Long story short - got rid of knee issues by doing physio over the last 3-4years. I can now run without knee pain, but do get stiff knees if I have to sit still for too long.
Now the issue is that I seems to have pulled / strained something down the back of my left leg [starting at glutes and extending down to back of knee]. I have been stretching, rolling, doing yoga. I have recently run a good-for-age 10K, with this strain. I am able to zone it out whilst running so it's uncomfortable but not painful enough to stop me from running. Walking is more uncomfortable. Did a 7.5km interval session yesterday and seem to have pulled something in my right leg now too. This is despite stretching before and after and not pushing myself at all. When I say 'intervals' it's never at full out sprint by any stretch of the imagination!
Am I just getting old [at 55? I don't think so!] and need to take it easy [I only run 3-4 x week and usually around 5K, so I can't really cut down much more, or I'll be doing nothing at all!] and should I just accept the odd twinge here and there. I would love to be able to finish a run feeling loose and fluid like I used to!