What it is (overview)

An XR Acromioclavicular Joints Bilateral test is a diagnostic imaging exam that uses X-ray technology to take pictures of both acromioclavicular (AC) joints. The AC joint is where the collarbone (clavicle) meets the highest part of the shoulder blade (acromion). Because this test is bilateral, it images the right and left sides, allowing side-by-side comparison.

This X-ray evaluates the alignment and spacing of the AC joints and looks for changes in the surrounding bones. It can help identify:

• Joint injury (such as a sprain or separation after a fall or sports injury)
• Dislocation or subluxation (the joint surfaces are not properly lined up)
• Arthritis or wear-and-tear (bone spurs, narrowing of the joint space, or irregular joint surfaces)
• Fractures near the end of the clavicle or acromion

In plain language, normal results typically mean the bones on both sides line up well, joint spacing looks similar, and there are no obvious fractures or arthritic changes. Abnormal results may show widening of the AC joint (suggesting a separation), uneven alignment (suggesting dislocation), or signs of arthritis such as joint space narrowing or bone spurs. Your clinician interprets the X-ray findings along with your symptoms, physical exam, and any history of trauma as part of an orthopedic examination.

When & why it's usually done

Doctors commonly order a bilateral AC joint X-ray when someone has shoulder pain, tenderness on top of the shoulder, or concerns about shoulder stability. Imaging both sides helps determine whether a finding is truly abnormal or simply a normal anatomical variation.

This test is often recommended if you have:

• Pain at the top of the shoulder, especially when reaching across your body, lifting, pushing, or doing overhead activities
• Swelling, bruising, or a visible bump over the AC joint after a fall or direct blow (common in contact sports, cycling, skiing, or a slip and fall)
• Clicking, popping, or a sense of instability in the shoulder region
• Limited range of motion or pain that persists despite rest and conservative care
• Suspected arthritis of the AC joint, particularly in people who do repetitive overhead work or weight training
• Follow-up after injury to assess healing or to guide treatment decisions (e.g., physical therapy vs. orthopedic referral)

It may also be used as part of diagnostic imaging before procedures or when symptoms do not match the results of a routine shoulder X-ray. In certain situations, clinicians may request special positioning (sometimes including weight-bearing views) to better evaluate the degree of AC joint separation.

Common diseases related to it

• Acromioclavicular (AC) joint sprain
• AC joint separation (shoulder separation)
• AC joint dislocation or subluxation
• Osteoarthritis of the AC joint
• Post-traumatic arthritis of the AC joint
• Distal clavicle fracture (fracture near the AC joint)
• Clavicle malalignment or deformity after prior injury
• Distal clavicle osteolysis (often related to repetitive stress/weightlifting)

Health goals where it may help

• Identifying the cause of persistent or sudden shoulder pain
• Evaluating joint injury after a fall, sports injury, or accident
• Assessing and improving shoulder stability to safely return to work, sports, or daily activities
• Monitoring arthritis progression in the AC joint and guiding symptom management
• Supporting an orthopedic examination and treatment planning (e.g., physical therapy, activity changes, injections, or surgical consultation)
• Comparing both shoulders to clarify whether imaging findings are abnormal or baseline for you (bilateral comparison)