Shoulder
Acromioclavicular
(AC) Joint Dislocations
Also known as shoulder separation, is a dislocation of the clavicle from the acromion.
The most common cause of an AC dislocation is a fall directly onto the shoulder. An acromioclavicular (AC) joint dislocation occurs when the clavicle (collarbone) separates from the acromion of the scapula due to ligament damage around the AC joint.
The most common cause of an AC dislocation is a fall directly onto the shoulder, that's why this injury is mostly seen in people active in sports aside from those who experienced an accidental fall.
What is an AC joint dislocation or separation?
AC joint injuries frequently result from high-impact trauma, such as collisions in contact sports, mountain biking crashes, or motor vehicle accidents. The force drives the scapula downward while the clavicle shifts upward, overstretching or tearing the AC and coracoclavicular (CC) ligaments. Risk factors include cycling, skiing, snowboarding, rugby, and falls on an extended arm (FOOSH).
Symptoms by severity
Typical symptoms of an acromioclavicular separation or joint dislocation include:
- Pain and tenderness over the AC joint
- Swelling, bruising, and visible deformity—especially in higher grade injuries, where a “bump” may appear on the shoulder
- Reduced range of motion and weakness, particularly when lifting or rotating the arm
- Instability and discomfort during overhead activity, as well as difficulty sleeping on the affected side
Common risk factors include:
- Participation in contact sports such as football, hockey, soccer, basketball, or rugby.
- Accidents such as motor vehicle crashes.
- Gender - males are more likely than females to experience shoulder separation.
- Being prone to falls either because of age, occupation or participation in sports where falls are common (such as cycling or gymnastics).
- Previous shoulder separation - the more this injury happens, the easier and more likely it is for it to reoccur.
The shoulder is made up of a complex arrangement of bones, ligaments and other structures that work together to provide an extraordinary range of movement. Unfortunately, these structures are thin and can be easily damaged by direct injury to the area.
Classification: Rockwood Types I–VI
AC joint dislocations are classified using the Rockwood system, which evaluates ligament damage, displacement, and surrounding soft tissue involvement:
- Type I: AC ligament sprain only; no displacement.
- Type II: AC ligament torn; partial CC ligament damage; mild elevation (<25%).
- Type III: Both AC and CC ligaments torn; up to 100% clavicle elevation.
- Type IV: Clavicle displaced posteriorly into trapezius.
- Type V: Severe superior displacement (100–300%), with delto-trapezial fascia disruption.
- Type VI: Clavicle displaced inferior to acromion or coracoid—a very rare presentation.
Diagnosis of an AC joint separation
Diagnosis involves evaluating both the history of the patient's injury and the injury itself. A physical examination of the shoulder is performed to assess signs of fracture or dislocation. The AC joint is right under the skin, so this examination involves carefully feeling the bones and tissues around the AC joint, as well as comparing the arm's position to the uninjured one on the other side.
In severe cases, the deformity of the acromion will be a visible indicator of an AC joint dislocation. For more moderate cases, other tests may be required including:
- Testing the patient's range of motion to isolate specific areas of pain or weakness.
- X-rays to help determine whether the injury is a separation, a fracture or a total dislocation.
Treatment by Injury Severity
Grade 1–2 (Mild to Moderate Sprains)
These injuries involve stretching or partial tearing of the AC ligaments without significant displacement of the clavicle.
Treatment is non-surgical.
Management includes:
-
Short period of sling support (1–2 weeks)
-
Activity modification and lifting restrictions
-
Targeted physiotherapy rehabilitation
-
Gradual return to sport and function
Most patients recover excellent strength and shoulder function without surgery.
Example of surgical treatment for
chronic issues requiring a tendon graft
Grade 3 (Complete Ligament Tear)
In Grade 3 injuries, both the AC and coracoclavicular ligaments are torn, allowing the clavicle to rise from its normal position.
Treatment may be surgical or non-surgical, depending on:
-
Patient activity level and goals
-
Occupation (e.g., overhead labour)
-
Sporting demands
-
Cosmetic concerns
-
Persistent pain or instability
Dr Brumby-Rendell assesses each patient individually to discuss whether stabilisation surgery is likely to provide meaningful benefit.
Grade 4–5 (Severe Displacement)
These injuries involve marked displacement of the clavicle and significant ligament disruption.
Surgical stabilisation is generally recommended, as outcomes are typically better than non-operative treatment for this level of injury.
Example of surgery for AC Joint Acute Injuries
Surgical Stabilisation of the AC Joint
AC joint stabilisation is performed using a minimally invasive open technique through a small incision over the front of the AC joint.
The procedure involves:
-
Reduction of the displaced clavicle back into anatomical alignment
-
Reconstruction of the torn coracoclavicular ligaments
-
Stabilisation using high-strength synthetic suture tape fixation
-
Creation of a biological scaffold to allow ligament healing
This restores normal shoulder mechanics and joint stability.
Distal Clavicle Excision (When Needed)
In some patients, a small portion of the end of the clavicle may also be removed during surgery. This may be beneficial when:
-
Pre-existing AC joint arthritis is present
-
The injury is subacute or chronic
-
There is persistent joint irritation or impingement
This does not affect shoulder strength and can improve long-term comfort.
Non-Surgical Treatment Overview
For suitable injuries, non-operative care focuses on restoring shoulder function while the ligaments heal.
Early care includes:
-
Ice and sling support to reduce pain and inflammation
-
Relative rest for 1–2 weeks
-
Gradual shoulder motion exercises
Rehabilitation then progresses to:
-
Range of motion restoration
-
Rotator cuff strengthening
-
Scapular control and shoulder blade mechanics
-
Return to sport or work-specific activity
When Surgery May Be Considered Earlier
Some patients may benefit from early stabilisation, including:
- Marked clavicle displacement
-
Posterior or unstable AC joint pattern
-
Heavy overhead workers
-
Collision or overhead athletes
-
Young highly active individuals
-
Persistent pain or deformity after rehabilitation
Recovery After AC Joint Stabilisation
Most patients follow a structured rehabilitation program focusing on:
-
Protected healing phase
-
Gradual motion restoration
-
Strength and scapular control
-
Return to sport or work
The goal is restoration of stable, pain-free shoulder function and normal shoulder contour.
Frequently Asked Questions
How Dr Oscar Brumby‑ Rendell can help?
At the Adelaide Shoulder & Upper Limb Clinic, Dr Oscar Brumby‑Rendell offers tailored care for AC joint injuries:
-
Precise diagnosis using clinical examination and imaging
-
Conservative strategies including immobilization plans and evidence-based physical therapy guidance
-
Surgical expertise in arthroscopic and open reconstruction techniques when needed
-
Personalized post-treatment rehab programs focused on shoulder stability, strength, and safe return to activity
Dr Brumby‑Rendell’s subspecialty experience ensures patients receive expert decision-making aligned with their lifestyle demands and recovery goals.
Patients benefit from his focused knowledge in shoulder trauma and advanced surgical techniques. With multiple clinics across Adelaide and a multidisciplinary rehab approach, he prioritizes effective healing, optimal functionality, and minimal downtime for active individuals and athletes alike.
Ready to learn more?
Learn more about shoulder-related injuries with Dr Oscar Brumby-Rendell. In this video we'll be talking about Shoulder Impignement & Bursitis.
Read more about them below:
Once you have a referral…
Book your consultation here.