四瀆 Sidu
“Four Rivers” · TH9
Hand Shaoyang · 9 of 23
Where. On the back of the forearm, about seven finger-widths below the elbow tip, between the two bones.
For. Toothache; one-sided headache; aching, numb arm.
Press. Gentle fingertip pressure, about a minute each arm.
四瀆，在肘前五寸外廉陷者中按 · Press with me
Six slow breaths
About a minute. Press as you breathe out, ease as you breathe in.
鄰 · Neighbouring leaves
Where Sidu Sits on the Back of the Forearm
The dataset places Sidu on the dorsum of the forearm, on the line connecting Yangchi (TH4) and the tip of the elbow, five cun below the olecranon, between the radius and the ulna. Unpacked landmark by landmark: the dorsum is the back of the forearm — the face you see when your palm rests down; the olecranon is the bony point at the back of the elbow; and Yangchi waits at the far end of that line, in the hollow along the crease at the back of the wrist. Five cun below the olecranon means five proportional units measured down the line, away from the elbow toward the hand. A cun is taken from the person being examined rather than from a ruler, and the working conversion most teaching uses sets one thumb-width to one cun — so the instruction becomes: come down about five thumb-widths from the bony tip of the elbow.
The two bones named in the location give the point its address. The radius is the forearm bone on the thumb side; the ulna runs to the little-finger side. Between them — padded with muscle and crossed by tendons that move the fingers and wrist — lies a soft corridor running the length of the forearm’s back. Sidu sits inside that corridor, roughly midway between the two bones, nearer the elbow than the wrist. Nothing prominent marks the spot: no bump, no visible hollow. That is exactly why the tradition measures from landmarks instead — the elbow tip and the wrist crease never move, and the point keeps its place relative to them.
Sidu shares this corridor with the channel’s other forearm points, strung along the same line between wrist and elbow like towns on one road. The next station toward the hand is Sanyangluo (TH8); beyond Sidu, around the bony elbow tip itself, sits Tianjing (TH10). Knowing the company helps orientation more than precision does: once you have found the line and the groove between the bones anywhere along this stretch, you are within reach of the family, and counting thumb-widths down from the elbow settles which station is which.
A Self-Palpation Walkthrough
Sit comfortably and lay one forearm on a table, palm down, so the muscles soften. First find the bony point at the back of the elbow — the olecranon. Next find Yangchi: where hand meets forearm at the back of the wrist runs a broad crease, and within it a small hollow lying just to the little-finger side of the cord-like tendon that straightens the fingers. Then imagine a straight line joining that wrist hollow to the elbow tip. Walk your fingertips from the elbow tip down the line, about five thumb-widths, and let them settle into the soft channel running between the two forearm bones: this is where Sidu lies.
A few confirmations help before any pressing begins. Roll the hand slowly from palm-down to palm-up and back again: the tendons glide under the skin, but the groove between radius and ulna stays fixed beneath your fingertip — a useful proof that you are in the corridor and not on a moving tendon. Compare sides with feather-light touch; many people notice a faint, dull awareness at the true point and little sensation a finger-width away. If you land on bare bone, ease sideways about half a thumb-width until the fingertip rests in soft tissue between the bones. If everything feels wrong, return to the elbow tip and count down once more, slowly.
The classic mistakes are mostly directional. Counting upward from the wrist instead of downward from the elbow leaves you short, because the measurement descends from the olecranon. Drifting toward the palm side loses the point entirely — Sidu belongs to the back surface of the forearm. And pressing on the edge of a bone rather than in the space between them turns gentle work into bruising work. When in doubt, retrace the whole sequence from landmarks: elbow tip, line, five counts, groove.
Reading the Name: Four Rivers
Si 四 means four. Du 瀆 is an old word for a great watercourse — at once a river channel and the idea of water moving freely in its own bed. Traditional Chinese geography gave the name Four Du to four great waterways — the Yangtze, the Yellow River, the Huai, and the Ji — honoured precisely because each ran in its own channel all the way to the sea. Lending that name to a point on the forearm announces an ambition of flow: a place where the movement of qi and blood is restored to something that had stopped moving.
The setting explains the metaphor. Here the channel travels the long groove between radius and ulna like a river between banks, and its neighbours keep the waterside imagery going all the way up the arm. From the fingers upward the images widen: a fluid gate (Yemen, TH2), a central islet (Zhongzhu, TH3), a yang pool (Yangchi, TH4), a branch ditch (Zhigou, TH6), then these four rivers, before the line climbs past a celestial well (Tianjing, TH10) and a clear cold abyss (Qinglengyuan, TH11) toward the shoulder. Classical texts also describe the san jiao as an official entrusted with dredging the body’s waterways, which makes the point’s name read like a job description: keep the channel open.
