I have this problem that has gotten worse over the years and now is to the point I basically can't run on the treadmill. It's difficult to describe, but after I get 2-3 miles in, my form starts to fall apart with my left leg's stride. My right leg feels completely normal, but my left leg almost collapses a bit while running and my stride gets all janky. It happens very suddenly around the 2-3 mile mark. My left hamstring/hip gets extremely tight after trying to run on the treadmill, especially if I run anything faster than slow easy pace. Last winter I did a tempo on the treadmill and I was on the foam roller for a week getting the knots out.
I know this is related to a past injury on the left side. I do have chronic issues with my left hamstring/hip that act up occasionally, but not too often if I stay off the treadmill. For some reason though running on the treadmill brings them to the forefront. I used to run plenty of miles the treadmill when I was in my 20s even though the chronic hamstring/hip issues started back in college.
Off the treadmill, I can stay relatively healthy running 60-90 miles a week. Unfortunately I live in a place with sometimes brutal winter weather and no indoor track, so not being able to run on the treadmill can be very limiting on my training.
Thanks for any input.