I run 2-3 times a week, between 5 and 10k each time, always on the treadmill at the gym. I also walk 2-3 miles a day while carrying a fairly heavy rucksack (commuting).
My knees have started playing up in the past couple of weeks, left knee in particular. They are mostly fine when I'm walking, and actually mostly fine when I run, but become a bit painful when I increase speed on the treadmill. Hamstrings are sometimes a bit sore, as if I've overstretched them, even though I've just been walking. If sitting in a chair at the office, when I extend my lower legs, knees sometimes 'pop' or click, all painless but it feels weird. Left knee feels irritated under the kneecap and a bit stiff.
I didn't run at all last weekend to give them a rest, but did quite a bit of walking, which was fine. I did 9k on Monday at a slower speed than normal and that was all good. I did 7k last night at a moderate speed and knees are really not happy today.
I really DO NOT want to have to stop running so please help! Any advice about particular stretches or exercises that I should do to help strengthen and support my knees? Should I stop running completely for a couple of weeks and do other non-impact stuff at the gym? All advice gratefully received. If it's relevant, I'm 39 and not overweight, no general health concerns