Posterior Subluxation Test: Purpose, Procedure, and Positive Findings

The Posterior Subluxation Test is a clinical shoulder examination maneuver used to assess suspected posterior glenohumeral instability. It helps clinicians identify abnormal posterior translation of the humeral head and possible spontaneous reduction during shoulder movement.

Posterior shoulder instability can present with pain, clicking, catching, or a sensation of the shoulder slipping out of place. Clinical assessment should combine the patient’s history, physical examination, and additional investigations when indicated. No single shoulder instability test is sufficient to establish a definitive diagnosis.[1–3]

What Is the Posterior Subluxation Test Used For?

The Posterior Subluxation Test is used to assess posterior instability of the glenohumeral joint, in which the humeral head moves abnormally toward the back of the glenoid.

It may help identify abnormal humeral head translation and a clunk associated with reduction of a subluxated joint. The findings should be interpreted alongside other examination maneuvers, such as the Jerk Test, Kim Test, and posterior load-and-shift test.[1,2]

How to Perform the Posterior Subluxation Test

The test is performed by a trained healthcare professional using controlled shoulder movements.

1. Patient position: Ask the patient to sit or stand comfortably, with the shoulder relaxed.
2. Examine the unaffected shoulder first: Use the unaffected side as a reference for comparison.
3. Initial arm position: Position the test arm in shoulder adduction, internal (medial) rotation, and approximately 70°–90° of forward flexion.
4. Apply a posteriorly directed force: Apply controlled pressure through the patient’s elbow in a posterior direction.
5. Move the shoulder: Slowly guide the shoulder into horizontal abduction and external (lateral) rotation while maintaining appropriate control of the applied force.
6. Observe the response: Note any palpable or audible clunk, abnormal humeral head translation, pain, apprehension, or reproduction of the patient’s symptoms.
7. Assess the affected shoulder: Repeat the examination on the symptomatic side and compare the findings.

Clinical note: Descriptions of shoulder instability maneuvers can vary between sources. Confirm the intended technique against the original reference before teaching or performing this specific test. Do not force the shoulder through a painful or unstable range of motion.

What Is a Positive Posterior Subluxation Test?

A positive result is described as a clunk associated with reduction of the humeral head into the glenoid during the movement.

This finding may indicate that the humeral head has undergone subluxation and subsequently returned toward its normal joint position. However, a clunk alone is not diagnostic of posterior shoulder instability; its significance depends on the examination technique, associated symptoms, and other clinical findings.

The examiner should also document:

• Whether the maneuver reproduces the patient’s familiar symptoms.
• Whether posterior translation or a sensation of instability is observed.
• Whether pain, apprehension, clicking, or catching occurs.
• Whether the findings differ between the affected and unaffected shoulders.

A comprehensive shoulder assessment is important because posterior instability can be subtle and may coexist with labral injuries or other shoulder pathology.[1–3]

Clinical Significance of Posterior Shoulder Instability

Posterior glenohumeral instability occurs when the humeral head demonstrates excessive or symptomatic movement toward the posterior aspect of the glenoid. It may develop after trauma, repetitive loading, or in association with capsular laxity and structural abnormalities.

Patients may report posterior shoulder pain, reduced sporting performance, clicking, catching, or symptoms during activities that load the shoulder in flexion, adduction, and internal rotation. The diagnosis is based on the overall clinical presentation rather than an isolated provocative test.[1,3]

Frequently Asked Questions (FAQ)

1. What does the Posterior Subluxation Test assess?

It assesses suspected posterior glenohumeral instability by evaluating humeral head translation and the response to a controlled shoulder movement.

2. What is considered a positive Posterior Subluxation Test?

In the technique described here, a clunk associated with reduction of the humeral head into the glenoid is considered a positive finding. The result should be interpreted alongside pain, apprehension, instability symptoms, and other examination findings.

3. Does a positive test confirm posterior shoulder instability?

No. A positive provocative test may support the clinical suspicion of instability, but no single test definitively confirms the diagnosis. A complete history and physical examination, with imaging when clinically indicated, may be required.[1,2]

4. What is the difference between the Posterior Subluxation Test and the Jerk Test?

The tests should not automatically be considered interchangeable. The Jerk Test is a recognized maneuver for evaluating posterior shoulder instability and may reproduce a sudden jerk as a posteriorly subluxated humeral head relocates. The exact technique and interpretation of the Posterior Subluxation Test should be verified against its original description.[1,2]

5. Which other tests are used to assess posterior shoulder instability?

Commonly described examination maneuvers include:

• Jerk Test: Assesses posterior instability and may reproduce pain or a sudden jerk during relocation.
• Kim Test: Evaluates suspected posteroinferior labral pathology and instability.
• Posterior load-and-shift test: Assesses posterior translation of the humeral head relative to the glenoid.
• Posterior drawer test: Evaluates posterior translation of the humeral head.

These maneuvers provide complementary information and should be interpreted as part of a comprehensive assessment.[1,2]

6. Is the Posterior Subluxation Test reliable on its own?

The available evidence does not support relying on an isolated shoulder instability maneuver to make a definitive diagnosis. A systematic review found limited evidence for several individual clinical tests used to identify posterior glenohumeral instability. Combining history and examination findings may improve clinical assessment.[2,4]

7. Can the test be performed on a painful shoulder?

It should be performed cautiously by a qualified healthcare professional. The maneuver should not be forced, particularly when there is severe pain, suspected acute dislocation, or significant apprehension. The examination should be modified or stopped if symptoms worsen.

References

1. StatPearls. Posterior Shoulder Instability. NCBI Bookshelf. Available at: https://www.ncbi.nlm.nih.gov/books/NBK557648/
2. Hegedus EJ, et al. Physical Exam and Evaluation of the Unstable Shoulder. Sports Health. 2018. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC5646139/
3. The Posterior Unstable Shoulder: Natural History, Clinical Evaluation and Imaging. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC5611895/
4. Evidence-Based Review of Clinical Diagnostic Tests and Predictive Clinical Tests That Evaluate Response to Conservative Rehabilitation for Posterior Glenohumeral Instability: A Systematic Review. PubMed. Available at: https://pubmed.ncbi.nlm.nih.gov/29356622/