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AC Joint Injuries

The acromioclavicular (AC) joint is the small joint located at the top of the shoulder where the collarbone meets the shoulder blade. Injuries to this joint are common after falls, sports collisions, or direct impacts to the shoulder. The AC joint can also become irritated gradually from repetitive loading, weight training, or age-related changes. 

This guide was created by Dr. Michael Hoiles as an educational resource for people experiencing pain around the top of the shoulder. This information is intended for general educational purposes and should not replace an individualized assessment or medical advice. 

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Quick Facts About AC Joint Injuries 

  • The AC joint connects the outer end of the clavicle (collarbone) to the acromion of the shoulder blade. 

  • A direct fall or impact onto the shoulder is one of the most common causes of an AC joint sprain. 

  • Pain is usually felt directly over the top of the shoulder. 

  • Reaching across the body, pressing, pushing, or lying on the injured shoulder often aggravates symptoms. 

  • AC joint sprains range from mild ligament injuries to more significant separations. 

  • Most lower-grade AC joint injuries can be managed without surgery using activity modification and progressive rehabilitation. 

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Anatomy of the AC Joint 

The acromioclavicular joint is located at the highest point of the shoulder. 

It is formed by: 

  • Clavicle: the collarbone 

  • Acromion: the outer portion of the shoulder blade 

  • AC joint capsule: surrounds and helps stabilize the joint 

  • Acromioclavicular ligaments: provide stability directly around the joint 

  • Coracoclavicular ligaments: connect the clavicle to the coracoid process and provide important vertical stability 

Although the AC joint is relatively small, it contributes to normal movement between the shoulder blade and collarbone as the arm moves overhead. 

When the supporting ligaments are injured, the relationship between the clavicle and shoulder blade can change. More significant injuries may produce a visible prominence or “bump” over the top of the shoulder. 

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What Is an AC Joint Injury? 

An AC joint injury occurs when the joint or the ligaments that support it are irritated, stretched, or torn. 

There are two broad ways AC joint pain commonly develops. 

Acute AC Joint Sprain or Separation 

This usually occurs after trauma such as: 

  • Falling directly onto the shoulder 

  • A collision during sport 

  • Falling from a bicycle 

  • Contact during hockey, football, rugby, or other sports 

  • Landing awkwardly on the shoulder 

Depending on the severity of the injury, the supporting ligaments may be: 

  • Mildly stretched 

  • Partially torn 

  • Completely torn 

More severe injuries can allow the shoulder blade to move downward relative to the clavicle, creating the appearance of a prominent bump at the top of the shoulder. 

Gradual or Chronic AC Joint Pain 

The AC joint can also become painful without a major traumatic event. 

Possible contributors include: 

  • Repetitive pressing exercises 

  • Heavy weight training 

  • Repeated overhead activity 

  • Previous AC joint injury 

  • Osteoarthritis of the AC joint 

  • Long-term repetitive loading 

 

AC Joint Sprain vs. Shoulder Separation 

These terms are often used interchangeably. 

An AC joint sprain refers to injury of the ligaments supporting the AC joint. 

A shoulder separation refers to a more significant AC joint injury where disruption of these ligaments allows abnormal separation between the clavicle and shoulder blade. 

Importantly, a shoulder separation is not the same as a shoulder dislocation. 

  • AC separation: occurs at the small joint on top of the shoulder. 

  • Shoulder dislocation: occurs when the head of the humerus comes out of the main glenohumeral shoulder socket. 

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Common Causes & Risk Factors 

Traumatic Causes 

Common mechanisms include: 

  • Direct fall onto the point of the shoulder 

  • Hockey or football collisions 

  • Cycling accidents 

  • Skiing or snowboarding falls 

  • Contact sports 

  • Falling while running 

  • Motor vehicle accidents 

  • Heavy impact during recreational activities 

Repetitive or Gradual Causes 

AC joint irritation can also develop from repeated loading, including: 

  • Bench pressing 

  • Dips 

  • Push-ups 

  • Heavy chest training 

  • Overhead pressing 

  • Cross-body movements 

  • Repetitive occupational activity 

Factors That May Increase Risk 

  • Participation in contact sports 

  • Previous AC joint injury 

  • Heavy or frequent upper-body strength training 

  • Repetitive overhead activity 

  • Age-related AC joint degeneration 

  • Returning to sport before strength and function have recovered 

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Common Symptoms 

AC joint symptoms can vary depending on the severity of the injury and whether it developed suddenly or gradually.

