Internal Rotation Resistance Stress Test is a supplement to a positive impingement test to differentiate an outlet impingement in the classical sense from a non-outlet (internal) impingement as a result of intra-articular pathology.
How it’s Performed?
The test is performed with the patient seated and the examiner standing behind the patient.
The patient’s arm is positioned in 90 degrees of abduction in the coronal plane and approximately 80 degrees of external rotation with the elbow flexed.
The patient is then asked to rotate the arm powerfully first internally and then externally against the examiner’s resistance.
What does a positive Internal Rotation Resistance Stress Test mean?
If the patient with a positive impingement test shows a clearly diminished strength of internal rotation in comparison to external rotation, then the test is considered positive, indicating a non-outlet impingement.
If the patient shows weakness during external rotation, that indicates a classic outlet impingement instead.
Sensitivity & Specificity
A prospective study by Zaslav1 to assess the accurecy of Internal Rotation Resistance Stress Test in differentiating between outlet impingement in the classical sense and a non-outlet (internal) impingement, he found the Sensitivity & Specificity as following:
Sensitivity: 88 %
Specificity: 96 %
A classic outlet impingement (primary impingement) is defined as a true constriction caused by sub-acromial spurs or hypertrophic acromioclavicular joint arthritis.
A non-outlet impingement (secondary impingement) is a functional narrowing due to an increase in volume of the sub-acromial structures, usually inflammatory or post traumatic in origin.
Non-outlet (Internal) Impingement
In Non-outlet (Internal) Impingement, internal contact of the rotator cuff occurs with the posterosuperior aspect of the glenoid when the arm is abducted, extended, and externally rotated as in the cocked position of the throwing motion.
It often occurs in throwers who have lost internal rotation of the shoulder. This loss causes the center of rotation of the humeral head to move upward so that the contact between the rotator cuff and the biceps tendon attachments increases.
Arthroscopic findings include partial rotator cuff tears, posterior and superior labral tears, and anterior shoulder laxity.
Early in the course of the condition, aggressive physical therapy with attention to regaining internal rotation and rotator cuff strengthening often is successful.
K R Zaslav: Internal rotation resistance strength test: a new diagnostic test to differentiate intra-articular pathology from outlet (Neer) impingement syndrome in the shoulder. J Shoulder Elbow Surg. Jan-Feb 2001;10(1):23-7. doi: 10.1067/mse.2001.111960. PMID: 11182732
Clinical Tests for the Musculoskeletal System, Third Edition book.
Mark Dutton, Pt . Dutton’s Orthopaedic Examination, Evaluation, And Intervention, 3rd Edition Book.