The Kim Test: Purpose, Procedure, and Interpretation for Shoulder Labral Tears

What is the Kim Test?

The Kim test is a specific orthopedic special test utilized by clinicians to assess for posteroinferior labral lesions of the glenohumeral joint, particularly those associated with posterior instability of the shoulder.

Introduction to the Kim Test

The shoulder joint, or glenohumeral joint, is a highly mobile ball-and-socket joint, making it susceptible to various injuries, especially those involving the glenoid labrum. The labrum is a fibrous rim of cartilage that deepens the glenoid fossa (shoulder socket), providing stability and attachment points for ligaments and the biceps tendon. Lesions to the labrum can lead to pain, clicking, and instability. The Kim test, developed by Dr. Jong-Hun Kim, is one of several clinical examination techniques designed to identify specific patterns of labral injury, specifically those affecting the posteroinferior aspect.

Purpose and Clinical Application

The primary purpose of the Kim test is to aid in the diagnosis of posteroinferior glenoid labral tears. These tears are often associated with conditions of posterior shoulder instability, where the humerus tends to translate excessively backward on the glenoid. Clinicians typically employ the Kim test when a patient presents with:

• Posterior shoulder pain: Especially during activities involving overhead movements or pushing.
• Clicking or clunking sensations: Felt in the posterior aspect of the shoulder.
• Symptoms of instability: A feeling that the shoulder is "giving way" or "coming out" posteriorly.

It is a valuable tool in the physical examination battery for shoulder pathologies, helping to narrow down the potential source of symptoms.

Anatomy and Biomechanics of the Shoulder Joint

Understanding the anatomy and biomechanics is crucial for appreciating the Kim test. The glenohumeral joint is formed by the head of the humerus (upper arm bone) and the glenoid fossa of the scapula (shoulder blade). The glenoid labrum significantly contributes to the joint's stability by increasing the depth and surface area of the glenoid.

• Posteroinferior Labrum: This specific region of the labrum is implicated in posterior instability. Injuries here can result from chronic microtrauma, acute trauma (e.g., direct impact, falling on an outstretched arm with the shoulder internally rotated and adducted), or repetitive activities involving forceful posterior loading, such as throwing or pushing.
• Muscles Involved: The rotator cuff muscles (supraspinatus, infraspinatus, teres minor, subscapularis) play a vital role in dynamic shoulder stability. While not directly tested for strength, their integrity influences overall joint mechanics and how a labral tear might present. The deltoid and other surrounding muscles also contribute to the forces applied during the test.
• Biomechanics of the Test: The Kim test aims to reproduce the mechanism of injury or stress the compromised posteroinferior labrum. By applying specific forces (axial compression, posterior shear, and diagonal elevation), it attempts to cause the humeral head to impinge upon or displace the torn labral tissue, eliciting pain or a palpable clunk.

How to Perform the Kim Test

The Kim test is typically performed with the patient seated, allowing for good stabilization of the scapula.

• Patient Position: The patient is seated with their back supported, or supine.
• Examiner Position: The examiner stands behind or beside the patient, supporting the affected arm.

Procedure:

1. Initial Positioning: The patient's affected arm is abducted to 90 degrees and the elbow is flexed to 90 degrees.
2. Axial Compression: The examiner places one hand on the patient's elbow, applying an axial compression force through the humerus towards the glenoid.
3. Diagonal Elevation: While maintaining the axial compression, the examiner elevates the patient's arm diagonally upwards, moving it approximately 45 degrees into forward flexion and 45 degrees into abduction. This position places the shoulder in a specific orientation that stresses the posterior capsule and labrum.
4. Posterior-Inferior Force: With the other hand, the examiner grasps the proximal humerus (just below the shoulder joint) and applies a strong posterior and inferior force, essentially attempting to shear the humeral head posteriorly and inferiorly against the glenoid.
5. Observation: The examiner carefully observes the patient's reaction and palpates the posterior aspect of the shoulder for any abnormal movement or sound.

Interpreting the Results

The Kim test is considered positive if the patient experiences one or more of the following:

• Sudden onset of posterior shoulder pain: This pain is often sharp and localized to the posterior aspect of the joint.
• Palpable clunk or click: The examiner may feel or hear a distinct clunk or click in the posterior aspect of the shoulder, indicating the humeral head shifting over or impinging upon a torn labral segment.
• Feeling of apprehension or instability: The patient may express a feeling that their shoulder is "giving way" or is about to dislocate posteriorly.

A positive Kim test suggests a high likelihood of a posteroinferior glenoid labral lesion, often associated with posterior shoulder instability.

Clinical Significance, Sensitivity, and Specificity

The Kim test is a valuable component of a comprehensive shoulder examination, but like most special orthopedic tests, it is not a standalone diagnostic tool.

• Diagnostic Value: It helps to differentiate between various shoulder pathologies. A positive Kim test points towards a specific area and type of injury, guiding further investigation.
• Sensitivity and Specificity: Studies have investigated the diagnostic accuracy of the Kim test:
  • Sensitivity: Refers to the test's ability to correctly identify individuals who do have the condition (true positives). The Kim test has been reported to have moderate to high sensitivity for posteroinferior labral tears.
  • Specificity: Refers to the test's ability to correctly identify individuals who do not have the condition (true negatives). The Kim test also generally demonstrates moderate to high specificity.
  • It's important to note that the exact values can vary between studies based on methodology and patient populations.
• Limitations:
  • Examiner Skill: The test requires a skilled and experienced examiner to correctly perform the maneuver and interpret the subtle findings.
  • Patient Cooperation: Pain or apprehension can limit the patient's ability to relax, potentially leading to false negative results.
  • Subjectivity: The pain response and palpable clunk can be subjective.
  • Confirmation Needed: A positive Kim test typically necessitates further diagnostic imaging, such as an MRI or Magnetic Resonance Arthrography (MRA), for definitive confirmation of a labral tear. It's rare for surgical decisions to be made solely on the basis of a physical examination test.

Complementary Assessments

No single orthopedic test is 100% accurate. Therefore, the Kim test is almost always performed as part of a battery of special tests and a comprehensive physical examination of the shoulder. Other tests that might be used alongside the Kim test to assess shoulder instability and labral integrity include:

• Jerk Test: Another test for posterior-inferior labral tears and posterior instability.
• Posterior Apprehension Test: Assesses for posterior instability.
• O'Brien's Test (Active Compression Test): Primarily used for superior labral tears (SLAP lesions).
• Speed's Test: Used for biceps tendinopathy or superior labral tears.
• Anterior Apprehension Test: Assesses for anterior instability.
• Sulcus Sign: Assesses for inferior instability.

Beyond special tests, a complete shoulder assessment includes evaluating range of motion, strength, palpation, and neurological screening to gain a holistic understanding of the patient's condition.

Conclusion

The Kim test is a valuable clinical tool for physical therapists, orthopedic surgeons, and other healthcare professionals in the assessment of shoulder pathology. By specifically stressing the posteroinferior aspect of the glenohumeral joint, it helps to identify potential labral tears associated with posterior shoulder instability. While a positive Kim test can strongly suggest the presence of such an injury, it is crucial to interpret its findings within the context of a thorough clinical history, a comprehensive physical examination, and, when indicated, advanced diagnostic imaging. It serves as a critical piece of the diagnostic puzzle, guiding appropriate management and treatment strategies for patients with shoulder pain and dysfunction.