I live in southern NH, and have been working with a great therapist from Exeter Athleticare at Exeter Hospital. I don't know what her personal experience with arthro is, but I've found her to be more knowledgeable than the average PT. I emailed her asking if she knew where you could get the information you need and got this response back today:
"So, to answer your question, although most PT's should be competent to treat this diagnosis a good manual/hands on orthopedic PT would be my suggestion. Depending on where she lives she could call clinics close to her and ask specifically if anyone has any advanced orthopedic manual skills specifically with the knee. The question would be how long she has had this problem for...whether it's a result of a post-op surgery, etc... With arthrofibrosis you end up with dense scar tissue which after a certain period of time can be very difficult to treat and some surgeons (depending on the patient) will end up doing a manipulation to break up the fibrous tissue and then immediately send to PT. If she has a significant flexion contracture and it's been a significant period of time then she should first get herself to a good orthopedic surgeon to see if she's at the point of needing a manipulation. In this area- Dr. McGovern (Exeter) and Dr.King (Portsmouth) would be my suggestions. A PT could also try dynamic splinting if needed, but again, it may not be helpful if the scar tissue is too scarred down/dense."
Hope this is helpful. It sounds like she's somewhat familiar with the problem. Let me know if you'd like her name.