Injuries to the acromioclavicular joint are common among both athletes and the general population. Numerous clinical diagnostic tests have been identified for the physical examination of the acromioclavicular (AC) joint. The purpose of this article is to provide an overview of the diagnostic accuracy of various clinical diagnostic tests that have been identified in the scientific literature for the assessment of the AC joint in order to better inform health practitioners such as physiotherapists.
Anatomy of the Acromioclavicular Joint
The acromioclavicular (AC) joint is one of four joints that make up the shoulder complex. It consists of the acromion process of the scapula and the distal end of the clavicle, as well as the anterior, posterior, superior and inferior acromioclavicular ligaments. Additional vertical stability is provided by the coracoclavicular ligaments (conoid and trapezoid ligaments), which branch from the coracoid process of the scapula to the inferior clavicle¹.
Injuries and degenerative changes at the AC joint are a common cause of shoulder pain and have important implications for the stability of the shoulder complex. Injuries may occur due to either a direct or indirect impact to the AC joint. A direct impact to the AC joint could occur, for instance, in a hockey player who falls onto the AC joint with the arm in an adducted position. An indirect impact could occur as a result of a fall onto an outstretched hand. In this case, the humerus is driven superiorly into the acromion process, which is in turn, driven superiorly relative to the distal clavicle, potentially causing an AC joint injury¹. Moreover, certain weight-lifting activities such as push-ups or dips have also been shown to aggravate the AC joint².
After having sustained an injury to the AC joint, the patient will typically report pain on the superior aspect of the shoulder. Pain may also be present in the area of the upper trapezius and/or anterior shoulder as well. In addition, swelling or deformity may be observed at the superior aspect of the shoulder² There may also be limitations and/or pain with active and passive range of motion, as well as increased joint laxity with accessory glides at the AC joint.
Clinical Diagnostic Tests for the Assessment of the AC Joint
An AC joint injury or instability may be diagnosed with proper history taking, physical examination and imaging¹. That being said, imaging tools are not necessarily readily available and often require that the patient be placed on a waiting list for an undetermined time period. Therefore, many health professionals, such as physiotherapists, must rely primarily on subjective history taking and physical examination.
As previously mentioned, numerous clinical diagnostic tests have been identified for the physical examination of the AC joint. Before I present these tests, I would just like to define several key statistical terms that will be relevant to the application of these tests. For the sake of simplicity, let us say that a certain test has been shown to have 90% sensitivity and 30% specificity. This means that in 90% of the cases, a positive test would correctly identify the presence of a certain condition, and in 30% of the cases, a negative test would indicate the absence of a certain condition. In this example, this test is said to have high sensitivity, but low specificity. Another important term is the likelihood ratio (LR). The likelihood ratio is the likelihood that a given test result would be expected in a patient with the condition compared to the likelihood that that same result would be expected in a patient without the condition. Simply put, it is the ratio of the probability that a test result is correct compared to the probability of the test result being incorrect. The likelihood ratio can be positive or negative, and is typically presented as a number (i.e. LR: + 6)³ A positive LR ≥ 10 provides a clinically significant degree of certainty that the patient with a positive test has the disorder for which you are testing. A negative LR ≤ 0.1 provides a clinically significant degree of certainty that the patient with a negative test result does not have the disorder for which you are testing⁴.
Now that we’ve covered some basic statistics, let’s get to the fun stuff. Below, you will find numerous clinical diagnostic tests identified in the scientific literature for the assessment of the acromioclavicular joint. Each test is explained in detail, and the diagnostic accuracy of each tests is presented as well.
1. Palpation of the Acromioclavicular Joint: this test is quite self-explanatory. It consists of palpating the acromioclavicular joint. Local AC tenderness with palpation would indicate a positive test. Diagnostic Accuracy:Sensitivity: 96%. Specificity: 10%. Likelihood Ratio: +1.07/-0.40⁵.
2. Cross-body Adduction Sign: performed with the arm flexed to 90° and then adducted across the body. The test is positive if it caused pain on the superior aspect of the shoulder near the AC joint². Diagnostic Accuracy: Sensitivity: 77%. Specificity: 79%. Likelihood Ratio: +3.67/-0.29².
Credit: Figure 1 – Taken From Chronopoulos et al., 2004 (see References)
3. AC Resisted Extension Test: the patient’s arm is brought into 90° of shoulder flexion and bent at 90° of elbow flexion. The patient is then asked to horizontally abduct the arm against resistance. The test is positive if pain is reproduced at the AC joint. Diagnostic Accuracy: Sensitivity: 72%. Specificity: 85%. Likelihood Ratio: +4.8/-0.33².
|Credit: Figure 2 – Taken From Chronopoulos et al., 2004 (See References)|
4. O’brien’s Test/Active Compression Test: performed with the shoulder flexed at 90° and adducted approximately 10°. The patient is then asked to resist a downward force on the arm with the thumb facing down and then with the thumb facing up. The test is considered positive if pain was localized to the AC joint with the first technique, but was reduced or eliminated with the second². Three studies examined the diagnostic accuracy of this test² ⁵ ⁷. However, their results were rather conflicting, except for the specificity of the test, which remained rather consistent throughout all three studies. Diagnostic Accuracy: Sensitivity: between 16-93%. Specificity: between 90-96%⁶.