Pinyin renders the name Sìdú. Si carries the falling fourth tone, a firm drop that gives “four” its decisive ring; du rises on the second tone, lifting like water beginning to move. The two hanzi 四瀆 fit in a glance, and like gates, pools, wells, and ditches elsewhere in the repertoire, the name compresses an instruction into two characters: treat this stretch of the body as a waterway to be kept open, not a knot to be forced apart.
Traditional Indications, Explained
The recorded indications read: pain and numbness of the arm; sudden loss of voice; deafness; toothache; one-sided headache; and paralysis of the upper limb — six entries in all. Framed as tradition rather than promise, classical practice reached for points along the forearm when the arm itself complained: aching, heaviness, numbness, and pins-and-needles sensations were approached wherever the channel passed nearby, and paralysis of the limb belonged to the broader classical project of coaxing strength back into a weak or unresponsive arm. Sudden loss of voice was a distinct traditional category — speech failing abruptly while the person remained otherwise themselves — and it stands at the head of this point’s historic portfolio.
The head-and-face entries make sense only on the map. The san jiao channel begins at the ring finger, climbs the outer arm past the shoulder, and threads upward across the side of the head; the catalogue’s later stations tell the story, with an Ear Gate (Ermen, TH21) in front of the ear near the end of the line and a final point, Sizhukong (TH23), at the outer tail of the eyebrow. A pathway that walked past ear, jaw, cheek, and brow was classically read as a route along which troubles of hearing, voice, teeth, and one-sided headache could be addressed from a distance — which is how a mid-forearm point came to carry so cosmopolitan a caseload. This distant-station logic is the working grammar of classical point selection, not a modern physiological claim.
It bears repeating plainly: these are traditional uses recorded in a licensed dataset and classical literature, offered here for cultural and historical understanding. They are not claims that pressing this point treats disease, and nothing here replaces assessment by a qualified clinician. Where modern research touches self-applied pressure at all, reviews suggest effects are modest and context-dependent, and evidence tied to any single point remains thin. Hold the tradition lightly, and hold the safety rules firmly.
Self-Care Acupressure at Home
With the point located by the walkthrough above, settle into position: seated or standing, shoulders easy, forearm supported palm-down. Rest the pad of your opposite thumb on the spot and begin with contact alone for a few breaths, then add small, slow circles, letting the skin glide over the tissue between the bones rather than grinding against either one. Pressure should register as pleasant dullness or mild warmth, never sharpness. A common home rhythm is one to three minutes per side, once or twice daily, matched where possible to slow exhales so each circle rides the breath out. Swap hands and repeat on the other side, keeping the two sessions symmetrical.
Quality matters more than duration. Light, patient, regularly repeated contact fits the wellness register this page practises; hard jabbing teaches the body nothing and risks bruising. Warm cold hands first, because chilled muscle guards. Choose a quiet corner over a screen, since the practice doubles as a pause: inhale through the nose, feel the forearm soften under still fingers, press gently on the long exhale. People who keep a routine often anchor it to an existing habit — morning coffee, an afternoon stretch, the commute home — because the forearm asks no special setting, and consistency, not intensity, is what self-care traditions actually request.
Treat the exercise as a small ceremony of attention rather than a treatment session. Across weeks, notice what changes: perhaps the forearm feels less heavy after long days at a keyboard, perhaps your sense of the two bones and the channel between them sharpens, perhaps nothing shifts except that you spend ninety unhurried seconds attending to yourself. Every one of those outcomes fits the honest scope of self-acupressure. What does not fit is escalation — pressing harder, longer, or deeper to force a result. When curiosity pulls that way, return to gentleness, or simply stop for the day.
Cautions and Safe Practice
Compared with sites like the chest wall, the back of the forearm offers forgiving terrain: muscle padding over two sturdy bones, far from the lungs and major organs, and gentle surface work here is generally well tolerated by healthy adults. Tolerance, though, is not licence for force. The intention stays in skin and superficial muscle; tools, elbows, and knuckles stay out of the picture; and pressure never drives hard inward toward either bone, however satisfying the dull ache may feel at first.
Practical skips follow ordinary common sense. Set the point aside over broken, irritated, or inflamed skin; after a recent forearm fracture, sprain, or surgery, wait until a clinician has cleared ordinary activity; and be cautious with any unexplained swelling in the area. Pregnant readers, and anyone managing a chronic condition, should consult a qualified practitioner before adding new point practices. During pressing, sharp, electric, or radiating sensation means stop at once and do not try again that day; tingling or numbness creeping into the fingers means easing off and shortening the next session.
