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Acromioclavicular Joint Sprains

What is an Acromioclavicular (AC) Joint Sprain?

An acromioclavicular (AC) joint sprain, often referred to as a “shoulder separation,” occurs when the ligaments that connect the clavicle (collarbone) to the acromion (part of the shoulder blade) are stretched or torn.

Unlike a shoulder dislocation, which involves the ball-and-socket joint, an AC separation affects the small joint at the top of the shoulder. This injury leads to pain, swelling, and sometimes a visible bump where the end of the collarbone becomes elevated.

AC joint separations are common in contact sports (football, hockey, wrestling), cycling accidents, and falls onto the shoulder. They can range from mild sprains to complete ligament tears with significant deformity.

The acromioclavicular joint connects two bones:

  • The clavicle (collarbone)
  • The acromion, a projection from the shoulder blade (scapula)

The joint is stabilized by two sets of ligaments:

  1. AC ligaments, which connect the clavicle directly to the acromion.
  2. Coracoclavicular (CC) ligaments, which connect the clavicle to another bony projection on the scapula called the coracoid process.

These ligaments maintain the alignment of the shoulder girdle and allow smooth overhead motion. When the shoulder experiences a direct blow or fall onto the tip of the shoulder, these ligaments can stretch or tear, resulting in separation.

AC joint separations are among the most frequent shoulder injuries—particularly in young, active individuals. They account for up to 10% of all shoulder injuries seen in athletes.

This injury typically occurs from:

  • Falling onto the shoulder with the arm tucked in.
  • Direct impact from contact sports.
  • Bicycle or motorcycle accidents landing on the shoulder.

Men are affected slightly more often than women, and most injuries occur in people under 40 years old.

AC joint injuries are classified by severity, based on the degree of ligament damage and displacement of the clavicle.

Type I – Mild Sprain

  • The AC ligaments are stretched but not torn.
  • The joint remains stable.
  • Symptoms: mild pain, swelling, and tenderness.

Type II – Partial Tear

  • The AC ligaments are torn, but the CC ligaments remain intact.
  • The clavicle may rise slightly.
  • Symptoms: pain with motion, mild deformity.

Type III – Complete Tear

  • Both AC and CC ligaments are torn.
  • The clavicle is elevated, creating a noticeable “bump” at the top of the shoulder.
  • Shoulder motion and strength are significantly limited.

Types IV–VI – Severe Displacement

  • The clavicle is displaced backward, downward, or upward through surrounding tissues.
  • These are rare but require surgical repair to restore alignment.

Common symptoms include:

  • Pain on top of the shoulder, especially after a fall or direct impact.
  • Swelling and bruising around the joint.
  • Tenderness or visible deformity (“step-off” at the collarbone).
  • Pain with lifting or overhead movement.
  • Weakness or instability when reaching across the body.

In severe cases, patients may notice the shoulder “drooping” slightly due to ligament disruption.

Dr. José Vega, Cleveland’s trusted orthopedic shoulder specialist, begins with a detailed history and physical examination. He will evaluate the injury mechanism, pain location, and range of motion.

Imaging studies help confirm the diagnosis and grade the injury:

  • X-rays: Standard front and angled views show clavicle elevation and joint spacing. Stress X-rays (with light weights) may help differentiate partial vs. complete tears.
  • MRI: Used for complex or chronic injuries to assess soft-tissue and ligament damage.

Treatment depends on the severity of the injury, activity level, and patient goals.

Nonsurgical Treatment

Most Type I, II and III injuries can be treated without surgery.

  • Rest and sling immobilization for 1–3 weeks to reduce pain and allow healing.
  • Ice and anti-inflammatory medication to reduce swelling.
  • Physical therapy to restore motion, strengthen shoulder stabilizers, and prevent stiffness.
  • Gradual return to sport or work once pain subsides and strength returns (usually 12+ weeks but may be sooner in low grade sprains).

Many patients regain full shoulder function and strength without surgical intervention.

Surgical Treatment

Surgery is considered for:

  • Severe injuries (Type IV–VI)
  • Persistent pain or dysfunction after conservative care (for chronic type III injuries)
  • High-demand athletes or laborers who require full shoulder stability

AC Joint Reconstruction

The goal is to restore normal alignment and stability by reconstructing the torn ligaments.

  • The clavicle is repositioned and stabilized using surgical anchors, suture loops, or tendon grafts.
  • Modern techniques often use a coracoclavicular fixation system for secure, minimally invasive repair.
  • In chronic cases, biologic grafts (from the hamstring or allograft tissue) may reinforce the repair.

Most patients return to sport or full activity within 3–6 months, once healing and strength are restored.

Rehabilitation focuses on restoring strength, motion, and coordination:

  • Early phase (0–6 weeks): Protect the joint in a sling, reduce swelling.
  • Intermediate phase (6-12 weeks): Begin active motion and gentle strengthening.
  • Advanced phase (12+ weeks): Progress strengthening, posture correction, and sport-specific training.

With consistent therapy, most patients regain full function and near pain-free movement. However, most patients continue to notice a bump at the AC joint that remains.

While accidents can’t always be avoided, you can lower your risk with:

  • Proper training and protective equipment in contact sports.
  • Shoulder and core strengthening to improve stability during impact.
  • Safe lifting techniques that minimize shoulder stress.
  • Early treatment of shoulder pain to avoid chronic instability.

An AC joint separation is a common shoulder injury that can range from a mild sprain to complete ligament rupture. With proper diagnosis, personalized care, and advanced surgical options when needed, patients typically make a full recovery and return to normal activity. If you’ve experienced a shoulder injury with pain or a visible bump at the top of your shoulder, contact Dr. José Vega’s office in Cleveland to schedule a comprehensive evaluation today.

References

  1. Beitzel K, Mazzocca AD, Bak K, et al. Current concepts in the treatment of acromioclavicular joint dislocations. Arthroscopy. 2013;29(2):387–397.
  2. Tamaoki MJ, Belloti JC, Lenza M, Matsumoto MH, Gomes Dos Santos JB, Faloppa F. Surgical versus conservative interventions for treating acromioclavicular dislocation of the shoulder in adults. Cochrane Database Syst Rev. 2019;10:CD007429.
  3. Cho CH, Hwang I, Shin HK, et al. Clinical outcomes of arthroscopic-assisted acromioclavicular and coracoclavicular ligament reconstruction for acute dislocation. Am J Sports Med. 2015;43(11):2676–2682.
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Dr. Jose Vega

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