Credit: Figure 3 – Taken From Chronopoulos et al., 2004 (See References)
5. Paxinos Sign: the examiner’s hand is placed over the injured shoulder. The thumb should be rested under the posterolateral aspect of the acromion and the index and long fingers of the same or contralateral hand are placed superior to the midpart of the ipsilateral clavicle. The examiner then applies pressure to the acromion with the thumb, in an anterosuperior direction, while applying a force inferiorly to the midpart of the clavicular shaft with the index and long fingers. The test is considered positive if pain was felt or increased in the region of the acromioclavicular joint and negative if there was no change in the pain level. Diagnostic Accuracy: Sensitivity: 79%. Specificity: 50%. Likelihood Ratio: +1.58/-0.42⁵.
Applying The Evidence
Before I wrap things up, I would like to emphasize that what has been presented in this article is essentially the evidence that is currently available to assess the clinical utility of the above tests. What you may be asking yourself is, “what do I do with all of this information?”. The clinical application is the hard part. That being said, let me simplify it for you. An article published in 2006 by Powell et al. did a great job at explaining how this information can be applied clinically⁸.
Based on the above information, three tests were consistently shown to have high sensitivity: the cross-body adduction sign, paxinos sign and AC joint palpation. This means that a negative result on the latter three tests (i.e. no pain) would indicate a decreased likelihood that AC joint dysfunction is present. Therefore, according to the evidence, to rule out a painful AC joint dysfunction, the cross-body adduction sign, paxinos sign and AC joint palpation should be negative⁸.
Based on the above information, three tests were consistently shown to have high specificity: the cross-body adduction sign, the resisted AC extension test and O’brien’s test. This means that a positive result on the latter three tests (pain reproduction at the AC joint) would indicate an increased likelihood that AC joint dysfunction is present. Therefore, according to the evidence, to rule in a painful AC joint dysfunction, the cross-body adduction sign, the resisted AC extension test and O’brien’s test should be positive⁸.
Anthony Teoli MScPT
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DISCLAIMER: This blog is not meant for diagnostic or treatment purposes. It should not substitute for professional diagnosis and treatment. This blog was not created to provide physiotherapy consultations, nor was it created to obtain new clients. The content of this blog is a resource for information only. This blog was created to serve as an information resource for both the general population and health professionals.
1. Saccomanno, M. F., De Ieso, C., & Milano, G. (2014). Acromioclavicular joint instability: anatomy, biomechanics and evaluation. Joints, 2(2): 87-92.
2. Chronopolous, E., Kim, T. K., Park, H. B., Ashenbrenner, D., & McFarland, E. G. (2004). Diagnostic Value of Physical Tests for Isolated Chronic Acromioclavicular Lesions. The American Journal of Sports Medicine, 32(3): 665-661.
3. Centre for Evidence-Based Medicine. (2017). Likelihood Ratios. Centre for Evidence-Based Medicine. Retrieved from: http://www.cebm.net/likelihood-ratios/
4. Davidson, M. (2002). The interpretation of diagnostic tests: A primer for physiotherapists. Australian Journal of Physiotherapy, 48(3): 227-233.
5. Walton, J. Mahajan, S., Paxinos, A., Marshall, J., Bryant, C., Shnier, R., Quinn R., & Murrell, G. A. C. (2004). Diagnostic Value of Tests For Acromioclavicular Joint Pain. Journal of Bone and Joint Surgery, 86A(4): 807-812.
6. Hegedus, E. J., Goode, A., Campbell, S., Morin, A., Tamaddoni, M., Moorman III, C. T., & Cook, C. (2007). Physical examination tests of the shoulder: a systematic review with meta-analysis of individual tests. British Journal of Sports Medicine, 42(2) : 80-92.
7. O’Brien, S. J., Pagnani, M. J., Fealy, S., McGlynn, S. R., & Wilson, J. B. (1998). The Active Compression Test: A New and Effective Test for Diagnosing Labral Tears and Acromioclavicular Joint Abnormality. The American Journal of Sports Medicine, 26(5): 610-613.
8. Powell, J. W., & Huijbregts, P. A. (2006). Concurrent Criterion-Related Validity of Acromioclavicular Joint Physical Examination Tests: A Systematic Review. The Journal of Manual and Manipulative Therapy, 14(2): 19-29.