Common symptoms include:

  • Pain directly over the top of the shoulder

  • Tenderness when pressing on the AC joint

  • Pain when reaching the arm across the body

  • Pain with overhead reaching

  • Pain when lifting or carrying objects

  • Discomfort with bench press, push-ups, dips, or overhead pressing

  • Pain when lying or sleeping on the affected shoulder

  • Swelling around the top of the shoulder after an acute injury

  • Bruising following a fall or direct impact

  • Reduced shoulder movement because of pain

  • Pain when pushing or pulling

  • Difficulty returning to weight training or sports

  • A clicking or uncomfortable sensation around the AC joint with certain movements

  • A visible bump or prominence over the AC joint with more significant separations

  • A feeling of instability or weakness following a more severe injury

Symptoms following a mild AC joint sprain may be primarily pain and tenderness, while more significant separations can produce swelling, loss of function, and a noticeable change in the appearance of the shoulder.

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How Is an AC Joint Injury Diagnosed?

AC joint injuries are usually diagnosed through a combination of your history and a physical examination.

An assessment may include:

  • Discussing how the injury occurred

  • Identifying where the pain is located

  • Checking for swelling, tenderness, or a visible bump

  • Assessing shoulder movement and strength

  • Using simple movements to determine whether the AC joint reproduces your pain

  • Checking for signs of a rotator cuff injury or other shoulder problem

X-rays may be recommended after significant trauma, particularly if there is a visible deformity, difficulty using the arm, or concern about an AC joint separation or fracture.

More advanced imaging is usually reserved for situations where another shoulder injury is suspected or the diagnosis remains unclear.

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What Helps AC Joint Injuries?

Most AC joint injuries can be managed conservatively. Treatment depends on the severity of the injury, symptoms, and activity demands.

Common strategies include:

  • Activity modification: Temporarily reduce painful activities such as heavy pressing, push-ups, dips, overhead lifting, or contact sports.

  • Keep the shoulder moving: Gentle movement is usually encouraged as pain allows to prevent unnecessary stiffness.

  • Exercise rehabilitation: Gradually rebuild shoulder mobility, rotator cuff strength, shoulder blade control, and tolerance to lifting.

  • Ice: May provide temporary pain relief following an acute injury.

  • Short-term sling use: May be helpful for comfort after a more painful AC joint sprain or separation.

  • Medication: Over-the-counter or prescription medication may sometimes help manage pain when appropriate.

  • Injections: Corticosteroid injections may occasionally be considered for persistent AC joint pain.

  • Surgery: Usually reserved for selected higher-grade injuries or persistent pain and functional limitations that do not improve with conservative care.

The goal is to protect the joint early, maintain comfortable movement, and progressively rebuild strength and function as symptoms improve.

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How Chiropractic Can Help 

Chiropractic care for an AC joint injury can focus on restoring comfortable movement, rebuilding strength, and helping you safely return to normal activities.

Depending on the injury, treatment may include:

  • Assessment: Determine whether symptoms are consistent with an AC joint injury and whether imaging or referral may be appropriate.

  • Manual therapy: Address shoulder, shoulder blade, or upper-back mobility when appropriate.

  • Soft tissue therapy: Help manage muscle tension and discomfort around the shoulder.

  • Exercise rehabilitation: Gradually restore shoulder mobility, strength, stability, and tolerance to load.

  • Activity modification: Identify which exercises or activities can be continued and which may need temporary modification.

  • Return-to-activity guidance: Progressively prepare the shoulder for work, weight training, sports, and other activities.

The goal is to restore function while gradually increasing what the shoulder can comfortably tolerate.

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Recovery Timeline 

Recovery depends on the severity of the AC joint injury, symptoms, and activity demands.

  • Phase 1 – Acute: Protect the joint, reduce pain and swelling, and maintain comfortable shoulder movement.

  • Phase 2 – Improving: Gradually restore normal range of motion and begin light strengthening.

  • Phase 3 – Strengthening: Progress rotator cuff, shoulder blade, pressing, pulling, and overhead strength.

  • Phase 4 – Return to Activity: Gradually return to heavier lifting, work, and sport as pain, strength, and function improve.

Mild AC joint sprains may improve within several weeks, while more significant separations can require several months to regain full strength and activity tolerance.

A visible bump may remain after an AC joint separation even when pain and function have significantly improved.

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Can I Still Exercise With an AC Joint Injury?

In many cases, yes—but some temporary modifications may be necessary.

Activities that are comfortable can usually be continued, including:

  • Lower-body and core exercises

  • Walking or cycling

  • Light pulling exercises

  • Rotator cuff and shoulder blade strengthening

  • Comfortable shoulder movements

Activities that may temporarily need to be reduced or modified include:

  • Bench press

  • Push-ups and dips

  • Heavy overhead pressing

  • Cross-body movements

  • Contact sports

As symptoms improve, gradually increase range of motion, resistance, and training intensity until you can comfortably return to your normal activities.

