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Frequently Asked Questions: AC Joint Injuries

AC joint injuries are common among those who participate in competitive athletics. Two of the most common ways people injure their AC joint is by falling on an outstretched arm or running directly into something.

In this article, Dr. Robert Rolf of Beacon Orthopaedics and Sports Medicine will explore AC joint injuries and some of the most frequently asked questions by patients. If you are experiencing any of the symptoms discussed in this article, schedule an appointment today.

What is the AC joint, and what symptoms should I look for to know it’s an AC joint injury?

Your shoulder is formed at the junction of the clavicle, the scapula, and the humerus. The joint between the end of the scapula (the acromion) and the clavicle is called the acromioclavicular joint (AC joint)—one of the important functional joints that allows a full range of movement in the shoulder joint held together by three ligaments which are acromioclavicular, coracoclavicular, and the coracoacromial ligaments.

Some of the signs and symptoms of AC injury are:

  • Pain on the top of the shoulder
  • Pain when lying on the involved side
  • Pain increases with heavy lifting or overhead and across body movements
  • Swelling and bruising along the shoulder
  • Tenderness over the AC joint
  • Decreased range of motion and stability
  • Decreased strength
  • A visible bump on the top of the shoulder
  • A popping sound or catching sensation

What are the Most Common Causes of AC Joint Pain?

Chronic irritation from repetitive overhead motions:

  • Baseball
  • Weightlifting
  • Volleyball
  • Basketball

Contact sports with high-risk for falls and collisions:

  • Football
  • Wrestling
  • Rugby
  • Biking
  • Snow sports
  • Hockey

What are the different types of AC joint injuries?

Type I: where the force applied to the acromioclavicular and coracoclavicular ligaments is too mild to tear them. This will result in only a sprain of the AC joint, and will hurt but not show any evidence of an acromioclavicular joint dislocation.

Type II: where heavier force is applied to the shoulder—disrupting the AC ligaments but leaving the coracoclavicular ligaments intact (but sprained).  When these injuries occur, the lateral clavicle becomes more prominent.

Type III: where the force applied to the shoulder completely disrupts the AC ligaments and coracoclavicular ligaments—leading to complete separation of the clavicle and the resulting protrusion or “bump.”

Type IV: where there is posterior displacement of the clavicle, buttonholing through the trapezius muscle.

Type V: where the clavicle is widely displaced as a result of disruption of muscle attachments.

Type VI (rare): where there is inferior displacement of the distal clavicle below the acromial process or the coracoid process.

Can Physical Therapy Help?

Once an AC joint injury is officially diagnosed, your physician will work with you to develop an individualized plan of action to start your recovery. Most patients with AC joint injuries will start to feel better within a few days or a week of the injury—but it can take at least six weeks for the AC ligaments to fully heal. During that time, it’s crucial to take the pressure off of the AC joint to protect from overstretching the immature scar tissue. While it’s helpful to use a sling, tape or a shoulder brace to de-load your AC joint, physical therapy will be the key to most AC joint injury recovery plans.

Physical Therapy Treatment Goals for AC Joint Injury:

  • Range of Motion – regain ability to move without pain.
  • Strength Training – regain the strength in the shoulder to better prevent re-injury.
  • Pain Management – reduce the amount of residual pain as you go about your normal activities.
  • Functional Training – increase your ability to move your shoulder correctly without putting undue pressure on your AC joint.

Who Should I Talk to About My Recovery Options?

Dr. Rolf of Beacon Orthopaedics received extensive training in advanced arthroscopic techniques and world-class experience in complex shoulder reconstructive procedures for tendon transfers, shoulder replacement, and reverse shoulder replacement procedures. If you think you might have sustained an AC joint injury, schedule an appointment today to speak with Dr. Rolf about your options. His experience and passion for sports medicine will ensure that you return to your favorite activities stronger and better than ever.