That Word Only Tells You What's Happening. It Doesn't Tell You Why
Shoulder impingement isn't really a diagnosis. I know that's what you've been told you've got, and it is real — something genuinely is getting pinched in there. But that word only tells you what's happening. It doesn't tell you why, or what's becoming impinged. And that's the whole problem, because the why is the bit that gets you better.
Here's the quick version. Impingement means the tendons or soft tissues in your shoulder are getting compressed and irritated in a space that's too tight when you lift your arm. The giveaway is a painful arc — it hurts somewhere in the middle as you lift your arm out to the side, then eases off again as you go right overhead. You'll often struggle reaching overhead, washing or drying your hair, putting a coat or jumper on, reaching behind you into a back pocket, or doing up a bra strap. Night pain is common too — laying on that side presses and squashes everything together, so people often wake when they roll onto that shoulder. It's normally a gradual thing, so there's usually no single injury — it creeps up over weeks or months.
But here's the bit that actually matters. That space didn't just get tight on its own. Something closed it down. And that's what decides whether this is something that settles, or drags on for months and years.
My name is Joe, an ex-professional football head physio and multi-clinic owner here in the UK. As always, this video is a guide to help you understand what's going on.
What's Actually Happening In The Shoulder
Let's start with what's actually happening in the shoulder. At the top of your shoulder there's a bit of bone that sits over the joint like a little roof — that's called the acromion. Underneath it there's a gap, called the subacromial space. Running through that gap you've got the tendons of your rotator cuff, and you've also got a bursa, which is a small, fluid-filled sac that sits there to stop everything rubbing. So you've got tendons and a bursa running through a gap, underneath a bit of bone.
Here's the thing: when you lift your arm, that gap gets smaller. That's normal — it's supposed to, and it happens in everybody. But if that space is already too tight or too small, or the ball isn't sitting where it should in the shoulder, those tendons and the bursa get squashed every single time you lift your arm. Squash and impinge a tendon a few thousand times and it will get irritated, swell, and feel painful. Squash the bursa too, and it will also get inflamed. That's what we refer to as an impingement — something getting compressed in a space that's too tight.
The Painful Arc: How Impingement Shows Up In Real Life
So how does it show up in real life? The classic sign is a painful arc, and it's a genuinely useful thing to test on yourself. Lift your arm out to the side slowly. The first part is usually fine, and then somewhere in the middle it'll hurt — that's the point where the space is at its tightest and the tendon often gets squashed. Then as you keep going up overhead, it often eases off again, because the shoulder blade rotates and the tendon clears that bit of bone. So: pain in the middle, better at the top. If that's you, that's a strong pointer.
You'll also notice it reaching up to a high shelf, washing or drying your hair, putting a coat or jumper on, reaching behind you into your back pocket, or doing up a bra strap. Night pain is common too — laying on that side presses everything together, and people often wake when they roll onto that shoulder and have to move to get comfortable. It's normally gradual, so there's usually no single injury — it creeps up over weeks or months, and people say it just started niggling and never really went.
Why It's Often Called Subacromial Pain Syndrome Now
A quick word on the term itself, because it's worth knowing. A lot of us have moved away from calling it impingement — you'll often hear it called subacromial pain syndrome instead. That's because "impingement" makes it sound like a plumbing problem, like there's a blockage, and the only answer is to go in there and make that space bigger.
For years, that is what happened. Lots of people had surgery to shave that bit of bone away, and we still do it — I see plenty of patients who've had a decompression. They just don't need it as often as we used to think. What happened was, it got properly tested against sham surgery, and most people did just as well without the bone being touched at all. That tells you something important: for most people, this isn't about the bone. It's about how the shoulder is working. And that's good news, because that part is in your control.
What Closes The Space Down (And When Surgery Actually Helps)
So what closes that space down? Usually it's things like tight pecs pulling your shoulder forward, tight lats stopping your arm getting overhead cleanly, a weak rotator cuff stopping the ball from sitting cleanly in the socket so it tends to ride up in the joint, or a shoulder blade that just doesn't rotate properly when you lift your arm. That's the vast majority of impingement right there — I've done a full video on those causes, so watch that one next, because that's where the actual fix lives.
The one exception is a bone spur — an extra bit of bone growing into that space. No amount of exercise will remove a piece of bone, and that's where an operation generally has a place. But that's the exception. If you've had a proper go at rehab and had no response at all, that's when it's worth imaging to see if there's a bone spur.
What This Means If You've Been Told You've Got Impingement
So, impingement means your tendons are getting compressed in a space that's too tight. But the word only describes what's happening — it doesn't tell you why. And the why is nearly always mechanical.
So if you've been told you've got impingement, don't just assume you're heading for an operation. It's a sign your shoulder isn't moving the way it should be, and it's usually fixable with physio.
This article is a guide to help you understand what's going on with your shoulder — it's not a diagnosis. If you're experiencing shoulder pain, get it properly assessed by a professional before assuming what's causing it or what treatment you need.
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