Pulsed Electromagnetic Fields (PEMF) are widely used, with excellent clinical outcomes. However, their mechanism of action has not yet been completely understood. The purpose of this review is to describe current observations on the mechanisms of PEMF, together with its clinical efficacy. Osteoblast responsiveness to PEMF is described on several scales, from the cell membrane to clinically relevant bone formation. PEMF has been shown to activate membrane adenosine receptors. The role of adenosine receptors in activating intracellular second messenger pathways, such as the canonical Wnt/β-catenin pathway and the mitogen-activated protein kinases (MAPK) pathway, is described. The responsiveness of osteoblasts and the synthesis of structural and signaling proteins constitute the role of PEMFs in promoting osteogenesis and bone matrix synthesis, and they are described. Multiple studies, ranging from observational and randomized to meta-analyses that investigate the clinical efficacy of PEMF, are described. This review presents a favorable conclusion on the clinical effects of PEMF while unlocking the "black box" of PEMF's mechanism of action, thus improving confidence in the clinical utility of PEMF in bone repair.