The biologic effects and the therapeutic mechanism of action of electric and electromagnetic field stimulation on bone and cartilage: new findings and a review of earlier work.

BACKGROUND: Muscle, ligament, bone, cartilage, blood, and adult stem-cell production all respond to electric and electromagnetic fields, and these biophysical field agents can be applied in therapeutic contexts. Postulated mechanisms at the cellular, subcellular, and molecular level are discussed. Electric and electromagnetic field stimulation enhance the repair of bone through the mediation of three areas at the cellular level: (1) the complex interplay of the physical environment; (2) growth factors; and (3) the signal transduction cascade. Studies of electric and electromagnetic fields suggest that an intermediary mechanism of action may be an increase in morphogenetic bone proteins, transforming growth factor-beta, and the insulin-like growth factor II, which results in an increase of the extracellular matrix of cartilage and bone. Investigations have begun to clarify how cells respond to biophysical stimuli by means of transmembrane signaling and gene expression for structural and signaling proteins.
METHODS: Review of meta-analysis trials of electrical stimulation of all types.
CONCLUSIONS: Further research in the form of methodologically sound, randomized, controlled studies are needed. Inter alia, resolutions are needed for the significant disparities between clinical targets, types of electrical stimulation, and clinical outcomes.