Kim Test: Purpose, Procedure, and Diagnosis of Shoulder Instability

What is a Kim Test?

The Kim test is a specific orthopedic provocative test used by clinicians to assess for posteroinferior shoulder instability, particularly in individuals experiencing posterior shoulder pain or a "dead arm" sensation, often indicative of a posterior labral lesion.

Understanding Shoulder Instability

The shoulder is a highly mobile ball-and-socket joint (glenohumeral joint), formed by the head of the humerus (arm bone) and the glenoid fossa of the scapula (shoulder blade). Its extensive range of motion is achieved at the expense of inherent stability. Stability is provided by static stabilizers (labrum, joint capsule, ligaments) and dynamic stabilizers (rotator cuff muscles, scapular stabilizers).

Shoulder instability occurs when the humeral head moves excessively or dislocates from the glenoid fossa. It can be classified based on direction (anterior, posterior, multidirectional) and etiology (traumatic or atraumatic). While anterior instability is most common, posterior shoulder instability accounts for a significant percentage of cases, often presenting with subtle symptoms that can be challenging to diagnose. Causes include direct trauma to the posterior shoulder, repetitive activities involving posterior loading (e.g., weightlifting bench press, follow-through in throwing sports), or underlying ligamentous laxity.

What is the Kim Test?

The Kim test is one of several clinical orthopedic tests designed to identify posterior and posteroinferior labral tears or general posterior glenohumeral instability. It was developed by Dr. Sang-Jin Kim and colleagues to specifically target lesions of the posteroinferior labrum, which can be difficult to detect with other common tests.

• Purpose: The primary purpose of the Kim test is to provoke symptoms related to posterior labral pathology or posterior glenohumeral instability. This includes reproducing the patient's pain, apprehension, or eliciting a palpable "clunk" or "jerk" as the humeral head subluxes posteriorly.
• Mechanism: The test works by applying a specific combination of forces and movements that stress the posterior aspect of the glenohumeral joint capsule and labrum. By compressing the joint and then applying a posterior-inferior shear force while internally rotating the arm, the test aims to push the humeral head against a potentially torn or detached posteroinferior labrum, thereby reproducing the patient's symptoms or causing a characteristic subluxation/reduction.

How is the Kim Test Performed?

The Kim test is typically performed with the patient in a seated position, allowing for optimal stabilization of the scapula by the examiner.

• Patient Positioning: The patient sits upright with the arm to be tested abducted to 90 degrees. The elbow is flexed to 90 degrees.
• Examiner Maneuver:
  1. The examiner stands behind the patient and uses one hand to firmly grasp the patient's elbow, while the other hand stabilizes the patient's scapula (specifically, the lateral border and inferior angle) to prevent its movement.
  2. The examiner then elevates the patient's arm to approximately 130-140 degrees of abduction.
  3. While maintaining scapular stabilization, the examiner applies an axial load (compression) along the humerus towards the glenoid.
  4. Simultaneously, a strong posterior and inferior force is applied to the proximal humerus while internally rotating the arm. This maneuver aims to stress the posteroinferior aspect of the joint.
• Positive Test Interpretation: The test is considered positive if one or both of the following occur:
  • Sudden, sharp posterior shoulder pain: This is often the primary indicator, suggesting a labral tear or instability.
  • A palpable "clunk" or "jerk" sensation: This indicates that the humeral head has subluxed posteriorly over the glenoid rim and then reduced, often associated with a detached labrum. The patient may also express apprehension or guarding due to the feeling of instability.

Clinical Significance and Interpretation

A positive Kim test is a valuable diagnostic clue for posterior shoulder pathology.

• What a Positive Test Indicates: A positive Kim test is highly suggestive of a posteroinferior labral tear (e.g., a reverse Bankart lesion) or general posterior glenohumeral instability. Studies have shown it to have good sensitivity and specificity for detecting these conditions, making it a useful part of a comprehensive shoulder examination.
• Differential Diagnosis: It's crucial to differentiate a positive Kim test from other causes of posterior shoulder pain, such as rotator cuff tendinopathy (e.g., infraspinatus/teres minor), internal impingement, or scapular dyskinesis. The specific nature of the pain (sharp, lancinating, and reproduced with the maneuver) and the presence of a "clunk" help narrow the diagnosis.
• Limitations: While useful, no single orthopedic test is definitive. The Kim test can be painful for the patient, potentially limiting full execution. It requires a skilled and experienced examiner to properly stabilize the scapula and apply the correct forces. False positives or negatives can occur, especially if the patient is guarding or if the tear is very subtle.

Complementary Tests

To confirm a diagnosis of posterior shoulder instability or a labral tear, the Kim test is often used in conjunction with other clinical assessments and diagnostic tools:

• Other Provocative Tests: The Jerk test, Posterior Apprehension Test, and Posterior Load and Shift test are other maneuvers that can help assess posterior shoulder stability.
• Physical Examination: A thorough assessment of range of motion, strength, palpation, and neurological status is essential.
• Imaging Studies:
  • MRI (Magnetic Resonance Imaging): Can visualize soft tissue structures like the labrum, capsule, and ligaments.
  • MR Arthrography: Involves injecting contrast dye into the joint before an MRI, which can significantly enhance the visualization of labral tears and capsular defects.
  • X-rays: Primarily used to rule out bony abnormalities or fractures.

When to Seek Professional Advice

If you are experiencing persistent shoulder pain, a sensation of instability, clicking, popping, or a "dead arm" feeling, especially after a fall, trauma, or repetitive activities, it is crucial to seek professional medical advice. A qualified healthcare professional, such as an orthopedic surgeon, sports medicine physician, or physical therapist, can perform a comprehensive clinical examination, including specific orthopedic tests like the Kim test, and order appropriate imaging to accurately diagnose your condition. Early and accurate diagnosis is key to developing an effective treatment plan, which may range from conservative management (e.g., physical therapy, pain management) to surgical intervention in more severe cases.

Conclusion

The Kim test is a valuable clinical tool for identifying posteroinferior labral tears and posterior glenohumeral instability. By expertly applying specific forces to the shoulder joint, it aims to reproduce the patient's symptoms or elicit a characteristic clunk, guiding the clinician towards an accurate diagnosis. While a significant component of a shoulder examination, it is always interpreted within the context of the patient's history, other physical findings, and, when necessary, advanced imaging studies, to ensure a comprehensive understanding of the shoulder pathology.