Fig. 5.

a Sagittal T2-weighted MRI study of an ankle with an OD. The vertical configuration of the water column (seen in the center of the talus) suggests that the water is pumped directly caudal under high pressure, perpendicular to the talar joint surface. b and c, Schematic diagrams of fissures in the subchondral bone plate of an unloaded ankle b and a loaded ankle c. When the ankle is loaded, the water is squeezed out of the cartilage into the subchondral bone. The diameter of the opening of the subchondral bone plate determines the pressure of the fluid flow (the smaller the diameter, the higher the pressure)