Single versus Double-coil Repetitive Peripheral Magnetic Stimulation Targeting Knee Cartilage and Ligaments: A Finite Element Analysis

Introduction: Despite the growing use of repetitive Peripheral Magnetic Stimulation (rPMS) in non-invasive rehabilitation over the past three decades, stimulation applicator designs have seen minimal innovation. A multi-coil approach with independently adjustable tilt and angle could broaden the possibilities of stimulation in physiotherapeutic practice. Aim: To theoretically compare the effects of single and doublecoil configurations on a simplified model of knee tissue. Materials and Methods: The present in-silico Finite Element Modelling (FEM) study was conducted using COMSOL multiphysics, without the involvement of human or animal participants and therefore without the need for ethical clearance. The development and simulations of both configurations were carried out at the Research Centre in Prague, Czech Republic. A simplified knee cartilage model was created to assess total magnetic energy, and a cylindrical ligament model was used to evaluate energy distribution with depth. Model outputs were deterministic and were analysed descriptively without statistical testing. Results: In the cartilage model, the double-coil configuration produced up to 20% greater total magnetic energy compared to the single coil. In the ligament model, the single coil delivered higher energy superficially (≤3 cm), whereas the double-coil generated 45-121% greater energy at deeper layers (3-8 cm). Conclusion: The study theoretically indicated the potential application of the novel double-coil configuration in physiotherapy. Its enhanced energy delivery may be beneficial for conditions such as osteoarthritis and ligament injuries, particularly when deeper tissue targeting is required. Further clinical studies are warranted to confirm these findings.