A common injury that people often misjudge
AC joint dislocation is a very common shoulder injury, especially after a fall directly onto the shoulder. Many patients call it a separated shoulder. They often come with pain at the top of the shoulder, difficulty lifting the arm, swelling, and a visible bump near the end of the collarbone. In Bangladesh, I see this after road traffic accidents, sports collisions, falls at home, and work-related trauma. [2]
One important point I explain early is that not every AC joint dislocation needs surgery, and not every visible bump means the shoulder is severely damaged. The real treatment decision depends on the grade of injury, the patient’s function, the level of pain, and the demands of work or sport. [2]
What the AC joint does
The AC joint is the small joint at the top of the shoulder where the collarbone meets the acromion, which is part of the shoulder blade. It helps connect the arm and shoulder girdle to the rest of the skeleton while still allowing movement. [1]
When the stabilizing ligaments of this joint are stretched or torn, the relationship between the collarbone and the shoulder blade changes. In more severe injuries, the outer end of the collarbone may appear raised. This is what causes the visible deformity or bump that many patients notice. [2]
How this injury usually happens
The most typical cause is a direct fall on the outer side of the shoulder. This can happen during football, cricket, cycling, motorbike accidents, slips on stairs, or workplace falls. The force drives the shoulder downward while the collarbone stays relatively fixed, stressing the ligaments around the AC joint. [2]
Patients often remember the injury clearly because the pain begins immediately. Many cannot comfortably lift the arm afterward. Some notice swelling and bruising within hours, while others become more concerned when they see the top of the shoulder looks different.
Symptoms patients commonly notice
The most common symptoms include:
- pain at the top of the shoulder
- swelling and tenderness over the AC joint
- difficulty lifting the arm
- discomfort when bringing the arm across the body
- a visible bump near the collarbone
- pain while sleeping on the injured side
In some mild injuries, the shape change is small and the pain is the main issue. In more severe injuries, deformity becomes more obvious. But appearance alone does not tell the full story. Some patients with a noticeable bump still recover well without surgery, while others with less obvious deformity remain functionally limited.
How I assess the severity
When I evaluate AC joint dislocation, I start with the history of trauma and then examine the shoulder carefully. I check where the tenderness is most severe, how much swelling is present, whether the arm can move, and whether there are signs of associated injury such as fracture or neck involvement.
X-ray is usually very helpful in this injury. It helps confirm the degree of displacement and identify associated bony injury. In most cases, diagnosis is based on a good combination of history, examination, and X-ray findings. The main goal is to decide whether the injury is likely to recover well with conservative care or whether closer follow-up and sometimes surgery may be needed.
