Ongoing bruising and extreme pain for 9 weeks and no answers

I'm hoping someone may be able to shed some light on what is happening to my teenage daughter. 9 weeks ago while walking she complained of pain just below her knee. Hours later a small bruise appeared. Over the course of 9 weeks, new bruise-like markings have appeared on her leg daily, covering the front and side of her lower leg. The area always starts out as a small red mark and then turns into a bruise-like appearance. The leg is also in constant pain ( a 7/10 pain).
We have been to heamotologists, oncologists, vein specialists, orthopeadic specialists and dermatologists - every blood test imaginable has been done, and a biopsy looking for panniculitis, but nothing has shown up anywhere. We are just heading down the path of a rheumatologist.
I'm hoping to find someone who has been through something similar and may have some answers for us.