Thanks for your query.
This history of red SI joints and the dilated veins suggest that the inflammation is not controlled. If he is not using anti-inflammatory medication, he will most likely need it. The persistence of these kind of inflammation for a long time may cause permanent damage to the affected joints and limitations of mobility. I suggest you make an appointment with a reumatologist, or a pediatrician
. If you have a pediatric reumatologist in your area, that would be perfect.
Have a nice day, and good luck.