Mine was my pediatric orthopedic doctor. I was 14 at the time, so I was still able to see the pediatric doctors. He knew me since I was about 6 or 7 from previous injuries from gymnastics (I was an accident-prone gymnast...imagine that). He dealt with my previous two breaks when I was younger, so he got to know that I was able to bounce right back into gymnastics pretty easily. Anyway, after I broke my foot, I went through the whole x-ray and cast deal. After the cast came off, I was given that camel walking boot thing and my doctor said that he trusted me, but just work on weaning off of the crutches first, then out of the boot. When I felt ready, I could go right back into gymnastics. Well, weeks passed and I was still on crutches because my foot just felt awful (RSD kicked in...it started when I was in the cast, but escalated after...). I could not seem to get myself off the crutches. My coaches at the gym noticed that something wasn't right since I always jumped back from injuries. My doctor took notice of it too since he knew I always bounced back. He did an MRI of my foot and then did bloodwork to rule out RA. He also had another RSD patient who was 3 years younger than me, so he was definitely familiar and didn't need to do any additional tests. I guess I was really lucky in a sense since he was familiar and didn't go through the whole trial and error. However, it took a few months after the onset of the RSD for me to officially be diagnosed with it.

Long story short I guess, an MRI, bloodwork, and general observations and manual tests were done by my pediatric orthopedic doctor to diagnose me with RSD.