Yinmen (BL37): The Back-of-Thigh Point for Sciatic Ache and Tight Hamstrings

Where Yinmen Sits

This point sits in the middle of the back of the thigh, on a straight line down from the middle of the buttock crease, a little less than halfway to the back of the knee. It lies in the soft groove between the two main hamstring muscles, right over the path of the large nerve of the leg.

It belongs to the line that Vietnamese and Chinese texts call the Bladder channel. That line starts at the inner corner of the eye, travels over the head and down both sides of the spine, then crosses the buttock and runs down the back of the leg to the little toe. On the thigh it makes only two stops. The first is in the buttock crease. This is the second, and it is the only point in the whole middle stretch of the back of the thigh.

The old texts place it six units below the buttock point. The unit here is a body-relative measure. The standard from the World Health Organization divides the back of the thigh, from the buttock crease to the crease behind the knee, into fourteen equal units. Six of them is a little less than half. For most people, two hand-widths laid flat one under the other, starting at the buttock crease, land close to the spot. You do not need to be exact. The probing in the next sections finds the precise place.

Under the skin, two muscles run side by side here. On the outer side is the outer hamstring (the biceps femoris). On the inner side is the inner hamstring (the semitendinosus), with a flatter partner beneath it. Between them runs a groove you can feel when the leg is relaxed. Deep in that groove lies the sciatic nerve, the largest nerve in the body, still a single thick cord at this level. It splits into its two branches a little lower, above the knee. The skin over the point is served by a thin nerve to the back of the thigh, from the second sacral root. That is why a firm press right in the groove can send a tingle downward, and why pressing slightly to one side, into the muscle, is kinder.

Why This Spot

On the anatomical side, the back of the thigh carries a heavy load. The hamstrings bend the knee, straighten the hip and hold you steady every time you lean forward to pick something up. They also shorten with years of sitting. Short, tight hamstrings pull on the pelvis and often take part in low back pain. When the sciatic nerve is irritated higher up, the tissue along its path frequently turns tender too, and this is the middle of that path. People with a sciatic ache often feel a band of soreness right here.

In this tradition, the line this point sits on carries the flow of the whole back of the body. Pain along the back of the leg is read as a sign that the flow has stalled somewhere on that line. This point stands in the long empty stretch between the buttock and the knee, so it is used to keep the line open when pain sits in the middle of the thigh.

The name describes the place. The back of the thigh is the fullest, most fleshy part of the leg, and the point is the gate through it. In Vietnamese the name Ân Môn carries the same meaning.

What the Old Texts Say About Yinmen

The Systematic Classic of Acupuncture and Moxibustion, the Jiayi Jing, written by Huangfu Mi in the third century, places this point six units below the point in the buttock crease. Like its neighbour, its position has stayed steady through the centuries. The classic tradition relied on the body's own proportions rather than rulers, so the distance grows and shrinks with each person, which is why a tall man and a small woman can both use the same description.

The Vietnamese handbook of points and channels by Ngô Trung Triều, published by Hồng Đức, lists it for pain in the low back and thigh, for disc problems in the low back, and for weakness of the lower limbs. Its method of finding is plain: in the groove between the inner hamstring and the outer hamstring, six units below the buttock crease. That is the method used on this page.

Notice how the handbook's list stays on one theme. The back, the disc, the thigh, the leg: every entry lies along the road the ache travels. In the wider tradition, this point is one stop in a sequence that teachers walk down the back of the leg, from the buttock to the heel. The idea is that pain which travels should be met along its whole route, gently, rather than attacked in one place. That reputation comes from long use, not proof. It is still a sensible way to work.

Points That Work With Yinmen

The first partner sits directly above, in the middle of the crease where the buttock meets the thigh, in line with the bony point you sit on. It is pressed by sitting on a tennis ball. In this tradition the two are worked together when the ache starts in the buttock and runs down the thigh.

The second sits in the middle of the crease at the back of the knee. Bend the knee a little and feel for the soft centre of the crease, between the two tendons. It is one of the most used points for back and leg pain in this tradition and is often the next stop after this one.

The third is on the back of the lower leg, where the two bellies of the calf muscle part and form a small inverted V, about halfway between the knee and the heel. It is used when the ache carries on past the knee into a tight calf.

How to Find and Press Yinmen

Getting Into Position

Sit on a firm chair and rest the heel of one foot on a low stool or a thick book, so the back of that thigh lifts off the seat and the muscles go soft. Keep the knee slightly bent. If reaching under the thigh is hard, lie on your back on a firm surface with the knee bent and slide a tennis ball under the middle of the thigh instead.

How to Find It

Reach behind and find the crease under the buttock, at its middle. Lay one hand flat below the crease, and the other hand flat below the first. The lower edge of your second hand, on the midline of the thigh, is the area. Run your fingertips side to side there and you will feel a soft groove between two firmer muscles.

Probe that groove with a rounded-tip pressing tool, or the tip of your thumb with the nail cut short, not the flat pad. Move in small steps, up and down the groove and a little to each side. Most of it will feel like ordinary muscle. One spot will sting: a small, sharp, pinpoint tenderness. That spot is the point. If you feel tingling or an electric line running toward the knee or calf, you are on the nerve. Lift off, move a fingertip's width to one side, and press more gently.

