Hypothesis One: Trauma
Trauma is a likely cause of the lameness as the owner suspected that the foal was stepped 
on by the mother.  Being a very young foal, and underfoot a great deal this could easily 
happen.  I would want to know if this is the mare's first foal or not indicating her 
experience as a mother.  Also some information about the birth process itself would be 
useful.  This may tell us if the foal could have injured himself in a dystocia or not.  If the 
mother had stepped on the foal's fetlock joint, there could be a fracture of the bone, a 
stress on the joint or simply inflammation and pain due to the pressure.  I also would like 
to know how long the foal has been lame, indicating how long the pain and swelling has 
been present.  If there was a small fracture, soft tissue and swelling would be likely 
sequela as the bone rubbed against tissues not usually encountered.  Also tendons and 
nerves could be affected primarily or secondarily leading to pain and lameness.  
If the mare and foal have been turned out or had access to other horses in the small herd, then the foal could have been kicked or stepped on by the other horses.  If the foal had attempted to nurse another mare or had been sleeping in the pasture, when the other horses decided to run around it could have been injured.