fractured ribs with very little pain

Let me start by stating my son has Tourettes Syndrome and some times hs violent "ticks".    Yesterday he had a follow up with the TS Dr., and one of my questions was concerning a knot on his ribs.  I thought it was muscular from the twitching.  Long story short, I was sent in for xrays.  I was told he has two old fractured ribs.  So of course, now the pediatricians are accusing child abuse.  He had little pain,(months earlier) and when I did call the pediatrician about the pain, they recommended Motrin, 600 mg, heat and cold. Then I was told it was probably sore muscles from the ticks and twitches.  He continued to play his sax in the band.  Broken ribs are supposed to hurt, right?  And hurt to breathe.  If coughing can cause broken ribs can twitching?  But why was the pain minimal?  I take my kids to the peditrician over a sniffle, how could I have not noticed broken ribs.