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AC Joint Injury

AC Joint Injury Overview

An injury to the acromioclavicular (AC), commonly known as a separated shoulder or a shoulder separation is quite common and is usually caused from direct trauma to the shoulder, such as a hard fall or blunt force during sports. An AC joint injury can result in a shoulder separation or any level of shoulder sprain, all leading to AC joint pain. Sports medicine specialist and orthopedic surgeon, Dr. Brian Waterman, shoulder specialist, can help patients remain active after experiencing an injury to the AC joint.

The AC joint is the location where the clavicle (collarbone) meets the highest point of the shoulder blade (acromion). The joint is held together by multiple ligaments and the ends of the bone are wrapped in cartilage to allow joint movement.

AC joint injuries cause damage to the ligaments and cartilage at some level. An AC joint injury is measured in multiple grades, Grade 1 through Grade 6. Grade 1 represents mild shoulder pain with no shoulder deformity. Grade 6 represents a complete disruption of the ligament, such as a separated shoulder where the clavicle is completely severed inferiorly. Grades 4, 5 and 6 AC shoulder separations are very rare and may cause extreme AC joint pain, deformity and shoulder instability.

Symptoms of an AC Joint Injury

An AC joint injury is marked by AC joint pain following injury, ranging from mild tenderness to intense, sharp pain. This is typically felt on top of the shoulder and bruising may occur. In many higher grade cases, patients may experience a popping sensation, visible deformity, swelling and bruising.

Diagnosis of a Separated Shoulder

A separated shoulder can be easy to diagnose when it causes deformity to the joint. When there is less deformity in the lower grade cases, a physical examination must be performed by Dr. Waterman to locate the area of AC joint pain and discomfort. X-rays and an MRI may be utilized to determine the grade of injury, assess what ligaments are damaged and ensure there is no shoulder fracture.
Treatment of AC Joint Pain


Treatment for a lower grade injury will consist of rest, stabilization in a shoulder sling, anti-inflammatory medications and a physical therapy program. The combination of these items leads to a decrease in AC joint pain in many cases. In most low grade injuries, patients are able to return to all activities within 1-6 weeks with appropriate non-operative care.


For higher grade separated shoulder, a surgical approach may be recommended by Dr. Waterman. If surgery is needed, the decision is reached with the patient and is based on the patient’s overall goals and activity level. Dr. Waterman commonly uses arthroscopic assisted AC joint stabilization to stabilize the AC joint and correct the separation of the clavicle and acromion. This procedure uses small incisions, a camera and special surgical instruments to offer patients a less-invasive surgery and an accelerated recovery time. The joint is typically reconstructed using a ligament graft, and sutures to restore stability. Surgery results are most effective when patients follow a physical therapy and shoulder exercise program following the procedure.

At a Glance

Dr. Brian Waterman, MD

  • Chief & Fellowship Director, Sports Medicine, Wake Forest
  • Team Physician, Wake Forest University, Chicago White Sox
  • Military affiliation/Decorated military officer and surgeon
  • Learn more

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