Freezing of gait (FOG) is a severely disabling gait disorder in Parkinson's disease (PD). Its poor response to current therapies reflects the shortfall in current knowledge on its exact pathophysiology. Case series suggest a therapeutic promise of spinal cord stimulation (SCS) for FOG, but double-blind randomised controlled trials with reliable FOG assessments are lacking. This randomised, double-blind, placebo-controlled cross-over trial aims to define the outcome, safety, optimal stimulation paradigm and underlying mechanism of SCS for FOG in PD, by exploring both clinical and neurophysiological parameters. Twenty-nine PD patients with refractory FOG will receive an implanted SCS lead connected to an external trial stimulator. During a 3-week trial, 3 stimulation paradigms will be tested in random order, including one sham paradigm. SCS outcome on FOG will be evaluated through wearable accelerometers, self-reported questionnaires and a FOG-provoking protocol at home. Spinal electrophysiological recordings will compare neural properties between PD patients with and without FOG and evaluate intra-patient differences (e.g., on/off medication, DBS states). In patients with deep brain stimulation (DBS) including BrainSense technology, the effect of SCS on pathological beta oscillations in the STN will be explored. A subsequent long-term open-label phase will be conducted in those patients who desire a definitive implanted stimulator. This project will provide new insights into the pathophysiology of FOG, pave the way for SCS implementation in clinical practice and enhance future patient selection.