The purpose of this study is to determine whether a new medical technology can help reduce post-operative total knee or hip pain when combined with a Cognitive-Behavioral intervention (CBI). This new medical technology, is called transcranial direct current stimulation (tDCS), it uses a very small amount of electricity to temporarily stimulate specific areas of the brain thought to be involved in pain reduction. The electrical current passes through the skin, scalp, hair, and skull and requires no additional medication, sedation, or needles. This study will investigate the effects of tDCS, the Cognitive-Behavioral (CB) intervention and their combination on pain among veterans following total knee arthroplasty (TKA) or total hip arthroplasty (THA). The Veteran may benefit in the form of decreased pain and opioid requirements following knee or hip replacement surgery. However, benefit is only likely if Veterans are randomized to one of the 3 (out of 4) groups. This study hopes to determine the effects of these interventions and combined effect on post-operative pain, opioid use and functioning during the 48-hour post-operative period following a total knee or hip replacement.