Pain is radiating from the left side of the spine (scapula area) through the shoulder blade and to the rear upper arm (triceps area). Pain subsides and returns but is nearly constant. When severe, the pain radiates down to the left little finger. The area inside the shoulder blade in the thoracic area is extremely tender. I am very active and suspect that I injured the muscle/nerve group immediately adjoining the spinal region. This pain sometimes diminishes for hours and sometimes, jittering or throbbing of the triceps muscle takes place. The condition has been present for approximately four days but has increased in severity in the past three days.