i dont usually inject painful muscles unless i know the patient for a long time and Physical therapy hasnt worked. For painful muscles TPI's are usually only a temporary benefit. Dry needling might have some benefit, but again i dont do it unless i know the patient very well. Patients dont always like when i dont inject them at their request. I send them to PT or massage them a bit during the exam. They frequently say "That feels great" and i sell them on the PT from there. Disclosure......I dont have any PT in the office and i make nothing from it.
edit....oh yea, the question....no ive never injected the SCM and probably wouldnt