Self Transcranial Direct Current Stimulation for Pain in Older Adults With Knee Osteoarthritis

Clinical Pain Intensity as Assessed by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) - Stiffness Subscale

The WOMAC is a self-administered questionnaire consisting of 3 subscales related to pain (pain subscale total score range, 0-20), stiffness (stiffness subscale total score range, 0-8), and impairments of physical function (functional impairment subscale range, 0-68), with higher scores indicating worse pain, stiffness, and impairments of physical function, respectively.

Time frame: 2 weeks

Clinical Pain Intensity as Assessed by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) - Functional Impairment Subscale

The WOMAC is a self-administered questionnaire consisting of 3 subscales related to pain (pain subscale total score range, 0-20), stiffness (stiffness subscale total score range, 0-8), and impairments of physical function (functional impairment subscale range, 0-68), with higher scores indicating worse pain, stiffness, and impairments of physical function, respectively.

Time frame: baseline

Clinical Pain Intensity as Assessed by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) - Functional Impairment Subscale

The WOMAC is a self-administered questionnaire consisting of 3 subscales related to pain (pain subscale total score range, 0-20), stiffness (stiffness subscale total score range, 0-8), and impairments of physical function (functional impairment subscale range, 0-68), with higher scores indicating worse pain, stiffness, and impairments of physical function, respectively.

Time frame: 2 weeks

Clinical Pain Intensity as Assessed by Short-Form McGill Pain Questionnaire-2 (SF-MPQ-2) - Continuous Pain Summary Scale

The SF-MPQ-2 measures the quality as well as the intensity of pain. Participants complete the SF-MPQ-2 by rating the extent to which they experienced each of 22 pain descriptors in the past week using an 11-point numeric rating scale (0 = "none" to 10 = "worst possible"). The continuous pain subscale assesses throbbing pain, cramping pain, gnawing pain, aching pain, heavy pain, and tender, and total score on the continuous pain subscale ranges from 0-60, with a higher score indicating worse pain.

Time frame: baseline

Clinical Pain Intensity as Assessed by Short-Form McGill Pain Questionnaire-2 (SF-MPQ-2) - Continuous Pain Subscale

The SF-MPQ-2 measures the quality as well as the intensity of pain. Participants complete the SF-MPQ-2 by rating the extent to which they experienced each of 22 pain descriptors in the past week using an 11-point numeric rating scale (0 = "none" to 10 = "worst possible"). The continuous pain subscale assesses throbbing pain, cramping pain, gnawing pain, aching pain, heavy pain, and tender, and total score on the continuous pain subscale ranges from 0-60, with a higher score indicating worse pain.

Time frame: 2 weeks

Clinical Pain Intensity as Assessed by Short-Form McGill Pain Questionnaire-2 (SF-MPQ-2) - Intermittent Pain Subscale

The SF-MPQ-2 measures the quality as well as the intensity of pain. Participants complete the SF-MPQ-2 by rating the extent to which they experienced each of 22 pain descriptors in the past week using an 11-point numeric rating scale (0 = "none" to 10 = "worst possible"). The intermittent pain subscale assesses shooting pain, stabbing pain, sharp pain, splitting pain, electric-shock pain, and piercing, and total score on the intermittent pain subscale ranges from 0-60, with a higher score indicating worse pain.

Time frame: baseline

Clinical Pain Intensity as Assessed by Short-Form McGill Pain Questionnaire-2 (SF-MPQ-2) - Intermittent Pain Subscale

The SF-MPQ-2 measures the quality as well as the intensity of pain. Participants complete the SF-MPQ-2 by rating the extent to which they experienced each of 22 pain descriptors in the past week using an 11-point numeric rating scale (0 = "none" to 10 = "worst possible"). The intermittent pain subscale assesses shooting pain, stabbing pain, sharp pain, splitting pain, electric-shock pain, and piercing, and total score on the intermittent pain subscale ranges from 0-60, with a higher score indicating worse pain.

