The invention is related with an external fixator that is used in high tibial osteotomy (HTO) surgeries, including at least one positioner for gripping the leg from both sides, at least one angulation device and a proximal arch that is connected to the positioner, at least one proximal schanz holder on the proximal arch, at least one distal schanz holder at the bottom of the angulation device, at least one osteotomy block that enables to set the size and location of the incision on the proximal arch, at least one fibular head positioning device that is connected to the angulation device and at least one angular indicator (scale) on the fixator, on which the correction can be adjusted and controlled.