That balance we need to strike between putting up with some discomfort and taking care to avoid being laid up with injuries is something I'm having to try and strike again.
For a while now, I've had a tight right hip whenever I wake up (and numb toes to various degrees), but all that goes away when I get up and active. If I sit in this chair at the desk, I can sometimes feel the niggles coming back, but if I get up it'll ease, and if I go for a run it'll all vanish and become comfortable.
Now from what my online research has led me to so far, this kind of thing is often a "weakest link in the chain" effect. From the tips of one's toes to the base of one's skull, all the moving parts are interconnected, and interactive. So sometimes your sore back is actually the result of your knee problem, in concrete terms. The knee gives warnings you don't detect, your chain of bones, muscles and tendons all accommodate those knee warnings, and a few steps up the chain the back gives in, unable to do what's needed.
Well in my case, I have the feeling that my left knee has been giving in a way that puts a corrective strain on my right hip. Result: Those muscles end up wanting to stiffen up when they rest after over-work. Maybe. I'm not even an experienced runner, let alone a physiotherapist. What has definitely happened is as that hip has improved over time, my left knee is beginning to "talk to me". I wouldn't even call it pain, yet, but something's not completely tickety boo there.
I'm a bit paranoid about that knee, because it's the one that once gave me black pain, the like of which I've never again experienced. I got water on the knee, and for a while my patella lay at 90 degrees from its normal position, straight up instead of flat. That was a long time ago, and it's actually the other knee (which someone drove straight into the ground just before some tryline, many years ago) that has given whatever knee problems I've had. Anyway, at this stage I need to be careful of that knee, lest it go from niggly to injured on me.
So, having become wiser by mixing here with you folk, I decided to take this run much easier. I went up my friendlier hill, taking care to keep those joints moving in a straight line, and not pushing too much; I went down the other side with enormous restraint instead of bounding off to reap my reward for climbing; and I finished on a chugg in which my attention was again all on making sure that the motions were not harmful. As a result I was quite a lot less tired than I've lately been, once it was all done. The care taken made me a bit stiff (as in tensed up), so there was no sprint left in me at the end, but even though I ended more tired, recovery came very quickly.
So it was a slow run, with which I'm well pleased, if not quite as delighted as something more reckless would have made me. If this helps with the niggles, I'll carry on this way; if they persist, I'll back it off a bit more; if they get worse, I might even go and take a preemptive visit to a physio. Hopefully by run 3 I'll be throwing this cramped caution to the wind, and go flying over the roads. I definitely feel a lot more comfortable now, some hours after the run, than I usually would be.