Purpose of Test: To test for the presence of a labral tear or acromioclavicular lesion.
Test Position: Sitting or standing
Performing the Test: The patient is instructed to place the shoulder into 90 degrees of flexion and 10 degrees of adduction. Next, the arm is actively internally rotated so the thumb is pointing downward. The instructor then applies a inferior directed force (into shoulder extension), first with the thumb pointing down and a second time with the thumb pointing up.
The test is considered positive for an acromioclavicular lesion if the patient has localized pain in the AC joint with the thumb pointing down & a decrease in pain with the thumb pointing up (supinates the forearm). The test is considered positive for a labral tear if the patient reports a painful clicking in the joint with the thumb pointed down, which is reduced or eliminated when the patient resists the inferior force with his thumb up (supinates the forearm).
Importance of Test: Both acromioclavicular joint separations and labral tears are common shoulder injuries. There are different degrees of an AC joint separation and different types of labral tears, so a careful clinical examination is crucial. Understanding the severity of each injury is an important component to your evaluation as it will affect the patient’s prognosis. When reviewing the anatomy, it is clear why the position of the thumb will alter the patient's pain response. When assessing for labral tears, the thumb is pointed down, the forearm is pronated and arm is internally rotated. This position displaces the biceps tendon inferiorly and medially, tensioning the bicipital-labral complex. Because approximately 50% of the biceps tendon fibers arise from the superior glenoid labrum (the other 50% arise from the supraglenoid tubercle), a shear force is created between the glenoid and labrum when the arm is in the interally rotated position. Similarly, when the arm was flexed to 90 degrees, pronated, internally rotated (thumb pointing down), and slightly adducted, the AC joint experiences the highest compressive forces. In this position, the greater tuberosity of the humerus pushes up on the lax AC joint and creates a painful shearing force when downward pressure is applied. When the thumb is point up (supination), the greater tuberosity moves out of the way and the tension is released from the AC joint, decreasing the pain response. Looking at the diagnostic accuracy, it is important to note that there are very wide ranges for several of the numbers.
2 Key points: The active compression test does have a high +LR for AC joint lesions. When assessing for labral tears, patients often have a distinct clicking sound in the glenohumeral joint.
Note: these tests should only be performed by properly trained health care practitioners.
Reference:
Obrien S, et al (1998). The Active Compression Test: A New andEffective Test for Diagnosing Labral Tearsand Acromioclavicular Joint Abnormality. The American Journal of Sports Medicine. 26. Web 10 Dec 2012.
