Standing in crib and falling.

kellelle01

DS started standing in his crib a week ago and sometimes he'll bend his knees and fall to his butt to get back down, but other times he will just free fall backwards with his legs stick straight.  He ends up hitting his head pretty hard against the other crib railing/slats in the crib.  It sounds pretty painful.  Just wondering if anyone else's LO is taking some pretty big falls with standing....

Also, has anyone purchased those guard rails for the crib railings to prevent teeth marks?  DS is also biting the railing...awesome.