What Is The AC Joint?
The AC joint is part of the shoulder. It’s a joint including the acromion (part of the scapula) and the clavicle. Its function is to stabilize the shoulder.
If you feel your clavicle and follow it towards the end, on the lateral side, that’s where the AC joint is.
How Do You Injure Your AC Joint?
One way you can hurt your AC joint is by hitting it directly against something (the floor, another person, playing football, rugby…).
Also, you can hurt it by falling on your outstretched arm, which can transmit the blow up to your shoulder.
What Do You Feel When You Hurt Your AC Joint?
Pain.
It hurts on the AC joint (see picture above). You can also see some bruising, like the skin is turning yellow or blue-ish.
Also, it may be hard to move your arm. It’s not like you can’t move it at all (like you would if you break it). Instead, pain limits your movements.
You may be able to raise your arm a little, but not above your head because it will hurt like hell.
However, if you help yourself with your other arm, you’ll be able to raise it a little more—we call that passive motion.
Once we know we may have an AC joint injure, there are two important things to figure out:
- we need to make sure there isn’t a fracture
- get an idea of how bad the injury is
For both these things, the best thing is an x-ray.
X-ray will show fractures: if you have a clavicle fracture or a shoulder fracture, it will show.
Also, it will show if the AC joint is in its place. If it is, then the injury is mild.
As the injury gets worse, the AC joint space gets wider. If it gets just a little wider, then some ligaments may have torn, mainly the AC ligaments. That’s like a bad sprain.
If the injury is even worse, the clavicle will displace in other directions, like upwards or backwards. That means there are other ligaments torn.
When the clavicle is really displaced because most of the ligaments have torn, those injuries have a high chance of requiring surgery.
Another useful test is a shoulder MRI. Shoulder MRI can show the ligaments and how much damage they have. However, it’s usually not necessary. It’s more useful to look at the x-ray and see how much the clavicle has moved.
These are some MRI images of an AC injury:
How To Treat AC injuries
In most cases, there is mild or moderate damage, and they can be treated with just rest, ice and painkillers. After some weeks, you can start moving your arm again and go back to your normal life.
For the most severe cases, when the clavicle is really displaced and the ligaments are torn, you’ll need surgery. Not always, but you need at least to talk to your doctor and find out if surgery will be the best option for you.
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