Low-amplitude, extremely low frequency magnetic fields for the treatment of osteoarthritic knees: A double-blind clinical study

Context . Noninvasive magnetotherapeutic approaches to bone healing have be en successful in past clinical studies. Objective . To determine the effectiveness of low-amplitude, extremely low frequency magnetic fields on patients with knee pain due to osteoarthritis. Design . Placebo-controlled, randomized, double-blind clinical study, Setting . 4 outpatient clinics. Participants. 176 patients were randomly assigned to 1 of 2 groups, the pla cebo group (magnet off) or the active group (magnet on), Intervention . 6-minute exposure to each magnetic field signal using 8 expo sure sessions for each treatment session, the number of treatment sessions totaling 8 during a 2-week period, yielded patients being exposed to unifor m magnetic fields for 48 minutes per treatment session 8 times in 2 weeks. The magnetic fields used in this study were generated by a Jacobson Resonat or, which consists of two 18-inch diameter (46-cm diameter) coils connected in series, in turn connected to a function generator via an attenuator to obtain the specific amplitude and frequency. The range of magnetic field am plitudes used was from 2.74 x 10(-7) to 3.4 x 10(-8) G, with corresponding frequencies of 7.7 to 0.976 Hz. Outcome Measures . Each subject rated his or her pain level from 1 (minimal ) to 10 (maximal) before and after each treatment and 2 weeks after treatme nt. Subjects also recorded their pain intensity in a diary while outside th e treatment environment for 2 weeks after the last treatment session (sessi on 8) twice daily: upon awakening (within 15 minutes) and upon retiring (ju st before going to bed at night). Results . Reduction in pain after a treatment session was significantly (P < .001) greater in the magnet-on group (46%) compared to the magnet-off gro up (8%). Conclusion. Low-amplitude, extremely low frequency magnetic fields are safe and effective for treating patients with chronic knee pain due to osteoart hritis.