Thank you all for your helpful responses. There was no history of trauma or a bleeding disorder. She just presented with leg length discrepancy. I have no other helpful clues. The most common answer I have received was a subperiosteal hematoma. One response included a “subperiosteal ganglion”. Another one also mentioned a subperiosteal osteosarcoma. A couple of people mentioned thigh splints.
I went with a subperiosteal hematoma and recommended correlation with history of trauma, bleeding disorder etc. Also recommended 3-6 month follow up just to be on the safe side.
Thank you again for all your help.
