Transcutaneous Vagal Stimulation in Knee Osteoarthritis

Transcutaneous Vagal Stimulation in Knee Osteoarthritis (TRAVKO): Protocol of a Superiority, Outcome Assessor- and Participant-blind, Randomised Controlled Trial.

This study will evaluate the efficacy of Transcutaneous Vagal Stimulation in people whit knee osteoarthritis.

Current treatments for knee osteoarthritis (KOA) are partially effective. It is, therefore, necessary to find new strategies that can complement the existing ones. In this scenario, transcutaneous vagal stimulation (TVS) neurophysiological effects could be a helpful solution. However, there is no evidence of the efficacy of TVS in KOA. This trial aims to assess the efficacy of TVS in decreasing pain in participants aged 55 years or older with KOA. A randomised controlled, two-arm, double-blind (participants and outcome assessors) and clinical superiority trial will be conducted for 70 patients with KOA. All the participants will carry out an exercise program. It consists of 12 sessions over four weeks. In addition, they will be randomly assigned to (1) active TVS plus physical exercise or (2) sham TVS plus physical exercise. The application of active TVS consists of electronic stimulation of the auricular concha using a portable device. Sham TVS condition consists of the stimulation of the earlobe that does not cause neurophysiological effects. The primary outcome is the reduction in pain intensity. Additionally, functional capacity, physical performance, pain-related interference, pain-related distress, quality of life in older adults and global change will be measured. Assessments will be conducted at the beginning of the study (baseline), at the end of the intervention and after 1 and 3 months of follow-up.

Inclusion Criteria:

1. Women and men aged 55 and over;
2. Medical diagnosis of osteoarthritis of the knee according to the criteria of the American College of Rheumatologists;
3. Chronic pain (i.e., 3 months or more)
4. Average pain of the last seven days among 30 mm and 80 mm on the Visual Analogue Scale;
5. Walking without technical aids or knee brace;
6. Availability to attend an exercise program three times a week for four weeks;
7. Access to communication via telephone;
8. Agree to participate in the study by signing an informed consent form.

Exclusion Criteria:

1. Presence of the following symptoms and signs: Fever or chills, large effusions, paresthesias or paresis of the lower limb;
2. Presence of medically diagnosed psychiatric or neurological diseases (cognitive impairment, Alzheimer's, Parkinson's, epilepsy, moderate or severe depression, bipolar disorders, obsessive-compulsive disorder, etc.)
3. Neuromuscular or cardiac disorders (i.e., arrhythmia, conduction cardiac block), stroke, generalised rheumatology, dia-betes mellitus II, morbid obesity (i.e., equal to or greater than III);
4. Medical contraindication of physical exercise;
5. Joint infiltration or lower limb surgery in the previous 6 months;
6. Surgery is planned for the next 6 months;
7. Take strong regular two or more kinds of medication;
8. Conditions that affect the lower limb and/or limit its functional capacity, such as previous fractures in the area, deformity, joint replacement, tibial osteotomy;
9. Participation in exercise programs in the last nine months;
10. Inability to follow instructions.