Statistical Analysis/Power Analysis: Sensitivity and specificity of diagnostic ultrasound and x-ray were calculated. MRI was used as the gold standard confirmatory test. Positive predictive value and Negative predictive value were also calculated for comparison. A priori power analysis determined a sample size of 186 was needed to obtain a power of 80%. The primary aim will be analyzed using a bootstrap test to compare the x-ray sensitivity to the ultrasound sensitivity. In order to account for the paired nature of the data, the bootstrap sampling will be at the subject level and will draw pairs with the x-ray and ultrasound outcomes associated with individual subjects. A statistician from the University of Virginia was hired for all statistical calculations.