This is a case of "black contrast effect" that was provided to me for the purpose of education. The arthrogram was performed with 15 mL of a mixture of 0.2 mL Gadovist in 20 mL normal saline, giving a 1:100 dilution ratio instead of the recommended 1:200 dilution ratio. The patient had no side effects and underwent a repeat arthrogram a few weeks later.