Cartilage is a poroelastic material for which application of load leads to fluid flow within and out from the porous solid matrix. The redistribution of fluids is a major factor in determining the mechanical properties and friction coefficients, which consequently depend in a complex way on the details of the load history and geometry. Although current poroelastic models for cartilage generally agree with the observed macroscopic behavior, critical tests of the underlying assumptions require direct measurements of the translational motion of the pore fluids. This chapter reviews magnetic resonance imaging investigations of water diffusion and flow in cartilage, with special emphasis on time-resolved measurements during dynamic loading.