Radar for indoor monitoring has recently attracted much attention that is driven by its safety, privacy-preserving, and non-wearable sensing mode. Micro-Doppler signatures offered by radars operating in the K-band can disclose intricate details and characteristics of human gait. This paper reveals key Doppler features associated with human legs in gait motions which have been overlooked or ignored by existing work in this area, including biomechanics simulators and electromagnetic modeling. These features are used to detect gait abnormalities and distinguish gait from other translational motions which exhibit similar signatures in the time-frequency domain, such as assistive walking devices.