I looked in the MedTent for a similar problem, but nothing seems to match. I have been running 20-25 miles per week and have developed consistent pain on my left leg at where i think is the hip flexor. Basically it feels like need to pick up my entire leg at my thigh/knee when I walk the day or so after a long run or a speed run. It has not hurt my running times (I just did PRs in the last month for both 5k and 5miles in the mid 7s). Also, the inside of my thigh is also sore and tender sometimes when the upper thigh/hip flexor is not . What is interesting is that after I get going on a run, the pain more or less goes away and the range of motion feels fine. I get regular adjustments from a chiropracter who sometimes needs to snap the hip into place, but that doesn't hurt. And I stretch regularly (about 5 per week, always after running and also after strength training). although I have always been very tight in the hips. My core strength is also decent and I am 5'10", 150 lbs, so not putting undue weight on my joints. I am not a new runnerI have been running for about three yearsand I have not increased mileage dramatically.