Acromioclavicular sprain

About 12% of shoulder injuries involve the acromioclavicular joint, making it one of the most common injuries among athletes and active individuals.

Here’s the good news: the vast majority of acromioclavicular sprains (Grades I and II) heal on their own without surgery. Your shoulder has a remarkable ability to heal itself when given the right conditions.

You will learn how to recognize an acromioclavicular sprain, understand the grading system (I to VI), and, most importantly, what treatment options are available depending on the severity of your injury.

What is an acromioclavicular sprain?

An acromioclavicular sprain (also known as an AC sprain or acromioclavicular dislocation) is an injury to the ligaments that hold your collarbone and acromion (the upper part of your shoulder blade) together.

This joint is located at the top of your shoulder, where you can feel the small bump of your collarbone. The ligaments that stabilize this area are:

• The acromioclavicular ligaments: which directly connect the clavicle to the acromion

• The coracoclavicular ligaments: which attach the clavicle to the coracoid process (a small bony protrusion below the clavicle)

When these ligaments are stretched or torn as a result of an injury, the joint loses its stability. In severe cases, the collarbone visibly shifts upward, creating a characteristic "bump" at the top of the shoulder.

This injury particularly affects participants in contact sports (such as rugby, hockey, and judo), cyclists, and skiers. Now that you understand the anatomy involved, let’s look at how this injury is classified based on its severity.

What are the different grades of acromioclavicular sprains?

The Rockwood classification system categorizes the severity of a sprain into six types, based on the extent of ligament damage and the displacement of the clavicle.

Grade I: Mild sprain

The acromioclavicular ligaments are stretched but intact. There are no tears or dislocations.

• Healing time: 1 to 3 weeks

• Treatment: Conservative (without surgery)

Grade II: Moderate sprain

The acromioclavicular ligaments are partially or completely torn, but the coracoclavicular ligaments remain intact. The clavicle becomes slightly unstable (the "piano key" sign).

• Recovery time: 4 to 6 weeks

• Treatment: Conservative in the vast majority of cases

Grade III: Complete separation

Both the acromioclavicular and coracoclavicular ligaments are torn. The clavicle is visibly elevated, causing a deformity at the top of the shoulder.

• Recovery time: 8 to 12 weeks

• Treatment: Conservative or surgical, depending on your activity level

Grades IV–VI: Severe displacement

These rare injuries involve significant displacement of the clavicle (posterior, superior, or inferior) and associated muscle tears.

• Recovery: 4 to 6 months (with surgery)

• Treatment: Surgical

Grades I and II account for about 70% of AC joint sprains, Grade III accounts for 20%, and Grades IV through VI account for less than 10% combined. These classifications help you understand where you stand, but how can you recognize this injury in the first place?

What are the symptoms of an acromioclavicular sprain?

Symptoms vary depending on the stage, but certain signs are consistent.

Immediate symptoms (first few hours)

Severe pain at the top of the shoulder

The pain is localized very precisely at the AC joint (the highest point of your shoulder). It is intense at the time of the injury and may radiate into the shoulder.

Difficulty raising the arm

Lifting the arm above the shoulder becomes very difficult or impossible. Movements that bring the arm across the front of the body are particularly painful.

Visible deformation (grades III to VI)

In Grade III sprains and higher, you'll notice an abnormal "bump" at the top of the shoulder: this is the end of your collarbone protruding upward.

Localized swelling

Swelling develops quickly at the AC joint. Unlike other shoulder injuries, the swelling is clearly visible and palpable.

Symptoms in the following days

• Bruise around the joint

• Severe pain on palpation

• Nighttime pain that disrupts sleep

• Instability or clicking during certain movements (Grades II and III)

When to seek emergency care

Seek medical attention immediately if you experience:

• A dramatic deformity of the shoulder

• A complete inability to move the arm

• Numbness or tingling in the arm

• Paleness in the arm or no pulse at the wrist

• Pain that worsens after 48 hours

If you notice several of these symptoms following a clear traumatic event, it’s time to confirm the diagnosis.

What causes an acromioclavicular sprain?

Unlike shoulder pain, which develops gradually, an AC joint sprain always results from a specific traumatic event. A specific triggering event is required.

Traumatic mechanisms

Direct fall onto the shoulder (70% of cases)

This is the most common mechanism. The impact occurs directly on the tip of your shoulder, with your arm held close to your body. The force pushes the acromion downward while the clavicle remains in place, causing a separation.

Examples: a bicycle fall, a tackle in rugby, a skiing fall, a motorcycle accident.

Fall onto an outstretched hand or arm (20% of cases)

The force of the impact travels up the arm and compresses the AC joint.

Direct blow to the shoulder (10% of cases)

A blow directly to the top of the shoulder can cause a dislocation.

High-risk sports

• Contact sports: rugby, ice hockey, soccer, judo

• Cycling sports: road cycling, mountain biking, motocross

• Winter sports: downhill skiing, snowboarding

• Equestrian sports: horseback riding, rodeo

Important point : If your pain developed gradually, without any obvious injury, it is not not an AC sprain. It is likely another condition involving the muscles or tendons. Now that we know what causes this injury, let’s look at how to diagnose it.

