Abstract: A method of operating a wind turbine and a method of determining fatigue in a wind turbine component are provided. The method of operating a wind turbine comprises determining a reference accumulated fatigue, determining an operational time, obtaining a partial load indicator, determining a real accumulated fatigue, comparing the real accumulated fatigue and the reference accumulated fatigue and controlling the operation of the wind turbine. The method of determining fatigue in a wind turbine component comprises determining an operational time, obtaining wind speed, obtaining turbulence intensity, determining a time for each combination of wind speed and turbulence intensity and determining a real accumulated fatigue. In a further aspect, this is also provided a wind turbine controller configured to perform any of the methods herein disclosed.