Without knowing exactly what you are referring to here are a few reasons why it would not be paid. If treating a fracture, the first cast/splint or strap application is included in the treatment of fracture and/or dislocation codes and therefore not reported separately.
If it is an initial treatment for sprained ankle or knee with no other treatment, it should be billed with 99070 with an E/M code.
Be sure to check the CMS’s policy and LCD's for any special instructions and when reporting an unlisted code or service, be sure to submit supporting documentation for the nature, extent, and need for the procedure as well as the time and effort necessary to provide the service.
If you are just doing strapping consider using 29540 if reporting strapping for ankle or foot.