Pain Inside Upper Arm: Common Causes and When to Worry

Pain inside upper arm is a very common complaint, and most of the time the cause is ordinary. The inner side of the upper arm is the soft side that faces your body. An ache there usually comes from a muscle that did more than it was ready for. Less often it comes from a bruise, a nerve, the shoulder or neck, or a swollen gland near the armpit.

This page is only about that inner side. If your ache sits on the outside, between the shoulder and the elbow, our page on upper arm pain between shoulder and elbow is the better fit.

Read this first. Arm pain in the left arm, or in either arm, with chest pain or tightness, breathlessness, sweating, or feeling sick or faint means call emergency services now. Do not wait to see if it settles. An arm that is swollen, warm, red and tender also needs same day care, because it can be a blood clot. Everything below is for pain that is not coming with those signs.

What may be behind pain inside upper arm

Think of the inner arm as a busy corridor. Muscles, nerves and glands all pass through it on the way between your trunk and your hand. So several things can make it ache.

A tired biceps or brachialis. The biceps is the muscle you see when you bend your elbow. The brachialis lies just under it and does a lot of the quiet work of bending. Carrying heavy bags, lifting a child, moving boxes or starting a new workout can overwork either one. The ache is dull, tender to press, and often loudest a day or two later. Bending the elbow against load makes it bite. Most mild strains feel better within about two weeks (NHS, 2024).

The small muscle near the armpit. The coracobrachialis is a slim muscle that runs from the front of the shoulder blade to the middle of the upper arm bone, on the inner side. It likes to complain after reaching, throwing, swimming or pulling. The pain sits high on the inner arm, close to the armpit, and may sharpen when you lift the arm forward or across your body.

A bruise. A knock from a door, a bag strap or a ball can leave a sore patch that is tender to touch, often with colour that changes over days. The inner arm is soft and bruises easily. A bruise that appears with no knock at all, or keeps growing, is worth mentioning to a doctor.

An irritated nerve. The big nerves that serve the arm and hand run down the inner upper arm. When one is squeezed or irritated, the pain may feel burning, electric or tingly, and it can travel into the forearm and hand. Sleeping with the arm under your head, leaning on it for a long time, or a stiff neck can all be involved. Tingling, numbness or a weak grip means it is time to see a doctor.

Pain from the shoulder or neck. The inner arm can echo trouble somewhere higher up. A stiff shoulder, as in frozen shoulder, or an irritated joint in the neck can send an ache down the arm. This is called referred pain, meaning you feel it away from where it starts. If turning your head or lifting your arm changes the ache, the source may be higher than the arm.

Swollen glands near the armpit. Lymph nodes are small glands that are part of your immune system. They sit in the armpit and can swell after a cold, an infection or a vaccine, giving a tender fullness at the top of the inner arm. This usually settles within a couple of weeks. Our page on armpit pain goes through glands and lumps in more detail. A lump that does not go away should be checked by your GP.

Is it something to worry about?

Most of the time, no. Pain that is dull, matches something you did, and changes as you move is usually muscular. Use this short list to sort the rest.

Call emergency services now for arm pain with chest pain or tightness, breathlessness, sweating, or feeling sick or faint. Seek same day care for an arm that is swollen, warm, red and tender. See a doctor for numbness, weakness, a lump that does not go away, or pain after a fall or a sudden pop with bruising. Also book a visit if the pain wakes you most nights or has not eased after a few weeks.

This page cannot tell you which cause you have. A clinician can usually sort it out in one visit with a few questions and a gentle exam.

What may help while it settles

Give the arm an easy few days. Carry things closer to your body, use two hands for heavy bags, and avoid long spells with the elbow bent tightly. If you sleep on that side, try a pillow in front of you to rest the arm on. Warmth often feels pleasant on a tired muscle.

Then notice how you use the arm. Many people reach with the elbow and nothing else. Next time you pick up a cup, notice whether your shoulder blade slides on your ribs, whether your chest moves a little, and whether your neck stays soft. Sharing the job across more of you means the biceps carries less of it. That is the idea behind the Feldenkrais Method®, which is slow movement with attention rather than effort. If your shoulder is also stiff, our frozen shoulder stretches lesson is a gentle place to begin.

If the pain is nearer the elbow than the shoulder, the inner elbow has its own story. We cover it in pain on the inside of the elbow.

Professional care runs in parallel with this. A physiotherapist can examine the arm and plan strengthening if it is called for. Yoga and stretching are different again, working through held positions. Plenty of people keep one of those and add quiet movement attention on top, with Feldy as one way to do that.

Find where to start

If your arm has ached on and off for weeks and you are not sure what kind of movement would suit you, it helps to start with the method rather than the exercise. The Feldy program for frozen shoulder shows what slow, attentive arm work feels like.

Curious what you might enjoy? Take the Movement Match quiz and get pointed to a movement method worth exploring first.

Common Questions about pain inside the upper arm (FAQ)

Is it safe to keep moving my arm when the inside of my upper arm hurts?

Usually yes, in easy amounts, if the pain is mild and eases as you move. Keep the arm doing light everyday jobs and rest it from heavy lifting for a few days. Do not move it, and get help first, if the pain came with chest symptoms, a fall, a pop with bruising, swelling, or numbness and weakness.

How often should I do gentle arm movement for pain inside the upper arm?

A minute or two, several times a day, is plenty. Slow and comfortable beats long and strong. Nothing needs counting, and nothing should be pushed into the sore spot.

How long does pain inside the upper arm take to settle?

A muscle strain from lifting or a new workout often feels better within a couple of weeks. A bruise fades over one to two weeks. Nerve and shoulder patterns can take longer. If there is no change after two to three weeks, or it is getting worse, book a review.

What should I avoid when the inside of my upper arm hurts?

For now, skip heavy lifting with the palm up, long carries with a bent elbow, and hard pressing or deep massage into the sore spot. Also avoid sleeping with the arm squashed under your head. Ease back to normal tasks in steps once it calms.

Is pain inside the upper arm a sign of a heart attack?

Pain that shifts when you move the arm or press the spot is rarely the heart. It turns urgent when arm pain, left side or either side, arrives with chest pain or tightness, breathlessness, sweating, or feeling sick or faint. Ring emergency services immediately instead of watching how it develops.

How is gentle movement different from physiotherapy for arm pain?

A physiotherapist can assess the arm, rule out causes, and give you a graded strengthening plan. That care sits alongside what is here. Slow Feldenkrais® style movement works on a different thing: how the shoulder blade, ribs and neck share each reach, so the arm does less alone. Yoga and stretching work through held shapes, which is another mechanism.

When should I see a doctor about pain inside the upper arm?

Now, by calling emergency services, if there are chest symptoms. The same day if the arm is swollen, warm, red and tender. Soon if there is numbness, weakness, a lump that does not go away, or pain after a fall or a sudden pop with bruising. Otherwise, book a visit if it has not eased in a few weeks.