Weiyang (BL39): The Outer Back-of-Knee Point for Tight Calves and a Sore Back

Where Weiyang Sits

This point sits on the crease behind the knee, toward the outer side, right inside the firm tendon that forms the outer edge of the back of the knee.

The line this point belongs to is the longest on the body. It starts at the inner corner of the eye, runs over the top of the head and down the back in two parallel strands beside the spine. The strands pass the buttock and the back of the thigh and meet at the back of the knee. From there the line runs down the middle of the calf, passes behind the outer ankle bone and ends at the little toe. Vietnamese and Chinese texts call it the Bladder channel. This is its thirty-ninth stop, on the outer strand, a short step before it joins the middle of the knee crease.

The old texts place it at the outer edge of the middle of the knee crease, between two tendons. The Vietnamese handbook gives an anatomical version: at the corner formed by the inner edge of the outer hamstring muscle and the inner edge of the outer head of the calf muscle, one body-inch outside the middle point of the knee crease, with the knee slightly bent. A body-inch here is close to the width of your thumb at the knuckle. The World Health Organization's 2008 standard says the same in short: on the knee crease, on the inner side of the outer hamstring tendon.

Underneath, the outer hamstring muscle (the biceps femoris) narrows into a firm tendon that runs down the outer back of the knee to the head of the thin outer leg bone. Below the crease, the outer head of the big calf muscle (the gastrocnemius) begins on the back of the thighbone. The point lies in the soft angle where these two meet. Deeper still, the back of the knee contains a pad of fat, the tibial nerve, and a large artery and vein, but these run closer to the middle of the knee.

The nerve that matters most here is the common fibular nerve. It leaves the large nerve of the back of the thigh and runs along the inner edge of the outer hamstring tendon, close to this point, before winding around the top of the outer leg bone. The skin is served by a branch of the nerve to the back of the thigh, from the upper sacral roots. This is why too much pressure against the tendon can send tingling down the outer leg.

Why This Spot

On the anatomical side, the back of the knee is where the hamstrings and the calf muscle meet. When the calves are tight or prone to cramp, the upper end of the calf muscle and the tendons around it are often tender. People who sit for long hours, or walk with stiff knees, tend to carry tension here. The outer tendon gives a clear landmark, and the spot inside it is easy to reach from a chair.

In this tradition the point carries a special role. It is the lower sea point of the triple burner, a system the tradition describes as governing the movement of water through the body. Lower sea points are placed on the legs, and each is said to connect with one of the hollow organs. That role is the reason old lists link this point with the passing of water as well as with the back and legs.

The name places it. The crook is the bend of the knee, where the middle point of the back of the knee sits. This point is on the outer, yang side of that crook. The Vietnamese name, Ủy Dương, carries the same meaning.

What the Old Texts Say About Weiyang

The Lingshu, the Spiritual Pivot, a Han-dynasty text, has a chapter on the lower sea points, the six places on the legs that connect to the hollow organs. It names this point as the lower sea point of the triple burner, placed at the outer side of the middle point of the knee crease. That makes it one of the few points on the back of the leg whose role was set in the oldest layer of the tradition.

The Vietnamese handbook of points and channels by Ngo Trung Trieu, published by Hong Duc, lists it for low back pain and for cramping of the calf muscle. It also carries an entry linked with the kidneys. That entry reflects the traditional link with water, not a medical finding, and it is never a reason to press instead of seeing a doctor. The first two entries are the ones that matter for pressing on yourself, and they follow the line of the channel down the back and into the calf.

The handbook's way of finding it is careful. Bend the knee slightly. Take the point at the top of the angle formed by the inner edge of the outer hamstring and the inner edge of the outer head of the calf muscle, one body-inch outside the middle of the crease. The method on this page uses the same landmarks in plainer words.

In the wider tradition, points behind the knee are the first ones teachers reach for when the lower back is stiff, following an old rule that the back is commanded from the back of the knee. That rule is usually applied to the middle point of the crease, and this point is its close neighbour. Long use rather than trials stands behind it, as with most points.

Points That Work With Weiyang

The first partner sits right next to it, in the middle of the crease behind the knee, halfway between the two tendons. In this tradition the two are commonly pressed together for a stiff lower back and tight hamstrings.

The second sits on the back of the calf. Point your toes and feel the two bellies of the calf muscle; where they part and form a soft dip, halfway down the back of the lower leg, is the point. It is used with this one when the calves are tight or cramp easily.

The third is on the outer side of the leg below the knee. Find the small, round bony knob on the outer leg and slide down and forward into the soft dip in front of it. It is used with this one when the whole leg feels tight, from the knee down.

