Armpit Pain: Muscle Causes and When to Get It Checked

Armpit pain is often not about the armpit at all. The ache you feel there usually comes from muscles and tendons nearby, and once you know which ones, the pain starts to make more sense. This page covers the common muscle causes, a short note on skin causes, and the signs that mean you should get it checked.

The armpit is a crowded space. Several muscles meet there, nerves and lymph nodes pass through it, and your arm moves in every direction around it. So pain from the shoulder, chest or ribs can easily show up in the armpit.

Muscle causes of armpit pain

Here are the usual suspects. Each one can make the armpit ache, or feel sore when you press on it.

The chest muscle (pectoralis). The pec runs from your breastbone to your upper arm, and its lower edge forms the front wall of the armpit. When it is tight or overworked, the front of the armpit can feel tender. Long hours at a desk, carrying heavy bags, or a lot of push ups can all load it. Our guide to tight chest muscles explains how to tell if chest tightness is muscular.

The lat (latissimus dorsi). This is the large, flat muscle on your back. It wraps around your side and forms the back wall of the armpit. Reaching overhead, pulling, swimming or climbing can strain it. If the ache runs from the armpit down the side of your ribs, the lat is a good candidate. There is more in our page on the latissimus dorsi stretch.

The serratus muscle. The serratus anterior sits on the side of your ribs, under the armpit, and holds your shoulder blade in place. When it works hard, for example after a lot of reaching or lifting, you can feel a deep ache or a sore, ridged feeling along the ribs.

Shoulder tendons. The small muscles around the shoulder joint, called the rotator cuff, can send pain toward the armpit, especially when you lift your arm out to the side. A stiff, sore shoulder can do the same. If your shoulder has also become hard to move, our page on frozen shoulder stretches is the place to start.

Overuse after something new. A new exercise class, a day of painting a ceiling, a long drive with your hands on the wheel, moving boxes: these are all very common starting points. The pain often shows up a day later and usually matches what you did.

A quick note on skin causes

Not every armpit pain is a muscle. Everyday skin causes are common too. Shaving can leave a rash or small sore bumps. A sweat gland can get blocked and irritated. These usually look different from muscle pain: you can see a red patch or small bumps, and the soreness stays in one small spot rather than moving with your arm.

If the skin is clearly the problem, it is a matter for a pharmacist or doctor. The rest of this page is about the muscle kind.

Swollen lymph nodes: the get it checked category

Your armpit holds lymph nodes. These are small glands that are part of your immune system. They can swell when you have an infection, and they can feel like a tender lump under the skin.

Swollen glands from an infection usually get better by themselves within 1 to 2 weeks (NHS, 2023). The NHS advises seeing a GP if swollen glands are getting bigger or have not gone down within a week. A lump that has not settled, or that is changing, is something to have a doctor look at. This page cannot tell you what a lump is, and no website can.

Red flags: when to get help

Please do not try to work out these signs on your own.

• A lump that has not gone down within about a week, feels hard or fixed in place, or keeps growing. See a doctor. The same goes for a lump with no sign of infection, or any new change in your breast.
• Night sweats, a high temperature, or weight loss you cannot explain. See a doctor.
• Redness or heat over the area. See a doctor soon.
• Swelling with trouble breathing or swallowing. Get urgent help now.
• Armpit or arm pain with chest pressure, shortness of breath, sweating or nausea. Call emergency services now. Pain from the heart can show up in the arm or armpit.

If none of these fit and the ache moves with your arm, a muscle cause is more likely. It is still reasonable to ask a doctor if you are unsure.

How to tell a muscle ache from something else

A muscle ache usually has a few features. It changes when you move your arm, lift something, twist or breathe deeply. It is tender when you press on the muscle. It often began after a particular activity. And it tends to ease a little when you rest in a comfortable position.

Pain that does not change with movement, that wakes you at night, or that comes with a lump or other symptoms is a reason to call a doctor.

What may help a muscle related ache

If a muscle cause seems likely, start with simple things. Pause the activity that set it off for a few days. Keep using the arm in comfortable ranges rather than holding it still, since muscles often do better with gentle use than with total rest. Warmth, such as a warm shower, feels good to many people.

Then try slow, easy movement. In the Feldenkrais Method®, you move in small, comfortable ranges and pay attention to how the whole side of your body takes part. Lie on your back, rest your hand on your ribs, and lift your arm a little way. Notice where your ribs and shoulder blade join in. Stop well before any sharp pain. The aim is curiosity, not effort. Feldy teaches this kind of movement, and our Feldypedia entry on frozen shoulder explains how the shoulder and ribs work together.

Medical care sits alongside this. A doctor or physical therapist can check the shoulder, rule out other causes and give you a plan. Stretching and strength work take another route, asking muscles to lengthen or build. Neither one rules out the other.

Find where to start

If your armpit ache seems tied to a stiff or guarded shoulder, a gentle movement practice may be a calm way in. Not sure where to begin? The quiz below suggests a movement method that suits you.

Which gentle method suits you? Try the Movement Match quiz, three short questions, then a movement method to explore at your own pace.

Common Questions about armpit pain (FAQ)

What causes pain in the armpit?

Most often it is muscle related. The chest muscle, the large back muscle called the lat, the serratus muscle along your ribs, and the shoulder tendons can all send an ache toward the armpit. Overuse after lifting, reaching or a new workout is common. Less often it is a shaving rash, an irritated sweat gland or a swollen lymph node. If you cannot tell which it is, a doctor can check.

Is armpit muscle pain serious?

Usually not. A muscle ache tends to change when you move your arm, press on the spot or take a deep breath, and it often eases over days to a couple of weeks. It is the signs around it that matter: a hard lump, redness, heat, fever, or any chest pressure. Those are reasons to get help, not to wait.

When should I see a doctor about armpit pain?

See a doctor if a lump has not gone down within about a week, feels hard or fixed in place, keeps growing, or comes with night sweats, a high temperature or weight loss you cannot explain. See one soon if the area is red or hot. Get urgent help if swelling comes with trouble breathing or swallowing. Call emergency services now if armpit or arm pain comes with chest pressure, shortness of breath, sweating or nausea.

How long does a pulled muscle in the armpit take to settle?

It varies. Many mild muscle strains settle within a couple of weeks, and some take longer, especially if you keep repeating the movement that irritated them. If the pain is not changing after several weeks, or is getting worse, have it looked at.

Can gentle movement help armpit muscle pain?

It may. Slow, easy movement that stays comfortable can help the chest, ribs and shoulder move more freely, and many people notice the ache feels less guarded. It is not a treatment, and it should not replace a check for a lump or swelling. Stop if anything sharpens the pain.

How is this different from stretching or physical therapy?

A physical therapist can assess the shoulder and chest and give you a plan with repetitions and a progression. Stretching asks a muscle to lengthen. Feldenkrais® style movement works differently: it is slow and gentle, and it invites you to notice how the arm, ribs and shoulder blade share a movement. These can sit side by side.