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Where is the AC joint?
The acromioclavicular, or AC, joint connects the outer end of the collarbone to the acromion, part of the shoulder blade. It sits on top of the shoulder. Ligaments around this junction and between the collarbone and shoulder blade help maintain their relationship.
It is different from the ball-and-socket joint of the upper arm. An AC separation therefore does not mean that the upper arm bone has left its socket. Understanding which joint is injured changes both the assessment and the treatment options.
Chapter sources [1]
Understand the picture
Two different shoulder joints
Collarbone
This bone meets the acromion above the shoulder.
AC joint
Ligaments support this small junction.
Main shoulder joint
The upper arm head sits lower, in its socket.
Chapter sources [1]
What symptoms help guide assessment?
After a fall directly onto the shoulder, pain may be concentrated on top, with swelling or a bump. Carrying a bag, raising the arm or reaching across the body may hurt. Pain and visible changes vary with the injury.
Without an accident, pain in this area may involve joint irritation or osteoarthritis. Location alone cannot confirm the cause: a broken collarbone or nearby tissues may also hurt. Repeatedly pressing or performing painful online tests is not a reliable way to diagnose yourself.
How does an AC injury happen?
A fall or impact can stretch or tear the stabilising ligaments. Depending on the damage, the bones stay close to their usual position or become more displaced. The weight of the arm and shoulder blade can make the collarbone end appear prominent.
Clinicians describe different grades of injury to discuss stability and management. These cannot reliably be identified from a photograph of a bump. Gradual pain with loading is a different situation and should not automatically be called a sprain.
Chapter sources [1]
What assessment is needed?
The clinician asks how the fall happened, checks pain, movement and skin, and examines sensation and circulation in the arm. X-rays may show displacement, detect a fracture and help assess injury severity. Other shoulder injuries can occur at the same time.
For longstanding pain without trauma, examination considers a symptomatic AC joint and alternative causes. Arthritic changes can appear on imaging without causing symptoms. The aim is to connect the examination and difficult activities with the images, rather than treat an imaging report alone.
When is urgent help needed?
A deformity after a fall, severe pain, substantial swelling or major difficulty using the arm needs prompt assessment. Very tight skin over bone, an open wound, a cold hand or loss of sensation increases the urgency. Do not press down on a bump to correct it.
Call 112 in Luxembourg for a serious injury, breathing difficulty or collapse. A red, hot shoulder with fever also needs urgent assessment, even without a fall. Exercise is not the first step in these situations.
How is treatment chosen?
Many AC injuries can be treated without surgery, using temporary protection, pain management and rehabilitation. A sling may be prescribed initially; the duration depends on the injury. Movement and loading should progress according to the instructions you receive.
A markedly displaced injury, particular work or sporting demands, or persistent symptoms may lead to a surgical discussion. The size of the bump alone does not decide this. Ask about expected functional benefits, risks and recovery restrictions in your situation, including the options without surgery.
Chapter sources [1]
In everyday life
Returning to carrying
Identify
Describe the weight and height your day requires.
Reduce
Start with a manageable task close to the body.
Prepare
Gradually add the particular demands of work or sport.
How can daily tasks be adapted?
During protection, avoid tasks that pull strongly on the joint or press directly onto it. A bag strap on the painful side or a weight held away from the body may be difficult. Keep useful objects within reach and arrange help with heavier loads.
Comfortable support under the arm can make rest easier. Follow the movements demonstrated for dressing and removing a prescribed sling. Do not replace instructions after an operation with advice intended for a mild sprain. The repaired tissues may need protection even when pain has eased.
What role do exercises have?
Rehabilitation aims to restore useful movement, followed by the strength and control needed for your tasks. Initial movements and their range must be cleared after trauma. An exercise suitable for tendon pain may put too much demand on recently injured AC ligaments.
Arm support, press-ups, weights and movements across the body are reintroduced according to tolerance and clinical guidance. Sharp local pain, a new symptom or worsening the next morning means the difficulty should be reduced and the programme reviewed.
What can recovery look like?
A mild injury may allow relatively early return to simple tasks, while heavy work and sport usually require more preparation. A major injury or operation can take several months to rehabilitate. Strength and comfort may keep changing after the initial improvement.
A bump can remain visible despite satisfactory function. This does not automatically mean that treatment failed. Continuing pain, instability or inability to resume important activities does justify a fresh discussion with the clinician. Recovery is assessed through function as well as appearance.
Chapter sources [1]
How do you prepare for greater demands?
Describe the actual goal: carrying a child, lifting at work, side sleeping or returning to contact sport. Progression might begin with an unloaded movement, then a light weight close to the body before greater load or reach.
Avoid increasing every difficulty on the same day. Observe the evening and next-morning response as well as how the exercise felt. If surgery is planned, ask for the rehabilitation protocol and weight-bearing restrictions. Less pain does not mean repaired ligaments are ready for unrestricted loading.
Your questions
Is AC separation the same as a dislocated shoulder?
No. It affects the collarbone–acromion junction. A dislocation of the main shoulder joint involves the upper arm head and needs a different assessment.
Does the bump have to disappear?
Not necessarily. A bump can remain while pain and function improve. Persistent symptoms should still be reassessed.
Chapter sources [1]
Should I have surgery just for the bump?
Appearance alone is insufficient. Stability, pain, displacement and activity requirements are discussed alongside the risks of surgery.
Chapter sources [1]
Can I strengthen with press-ups?
Weight-bearing may be premature after an AC injury or repair. Wait for your team’s guidance and a suitable progression.
Chapter sources [1]
Sources and references
- [1] AAOS OrthoInfo · Shoulder separation
- [2] AAOS OrthoInfo · Arthritis of the shoulder
- [3] AAOS OrthoInfo · Shoulder trauma: fractures and dislocations
- [4] NHS · Shoulder pain
- [5] CGDIS Luxembourg · 112
- [6] NHS · Septic arthritis
- [7] NHS Inform · Exercises for shoulder problems
- [8] NHS · Heart attack
Text updated on
Medical review: awaiting Hasib Selimovic.