The Federation ofState Boards of Physical Therapy (FSBPT) is in the nascent stage of developinga Physical Therapy license compact.  FSBPT’saim is to reduce regulatory burdens by allowing cross-state practice for licensedPhysical Therapists.  The nursingprofession has had a nursing compact since 2000.  According to FSPBT, 24states participate in the nursing compact.
FSBPT’s AdvisoryTask Force hasrecommended a similar model to the nursing compact. 
The licenseeparticipant must hold one valid, current, unrestricted license his or herprimary state of residence, notify any remote states in which s/he will bepracticing and pay a fee to the remote state.

The final language isexpected to be ready for review in mid-2015. If a state wishes to participate in the PT license compact, that statewill need to pass the final language into law. This likely requires state legislative action.
FSPBT has a seriesof articlesand FAQson their webpage.