What is the main difference between Mill's test and Cozen's test for lateral epicondylitis?

Main Differences Between Mill's Test and Cozen's Test for Lateral Epicondylitis

The main difference between Mill's test and Cozen's test is that Mill's test evaluates lateral epicondylitis by passively stretching the extensor tendons with wrist flexion, while Cozen's test actively stresses these tendons through resisted wrist extension.

Diagnostic Tests for Lateral Epicondylitis

Lateral epicondylitis (tennis elbow) is a common overuse tendon problem affecting the lateral aspect of the elbow, occurring 7-10 times more frequently than medial epicondylitis and typically involving the dominant arm in 75% of cases 1.

Mill's Test

• Involves passive stretching of the extensor tendons by flexing the patient's wrist while the elbow is extended 2
• Tests for pain at the lateral epicondyle when the wrist is passively moved into flexion
• Evaluates the extensibility and pain response of the common extensor tendon under stretch
• Positive when pain is reproduced at the lateral epicondyle during passive wrist flexion 3

Cozen's Test

• Involves active contraction of the extensor muscles against resistance 2
• Performed by having the patient extend the wrist against resistance provided by the examiner
• Tests for pain at the lateral epicondyle during active muscle contraction
• Positive when pain is reproduced at the lateral epicondyle during resisted wrist extension 3

Clinical Significance and Application

• Both tests have identical positivity rates in patients with lateral epicondylitis, with studies showing 100% positivity in acute cases, decreasing to approximately 50% after one month of treatment 2
• These tests are essential components of the physical examination for diagnosing lateral epicondylitis, though neither is completely specific for the condition 4
• A negative Cozen test may suggest an atypical presentation and should prompt further investigation for potential misdiagnosis of lateral elbow pain 4

Considerations in Test Performance

• Grip strength measurements during these tests may vary based on wrist position, with studies showing greater grip strength at 15 degrees of wrist extension compared to 35 degrees in patients with lateral epicondylitis 3
• The tests should be performed bilaterally to compare involved and uninvolved sides, as significant differences in grip strength between sides have been observed, particularly in non-athletes 3

Potential Pitfalls

• Relying solely on these tests may lead to misdiagnosis, as approximately 11% of patients diagnosed with lateral epicondylitis may have other conditions 4
• Young patients (≤30 years) with lateral elbow pain, history of trauma, limitation of range of motion, elbow swelling, or atypical pain location should be evaluated more thoroughly as they have higher risk of misdiagnosis 4
• Multiple corticosteroid injections without improvement should raise suspicion for alternative diagnoses 4

Imaging Considerations

• When clinical tests are inconclusive or symptoms persist despite treatment, imaging may be warranted 1
• Ultrasound or MRI without IV contrast is usually appropriate as the next imaging study after normal or indeterminate radiographs when tendon or ligament injury is suspected 1
• Ultrasound has moderate agreement with MRI for diagnosing common extensor tendon tears (sensitivity 64.52%, specificity 85.19%, accuracy 72.73%) 1