AC Joint Sprain

These two sound alike and get mixed up all the time. A separated shoulder is an AC joint injury. The problem is at the top of the shoulder, where the collarbone meets the shoulder blade ⁴, and the tenderness is on one spot directly over that joint ¹.

A dislocated shoulder is a different injury in a different joint: the ball at the top of your upper arm bone coming out of its socket. If you're not sure which one you've done, get it assessed.

An examination and a plain X-ray usually settle this. MRI isn't a routine test for it ¹. You'll be examined sitting or standing, because the weight of your arm hanging makes any step at the joint easier to see ¹. We also look for swelling and bruising over the end of the collarbone, see how far pain limits your shoulder movement, and check for other injuries from the same fall ¹.

X-ray is the first choice for confirming and grading the injury ¹, though a mild sprain can look normal on one ³. Holding a weight during the X-ray used to be common. It isn't routinely recommended now: it's uncomfortable and it doesn't change the treatment ¹.

The first job is confirming it's the AC joint. Pressing directly on the joint is usually tender. Bringing your arm across your body tends to bring the pain on, which is called the cross-body adduction test ^1,2. We may also use O'Brien's test or the Paxinos sign ². If there's a visible deformity, or the injury looks higher-grade, an X-ray is how it gets properly graded ¹.

For the common, lower-grade sprains:

An AC joint sprain is worked through in the three phases of The Well Motion Recovery Path™. You step up a phase on what the shoulder can do, whatever the date.

• Reset: the first days after the fall. A sling for comfort ³, an X-ray if a bump or step needs grading ¹, and manual therapy if your neck and upper shoulder have tightened up. Expect the top of the shoulder to stay tender to press after the arm feels easier. We move you on once you are out of the sling and moving within your pain-free range.
• Rebuild: most of the work. Sports physiotherapy adds load as the pain settles ³. Expect reaching overhead and across your body to come good last. We move you on when the shoulder moves normally and loaded exercise no longer stirs the pain up.
• Return: back to contact sport, the bike or manual work. We test the positions your sport or job asks for, at the load it asks for. You leave with a strength program, and knowing that a bump can stay even when the shoulder works well ³.

How long it usually takes. Lower-grade sprains typically settle in 4 to 6 weeks ³. Not everyone does: in one retrospective study quoted in a 2024 review, some people with type I and II injuries still had symptoms at 6 weeks ². Types IV to VI are generally treated surgically ¹, and then your surgeon sets the timeline.

Nobody has run a trial on preventing AC joint injuries, so this is built on how they happen and what's been measured in the lab:

• Contact is where it happens. In elite rugby union the AC joint was the most often injured part of the shoulder, and the main cause was a direct hit to the shoulder from another player or the ground ⁵. The researchers pointed to tackle skills and shoulder pads as the things to look at ⁵.
• Shoulder pads. In one study, pads cut the peak force over the AC joint by about 40% in tackles ⁶. A lab test of four pads found they "bottom out" under heavier impacts, which is when you'd need them most ⁷. Neither study counted injuries.
• The return. Movement in the pain-free range comes first, then loaded exercise as the pain settles. Sport or manual work waits until the pain has gone and the shoulder moves normally, which can take four to six weeks ³.