What is an AC joint sprain? 

An AC (acromioclavicular) joint sprain is an injury to the joint at the top of the shoulder where your clavicle (collarbone) meets the acromion (part of the shoulder blade). It commonly occurs when ligaments supporting the joint are stretched or torn due to trauma or an impact. 
Common related conditions
Rotator Cuff Tear Separated Shoulder Shoulder Labral Tear or Strain Shoulder Sprain or Strain

Causes of an AC joint sprain 

An AC joint sprain is typically caused by a direct blow to the top of the shoulder, usually from a fall or collision. It can also result from falling on an outstretched arm or repetitive stress in overhead athletes. 

Risk factors for an AC joint sprain 

  • Contact sports (e.g., football, hockey or rugby) 
  • Cycling or skateboarding accidents 
  • Falls onto the shoulder or outstretched hand 
  • Overhead movements in sports like tennis or weightlifting 

Symptoms of an AC joint sprain 

  • Pain at the top of the shoulder 
  • Swelling and bruising around the joint 
  • A visible bump or deformity on the shoulder 
  • Pain when lifting the arm or reaching across the body 
  • Tenderness or instability at the joint 

Diagnosing an AC joint sprain 

Your doctor will perform a physical exam and may order X-rays to assess alignment of the joint and rule out fractures. In more severe cases, an MRI may be needed to evaluate soft tissue damage. 

Treatment of an AC joint sprain 

Treatment depends on the grade (severity) of the sprain. Mild sprains may heal with rest, ice, a sling, and anti-inflammatory medication. Moderate to severe sprains may require physical therapy, and in some cases, surgical repair if the joint is severely displaced or unstable. 

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