EE was performing inspection on truck to start afternoon shift. EE lost EE's footing, regained EE's balance before falling, but felt a pop/burn in EE's upper right thigh. EE finished EE's shift, but decided to get a medical opinion on Monday. EE had a hip flexor muscle strain, EE was told to rest/ice for two weeks. Freezing rain and blowing snow conditions at the time of incident.