Time frame: 2 weeks

Clinical Pain Intensity as Assessed by Short-Form McGill Pain Questionnaire-2 (SF-MPQ-2) - Neuropathic Pain Subscale

The SF-MPQ-2 measures the quality as well as the intensity of pain. Participants complete the SF-MPQ-2 by rating the extent to which they experienced each of 22 pain descriptors in the past week using an 11-point numeric rating scale (0 = "none" to 10 = "worst possible"). The neuropathic pain subscale assesses hot-burning pain, cold-freezing pain, pain caused by light touch, itching, tingling or 'pins and needles', and numbness, and total score on the neuropathic pain subscale ranges from 0-60, with a higher score indicating worse pain.

Time frame: baseline

Clinical Pain Intensity as Assessed by Short-Form McGill Pain Questionnaire-2 (SF-MPQ-2) - Neuropathic Pain Subscale

The SF-MPQ-2 measures the quality as well as the intensity of pain. Participants complete the SF-MPQ-2 by rating the extent to which they experienced each of 22 pain descriptors in the past week using an 11-point numeric rating scale (0 = "none" to 10 = "worst possible"). The neuropathic pain subscale assesses hot-burning pain, cold-freezing pain, pain caused by light touch, itching, tingling or 'pins and needles', and numbness, and total score on the neuropathic pain subscale ranges from 0-60, with a higher score indicating worse pain.

Time frame: 2 weeks

Clinical Pain Intensity as Assessed by Short-Form McGill Pain Questionnaire-2 (SF-MPQ-2) - Affective Description Subscale

The SF-MPQ-2 measures the quality as well as the intensity of pain. Participants complete the SF-MPQ-2 by rating the extent to which they experienced each of 22 pain descriptors in the past week using an 11-point numeric rating scale (0 = "none" to 10 = "worst possible"). The affective description subscale assesses tiring-exhausting, sickening, fearful, and punishing-cruel, and total score on the affective description subscale ranges from 0-40, with a higher score indicating worse pain.

Time frame: baseline

Clinical Pain Intensity as Assessed by Short-Form McGill Pain Questionnaire-2 (SF-MPQ-2) - Affective Description Subscale

The SF-MPQ-2 measures the quality as well as the intensity of pain. Participants complete the SF-MPQ-2 by rating the extent to which they experienced each of 22 pain descriptors in the past week using an 11-point numeric rating scale (0 = "none" to 10 = "worst possible"). The affective description subscale assesses tiring-exhausting, sickening, fearful, and punishing-cruel, and total score on the affective description subscale ranges from 0-40, with a higher score indicating worse pain.

Time frame: 2 weeks

Experimental Pain Sensitivity as Assessed by a Multimodal Quantitative Sensory Testing (QST) Battery - Heat Pain Threshold (HPTH)

In order to measure experimental pain sensitivity, a multimodal Quantitative Sensory Testing (QST) battery will be completed: heat pain threshold (HPTH); heat pain tolerance (HPTO), pressure pain threshold (PPT), punctate mechanical pain (PMP), and Conditioned Pain Modulation (CPM). To assess HPTH, heat stimuli were delivered to the participant's arm or knee using a computer-controlled TSAII NeuroSensory Analyzer. From a baseline of 32 degrees Celsius, the temperature increased by 0.5 degrees Celsius per second until the participants responded by pressing a button to stop heat stimuli. Participants were instructed to press the button when the sensation ''first becomes painful" to assess the heat pain threshold (HPTH). The temperature at which participants pressed the button to indicate the sensation ''first becomes painful" is reported.