 

Exercises Commonly Recommended 

Exercises should be selected based on the severity of the injury, symptoms, and stage of recovery.

Phase 1 – Reduce Pain & Restore Movement

  • Pendulum exercises

  • Assisted shoulder flexion

  • Wall slides

  • Scapular retractions

  • Gentle rotator cuff isometrics

Goal: Maintain comfortable movement while allowing the AC joint to settle.

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Phase 2 – Restore Strength & Stability

  • Resistance-band external rotation

  • Resistance-band rows

  • Scaption raises

  • Wall push-up plus

  • Serratus wall slides

  • Light loaded carries

Goal: Rebuild shoulder strength, stability, and tolerance to load.

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Phase 3 – Return to Full Activity

  • Progressive push-ups

  • Dumbbell or bench press progressions

  • Overhead pressing

  • Rows and pulling exercises

  • Loaded carries

  • Sport- or work-specific exercises

Goal: Restore strength and gradually prepare the shoulder for normal exercise, work, and sport.

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Common Mistakes That Slow Recovery 

Common mistakes that may delay recovery include:

  • Returning to heavy lifting too quickly, especially bench press, dips, or overhead pressing

  • Resting the shoulder for too long instead of gradually restoring movement

  • Repeatedly testing painful movements to see if the injury still hurts

  • Stopping rehabilitation once the pain improves before strength has fully returned

  • Returning to contact sports too early before the shoulder is ready for impact

  • Focusing only on the visible bump rather than pain, strength, and function

A gradual return to normal activity usually gives the shoulder time to rebuild strength and tolerance without repeatedly aggravating the joint.

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When Should I Seek an Assessment? 

Consider having your shoulder assessed if: 

  • Pain followed a fall or direct impact 

  • You notice a new bump or deformity 

  • Pain is concentrated directly over the AC joint 

  • You cannot comfortably raise your arm 

  • Shoulder pain is worsening rather than improving 

  • Symptoms interfere with sleep 

  • You cannot return to normal exercise or work 

  • Pain persists for several weeks 

  • You are unsure whether the injury is an AC sprain, fracture, rotator cuff injury, or another shoulder condition 

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Seek Prompt Medical Assessment If: 

  • There is significant shoulder deformity after trauma 

  • You cannot use the arm following a major injury 

  • You have severe swelling or bruising 

  • You develop numbness, tingling, or significant arm weakness 

  • Your hand becomes unusually cold, pale, or discoloured 

  • There is concern about a fracture 

  • The shoulder becomes hot, red, swollen, and you feel unwell 

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Frequently Asked Questions 

Is an AC joint separation the same as a shoulder dislocation?

No. An AC joint separation affects the joint between the collarbone and shoulder blade, while a shoulder dislocation involves the main ball-and-socket joint of the shoulder.

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Will the bump from an AC joint separation go away?

Not always. A visible bump may remain after a more significant AC joint separation even when pain, strength, and shoulder function have returned.

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Does an AC joint separation need surgery?

Most mild to moderate AC joint injuries can be managed without surgery, while certain severe injuries or persistent symptoms may require an orthopedic assessment.

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Can I exercise with an AC joint injury?

Usually, yes. Painful exercises such as bench press, dips, push-ups, or overhead pressing may need temporary modification while comfortable activities can often be continued.

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How long does an AC joint injury take to heal?

Mild sprains may improve within several weeks, while more significant AC joint separations can require several months to regain full strength and activity tolerance.

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Summary 

✅ AC joint injuries commonly cause pain and tenderness at the top of the shoulder. 

✅ Falls, direct impacts, sports injuries, and repetitive loading are common causes. 

✅ Most mild to moderate AC joint injuries can be managed without surgery. 

✅ Staying active while temporarily modifying painful activities can help support recovery. 

✅ Progressive exercise can help restore shoulder movement, strength, and stability. 

✅ Significant trauma, visible deformity, or difficulty using the arm should be appropriately assessed. 

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Ready to Get Back to Moving Comfortably? 

If pain at the top of your shoulder is preventing you from exercising, working, sleeping comfortably, or doing the activities you enjoy, an assessment can help determine what may be contributing to your symptoms and what you can do about it. 

Dr. Michael Hoiles is a Calgary chiropractor who provides evidence-informed care combining hands-on treatment, exercise-based rehabilitation, and practical advice to help people recover from injury, move better, and stay active. 

Book an appointment today to have your shoulder assessed and to begin working toward your recovery. 

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Related Conditions 

AC joint injuries can sometimes have symptoms that overlap with other shoulder conditions. Depending on your symptoms, you may also want to learn more about:

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