SteelerGirl

I submitted my initial claim for multiple issues back in 2015. They denied all and then I appealed it last yr and denied again. My rep submitted another claim for my right leg and knee 2 months ago. I was examined and got a 10% rating for my knee only. I was under the impression I would get retroactive pay from my initial claim since my knees and legs were included. The letter I received states effective Sep 2017. Why was it not retroactive from the initial submission from 2015? Do I have to dispute that too?