Time frame: baseline

Experimental Pain Sensitivity as Assessed by a Multimodal Quantitative Sensory Testing (QST) Battery - Heat Pain Threshold (HPTH)

In order to measure experimental pain sensitivity, a multimodal Quantitative Sensory Testing (QST) battery will be completed: heat pain threshold (HPTH); heat pain tolerance (HPTO), pressure pain threshold (PPT), punctate mechanical pain (PMP), and Conditioned Pain Modulation (CPM). To assess HPTH, heat stimuli were delivered to the participant's arm or knee using a computer-controlled TSAII NeuroSensory Analyzer. From a baseline of 32 degrees Celsius, the temperature increased by 0.5 degrees Celsius per second until the participants responded by pressing a button to stop heat stimuli. Participants were instructed to press the button when the sensation ''first becomes painful" to assess the heat pain threshold (HPTH). The temperature at which participants pressed the button to indicate the sensation ''first becomes painful" is reported.

Time frame: 2 weeks

Experimental Pain Sensitivity as Assessed by a Multimodal Quantitative Sensory Testing (QST) Battery - Heat Pain Tolerance (HPTO)

In order to measure experimental pain sensitivity, a multimodal Quantitative Sensory Testing (QST) battery will be completed: heat pain threshold (HPTH); heat pain tolerance (HPTO), pressure pain threshold (PPT), punctate mechanical pain (PMP), and Conditioned Pain Modulation (CPM). To assess HPTO, heat stimuli were delivered to the participant's arm or knee using a computer-controlled TSAII NeuroSensory Analyzer. From a baseline of 32 degrees Celsius, the temperature increased by 0.5 degrees Celsius per second until the participants responded by pressing a button to stop heat stimuli. Participants were instructed to press the button when they ''no longer feel able to tolerate the pain." The temperature at which participants pressed the button to indicate they could ''no longer feel able to tolerate the pain" is reported.

Time frame: baseline

Experimental Pain Sensitivity as Assessed by a Multimodal Quantitative Sensory Testing (QST) Battery - Heat Pain Tolerance (HPTO)

In order to measure experimental pain sensitivity, a multimodal Quantitative Sensory Testing (QST) battery will be completed: heat pain threshold (HPTH); heat pain tolerance (HPTO), pressure pain threshold (PPT), punctate mechanical pain (PMP), and Conditioned Pain Modulation (CPM). To assess HPTO, heat stimuli were delivered to the participant's arm or knee using a computer-controlled TSAII NeuroSensory Analyzer. From a baseline of 32 degrees Celsius, the temperature increased by 0.5 degrees Celsius per second until the participants responded by pressing a button to stop heat stimuli. Participants were instructed to press the button when they ''no longer feel able to tolerate the pain." The temperature at which participants pressed the button to indicate they could ''no longer feel able to tolerate the pain" is reported.

Time frame: 2 weeks

Experimental Pain Sensitivity as Assessed by a Multimodal Quantitative Sensory Testing (QST) Battery - Pressure Pain Threshold (PPT)

In order to measure experimental pain sensitivity, a multimodal Quantitative Sensory Testing (QST) battery will be completed: heat pain threshold (HPTH); heat pain tolerance (HPTO), pressure pain threshold (PPT), punctate mechanical pain (PMP), and Conditioned Pain Modulation (CPM). To assess PPT, a handheld digital pressure algometer (Wagner, Greenwich, CT) was applied at a constant rate of 0.3 kilograms force per centimeter squared (kgf/cm\^2) per second to the participant's medial knee, lateral knee, or trapezius. Participants were asked to notify the experimenter when the pressure sensation ''first becomes painful." The pressure at which participants pressed the button to indicate that the pressure sensation ''first becomes painful" is reported.

Time frame: baseline

Experimental Pain Sensitivity as Assessed by a Multimodal Quantitative Sensory Testing (QST) Battery - Pressure Pain Threshold (PPT)

In order to measure experimental pain sensitivity, a multimodal Quantitative Sensory Testing (QST) battery will be completed: heat pain threshold (HPTH); heat pain tolerance (HPTO), pressure pain threshold (PPT), punctate mechanical pain (PMP), and Conditioned Pain Modulation (CPM). To assess PPT, a handheld digital pressure algometer (Wagner, Greenwich, CT) was applied at a constant rate of 0.3 kilograms force per centimeter squared (kgf/cm\^2) per second to the participant's medial knee, lateral knee, or trapezius. Participants were asked to notify the experimenter when the pressure sensation ''first becomes painful." The pressure at which participants pressed the button to indicate that the pressure sensation ''first becomes painful" is reported.

