Could the scar tissue have attached to a muscle along underneath my arm?

It is very common to notice lumps in the underarm area after the procedure.  The things that you may do to help with this are stretching and massage of the area.  It may take several months for this to resolve.  If this persist then you may want to return to the providers office where you had the procedure performed for evaluation.

Thank you for your question.  It is common and probably normal to have lumps after Miradry.  These can last for several months but will gradually resolve.  If you have one area that seems markedly different than the the other lumps then I would recommend you follow up with the provider to get a recommendation on what, if there is, the problem would be and how to treat it.  Likely it will be just more time and message.  Jeffrey Thaxton, MD FACSCertified, American Board of Plastic SurgeryMember, American Society of Plastic SurgeryMember, American Society of Aesthetic Plastic Surgery

Thank you for your question! 
Firstly, I recommend you speak to the physician or practitioner that performed your miraDry treatment, they will be able to review your history and perform an exam and hopefully give you the best resources to help with your concerns. 
That being said, it's common for patients to feel lumps or scar tissue or a pulling, tugging sensation in the underarm area when stretching or moving. I had the miraDry treatment, myself, and experienced something very similar. What worked for me and what I recommend my patients do is continue to perform their normal, everyday leisure and physical activities, but to make sure they incorporate a consistent, gentle stretching session to help release those lumps or bands. It may take several weeks to months, but you should notice a gradual improvement and return back to your normal state. 
I hope this helps, best of luck to you!