Deep heating therapy via microwave diathermy relieves pain and improves physical function in patients with knee osteoarthritis: a double-blind randomized clinical trial

Background. Deep heating therapy (DHT) has shown to improve pain and function in patients with knee osteoarthritis (OA) in the short term. Benefits of superficial heating therapy (SHT) are controversial. Longterm effects of both heating modalities have not yet been investigated. Aim. To compare the effects of DHT and SHT in patients with symptomatic knee OA, and to determine the long-term effects of heat therapy. Design. Double-blind randomized clinical trial. Setting. Outpatient clinic of Geriatrics and Physiatrics, University Hospital. Population. Fifty-four patients with radiologically established diagnosis of moderate knee OA (Kellgren-Lawrence grade II or III) and pain lasting for at least three weeks. Methods. DHT: local microwave diathermy (three 30-min sessions a week for four weeks); SHT: application of hot packs (three 30-min sessions a week for four weeks). Primary outcome measure: Western Ontario and McMaster Universities (WOMAC) index for the assessment of joint pain, stiffness and physical function limitations. Secondary outcome measures: British Medical Research Council (BMRC) rating scale for the evaluation of muscle strength, and a visual analogue scale (VAS) for pain assessment. Follow up: 24 weeks for all outcome measures; 12 months for the primary outcome. Results. Intention-to-treat analyses showed a treatment effect in favor of DHT for all outcome measures. No clinically relevant changes were observed in the SHT group. Benefits of DHT were maintained over 12 months of follow-up. Conclusions. DHT via localized microwave diathermy improves pain, muscle strength and physical function in patients affected by knee OA, with benefits maintained over the long term. No clinically relevant improvements were observed in patients who underwent SHT. Clinical Rehabilitation Impact. DHT via microwave diathermy delivered three times a week for four weeks significantly improves pain and function in patients affected by moderate knee OA, with benefits retained for at least 12 months. No clinically relevant changes are observed in knee OA patients treated with SHT.