a single-blinded, randomized clinical trial, 68 patients divided into 2 groups: active and sham treatment. Afferents of the Auricular branch of vagus nerve are stimulated using a transcutaneous Vagus Nerve Stimulation device (TENS 7000TM). The electrode was placed in the left cymba concha with direct contact on the skin. The stimulation for both groups will last for 30 minutes once a day for 3 days per week for 12 weeks. The amplitude of the output current was between 0.25-2.0 mA as tolerated and 250 µs width at 25 Hz. All participants initially will be evaluated before and after intervention and 3 months after the end of the sessions.

The included study population is 68.

• Group (1): (tVNS group): This group of study subjects will include 34 patients of knee osteoarthritis and will be subjected to tVNS.
• Group (2): (sham group): This group of study subjects will include 34 patients of knee osteoarthritis and will be subjected to sham treatment.

DESCRIPTION OF THE TECHNIQUE

Active treatment:

Afferents of the Auricular branch of vagus nerve were stimulated using a t-VNS device (TENS 7000TM made by Roscoe Medical Inc., will be used. TENS 7000TM device was labeled as nerve stimulator and low-risk medical device (Instruction manual for TENS 7000). The electrode was placed in the left cymba concha with direct contact on the skin after cleaning with an alcohol swab. The stimulation for both groups will last for 30 minutes once a day for 3 days per week for 12 weeks. The amplitude of the output current was between 0.25-2.0 mA as tolerated and 250 µs width at 10 Hz.

Sham procedure:

For sham-t-VNS device was turned 180°, stimulating the outer earlobe which does not contain fibers of the ABVN. A similar protocol as for active stimulation was used.

All participants initially will be evaluated before and after intervention and 3 months after the end of the sessions by the following:

OUTCOME MEASURES AND ASSESSMENT QUESTIONNAIRES

1. Visual analogue scale (VAS)
2. PainDETECT questionnaire
3. DN4 questionnaire
4. Radiological Imaging
5. Knee injury and Osteoarthritis Outcome Score
6. Hospital Anxiety Depression Scale
7. Physical Function Tests
8. Quantitative sensory testing
9. The Central Sensitization Inventory

Inclusion Criteria:

• Both genders.
• Adult over 18 years.
• People who were diagnosed.
• Reported pain on visual analogue scale (VAS)>4/10.
• Able to understand the informed consent.

Exclusion Criteria:

• Peptic ulcer
• Pace maker
• Asthma or severe chronic obstructive pulmonary disease
• Pregnancy.
• Cellulites, skin ulceration at area of therapy application.
• Inability to fulfill follow-up criteria.