How to Find and Press Weiyang

Getting Into Position

Sit on the front edge of a firm chair with the knee slightly bent and the heel resting on the floor. The back of the knee must be free, not pressed against the chair. If reaching behind the knee is hard, lie on your back with the knee bent and the foot flat, or sit on a bed with the knee raised on a pillow.

How to Find It

Reach behind the knee with your fingertips and find the crease that runs across the back of it. Follow it toward the outer side. Near the outer end, you will meet a firm, rope-like cord running up and down. If you cannot feel it, bend the knee a little more against the floor and it will tighten. Move your fingertip back onto the crease right inside that cord. The soft angle there, above the start of the calf muscle, is the area.

Now probe it with a rounded-tip pressing tool, or the tip of your thumb with the nail cut short. Move slowly in small steps. Most of it will feel like ordinary tissue. One spot will sting: a small, sharp, pinpoint tenderness. That spot is the point. If you feel tingling or an electric feeling down the outer leg, you are pressing on the nerve beside the tendon. Lift off, move a little toward the middle of the crease, and press more gently.

How to Press It

Keep the tip of the tool or thumb on the stinging spot and rub in small circles, about the size of a fingernail, roughly one each second. Aim the pressure forward, toward the front of the knee, not sideways into the tendon. Rest your other hand on the front of the knee to keep the leg still. Keep the tip on the same spot; do not let it slide.

How Much Pressure

Sharp under the tool is right. That small sting tells you that you are on the point. The test is what happens when you lift off: the sting should fade within moments. If the pain stays after you lift the tool, 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, numbness or throbbing. If you are holding your breath, you are pressing too hard.

How Long

Work each leg for one to three minutes. In the first sessions keep to about one minute, because the point is often most 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 is tight. Once or twice a day is plenty. Pressing longer does not add benefit; it mostly adds soreness.

When to Do It

Morning suits a back and legs that are stiff on waking. Late afternoon suits calves that have tightened after standing, walking or a long drive. Before bed is a good time too, especially if your calves are prone to cramp. Do not press in the middle of the night. If a cramp wakes you, pressing then tends to wake you further. Keep the pressing for the day and the evening.

What This Won't Do

It will not remove the reason your calves cramp or your back aches. Calf cramps often come from medicines, too little fluid, low levels of certain minerals, long hours of sitting, or calves that are never stretched. Low back pain often comes from stiff joints in the spine, weak trunk muscles, long sitting, or a disc that irritates a nerve. A point behind the knee cannot change any of that. Pressing works best alongside the plain things: a calf stretch before bed, regular walking, enough water, and gentle exercise for the back.

It will not replace a diagnosis either. One calf that is suddenly swollen, warm and painful needs urgent assessment, because it can mean a clot in a deep vein. A lump behind the knee that grows needs to be checked. Back pain with numbness in the groin, trouble passing water, or weakness in the legs needs urgent care. Back pain with fever, or with weight loss you cannot explain, belongs with a doctor. Cramps that come every night, or come with weakness, are worth a check too.

Safety First

Do not press over skin that is broken, burned, infected, badly bruised or rashy, or over bulging veins. Leave the area alone if there is a swelling or lump behind the knee, a recent injury, or a plate, pin or implant under the skin. Skip this point if the knee is hot and swollen, or if you had surgery on that knee recently. 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 the pain stays after you lift off, spreads, or if the area becomes swollen, hot or red. Stop too for any tingling or numbness down the leg. Nothing here requires 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 Weiyang (BL39) pressure point? Weiyang (BL39) sits on the crease behind the knee, toward the outer side. Bend the knee a little and feel the firm cord at the outer back of the knee; the point is on the crease right inside that cord. In English it is called the Outside of the Crook; in Vietnamese, Ủy Dương.

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

How is Weiyang (BL39) different from Weizhong (BL40)? Both sit on the crease behind the knee. Weizhong (BL40) is in the middle of the crease. Weiyang (BL39) is about a thumb-width toward the outer side, beside the outer tendon. They are often pressed in the same sitting.

Can it help a calf that cramps? The Vietnamese handbook lists cramping of the calf among its uses, and in this tradition it is commonly pressed for tight calves. Press it in the daytime and before bed, not during the night. Frequent cramps are worth mentioning to your doctor, since some medicines and low minerals can cause them.

I feel tingling down my leg when I press. Is that normal? No. Lift off. A nerve runs close to the outer tendon behind the knee, and tingling or an electric feeling means you are pressing on it. Move your tip a little toward the middle of the crease and press more gently. You want a small sting under the tip, nothing that travels.

Is it safe to press behind the knee? The middle of the back of the knee carries a large artery and vein, so keep to the spot beside the outer tendon and use moderate pressure. Do not press if there is a lump or swelling behind the knee, or if the calf is suddenly swollen and warm. Those need a doctor first.

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: BL39 · Weiyang · Outside of the Crook · Ủy Dương.)