB 36” and “Chengfu” searches return protocol trials and unrelated material — Chengfu matches personal and place names. 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; the BL-37 and BL-40 distances summed and checked, and the haemorrhoid-action set counted, against our own data).