text: A second limitation is that we did not know about the 
  subjects’ prior experiences with physical 
  therapy, or 
  whether they arrived at physical therapy through direct 
  access or referral from another provider. These factors 
  could be associated with treatment expectations, which 
  have known effects on treatment outcomes [52, 53]. We 
  also did not collect specific information on treatment. 
  But by including changes 
  in pain, disability, and 
  pain-related psychological distress in the models, we 
  were able to account for treatment response. The benefit 
  of this approach is that models are generalizable for pre- 
  dicting utilization outcomes across “real-world” prag- 
  matic 
  treatment 
  variation is expected. The drawback is that we are pro- 
  hibited from making conclusions regarding which char- 
  influence 
  acteristics of 
  subsequent pain-related healthcare utilization. Important 
  characteristics to consider would include number of 
  visits, type of interventions or whether patients com- 
  pleted their course of physical therapy. These have been 
  proposed or identified as important contributors to 
  downstream costs following physical therapy [54, 55] 
  and may be a source of unexplained variance in our 
  models. Characteristics of the clinical encounter should 
  be considered in future studies to refine the prediction 
  models developed in our analyses. 
  
  physical  therapy  settings where 