The MCL apprehension sign: A novel test for MCL instability.

Purpose: This study describes a new clinical sign to diagnose clinically relevant medial collateral ligament (MCL) injury and evaluates its use in diagnosis and planning treatment for MCL injuries. Methods: A total of 30 consecutive patients with suspected MCL injury, visiting the sports knee clinic were screened by the senior author and the knee fellow for any clinical laxity. Of these, 9 patients did not have any clinically demonstrable laxity but did have MRI evidence of MCL injury. The presence of apprehension sign was compared against the standard criteria for MCL laxity and was evaluated as a novel test to diagnose clinically significant MCL laxity. Results: Of the 21 patients who were diagnosed to have MCL laxity, 18 had a positive apprehension sign at the time of presentation. Eight out of the nine patients who were negative for MCL laxity, did not have a demonstrable apprehension sign. According to the gold standard index, the apprehension sign had a sensitivity of 85.7% and a specificity of 88.8%. The positive and negative predictive values were 94.7% and 72.7% respectively. The pre-test probability of MCL laxity based on the diagnostic criteria was 70% and increased to 94.7% with a positive apprehension sign. Conclusions: A positive apprehension sign is suggestive of MCL injury requiring active treatment. It also helps in deciding the length of bracing required and the need for further operative treatment. The authors recommend its use as a reliable & reproducible adjunct to standard clinic-radiological work-up for MCL injuries.