The purpose of this research is to study the effects of Transcranial Direct Current
Stimulation (tDCS) on clinical pain, mobility disability, and pain sensitivity to gain a
better understanding of the factors that cause pain and disability in people with knee
osteoarthritis (OA). In particular, people from different ethnic and racial groups may
experience OA pain differently which is why the focus will be on older Asian Americans and
non-Hispanic whites. It is important to find a reason for such difference so that a better
treatment can be found for all OA patients. In addition, the research study will examine if
there is any ethnic differences in pain and mobility disability. The investigator
hypothesize that Asian Americans will report greater pain and mobility disability than
non-Hispanic whites, and that active tDCS will result in improvement in pain and disability
compared to sham tDCS.
If you participate in the study, the following will happen:
Randomized into one of two groups. Which will either receive the full length session of
brain stimulation or a much shorter session of brain stimulation. The shorter version of
stimulation looks like and is performed in the same way as the longer electrical stimulation
session, but stimulation is stopped before it can have much of an effect on the brain. You
will not know which group you have been assigned to while participating in the research, but
you may find out at the completion of the research study.
X-Rays will be done on both knees while standing up.
Questionnaires about arthritis pain you are having, your thoughts and feelings about it, and
any stress that you may have experienced.
Walking Test will be performed on a flat surface for 6 minutes at a fast pace without help
from an assistive device (cane or walker) or another person.
Assessment of Physical Performance requires walking at short distance (about 13 feet), stand
up from a chair 5 times without using your arms, and stand in 3 different positions while
keeping your balance.
Assessment of Sensitivity to Heat. Heat pain sensitivity will be tested using a commercially
available thermal sensory testing machine (Medoc, Inc.) used widely in clinical settings.
This machine has a small (about 1 inch by 1 inch) square piece that is used to apply heat to
the skin. Heat will be applied to the knees and arms. The amount of heat is controlled by a
computer. One or more of the following types of heat stimuli will be delivered: 1) a slowly
increasing heat that can be stopped by pressing a button when it becomes warm, painful, or
intolerable; 2) a series of 5-10 heat pulses that are brief (less than 2 seconds in
duration), and rate how painful each heat pulse feels; and 3) a few longer heat pulses
(15-30 seconds) at different temperatures to rate how painful each heat pulse feels. The
procedures can be stop at any time.
Assessment of Sensitivity to Pressure will be done using a handheld device with a small
rubber tip to apply pressure to the knee, thigh, and shoulder.
Assessment of Sensitivity to Mechanical Stimulation will be done using a handheld probe that
has a small nylon tip to tap both the knee and hand.
Blood Draw: Blood will be taken at the baseline visit and at the last visit.
Brain Stimulation: The stimulation technique called transcranial direct current stimulation
(tDCS) and it involves placing two sponge-like electrodes on your head and delivering a very
weak electrical current to your scalp, which is generated by a 9 volt battery.
In addition, weekly phone calls will be done for the next 3 weeks.
- they have self-reported unilateral or bilateral knee OA pain according to American
College of Rheumatology criteria
- they can understand, speak and read English
- they are able to walk for 6-minutes
- they are willing to be randomized to either the intervention or control group
- they are available for five consecutive daily sessions and for a follow-up phone
interview each week for three weeks post-stimulation sessions
- they have no plan to change medication regimens for pain throughout the trial
- they are willing and able to provide written informed consent
- knee replacement or non-arthroscopic surgery to the affected knee
- serious medical illness, such as uncontrolled hypertension (i.e., Systolic Blood
Pressure/Diastolic Blood Pressure of ≥ 150/95), congestive heart failure, pacemaker,
or history of acute myocardial infarction
- peripheral neuropathy
- systemic rheumatic disorders, including rheumatoid arthritis, systemic lupus
erythematosus, and fibromyalgia
- alcohol/substance abuse
- cognitive impairment (i.e., Mini-Mental Status Exam score ≤ 23)
- history of brain surgery, tumor, seizure, stroke, or intracranial metal implantation
- pregnancy or lactation for females
- hospitalization within the preceding year due to psychiatric illness
Hyochol Ahn, PhD, ARNP
The University of Texas Health Science Center, Houston