Resisted AC-Joint Extension Test

The Resisted AC Joint Extension Test, also known as the AC Resisted Extension Test, is used to identify pathology in the acromioclavicular (AC) joint in both traumatic and non-traumatic (overuse-related) cases¹.

The test can also be useful for differentiating AC joint pathology from subacromial impingement syndrome².

Test execution

Patient position

• The patient sits upright while the examiner stands behind.

Procedure

1. The shoulder is positioned in 90° flexion and internal rotation.

2. The elbow is flexed to 90°.

3. The examiner places one hand on the patient’s elbow.

4. The patient is asked to perform horizontal abduction against isometric resistance.

Interpretation

• Positive test: Localized pain at the AC joint.

Diagnostic validity and evidence

Diagnostic accuracy values for the Resisted AC Joint Extension Test⁵:

Parameter	Value (%)
Sensitivity	72
Specificity	85
Positive Predictive Value (PPV)	20
Negative Predictive Value (NPV)	98

Test item cluster

This test can be combined with the Cross Body Adduction Test and O’Brien’s Active Compression Test to increase diagnostic accuracy.

Diagnostic accuracy of combined tests⁵:

Positive tests	Sensitivity (%)	Specificity (%)	PPV (%)	NPV (%)
3/3 positive	25	97	31	96
2/3 positive	81	89	28	99
1/3 positive	0	74	17	100

Clinical relevance

• A positive test alone has moderate sensitivity and specificity, but a high negative predictive value (98%), which means a negative test strongly rules out AC joint pathology.

• Test combination: When two or more of the cluster tests are positive, diagnostic accuracy increases substantially.

• Indication for use: This test should be included in the clinical examination of patients with shoulder pain when AC joint pathology is suspected.

Conclusion

The Resisted AC Joint Extension Test is a reliable tool for identifying AC joint pathology. While its standalone diagnostic accuracy is limited, its high NPV makes it valuable for ruling out AC joint involvement. When combined with Cross Body Adduction and O’Brien’s Active Compression Test, diagnostic precision improves significantly.

References

1. Miller MD & Thompson SR. DeLee & Drez's Orthopaedic Sports Medicine (4th Ed). Philadelphia, PA: Elsevier.

2. Frontera WR, Silver JK, Rizzo TD (Jr). Essentials of Physical Medicine and Rehabilitation (3rd Ed). Philadelphia, PA: Elsevier.

3. Cook CE & Hegedus EJ. Orthopedic Physical Examination Tests: An Evidence-Based Approach (2nd Ed). Boston, MA: Pearson.

4. Resisted AC Joint Extension Test from https://www.youtube.com/watch?v=YHdZQnV0KhU. Last accessed April 1, 2016.

5. Chronopoulos E1, Kim TK, Park HB, Ashenbrenner D, McFarland EG. Diagnostic value of physical tests for isolated chronic acromioclavicular lesions. Am J Sports Med, 2004; 32(3): 655-61.