Diagnostic accuracy and clinical utility of the medicine ball lift test (MBLT) for identifying extensor carpi radialis brevis (ECRB) involvement in lateral epicondylitis

Background. Lateral epicondylitis, commonly called tennis elbow, is one of the most common musculoskeletal conditions caused by tendinopathy of the common extensor tendon, primarily involving the extensor carpi radialis brevis (ECRB). Although different tests, such as Cozen's, Mill's, and Maudsley's tests, are frequently used, none of them help identify the ECRB, which is the principal muscle involved in LE. This diagnostic accuracy study evaluates the newly developed medicine ball lift test, targeting the ECRB specifically, and its association with traditional diagnostic tests and musculoskeletal ultrasound. The study aims to validate the MBLT and measure its sensitivity, specificity, and ability to isolate ECRB involvement in lateral epicondylitis. Methods. A prospective validation study involving 110 patients diagnosed with LE. The MBLT was performed on all participants, supplemented with Cozen's test, Mill's test, and Maudsley's test, along with ultrasonographic analysis of musculoskeletal structures, including tendon thickness, echotexture, and other pathologic features. Sensitivity, specificity, and correlation with ultrasound findings were assessed. Results. The AUC for various tests ranged widely. Cozen's test showed an AUC of 0.495 (p = 0.948), with a sensitivity of 78.9% and specificity of 80.0%. Maudsley's test exhibited an AUC of 0.562 (p = 0.460), with a sensitivity of 91.6% and specificity of 80.0%. Musculoskeletal ultrasound measurements for ECRB involvement, particularly tendon thickness, achieved an AUC of 0.739 (p = 0.001), with a sensitivity of 87.4% and specificity of 46.7%. In contrast, other parameters, such as echogenicity (AUC = 0.360, p = 0.054) and fluid presence (AUC = 0.486, p = 0.863), showed weaker correlations with LE diagnosis. Conclusion. The medicine ball lift test holds promise in diagnosing lateral epicondylitis with specific ECRB involvement. The strong correlation it shows with ultrasonographic findings suggests that it may serve as an adjunct to musculoskeletal ultrasonography in diagnosing LE.