7T MRI provides excellent resolution of the structures in the knee. Fat-saturated T2-weighted imaging at 7T has been used clinically for assessing knee joint effusion, but may provide different contrast than 3T MRI in cases of acute injury involving suspected blood products in the fluid. Here, we show three cases in which joint effusion due to acute injury had dark contrast in T2-weighted images acquired at 7T. For one case, T2-weighted 3T MRI was acquired in which the effusion appeared bright. These differences illustrate the potential for high field MRI to elucidate pathological components not observable at lower field strength.