Because it sticks out the farthest, the spine of the scapula bears the most weight.
The pressure actually comes from the weight of the sow that presses downward, resting on the point of the spine of the scapula, much like the weight is concentrated while wearing high heels.
Continual pressure on the tissues overlying the scapula restricts their blood supply and eventually without blood, these tissues die.
Because the nerves that supply the area also lose their blood supply and die, the condi- tion is probably not painful.