Time frame: 2 weeks

Experimental Pain Sensitivity as Assessed by a Multimodal Quantitative Sensory Testing (QST) Battery - Punctate Mechanical Pain (PMP)

In order to measure experimental pain sensitivity, a multimodal Quantitative Sensory Testing (QST) battery will be completed: heat pain threshold (HPTH); heat pain tolerance (HPTO), pressure pain threshold (PPT), punctate mechanical pain (PMP), and Conditioned Pain Modulation (CPM). To assess PMP, punctate mechanical pain is delivered to the patella or hand by a calibrated nylon monofilament for 10 contacts of the monofilament at one contact per second. Participants rate the pain intensity on a scale from 0 (no pain) to 100 (maximum imaginable pain).

Time frame: baseline

Experimental Pain Sensitivity as Assessed by a Multimodal Quantitative Sensory Testing (QST) Battery - Punctate Mechanical Pain (PMP)

In order to measure experimental pain sensitivity, a multimodal Quantitative Sensory Testing (QST) battery will be completed: heat pain threshold (HPTH); heat pain tolerance (HPTO), pressure pain threshold (PPT), punctate mechanical pain (PMP), and Conditioned Pain Modulation (CPM). To assess PMP, punctate mechanical pain is delivered to the patella or hand by a calibrated nylon monofilament for 10 contacts of the monofilament at one contact per second. Participants rate the pain intensity on a scale from 0 (no pain) to 100 (maximum imaginable pain).

Time frame: 2 weeks

Experimental Pain Sensitivity as Assessed by a Multimodal Quantitative Sensory Testing (QST) Battery - Conditioned Pain Modulation (CPM)

In order to measure experimental pain sensitivity, a multimodal Quantitative Sensory Testing (QST) battery will be completed: heat pain threshold (HPTH); heat pain tolerance (HPTO), pressure pain threshold (PPT), punctate mechanical pain (PMP), and Conditioned Pain Modulation (CPM). CPM is reported as the change in PPT before and immediately following immersion of the contralateral hand up to the wrist in a cold water bath (12 degrees Celsius) for up to one minute. To assess PPT, a handheld digital pressure algometer (Wagner, Greenwich, CT) was applied at a constant rate of 0.3 kilograms force per centimeter squared (kgf/cm\^2) per second to the participant's trapezius. Participants were asked to notify the experimenter when the pressure sensation ''first becomes painful." The pressure at which participants pressed the button to indicate that the pressure sensation ''first becomes painful" is reported.

Time frame: baseline

Experimental Pain Sensitivity as Assessed by a Multimodal Quantitative Sensory Testing (QST) Battery - Conditioned Pain Modulation (CPM)

In order to measure experimental pain sensitivity, a multimodal Quantitative Sensory Testing (QST) battery will be completed: heat pain threshold (HPTH); heat pain tolerance (HPTO), pressure pain threshold (PPT), punctate mechanical pain (PMP), and Conditioned Pain Modulation (CPM). CPM is reported as the change in PPT before and immediately following immersion of the contralateral hand up to the wrist in a cold water bath (12 degrees Celsius) for up to one minute. To assess PPT, a handheld digital pressure algometer (Wagner, Greenwich, CT) was applied at a constant rate of 0.3 kilograms force per centimeter squared (kgf/cm\^2) per second to the participant's trapezius. Participants were asked to notify the experimenter when the pressure sensation ''first becomes painful." The pressure at which participants pressed the button to indicate that the pressure sensation ''first becomes painful" is reported.

Time frame: 2 weeks

Number of Participants Who Were Assessed by Functional Near-infrared Spectroscopy (fNIRS)

Pain-related cortical response will be measured using a continuous-wave, multichannel fNIRS imaging system (LIGHTNIRS, Shimadzu, Kyoto, Japan) with three semiconductor lasers at 780, 805, and 830 nm. Optical recordings will be collected during thermal pain stimulation.

