What Is an AC Joint Injury? (And Why It’s So Common in Sport)
- Murray Leyland
- Apr 24
- 3 min read
Updated: Apr 29
If you’ve ever landed hard on your shoulder and had pain right on the top of it — this is for you.
It’s one of the most common shoulder injuries we see.
AC joint injuries.
And despite how common they are, most people aren’t totally sure what they’ve actually done — or what they should be doing about it.
Let’s break it down.
what IS aC JOINT?
The AC joint (acromioclavicular joint) sits right on the top of your shoulder.
It’s where: Your collarbone (clavicle), meets the tip of your shoulder blade (acromion)
It’s a small joint — but it takes a lot of load, especially:
When you land on your shoulder
When you lift your arm overhead
During contact or tackling
HOW DO AC JOINT INJURIES HAPPEN
Most of the time, it’s pretty straightforward: A fall directly onto the point of the shoulder
Common in:
Footy / rugby
Cycling crashes
Snow sports
Falls during general activity
The force pushes the shoulder down and the collarbone up — stressing or tearing the ligaments.
WHAT DOES IT FEEL LIKE?
AC joint injuries have a pretty recognisable pattern:
Pain right on top of the shoulder
Pain when lifting the arm (especially overhead)
Pain reaching across your body
Difficulty with pushing movements (push-ups, getting out of a chair)
Tender to touch over the joint
In more significant injuries, you might notice: A visible bump on the top of the shoulder
not all ac injuries are the same
These injuries are graded based on severity.
Lower grades (most common):
Ligaments are strained or partially torn
Painful, but stable
Settle well with the right rehab
Higher grades:
Complete ligament tears
Visible deformity
May require surgical opinion
The key takeaway? Most AC joint injuries do not need surgery.
what actually helps it settle?
This is where people often get stuck.
They either:
Rest it completely for too long
Or push through pain too early
Neither works well.
Early Phase
Settle pain and inflammation
Modify aggravating movements
Gradual return to comfortable range
Mid Phase
Restore movement
Start loading the shoulder properly
Build strength around the joint
Late Phase
Return to sport-specific loading
Contact preparation (if relevant)
Build confidence in overhead and impact positions
the big mistake we see
Avoiding using the shoulder for too long
This leads to:
Stiffness
Weakness
Longer recovery
The goal isn’t just to rest it. It’s to progressively reload it properly.
how long should you get it checked?
If you’ve had a fall and:
Pain isn’t improving after a few days
You can’t lift your arm properly
There’s a visible bump
You’re unsure how to return to sport
the bottom line
AC joint injuries are common — and frustrating
But with the right approach, they recover really well.
The key is simple:
Load it gradually
Strengthen it properly
Don’t rush… but don’t avoid it either
need help with shoulder pain?
If you’ve landed on your shoulder and it’s not settling — or you’re unsure how to safely get back to sport — that’s where we can help.
We’ll assess it properly, guide your rehab, and make sure you’re progressing with confidence.
Book in with the team at Thornton Physio and let’s get you moving again — stronger and pain-free.
Your Personal Best, Our Priority.
Murray Leyland
Director, Thornton Physiotherapy
🎥 Didn’t catch the video earlier? Watch the video here.
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