A positive cross arm test, also known as a cross-body adduction test or a scarf test, indicates pain in the acromioclavicular (AC) joint. This test is used to assess the AC joint for conditions like osteoarthritis or ligament injuries (sprains or separations).
How the Test Works
The examiner supports the patient's arm with one hand while placing the other hand on the opposite shoulder to prevent upper body rotation. The patient's arm is then passively adducted across the body towards the opposite shoulder.
Interpreting the Results
- Positive Test: Pain during this maneuver signifies a positive cross arm test. This pain is usually localized to the AC joint.
- Negative Test: Absence of pain indicates a negative result.
Conditions Indicated by a Positive Test
A positive cross arm test commonly suggests:
- Acromioclavicular (AC) joint osteoarthritis: Degeneration and inflammation of the AC joint.
- AC joint ligament injuries: Sprains or separations of the ligaments supporting the AC joint.
Sensitivity and Specificity
Studies have shown varying sensitivity of the test. For example, one study reported a sensitivity of 67%. It's important to remember that this is just one test, and a comprehensive evaluation of the shoulder is necessary for an accurate diagnosis.
The references highlight the importance of pain as the key indicator of a positive result. The test's purpose is to reproduce the patient's pain, localizing it to the AC joint. While the maneuver itself involves adducting the arm across the body, the crucial element is the presence of pain, making it a positive finding.
