title: [Electrical fields in the knee joint induced by external magnetic fields: results of an experimental study].
abstract: OBJECTIVE
  Magnetic fields are used in the treatment of osteoarthritis. So far the efficiency has not been scientifically proven. The comparability of induced electrical fields with those produced endogenously within the cartilage tissue is unknown.
  
  
  METHODS
  The study was performed on a knee joint model which was exposed to magnetic fields (2mT and 4.9 mT, 50 Hz). The measurements were performed using small spherical electrodes within the knee joint located at positions defined by three cartesian coordinates. The electrical potentials were amplified 100-fold and plotted on an oscilloscope. The results were checked by post-mortem examinations on a human knee joint.
  
  
  RESULTS
  In relation to the magnetic flux density and the steric orientation of the electrodes, we found electric field strengths between 60 and 410 micro V/cm. When performing the procedure on the human knee joint, field strengths of up to 400 micro V/cm were measured.
  
  
  CONCLUSIONS
  Electrical fields in the knee joint which are induced by external magnetic fields can be verified. When compared with the endogenous electrical potentials, the measured values were about 30 times smaller. Given these results, we can make no conclusions about therapeutic efficiency.
authors.affiliation: Orthopädische Klinik der RWTH Aachen, Germany. bernhard.schmidt@post.rwth-aachen.de
authors.forename: B
authors.initials: B
authors.lastname: Schmidt-Rohlfing
authors.forename: N
authors.initials: N
authors.lastname: Ihme
authors.forename: J
authors.initials: J
authors.lastname: Silny
mesh_terms: D004574:Electromagnetic Fields; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008953:Models, Anatomic