A 28-year-old G1P0 presents to your office at 18 weeks gestational age for an unscheduled visit secondary to right-sided groin pain. She describes the pain as sharp and occuring with movement and exercise. She denies any change in urinary or bowel habits. She also denies any fever or chills. The application of a heating pad helps allete the discomfo. As her obstetrician, what do you tell this patient is the most likely etiology of this pain?