Total knee arthroplasty (TKA) is widely performed to reduce pain from advanced osteoarthritis, yet many patients experience severe postoperative pain and up to 25-44% develop chronic postsurgical pain (CPSP). Transcranial direct current stimulation (tDCS), a non-invasive neuromodulation technique, has shown promise in reducing pain and opioid use in early studies but has not been evaluated using comprehensive perioperative, home-based protocols. This study will test whether a home-based tDCS intervention delivered before and after TKA can improve acute pain management and reduce the development of CPSP.

Participants will self-administer 15 tDCS sessions using a home-based device during the perioperative period. Feasibility and acceptability will be assessed through device-recorded adherence data, participant diaries completed during the intervention period, and follow-up diary entries on postoperative days 14, 30, and 90. Findings will be used to refine the protocol and inform the design of a future large-scale trial evaluating the efficacy of home-based tDCS for postoperative pain management following TKA.

Inclusion Criteria:

1. 18 years of age or older.
2. American Society of Anesthesiologists (ASA) Physical Classification Status I-III.
3. Scheduled to undergo unilateral elective primary total knee arthroplasty for advanced osteoarthritis of the knee.
4. Access to a device running iOS Version 10.0 or above, or Android Version 5.0 or above that can connect to the internet.

Exclusion Criteria:

1. History of brain surgery, central nervous system tumors, seizures (including epilepsy), stroke or intracranial implants (e.g plates, screws, deep brain stimulators)

2. Have vascular, traumatic, infectious, or metabolic lesions or diseases of the brain

3. Active diagnosis of a sleep disorder, defined as a documented diagnosis of any of the following conditions within the past 12 months, based on patient history or medical record review:

   • Insomnia disorder (e.g., difficulty initiating or maintaining sleep, early morning awakening)
   • Obstructive sleep apnea (OSA)
   • Central sleep apnea
   • Narcolepsy
   • Restless legs syndrome
   • REM sleep behavior disorder
   • Circadian rhythm sleep-wake disorders
   • Parasomnias (e.g., sleepwalking, night terrors)

4. Active diagnosis of alcohol use disorder, defined as meeting DSM-5 criteria or documented in the patient's medical record within the past 12 months.

5. Patients taking opioid medications with a daily Oral Morphine Equivalent (OME) of ≥ 80 mg

6. Current use of medications or substances known to alter cortical excitability or possess psychoactive properties (e.g., antiepileptics, benzodiazepines, antidepressants, antipsychotics, hallucinogens, dissociatives), as determined by review of the patient's medication list, chart review, and patient history. This includes prescribed medications and illicit substances used within the past 30 days.

7. Have metallic implants or objects in or on the head, including mouth (e.g. electrodes, stents, clips, pins, braces, shrapnel, jewellery (unremovable)

8. Use passive or active implanted medical devices (e.g., pacemakers, defibrillators, cochlear implants, natural implants or active body-worn medical devices (e.g., neural stimulation or medication infusion devices)

9. Have defects in the neurocranium (e.g., post-skull trepanation)

10. Have large vessel occlusions (e.g., complete blockage of the internal carotid artery or other conditions affecting brain perfusion

11. Have skin diseases of the scalp

12. Are using other brain stimulation devices concurrently

13. Are pregnant

14. Are unable to provide informed consent

15. Are unable to wear or tolerate the study device

16. Unable to speak or read English, or understand device operation instructions

As noted above, only the company created the randomization will be aware of allocation assignment. The participant, Investigator, surgeon and outcomes assessors will be blinded to minimize bias.