AC Joint Injury: Causes, Symptoms, Grades & Treatment Options
Home Blog AC Joint Injury: Causes, Symptoms, Grades & Treatment Options
Created At: Nov 03, 2025 Updated At: Nov 03, 2025
Author: Dr. Garima Bishwas
PHYSIOTHERAPY 0

Sudden shoulder pain from a fall, impact, or overexertion can make daily tasks feel impossible. Activities like dressing, lifting, or even lying on your side may become painful. For athletes, cyclists, laborers, and anyone prone to falls or physical strain, one of the most common shoulder injuries is an AC joint injury.

The acromioclavicular (AC) joint connects the collarbone (clavicle) to the highest point of the shoulder blade (acromion). It plays a key role in shoulder movement and stability.

Athletes in contact sports, cyclists who fall on their shoulders, or workers lifting heavy objects are particularly at risk.

In this blog, we’ll explore what an AC joint injury is, how it happens, and the best treatment options available.

What Is an AC Joint Injury?

An AC joint injury refers to damage at the junction where the collarbone (clavicle) meets the top of the shoulder blade (acromion). It is commonly referred to as an "AC separation" or "shoulder separation."

This type of injury may involve:

  • Strain (mild stretching of the ligaments)

  • Partial tears

  • Complete dislocations (the collarbone gets pushed out of position)

A mild AC joint injury may feel like soreness after a workout, while severe forms can visibly dislocate the shoulder and cause intense pain.

Anatomy of the AC Joint

The AC joint is essential for raising the arm overhead and providing shoulder flexibility.

Ligaments Supporting the AC Joint:

  • AC Ligament: Directly stabilizes the joint.

  • Coracoclavicular (CC) Ligaments: Two strong bands (trapezoid and conoid) that support vertical shoulder stability.

When these ligaments stretch or tear, pain and instability occur.

These ligaments prevent excessive movement and allow for fluid shoulder motion. Damage to any part of this structure can significantly affect upper-body function.

Types/Grades of AC Joint Injury

Grade

Description

Severity

I

Minor strain or ligament stretching

Mild

II

Partial tear of the AC ligament

Moderate

III

Complete tear of the AC and CC ligaments

Severe

IV

Clavicle dislocation into/behind the muscle

Severe

V

Major displacement with muscle detachment

Very severe

VI

Downward displacement (rare)

Very severe

AC Joint Injury Common Causes

Injuries to the AC joint can result from both trauma and overuse. Common causes include:

  • Direct fall onto the shoulder (e.g., falling off a bike or slipping)

  • Sports collisions, especially in rugby, hockey, and football

  • Heavy lifting with poor form

  • Traffic accidents involving the shoulder hitting the ground or dashboard

  • Repetitive strain from certain jobs or exercises (e.g., bench pressing, swimming)

Symptoms of AC Joint Injury

You might suspect an AC joint injury if you notice:

  • Sharp pain at the top of the shoulder

  • Visible bump or deformity on top of the shoulder

  • Swelling or bruising around the joint

  • Pain when lifting the arm, especially overhead

  • Limited range of motion

  • Clicking, popping, or instability in the shoulder

AC Joint Injury Diagnosis

1. Physical Examination:

  • Palpation to identify pain spots

  • Arm movement tests

  • Evaluation of the range of motion and strength

2. Imaging Tests:

  • X-ray: Best for identifying bone displacement and grading the injury (Rockwood classification)

  • MRI: Useful for evaluating ligament tears and soft tissue damage

Accurate diagnosis helps determine whether surgery is necessary.

AC Joint Injury Treatment Options

a. Non-Surgical Treatment

For Grades I–III, conservative treatment often helps:

  • Rest and avoid strenuous activity.

  • Ice therapy to reduce swelling

  • Arm sling for 1–2 weeks

  • Anti-inflammatory medications (e.g., ibuprofen)

  • Physiotherapy for mobility and strength

  • Gradual return to normal activity under guidance

b. Surgical Treatment

Surgery is considered for Grades IV–VI or when:

  • Chronic pain persists.

  • Cosmetic deformity affects function.

  • Conservative treatment fails.

Surgical procedures include:

  • AC joint reconstruction with grafts or screws

  • Fixation techniques to stabilize the joint

  • Post-operative physiotherapy for 2–3 months

AC Joint Injury Recovery Timeline

Recovery varies based on severity and treatment.

Grade

Recovery Time

Grade I–II

2–6 weeks

Grade III

6–12 weeks

Post-surgery

3–6 months

Rehabilitation Phases:

  1. Rest & Immobilization (1–2 weeks)

  2. Mobility Exercises (2–4 weeks)

  3. Strength Training (4–8 weeks)

  4. Return to Activity (after 8+ weeks)

AC Joint Injury Prevention Tips

Minimize your risk with these proactive measures:

  • Wear protective gear in contact sports.

  • Always warm up and stretch before workouts.

  • Avoid lifting heavy objects without proper posture.

  • Strengthen rotator cuff and deltoid muscles.

  • Correct slouching or poor posture at work.

When to See a Doctor for AC Joint Injury

Seek medical attention if:

  • Severe swelling or an obvious bump appears.

  • Shoulder feels unstable or weak.

  • Pain lasts more than two weeks.

  • You experience numbness or tingling in the arm.

Timely care can prevent chronic pain and loss of function.

Summary

AC joint injuries are common but manageable. With proper rest, diagnosis, and physiotherapy, most people regain full shoulder function without surgery.

Disclaimer: Consult a physiotherapist or orthopedic expert for a personalized shoulder recovery plan.

Need help with shoulder pain? Visit Omansh.org to connect with our physiotherapy experts today.

Frequently Asked Questions

It’s damage to the junction where the collarbone meets the shoulder blade.


Usually from falls, sports injuries, or heavy lifting.

Grades I–VI, based on ligament damage and displacement.

Through physical exams and imaging like X-rays and MRI.

Anywhere from 2 weeks to 6 months, depending on severity.


Yes, most mild and moderate injuries heal with rest and physiotherapy

Pain, swelling, deformity, and limited shoulder movement.

Pendulum swings, wall crawls, band resistance exercises.

Yes, it speeds up recovery and restores function.

AC joint injuries affect bone-ligament junctions; rotator cuff injuries involve muscles/tendons.

Yes, after full recovery and with proper guidance.

Use a pillow to elevate the arm and avoid sleeping on the injured side.

Protein-rich foods, omega-3s, vitamin C, zinc, and collagen.

If pain lasts beyond two weeks or you see a deformity.

Yes, most do with proper rehab.


Strengthen muscles, use correct technique, and avoid overuse.
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