There is a small joint on top of your shoulder where the collarbone meets the shoulder blade. It is easy to forget about until it hurts, at which point it becomes the only thing you can think about when you reach for a seatbelt.
It also has one of the cleanest self-tests on this site.
Two tests you can do now
Both take a few seconds and between them they separate this from most of the alternatives.
- Point at it. If you can cover the sore spot with one fingertip, and it sits on top of the shoulder rather than on the outer arm, that is characteristic.
- Reach across your chest. Bring the arm straight across towards the opposite shoulder and pull gently. Sharp pain on top points at this joint.
Pain felt lower down, on the outside of the upper arm, and worse reaching away from the body is more likely a rotator cuff problem instead.
Telling the shoulder problems apart
| AC joint | Rotator cuff | Frozen shoulder | |
|---|---|---|---|
| Where | On top, pinpoint | Outer upper arm | Deep and diffuse |
| Cross-body reach | Sharply painful | Uncomfortable at most | Limited by stiffness |
| Overhead | Painful at the very top | Painful through the arc | Cannot get there |
| Lying on it | Painful | Painful | Painful |
| Passive movement | Largely preserved | Largely preserved | Markedly reduced |
| Read more | This page | Rotator cuff pain | Frozen shoulder |
How it usually starts
Two quite different routes, and the history usually makes it obvious which.
The traumatic version follows a fall onto the point of the shoulder — off a bike, on ice, in contact sport. There may have been a visible step or lump at the time. Those are graded, and most of the milder grades are managed without surgery.
The gradual version is wear in the joint, which is near-universal on imaging after forty and frequently symptomless. As with the knee and the neck, a report describing degenerative change at this joint is not on its own an explanation of pain.
What to change, particularly in the gym
This is where most people find their answer, and it rarely means stopping training.
| Instead of | Try | Why |
|---|---|---|
| Deep dips | Shallower, or a different press | The bottom of a dip loads the joint hard |
| Wide-grip bench press | A narrower grip, less depth | Reduces the end-range compression |
| Behind-the-neck work | Front, and lighter | Extreme positions provoke it |
| Sleeping on that side | A pillow under the arm | Reduces the overnight load |
| Carrying a bag on that shoulder | The other side, or across the body | Direct pressure on the joint |
| Stopping training entirely | Modifying it | Deconditioning helps nobody |
A note on the traumatic grades
If this started with a fall, the grade matters and it is worth knowing roughly where you sit.
The milder separations — where the ligaments are strained or partly torn but the collarbone has not visibly displaced — are managed without surgery and generally settle over weeks to a few months. A visible step at the top of the shoulder suggests a higher grade, and that is a conversation with an orthopaedic surgeon rather than a decision to make from a web page.
Even among the higher grades, plenty are managed conservatively with good function. A visible bump does not automatically mean an operation.
What rebuilds it
The same principle as everywhere else on this site: load modification first, then strengthening, and time.
Scapular and rotator cuff strengthening supports the whole complex and lets the joint tolerate more. It will not reverse wear, and it does not need to — the aim is a joint that copes with what you ask of it.
Penn State Health publishes patient material on shoulder conditions if you want a fuller clinical reference.
The night problem
Almost everyone with a shoulder complaint mentions sleep, and it is worth one practical note rather than sympathy.
Lying on the affected side compresses the joint for hours. A pillow tucked under the arm when lying on the other side stops the affected arm dropping across the body, which is the position that provokes it. Small change, and it often makes the difference between a broken night and a whole one.
Where acupuncture and massage fit
For the pain and the surrounding muscular tension, which lets the strengthening happen. That is the same supporting role described throughout this site, and it is worth being consistent about it.
Needling does not change a worn joint surface. What it can do is make the weeks more tolerable while the load modification and the strengthening do the work that lasts.
When to see a doctor
See a doctor for a visible step or deformity after a fall, for an inability to lift the arm at all, for numbness or tingling down the arm, for a shoulder that is hot and swollen with fever, or for pain that has not improved after eight to twelve weeks of genuine modification and strengthening.
Booking a session in Beverly
Acupuncture is $75 a session and massage is $45 for 30 minutes, $75 for 60 and $105 for 90 — all on our rates page.
See also rotator cuff shoulder pain, frozen shoulder and thoracic outlet syndrome. Browse all our articles or get in touch.
Frequently asked questions
Where exactly is AC joint pain felt?
Right on top of the shoulder, at the small joint where the collarbone meets the shoulder blade. People point at it with one fingertip, which is unusual and diagnostically useful. Rotator cuff pain is felt lower, on the outer upper arm.
What is the cross-body test?
Reaching the affected arm straight across your chest towards the opposite shoulder. If that reproduces sharp pain on top of the shoulder, it points at the AC joint. It is something you can try while reading this.
What causes it?
Two routes. A fall onto the point of the shoulder or onto an outstretched hand, which strains or separates the joint. Or gradual wear, which is extremely common after forty and often shows on scans in people with no symptoms at all.
What should I stop doing in the gym?
Deep dips, wide-grip bench pressing and anything that takes the arm far across the body under load. Narrowing the grip and reducing depth usually lets people keep training rather than stopping.
Does it need surgery?
Rarely. Most cases settle with load modification and strengthening. Surgery to trim the end of the collarbone exists for cases that do not settle, and it sits well after the conservative measures.
This article is general information, not medical advice. Acupuncture is intended to work alongside the care of your doctor, not to replace it. Please speak to a clinician about any new, severe or changing symptom.