Various embodiments for detecting and rejecting false, unintended rotations of rotary inputs of electronic devices are disclosed herein. In one example, an electronic device is provided with an optical detector that measures the distance between the electronic device and the wearer's forearm or hand, and when the distance is smaller than a threshold distance, the turns of the rotary input are false, unintended turns. In another example, a crown of a rotary input includes a plurality of capacitive sensors that detects the presence of a wearer's finger, which when absent, the turns of the rotary input are false turns. In another example, deflections or positions of a shaft of the rotary input are measured and if the deflections/positions indicate an upward force on the rotary input (which are likely caused by the wearer's forearm or hand), the turns of the rotary input are false turns. Other embodiments are described herein.