The aim of the study is to evaluate the efficacy of a wearable device using pulse electromagnetic fields on pain intensity reduction, measured by visual analogue score (VAS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), in patients affected by osteoarthritis Secondary aim is the evaluate the effect on knee effusion reduction, when present and to evaluate pain intensity changes corrected by pain threshold measured by pressure algometry.

Inclusion Criteria:

• a diagnosis of primary OA of the knee according to the ACR criteria, including radiologic evidence of OA
• age >40 years
• symptomatic disease for at least 6 months prior to enrollment
• persistent pain despite receiving the maximum tolerated doses of conventional medical therapy, including acetaminophen (4 gm/day) and/or a nonsteroidal antiinflammatory drug (NSAID), with persistent pain defined as a minimum mean score of 25 mm on the visual analog scales (VAS) for global pain (0-100-mm range for each) daily pain during the month prior to study enrollment
• ability to attend followup appointments

Exclusion Criteria:

• secondary causes of OA
• local or systemic infection
• diabetes mellitus
• systemic arthritis
• allergy to anesthetic agent or contrast material
• coagulopathy
• anticoagulant therapy
• had previous IA steroid injection
• avascular necrosis of bone
• patients who are on specific OA pharmacological therapy (NSAIDS, opioids) for more than 2 weeks prior enrollment