AC Joint Injuries
What Is the AC Joint?
The acromioclavicular (AC) joint is located at the top of the shoulder where the collarbone (clavicle) meets the highest point of the shoulder blade (acromion). This joint helps support shoulder movement and allows the arm to lift and rotate.
An AC joint injury occurs when this connection is stretched or torn, often due to a fall or direct impact to the shoulder. These injuries are sometimes called a “shoulder separation.”
At OIBortho, our physicians evaluate and treat AC joint injuries for patients throughout Middlesex, Monmouth, and Ocean Counties.
Types of AC Joint Injuries
AC joint injuries are typically graded based on severity:
- Grade I (mild sprain): ligaments are stretched but not torn
- Grade II (partial tear): partial ligament tearing with mild separation
- Grade III (complete tear): complete ligament rupture with visible shoulder separation
- Higher-grade injuries (IV–VI): more severe displacement, less common
The higher the grade, the more instability and deformity in the shoulder.
Symptoms of an AC Joint Injury
Symptoms can vary depending on severity.
Common symptoms include:
- Pain at the top of the shoulder
- Swelling and bruising
- A visible bump or deformity at the AC joint
- Shoulder tenderness when touched
- Pain with lifting the arm
- Weakness in shoulder movement
- Difficulty lifting or carrying objects
- Pain that worsens with cross-body motion
More severe injuries often cause a noticeable “step-off” at the shoulder.
Causes and Risk Factors
AC joint injuries are usually caused by trauma or direct impact.
Common causes include:
- Falling directly onto the shoulder
- Sports injuries (football, hockey, cycling, wrestling)
- Motor vehicle accidents
- Contact or collision sports
- Direct blow to the top of the shoulder
These injuries are especially common in athletes involved in high-impact sports.
How AC Joint Injuries Are Diagnosed
A physician will perform a physical exam and evaluate shoulder alignment, tenderness, and range of motion.
Diagnostic tools may include:
- X-rays (to assess joint separation)
- Stress views in some cases
- MRI (to evaluate ligament damage and soft tissue injury)
Imaging helps determine the severity (grade) of the injury.
Understanding AC Joint Injuries
The AC joint is stabilized by ligaments that hold the collarbone and shoulder blade together. When these ligaments are damaged, the collarbone can shift upward, creating pain and visible deformity.
Mild injuries often heal without surgery, while more severe separations may require surgical reconstruction.
Treatment Options
Treatment depends on injury grade and patient activity level.
Common options include:
- Rest and activity modification
- Ice therapy
- Sling immobilization
- Anti-inflammatory medications
- Physical therapy
- Cortisone injections in select cases
- Surgical repair or reconstruction for severe injuries
Most Grade I–II injuries heal without surgery.
Why Choose OIBortho?
OIBortho provides expert evaluation and treatment for AC joint injuries using a personalized approach focused on restoring shoulder function and reducing pain. Our physicians help patients return safely to work, sports, and daily activities.
We serve patients throughout Middlesex, Monmouth, and Ocean Counties with comprehensive orthopaedic care close to home.
Call 732-800-9000 to speak with one of our scheduling specialists or click here to schedule online 24/7!
Frequently Asked Questions
What is an AC joint injury?
It is an injury to the ligaments connecting the collarbone to the shoulder blade, often called a shoulder separation.
How does it happen?
It usually occurs from a fall directly onto the shoulder or a hard impact.
What does it feel like?
Pain at the top of the shoulder, swelling, and sometimes a visible bump are common.
Does it always require surgery?
No, most mild to moderate injuries heal without surgery.
How long does it take to heal?
Mild injuries may heal in a few weeks, while more severe cases can take longer.
Can I still move my arm?
Yes, but movement may be painful depending on the severity of the injury.