Shoulder impingement (subacromial pain syndrome)

This is the commonest cause of shoulder pain in adults. The arm seems to work, but lifting it above a certain height hurts, reaching behind your back hurts, and at night, if you lie on that side, the pain wakes you. One thing is worth understanding from the start: a shoulder gets better with movement, not with rest, and improvement arrives over weeks rather than days. Most people give up in the second week, having decided it is not working — which is exactly why they then put up with it for six months.

How to recognise this pain

Shoulder impingement has a fairly recognisable pattern of complaints:

• pain in the middle of the range. You start raising the arm out to the side: the first part is comfortable, then comes a painful stretch, and if you manage to lift the arm all the way, it eases again at the top. That "painful arc" is the most characteristic feature;
• pain on reaching behind your back — fastening a bra, getting a wallet out of a back pocket, finding the sleeve of a coat;
• pain working above head height — hanging curtains, getting a jar off the top shelf, painting a ceiling;
• pain down the outside of the upper arm, sometimes as far as the middle of the forearm, but not into the hand;
• worse at night, particularly lying on that shoulder; many people first go to a doctor precisely because they have stopped sleeping;
• the arm feels weak, but the weakness comes from the pain: without the pain the strength would be there.

At rest, with the arm hanging down, it usually does not hurt. The shoulder also still moves in every direction — it is simply that some movements are unpleasant. It can start abruptly, after a day of working overhead, or gradually, for no reason at all.

What is happening in the shoulder

The shoulder joint is held together less by ligaments than by muscles. Four of them, the rotator cuff, wrap around the head of the upper arm bone, and their tendons pass beneath a bony ledge of the shoulder blade called the acromion. Between tendon and bone lies a gliding sac. The space there is narrow, and as the arm goes up all of it has to slide freely.

When the tendon is irritated and thickened and the sac is inflamed, that sliding is disturbed — hence pain in one particular sector of movement. There are usually several causes at once: long spells of work with the arms raised, a sudden increase in load after a break, age-related changes in the tendon itself, weakness of the muscles that steady the shoulder blade, a hunched posture at a desk. In some people the shape of the acromion plays a part too.

The name is a historical leftover, and it misleads a little: for a long time it was believed that the bone literally wears the tendon away. It is now understood that the issue is more often an overloaded tendon that tolerates work badly than a mechanical rub. That is not a fine point for the patient: the old picture implied taking the rubbing away — protecting the arm or operating — while the new one implies teaching the tendon to accept load, gradually.

Why the treatment is exercise, not a sling

A shoulder that is not moved does not recover; it loses movement. A sling, complete rest and "resting it for a month" make impingement worse: the muscles weaken, the joint stiffens, and on top of the original pain comes a stiffness that is far harder to treat.

The treatment that works looks dull and demands patience. It is a set of exercises chosen by a doctor or physiotherapist: first to restore free movement and to work the muscles that steady the shoulder blade, then progressive loading of the rotator cuff against resistance, with the weight and the repetitions built up slowly. They are done almost daily, at home, in ten or fifteen minutes.

Three things are worth knowing in advance, because otherwise people stop:

• The first improvements come after several weeks, and a clear result usually takes six to twelve weeks. Sometimes longer. That is the normal timescale for a tendon, not a sign that the treatment is failing.
• Moderate pain during the exercises is acceptable. The guide is simple: bearable pain that settles soon after the session and does not leave the shoulder worse the next morning is doing no harm. Sharp pain lasting hours means the load was too much.
• Progress is uneven. A bad day does not cancel two good weeks; what to watch is the change from month to month.

It is the exercises that give the lasting result. Everything else — pain relief, injections — only creates the opportunity to do them, but does not mend the shoulder by itself.

What you can do yourself

• Change the load rather than remove it. Drop for a while whatever clearly provokes the pain: long spells with the arms up, front crawl, serving at tennis, overhead pressing. Carry on with everything that does not hurt badly.
• Pain relief. Paracetamol or an anti-inflammatory painkiller in a short course helps you sleep and lets you exercise. With stomach or kidney problems, heart conditions or blood-thinning medicines, anti-inflammatories are chosen only with a doctor; gel forms applied to the skin are easier to tolerate.
• Cold or heat, whichever suits. Cold tends to help after activity, heat with morning stiffness. Fifteen to twenty minutes, always through a cloth.
• At night lie on the good side or on your back, with a pillow under the sore arm so the shoulder does not hang backwards. For many people this restores sleep within the first few nights.
• Sort out your desk: elbows supported, screen at eye level, never a phone wedged against the shoulder. An hour hunched over easily undoes fifteen minutes of exercises.
• Do not jerk the arm about or try to "work the shoulder loose" through severe pain. Exercise is measured loading, not endurance.