How to Press It

Keep the tip on the stinging spot and rub in small circles about the size of a fingernail, roughly one each second. Aim the pressure straight into the thigh, toward the front of the leg. Use your other hand to steady the thigh or to support the hand that presses. Keep the tip on the same spot; do not let it slide along the muscle. If your thumb tires, switch to the tool.

How Much Pressure

A sharp sting under the tip is right. When you lift off, it should fade within moments. If the pain stays after you lift off, if it spreads, or if the area turns swollen, hot or red, stop and leave it for several days. Stop at once for any tingling or numbness. If you are holding your breath, you are pressing too hard. Ease off until you can breathe slowly through the sting.

How Long

One to three minutes on each leg. In the first sessions keep to about one minute, because this point is often tender at the start. As the days go on, add a little time, up to three minutes. Do both legs, even when only one side complains. Once or twice a day is plenty. Pressing longer does not add benefit; it mostly adds soreness.

When to Do It

Morning suits a thigh and back that are stiff on waking. Late afternoon suits an ache that builds after long sitting or driving. Before bed is a good time too, as part of winding down. Do not press in the middle of the night. If the ache wakes you, pressing then tends to wake you further. Keep it for the day and the evening.

What This Won't Do

It will not change the reason your leg hurts. Most sciatic pain begins in the lower back, where a nerve root is pressed by a worn disc, a narrowed channel in the spine, or thickened joints. Some comes from muscles deep in the buttock. A point in the middle of the thigh cannot reach any of that. Tight hamstrings will not lengthen from pressing alone either; they respond to regular gentle stretching and walking. What this point can offer is local relief for tender, tight tissue, and a way to take part in your own care each day.

Some leg pain is an emergency. Go to hospital the same day if you have numbness in the saddle area, between the legs or around the back passage, or any new loss of control of your bladder or bowels. Get seen urgently, too, for a leg or foot that turns weak, a foot that drags or catches, or numbness that keeps spreading. A thigh or calf that is suddenly swollen, warm and painful can mean a clot in a deep vein and needs urgent assessment, not pressure. See a doctor promptly for leg pain after a fall, pain with fever or unexplained weight loss, or pain that worsens week on week.

Safety First

Do not press over skin that is broken, infected, badly bruised or rashy. Leave the area alone with a recent hamstring tear, a fresh bruise in the muscle, unexplained swelling, or a lump in the thigh. If you take blood thinners, bruise easily, have a bleeding disorder or have reduced feeling in your legs, use lighter pressure, keep sessions short, and talk to your doctor first.

Stop at once if pain stays after you lift off, spreads, or brings tingling or numbness. Nothing here asks you to push through pain. For the full list of cautions and the situations where pressing on yourself is not appropriate, read the full safety guide before you begin.

Questions People Ask

Where is the Yinmen (BL37) pressure point? Yinmen (BL37) sits in the middle of the back of the thigh, on a straight line down from the middle of the buttock crease. It is a little less than halfway from that crease to the back of the knee, roughly two hand-widths down. It lies in the soft groove between the two hamstring muscles. In Vietnamese it is called Ân Môn.

Can I reach Yinmen with my own hand? Usually yes. Sit on a firm chair with your heel on a low stool so the back of the thigh lifts off the seat. Reach under the thigh with the tip of your thumb or a rounded-tip tool. If your hands are weak, sit on a tennis ball placed under the middle of the thigh and let your weight do the work.

Is Yinmen (BL37) used for sciatica? In this tradition it is commonly used for sciatic ache and for low back pain that runs into the back of the thigh. It sits right over the path of the large nerve of the leg. It can ease tight, tender tissue along that path. It does not change what is irritating the nerve higher up in the back.

How long should I press Yinmen? One to three minutes on each leg. Keep the first sessions to about a minute, then add a little time as the days go on, up to three. Once or twice a day is plenty. Work both legs, even if only one side aches.

I feel a tingle down to my calf. Is that normal? No. Stop and lift off. The sciatic nerve runs deep under this point, and tingling or an electric feeling means you have pressed onto it. Move your tool a little to one side, into the muscle, and use less force. The feeling you want is a small sting under the tip, nothing that travels.

What does the name Yinmen mean? It is usually translated as Gate of Abundance. The back of the thigh is the fullest, most fleshy part of the leg, and the point sits in the middle of it like a gate in a thick wall. The Vietnamese name, Ân Môn, carries the same idea.

Other Points in This Library

Each of these sits within reach of the same hand. They are often worked in the same sitting.

This page shares general information about a traditional practice. It is not medical advice and does not replace what your doctor has given you. If you are pregnant, managing a health condition, or unsure whether this applies to you, check with your doctor first.

The whole inner edge of the foot, laid out on one page with photographs, is in The Foot Map — the free book. For every point in this library, see the full pressure point index.

(Point shown: BL37 · Yinmen · Gate of Abundance · Ân Môn.)