How is an acromioclavicular sprain diagnosed?

The diagnosis is based primarily on a clinical examination, supplemented by X-rays to determine the exact grade.

Clinical examination

Your physical therapist or doctor will look for:

History of the injury

The details of your accident are crucial. A typical mechanism (falling onto the shoulder, direct impact) strongly suggests an AC sprain.

Visual inspection

• Visible deformity at the top of the shoulder (grades III to VI)

• Localized swelling at the AC joint

• Bruise

Palpation and tests

• Extreme tenderness on palpation of the AC joint

• "Piano key" test: the collarbone depresses and then springs back up

• Horizontal adduction test: bringing the arm in front of the body causes localized pain

X-rays

X-rays are essential for:

• Confirm the diagnosis

• Determine the exact grade (I to VI)

• Ruling out a clavicle or acromion fracture

X-ray images : frontal view of both shoulders for comparison, axillary view; sometimes X-rays with weight-bearing (weights held in the hands) to highlight the displacement. Did you know? In Quebec, physical therapists can order X-rays if the injury occurred less than 72 hours ago.

Additional tests (complex cases)

• Ultrasound: visualizing the ligaments and assessing the extent of the tears

• MRI: Assessing Muscle Damage and Detecting Associated Lesions

• CT scan: for stages IV to VI to plan surgery

Once the diagnosis has been confirmed and the severity determined, the question becomes: How should this injury be treated?

What are the treatment options based on the severity of the acromioclavicular sprain?

Treatment varies considerably depending on the grade. Grades I and II respond very well to treatment without surgery; the approach for grade III is a matter of debate; and grades IV through VI require surgery.

Treatment of Stage I and II: Conservative Approach

Phase 1: Protection and Relief (0 to 7 days)

• Relative rest: Avoid activities that cause pain without completely immobilizing yourself

• Scarf: 1 to 4 days maximum if the pain is severe

• Ice: 15 to 20 minutes, 3 to 4 times a day for 48 to 72 hours

• Medication: Pain relievers (acetaminophen) or anti-inflammatory drugs as recommended

Phase 2: Gradual mobilization (7 to 21 days)

• Gentle mobility exercises (Codman swings, assisted passive elevation)

• A gradual return to light daily activities

Phase 3: Strengthening and Return to Function (3 to 6 weeks)

• Strengthening the rotator cuff

• Scapular stabilization

• Return to sports: 2 to 3 weeks (Grade I), 4 to 6 weeks (Grade II)

Treatment of Grade III: Conservative vs. Surgical Approach

About 60% to 70% of patients recover very well with conservative treatment (8 to 12 weeks). Surgery may be recommended for:

• Elite athletes (overhead sports)

• Manual laborers who place heavy strain on their shoulders

• Young, very active patients

• Failure of conservative treatment after 3 months

Optimal timeframe : If surgery is chosen, it should ideally be performed within 2 to 3 weeks of the injury.

Treatment of stages IV to VI: surgical

These grades almost always require surgery because the displacement is too severe for proper healing.

Post-surgical recovery :

• Immobilization: 4 to 6 weeks in a sling

• Physical therapy: begins after 6 weeks; treatment plan lasting 4 to 6 months

• Returning to sports: 6 to 12 months

Surgery is just one step. It is rehabilitation that determines your final outcome.

What is the role of physical therapy in rehabilitation?

Whether your sprain is treated conservatively or surgically, physical therapy for shoulder pain is essential for regaining optimal function.

Rehabilitation protocol based on severity

Grades I and II (conservative)

• Pain Management and Restoration of Mobility

• Progressive strengthening (scapular stabilization, rotator cuff)

• Physical Therapy

• Schedule: 4 to 12 sessions over 4 to 8 weeks

Grade III (conservative)

• A similar protocol, but longer (12 to 16 weeks)

• Focus on maximum reinforcement to compensate for residual instability

Surgically treated conditions

• Phase 1 (0 to 6 weeks): Immobilization; passive exercises only

• Phase 2 (6 to 12 weeks): Weaning off the sling, beginning of active movements

• Phase 3 (3 to 6 months): Strength training with progressive resistance

• Phase 4 (6 to 12 months): Return to sports (criteria: full range of motion, strength ≥90%)

• Schedule: 15 to 25 sessions over 6 to 12 months

Even with regular physical therapy sessions, there’s a lot you can do at home to speed up your recovery.

What can you do at home for an acromioclavicular sprain?

Your recovery isn't limited to physical therapy sessions. What you do every day at home directly affects the speed and quality of your recovery.

