The McCann Test: Purpose, Performance, and Interpretation for Shoulder Instability

What is the McCann Test?

The McCann Test, formally known as the McCann et al. Anterior Apprehension/Relocation Test, is an orthopedic assessment primarily used to evaluate anterior glenohumeral (shoulder) instability, identifying apprehension or pain that is alleviated by posterior humeral head pressure.

Understanding the McCann Test: An Overview

The McCann Test is a clinical diagnostic maneuver employed by healthcare professionals to assess the integrity and stability of the glenohumeral joint, specifically targeting anterior instability. It is a variant of the traditional apprehension-relocation test, designed to provoke symptoms related to anterior shoulder subluxation or dislocation and then observe if these symptoms can be relieved by manual correction of the humeral head's position.

• Purpose and Background: The primary purpose of the McCann Test is to identify anterior glenohumeral instability. It is particularly useful in individuals who report a history of shoulder dislocations, subluxations, or a feeling of apprehension (fear of dislocation) when their arm is placed in positions of abduction and external rotation. The test was described by McCann et al. in 1993, building upon the well-established apprehension test.
• Context: While the term "McCann test" might not be as universally recognized as some other orthopedic tests, it refers to a specific application of the apprehension-relocation principle, which is a cornerstone of shoulder instability assessment. It helps differentiate true instability from other causes of shoulder pain.

Anatomy and Biomechanics: The Underlying Principles

Understanding the anatomical and biomechanical basis of the McCann Test is crucial for accurate interpretation.

• Joint Involved: The test focuses on the glenohumeral joint, the highly mobile ball-and-socket joint formed by the head of the humerus (ball) and the glenoid fossa of the scapula (socket).
• Mechanism of Instability: Anterior glenohumeral instability occurs when the humeral head translates excessively forward on the glenoid, often due to laxity or damage to the anterior joint capsule, glenohumeral ligaments, or the anterior labrum (e.g., Bankart lesion). When the arm is abducted and externally rotated, the humeral head is driven anteriorly, potentially stretching compromised structures and eliciting pain or apprehension.
• Role of the Test: The McCann Test manipulates the joint to deliberately place stress on these anterior structures. The "apprehension" phase provokes symptoms by positioning the arm in a vulnerable state, while the "relocation" phase aims to reduce the anterior translation of the humeral head, thereby alleviating the stress and symptoms if instability is present. This change in symptoms (apprehension to relief) is the key indicator.

How the McCann Test is Performed

The McCann Test is typically performed with the patient in a supine position to allow for full relaxation and optimal control by the examiner.

• Patient/Client Positioning: The patient lies supine (on their back) on an examination table, with their arm relaxed and the affected shoulder positioned near the edge of the table.
• Examiner Positioning: The examiner stands beside the patient, supporting the arm being tested.
• Execution Steps (Apprehension Phase):
  1. The examiner gently abducts the patient's arm to approximately 90 degrees.
  2. The elbow is flexed to 90 degrees.
  3. While stabilizing the scapula or proximal humerus with one hand, the examiner slowly and progressively applies an external rotation force to the forearm, bringing the shoulder into maximal external rotation.
  4. During this maneuver, the examiner carefully observes the patient's face and verbal cues for signs of apprehension (a feeling of impending dislocation, fear, or protective muscle guarding) or pain. This is the Apprehension Test component.
• Execution Steps (Relocation Phase):
  1. If apprehension or pain is elicited in the apprehension phase, the examiner maintains the arm in that position.
  2. The examiner then applies a firm, posterior-directed force to the anterior aspect of the humeral head (pushing the humerus back into the glenoid).
  3. The examiner observes if the apprehension or pain is reduced or completely eliminated with this posterior force. This is the Relocation Test component.
• Execution Steps (Release/Surprise Phase - Optional but often included):
  1. While maintaining the arm's position, the examiner quickly but carefully removes the posterior-directed force from the humeral head.
  2. The examiner observes if the apprehension or pain immediately returns or increases. This "surprise" can further confirm instability.

Interpreting the Results

Interpreting the McCann Test involves a careful assessment of the patient's subjective experience during the different phases of the test.

• Positive Test Indication: A positive McCann Test is indicated when:
  • The patient experiences apprehension or pain during the Apprehension Phase (abduction and external rotation).
  • And, this apprehension or pain is significantly reduced or completely eliminated when a posterior-directed force is applied to the humeral head during the Relocation Phase.
  • If the "surprise" phase is performed, a rapid return of apprehension upon release of the posterior force further supports a positive finding.
• Clinical Significance: A positive McCann Test is highly suggestive of anterior glenohumeral instability. It indicates that the humeral head is prone to anterior translation, leading to symptoms, and that stabilizing it posteriorly alleviates these symptoms. It does not identify the specific structural lesion (e.g., Bankart lesion, capsular laxity) but points to the presence of instability.
• Differential Diagnosis: The test helps differentiate true mechanical instability from other causes of shoulder pain, such as rotator cuff impingement, tendinopathy, or adhesive capsulitis, which typically do not present with the same apprehension-relief pattern.

Clinical Relevance and Application

The McCann Test is a valuable component of a comprehensive shoulder examination, guiding diagnosis and management strategies.

• When is it Used? The McCann Test is primarily used in clinical settings (orthopedic clinics, physical therapy, sports medicine) for individuals presenting with:
  • A history of recurrent shoulder dislocations or subluxations.
  • A feeling of "dead arm" or apprehension during overhead activities, throwing, or reaching maneuvers.
  • Generalized shoulder pain where instability is suspected.
• Integration with Other Tests: No single orthopedic test is definitive. The McCann Test is most powerful when combined with other shoulder instability tests (e.g., Load and Shift Test, Sulcus Sign for multidirectional instability, Kim or Jerk Test for posterior instability) and a thorough patient history and physical examination. This battery of tests helps confirm the diagnosis and determine the direction and degree of instability.
• Rehabilitation and Training Implications: A positive McCann Test guides treatment decisions. For anterior instability, conservative management often focuses on strengthening the dynamic stabilizers of the shoulder, particularly the rotator cuff muscles (subscapularis, infraspinatus, teres minor) and scapular stabilizers, to improve joint centering and control. In cases of recurrent, symptomatic instability, surgical intervention to repair damaged structures (e.g., labral repair, capsular plication) may be considered. For trainers, understanding this test helps in modifying exercises to avoid positions that provoke apprehension and in designing programs that enhance shoulder stability.

Conclusion: A Valuable Diagnostic Tool

The McCann Test, or more formally the McCann et al. Anterior Apprehension/Relocation Test, remains a fundamental and clinically relevant orthopedic assessment for identifying anterior glenohumeral instability. By systematically provoking and then alleviating apprehension or pain, it provides critical information that helps clinicians confirm the presence of instability, guide further diagnostic workup (e.g., MRI), and formulate appropriate conservative or surgical management plans. For fitness professionals, understanding this test enhances awareness of potential shoulder vulnerabilities and informs safer, more effective exercise programming.