A pilot study comparing the efficacy of radiofrequency and microwave diathermy in combination with intra-articular injection of hyaluronic acid in knee osteoarthritis

[Purpose] This study aimed to compare the efficacy of radiofrequency diathermy with that of microwave diathermy in combination with intra-articular injection of hyaluronic acid into the knee of patients with osteoarthritis (OA). [Subjects] A total of 17 patients with knee OA were enrolled. The participants were randomly divided into two groups: a radiofrequency diathermy group (RF group, 9 subjects), and a microwave diathermy group (MW group, 8 subjects). [Methods] Subjects received radiofrequency or microwave thermal therapy 3 times at 1-week intervals. Intra-articular injection of hyaluronic acid was administered 10 min before every thermal therapy session. The outcome was evaluated using the Japan Orthopaedic Association (JOA) and the Lequesne Index (LI) at baseline, at weeks 1 (1 week after the first thermal therapy) and 3 (1 week after the last thermal therapy). [Results] The JOA scale increased significantly after three sessions of thermal therapy in the RF group, while no significant increase was observed in the MW group. LI decreased significantly after 3 weeks in the RF group. In the MW group, there was no significant difference in LI between the two time points. [Conclusion] This study revealed that symptom relief in patients with knee OA was greater with radiofrequency diathermy than with microwave diathermy with concurrent use of hyaluronic acid injection, presumably due to the different heating characteristics of the two methods.