Very sorry to hear about the early onset arthritis. Yes I imagine it´s quite easy to avoid getting the calcium thru milk and milk products. Since I too dislike milk, I try to get calcium from veggies, nuts, sesame - tahini, comes to mind, yoghurt as well.
Found that the more cleansing ones does (and avoids the SAD food) the more the symptoms of Arthritis goes away. So I´d look into the cleansing forums and the Ask Moreless forum also comes to mind. Many CZers have had amazing results from going with his protocoll, tho it is a tedious "journey". There´s really LOTS you can do at your young age to reverse this condition and you´ll find any amount of incredible info here at CZ!
Blessings and good health to you!