PEACE & LOVE Principles for the Acute Phase (0 to 72 hours)

PEACE : Protection (wear a sling for up to 3–4 days), Elevation (keep the arm elevated), Avoid anti-inflammatory medications (opt for acetaminophen instead), Light compression, Education about the injury LOVE : Load (gradual increase starting 48 to 72 hours later), Optimism, Vascularization (light cardio exercise), Prescribed exercises as soon as possible

Progressive exercises to do at home

Warning : Consult your physical therapist before starting these exercises. Weeks 1–2 : Codman exercises (small circles, 3 times a day), assisted elevation using the healthy arm Weeks 2–4 : Scapular retraction (bring your shoulder blades together, hold for 5 seconds) Weeks 3–6 : External rotation with elastic band (elbow at 90°) Weeks 4–8 : Gradual strength training with light weights (0.5 to 2 kg)

Tips for promoting healing

Sleep : Sleep on your back with a pillow under your injured arm, or on your healthy side with a pillow between your arms. Avoid sleeping on your injured shoulder. Activities to Avoid :

• 0–2 weeks: Heavy loads, overhead lifting, sudden movements

• 2–6 weeks: Contact sports, heavy lifting, pull-ups

• 6–12 weeks: Returning to sports too soon, heavy overhead lifts

Recovering from an AC joint sprain takes patience, but with a good home exercise program and professional guidance, you’ll maximize your chances of regaining full function.

What are the possible complications and the prognosis?

The vast majority of AC sprains heal without major complications, but it is important to be aware of the risks and expected outcomes.

Prognosis by grade

Grade	Healing	Timeline	Return to sport
I	100%	2-3 weeks	2-4 weeks
II	95-100%	4–6 weeks	6-8 weeks
III (conservative)	70-80% excellent	8-12 weeks	10-16 weeks
III (surgical)	85-95%	4-6 months	6-12 months
IV-VI (surgical)	80-90%	6-12 months	9-12 months

Note : A Grade III conservative treatment may result in a cosmetic deformity (a small bump) that is generally not disabling. Success factors : Young age, good compliance with physical therapy, early rehabilitation, non-smoker. Your commitment to rehabilitation makes all the difference.

Frequently Asked Questions About Acromioclavicular Sprains

Can I work with an AC sprain?

It depends on the severity and the type of work. Office work: return to work after a few days (Grade I), 1 to 2 weeks (Grade II). Physical labor: 3 to 4 weeks off work (Grade I), 6 to 8 weeks (Grade II), 12 weeks or more (Grade III).

Should I wear a scarf?

The sling can be worn for up to 2 to 4 days to relieve pain. Prolonged immobilization is not recommended, as it can lead to stiffness. Remove the sling several times a day to move gently.

Can I drive with an AC sprain?

Grade I: as soon as the pain allows (a few days). Grade II or III: wait at least 1 to 2 weeks. Consult your physical therapist for personalized advice.

How long before I can go back to the gym?

Light exercise (cycling, walking): after 1 week (Grade I). Upper-body exercises: avoid for 3 to 4 weeks (Grade I), 6 to 8 weeks (Grade II), 12 weeks (Grade III). Resume very gradually, using 30% to 50% of your usual workload.

Will the lump on top of my shoulder go away?

Grades I and II: Generally, no permanent deformity. Grade III: The deformity often persists with conservative treatment, although it may improve slightly with muscle strengthening. If it really bothers you, discuss surgical options with an orthopedic surgeon.

Do I need surgery for my stage III cancer?

Not necessarily. About 60% to 70% of Grade III sprains heal very well without surgery. Surgery is mainly considered for elite athletes, manual laborers, or if conservative treatment fails after 3 months.

How many physical therapy sessions will I need?

Grade I: 4 to 8 sessions over 4 to 6 weeks. Grade II: 8 to 12 sessions over 6 to 8 weeks. Conservative treatment for Grade III: 12 to 16 sessions over 12 weeks. Surgery: 20 to 30 sessions over 6 to 12 months.

Conclusion

An acromioclavicular sprain is a common shoulder injury that results from direct trauma. Although it may seem serious and be painful at first, the vast majority of these injuries heal very well.

Key points to remember:

• Grade I and II injuries heal very well with conservative treatment within 2 to 6 weeks

• Grade III can be treated conservatively or surgically, depending on your specific situation

• Stages IV through VI generally require surgery

• Physical therapy is essential for regaining optimal function

• Your commitment to the rehabilitation program directly affects your final outcome

If you have suffered a shoulder injury and are experiencing the symptoms described in this article, see a physical therapist or doctor as soon as possible to get an accurate diagnosis and begin the appropriate treatment.

Sources

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• Gorbaty JD, Hsu JE, Gee AO. Classifications in brief: Rockwood classification of acromioclavicular joint separations. Clin Orthop Relat Res. 2017;475(1):283-287.

• Mouhsine E, Garofalo R, Crevoisier X, Farron A. Grade I and II acromioclavicular dislocations: results of conservative treatment. J Shoulder Elbow Surg. 2003;12(6):599-602.

• Bannister GC, Wallace WA, Stableforth PG, Hutson MA. The management of acute acromioclavicular dislocation. A randomized prospective controlled trial. J Bone Joint Surg Br. 1989;71(5):848-850.

• Cook JB, Shaha JS, Rowles DJ, et al. Early versus delayed surgical treatment of acute acromioclavicular joint dislocations. J Shoulder Elbow Surg. 2014;23(9):1351-1358.