Son has a 2mm separation in the pars articularis of the l5 on right & a current stress fracture on the same l5 on the left. he is in pain. football?

Could be: Contact sports create stress fractures and disc injuries, disarticulations, fractures, malignments, etc. by their nature. A good set of X-Rays and a skilled orthopedic clinician are essential to get the right treatment after a spinal injury and to avoid further trauma and loss of function. The rule of thumb is early diagnosis to reduce loss of post-recovery functional level