Here's a patient of mine that developed a callous under the second metatarsal head. The patient came in wondering what caused this and it was quite a lengthy discussion. It is usually caused by increased pressure to that area. But this patient has the mechanics of the foot working a little bit differently so that the patient does not put the pressure underneath the big toe joint but rather pivots off the side of the big toe joint causing a callous on the side of the big toe (pinch callous).
As result the pressure from underneath the first metatarsal head moves over to where the calluses under the second metatarsal head. In order treat this we can take off the callous occasionally we can try different types of pads but the best way is to treat it was an orthotic that will take the pressure from underneath the second metatarsal head and redistributed amongst all the other bones as well make the big toe join work better.