Unlike us, cows don’t walk on the soles of their feet. Neither do horses. Most of the weight bearing surface is at the bottom of the walls of the hooves. They walk on the walls of their hooves.
That means the attachment of the triangular shaped pedal bone inside the hoof and the wall of the hoof must be very strong, other wise the bone would push down through the sole of the hoof. The hormones present in the cow at calving act to soften the ligaments of the pelvis to aid expulsion of the calf. Those same hormones have a similar effect on the pedal bone/hoof wall attachment and can result in the pedal bone putting downward pressure on the sole of the hoof. If the effect is prolonged, and the cows walk long distances they bear weight on the flattened sole which squashes the sensitive tissue between the pedal bone and the sole (the corium). That leads to sole bruising, sometimes in all 4 hooves, and a prolonged state of lameness.
The softening of the pedal bone /hoof wall attachment is prolonged when the animals are under stress. It is most common in first calvers.