Injections and surgery: the honest version

Steroid injections need talking about frankly, because rather more is expected of them than they deliver. An injection into the subacromial space really does take the pain away, often quickly. But the effect is temporary: it lasts a few weeks, rarely longer, and then the pain returns if nothing has changed in the muscles meanwhile. The point of the injection is to break the circle of pain, not moving, weakening and more pain, and to make exercising possible.

Hence two rules. First, an injection does not replace the exercises; it opens a window for them, and the exercises have to start while it is still working. Second, such injections should not be repeated often. Steroid given repeatedly into the same area weakens the tendon, and if there is no result after the first or second, carrying on in the same vein makes no sense — the diagnosis needs revisiting rather than the injections adding up.

The operation to widen the space beneath the acromion was once done a great deal. It is now viewed more cautiously: in trials, in people with ordinary impingement, it showed no advantage over a properly conducted exercise programme. It comes up for discussion when several months of real rather than nominal treatment have achieved nothing, or when imaging finds a different cause — a significant cuff tear, say, or calcium deposits in the tendon.

When it is not impingement

Several conditions look similar, and telling them apart matters because what you do about them differs.

A rotator cuff tear. If after a fall, a sudden jerk or an attempt to hold something heavy the arm has stopped lifting altogether — not "it hurts to lift", but it does not go up, although someone else can lift it for you — that is a torn tendon, not impingement. The same applies if the strength in the arm dropped abruptly and has not come back. This needs assessment within days and, in all likelihood, a scan: with some tears in active people, deciding early about surgery changes the outcome.

Adhesive capsulitis, or "frozen shoulder". The distinguishing feature is that the shoulder loses movement in every direction, and not only when you move it yourself: a doctor moving your relaxed arm also meets a hard stop. Rotation outwards suffers most — combing your hair is difficult, turning the forearm away from the body is impossible. In impingement, passive movements are free. Frozen shoulder is commoner in people with diabetes and thyroid disease, runs in phases and is treated differently.

Other causes. Shoulder pain can come from the neck: it then tends to run down the arm past the elbow, comes with numbness or pins and needles, and changes with the position of the head. Sudden, very severe pain without injury, with the arm virtually unusable, is typical of calcium deposits in the tendon. In older people, pain and stiffness may come from arthritis of the joint itself.

Signs that need urgent help

Do not put off being seen if:

• after a fall or a blow the shoulder is deformed and has changed shape, the arm will not move, or the hand is numb and cold — that is a fracture or a dislocation and needs looking at immediately;
• the joint is hot, swollen and red, there is a temperature and shivering, and any movement causes sharp pain — that is how a joint infection presents, and it needs hospital the same day;
• the shoulder pain came on together with breathlessness, pressure or heaviness in the chest, cold sweat or nausea, or spreads to the jaw or the left arm — this may be the heart rather than the shoulder. Call an ambulance (112, the single European emergency number) and do not wait for it to pass;
• the shoulder pain comes with coughing up blood, weight loss, a drooping eyelid or weakness of the hand on the same side;
• a growing lump has appeared around the shoulder, or the pain keeps you awake and worsens week by week despite treatment.

Separately: pain in the right shoulder and across the top of the back that comes in episodes after fatty food, together with pain under the right ribs, is more often the gallbladder than the joint.

Online consultation

The shoulder is a subject where talking gets you a long way. In an online appointment the doctor goes through exactly which movements hurt, how it all started and what has changed over time, and from that alone can separate impingement from frozen shoulder, from a cuff tear and from pain coming out of the neck. They can also take you through a few simple tests in front of the camera: raising the arm to the side, reaching behind your back, turning the forearm outwards.

Prepare like this: note in advance which movement brings on the pain and at what point, whether you sleep on that shoulder, whether there was a fall or an unusual effort beforehand, and how long it has been going on. Mention your work and your sport, any other conditions — diabetes and thyroid disease especially — and the medicines you take.

At the end of it the doctor explains what to expect and over what timescale, gives you an exercise programme and pain relief, and — no less importantly — books a follow-up conversation so that you do not abandon it halfway. If the picture points to a tear, to frozen shoulder or to the neck, you will be referred for a face-to-face assessment and a scan. With the signs in the previous section an online appointment is not the right route: that needs care in person, and urgently.

This material is for information only and does not replace medical advice.