Time frame: 2 weeks

Feasibility as Assessed by a Survey of Participants' tDCS Experience - Ease of Using Device

Data will be collected on participants' tDCS experience at the conclusion of tDCS treatment on a scale of 0 (strongly disagree) to 10 (strongly agree): Q1) "Overall the device was easy to use"

Time frame: 2 weeks

Feasibility as Assessed by a Survey of Participants' tDCS Experience - Ease of Preparation of Device

Data will be collected on participants' tDCS experience at the conclusion of tDCS treatment on a scale of 0 (strongly disagree) to 10 (strongly agree): Q2) "It was easy to prepare the device and accessories"

Time frame: 2 weeks

Feasibility as Assessed by a Survey of Participants' tDCS Experience - Effectiveness of Treatment Over Time

Data will be collected on participants' tDCS experience at the conclusion of tDCS treatment on a scale of 0 (strongly disagree) to 10 (strongly agree): Q3) "The effectiveness of the treatment increased over the course of treatment."

Time frame: 2 weeks

Tolerability as Assessed by Number of Participants With Side Effects

The participants will be asked in an open-ended manner whether they have experienced any side effects, and they will then be asked specifically about tingling, itching sensation, burning sensation, pain at the stimulation site, fatigue, nervousness, headache, difficulty concentrating, mood change, and changes in vision or visual perception.

Time frame: 2 weeks

Anxiety as Assessed by the PROMIS Anxiety-short Form

The 7-item PROMIS anxiety-short form assesses the pure domain of anxiety in individuals age 18 and older, and each item on the measure is rated on a 5-point scale (1=never; 2=rarely; 3=sometimes; 4=often; and 5=always) with a range in score from 7 to 35 with higher scores indicating greater severity of anxiety.

Time frame: baseline

Anxiety as Assessed by the PROMIS Anxiety-short Form

The 7-item PROMIS anxiety-short form assesses the pure domain of anxiety in individuals age 18 and older, and each item on the measure is rated on a 5-point scale (1=never; 2=rarely; 3=sometimes; 4=often; and 5=always) with a range in score from 7 to 35 with higher scores indicating greater severity of anxiety.

Time frame: 2 weeks

Depression as Assessed by the PROMIS Depression-short Form

The 8-item PROMIS depression-short form assesses the pure domain of depression in individuals age 18 and older, and each item on the measure is rated on a 5-point scale (1=never; 2=rarely; 3=sometimes; 4=often; and 5=always) with a range in score from 8 to 40 with higher scores indicating greater severity of depression.

Time frame: baseline

Depression as Assessed by the PROMIS Depression-short Form

The 8-item PROMIS depression-short form assesses the pure domain of depression in individuals age 18 and older, and each item on the measure is rated on a 5-point scale (1=never; 2=rarely; 3=sometimes; 4=often; and 5=always) with a range in score from 8 to 40 with higher scores indicating greater severity of depression.

Time frame: 2 weeks

Sleep Disturbance as Assessed by the PROMIS Sleep Disturbance-short Form

The 8-item PROMIS sleep disturbance-short form assesses the pure domain of sleep disturbance in individuals age 18 and older, and each item on the measure is rated on a 5-point scale (1=never; 2=rarely; 3=sometimes; 4=often; and 5=always) with a range in score from 8 to 40 with higher scores indicating greater severity of sleep disturbance.

Time frame: baseline

Sleep Disturbance as Assessed by the PROMIS Sleep Disturbance-short Form

The 8-item PROMIS sleep disturbance-short form assesses the pure domain of sleep disturbance in individuals age 18 and older, and each item on the measure is rated on a 5-point scale (1=never; 2=rarely; 3=sometimes; 4=often; and 5=always) with a range in score from 8 to 40 with higher scores indicating greater severity of sleep disturbance.

Time frame: 2 weeks