AC Joint Grading System Overview

An acromioclavicular (AC) joint separation is the medical classification for the separation of the collarbone from the shoulder blade. An AC joint separation is a common injury in the active population and typically occurs from a hard fall or direct hit to the AC joint. AC joint separation grading helps physicians properly diagnosis and plan for proper treatment based on the extent of injury. The AC joint grading system includes a scale of six grades, and is determined by the level of separation found in the diagnostic x-ray and MRI. The most common AC separations are grade 1 through grade 3. Dr. Peter Millett specializes in diagnosing and treating AC joint injuries, helping patients return to the athletic activities they love.

AC Joint Separation Grading Scale

During an injury to the AC joint, soft tissues may become torn, leading to a varying amount of damage. An AC joint separation is graded by the extent of damage sustained to the ligaments. An AC joint separation grading scale includes:

  • Grade 1 – AC joint separation is a mild shoulder separation where the AC ligament is stretched or partly torn.
  • Grade 2 – AC joint separation is a partial separation of the AC joint where the AC ligament is completely torn but the coracoclavicular (CC) ligaments are intact.
  • Grade 3 – AC joint separation is a complete separation of the joint where the AC ligament and CC ligaments are completely torn, as well as the joint capsule.
  • Grades 4, 5 and 6 – AC separations are extremely rare and occur when there is significant posterior movement of the clavicle (collar bone) in relation to the acromion (bony process on the shoulder blade).

What are the symptoms of AC joint separation?

The symptoms of an AC joint separation vary based on the extent of the injury. Treatment treatment options are dependent on the extent of the injury based on the AC joint grading system.

  • Grade 1 – A grade 1 injury typically causes mild tenderness, bruising and minor pain.
  • Grade 2 – A grade 2 injury typically causes moderate to severe pain, swelling and a small bump may be present on the top of the shoulder where the clavicle ends.
  • Grade 3 – A grade 3 AC joint separation injury causes severe pain, swelling, instability and visible deformity.

Have you sustained an AC joint injury and would like information on the severity?

There are two ways to initiate a consultation with Dr. Millett:

You can provide current X-rays and/or MRIs for a clinical case review ($250).

You can schedule an office consultation with Dr. Millett.

Request Case Review or Office Consultation

AC Joint Separation Grading MRI and AC Joint Separation Grading X-Ray

In order to diagnose an AC joint injury and determine the injury level based on the AC joint grading system, Dr. Millett will perform a complete medical review and physical examination. He typically moves and feels the injured joint to get a better understanding of injury and to identify areas of pain and weakness. In many cases, Dr. Millett will perform an AC joint separation grading MRI and AC joint separation grading x-ray. Both diagnostic tests will help determine injury grade and an appropriate treatment plan.

The treatment of an AC separation depends on the injury grade. Grades 1-3 are commonly treated with non-operative measures such as rest, ice medication and arm stabilization in a sling.

Certain patients with a grade 3 AC joint separation will need a surgical treatment to fully recover. The surgical technique most commonly performed by Dr. Millett involves the reconstruction of the CC ligaments and the removal of a small piece of the clavicle at the shoulder. Using a screw or suture loop, he will stabilize the joint which allows for a full recovery in most patients.

For more resources on the AC joint separation grading scale, or to determine your grade of injury with an AC joint separation grading x-ray and MRI, please contact the orthopedic office of Dr. Peter Millett.

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