And the wider rule stands over everything: this page is educational, and acupressure is self-care, not diagnosis or therapy. Seek prompt medical care — not a pressure routine — for sudden unexplained hearing loss or ringing, abrupt loss of the voice, new weakness or numbness in an arm or hand, or a headache unlike anything you have felt before. Persistent symptoms of any kind belong with a licensed practitioner, whether Western or East Asian medicine suits the complaint. Four rivers make a fine image; the safest flow they can teach is knowing when to hand your care to someone qualified.
Sidu, the Four Rivers, holds a middle reach of the san jiao channel where it crosses the back of the forearm. Classical practice reached for this point when the arm ached or went numb, when the voice failed without warning, or when hearing dimmed. This guide walks through finding it in the groove between the two forearm bones and pressing it gently at home.
Self-care limits
Frequently asked
- How do I find Sidu without knowing anything about cun?
- Use the elbow as the anchor. Find the bony point at the back of the elbow, find the small hollow at the centre-back of the wrist, imagine a straight line joining the two, then come down the line about five thumb-widths from the elbow tip and feel for the soft channel between the two forearm bones. Cun measurements simply encode that same landmark walk in proportional language — one thumb-width to one cun is the conversion most teaching uses.
- Is pressing Sidu myself actually safe?
- Gentle fingertip pressure on the padded back of the forearm is generally reasonable self-care for healthy adults — the site sits over muscle and bone, well away from delicate structures. Keep the work superficial, use finger pads only, and respect the stop signals: sharp or electric sensation, worsening pain, or numbness spreading into the hand all mean finish immediately and try again another day, more lightly.
- What did classical practice use Sidu for?
- The traditional record lists pain and numbness of the arm, sudden loss of voice, deafness, toothache, one-sided headache, and paralysis of the upper limb. Classical teaching gathered head-and-face complaints onto this stretch of channel because the pathway passes the ear and the brow higher up — a distance-addressing logic, not a modern clinical claim. These entries are documented for cultural context, not offered as evidence-backed treatment promises.
- Why would a forearm point have anything to do with ears, voice, or headaches?
- In the classical map, points act like stations on a route, and a route that climbs from the ring finger up the outer arm to the temple passes regions where those complaints live — later points on this same channel sit in front of the ear and at the outer tail of the eyebrow. Working a lower station was traditionally understood to influence conditions along its own route. It is an elegant framework worth understanding on its own terms, quite apart from any question of treatment outcomes.
- Can acupressure at Sidu replace seeing a doctor?
- No. Self-acupressure is a comfort practice, not a diagnostic tool. Sudden hearing changes, abrupt loss of voice, new weakness or numbness of a limb, or a severe unusual headache need prompt professional assessment, not a pressure session. Think of the two as different trades sharing one workshop: daily self-care keeps its hands busy downstairs, and clinical medicine works the consulting room upstairs that you visit when symptoms persist, worsen, or frighten you. Neither substitutes for the other.
Sources
- 01WHO Standard Acupuncture Point Locations in the Western Pacific Region (2008), World Health Organization — nomenclature conventions.
- 02A Manual of Acupuncture, Peter Deadman, Mazin Al-Khafaji and Kevin Baker — point-name tradition, waterway imagery, and channel context.
- 03aijiu-mpvue (MIT License) licensed dataset, entry for TH9 Sidu — location, point class, actions, and indication record.
Last reviewed
牌記This leaf, for machines
Old books ended with a colophon saying who printed them. Every leaf here carries the same facts as structured data for agents and search, with no layout in the way.
- GET /en/points/th9/leaf.json
- GET /zh-hant/points/th9/leaf.json
- GET /zh-cn/points/th9/leaf.json
- /llms.txt — the index of every leaf
- JSON-LD in the page: MedicalWebPage, MedicalEntity and FAQPage
{
"id": "TH9",
"name": {
"en": "Sidu",
"gloss": "Four Rivers",
"zh-Hant": "四瀆",
"zh-Hans": "四渎"
},
"channel": {
"id": "TH",
"order": 9,
"of": 23
},
"location": {
"text": "On the back of the forearm, about seven finger-widths below the elbow tip, between the two bones."
},
"for": [
"toothache",
"one-sided headache",
"aching",
"numb arm"
],
"press": {
"text": "Gentle fingertip pressure, about a minute each arm.",
"seconds": 60,
"sides": "both"
},
"cautions": [],
"source": "Zhenjiu Jiayi Jing, book 3",
"url": "https://acupoints.com/en/points/th9",
"lastReviewed": "2026-08-24"
}