Ed68 I had surgery to trim the cartilage a year ago and have been very careful since I started running again last March but if the cartilage has worn away and you are getting bone on bone then resting isn't going to fix it. I have take the common sense approach that if I want to be able to walk later in life without having a knee replacement it is better to stop running now. Walking is still a bit painful so I have top stop running. Even the other knee feels a bit sore in the same place so I guess I have worn my knees out.
You do need to do strength training for your legs as per Ickles advice. I have had lots of niggles over the years but after following a strict exercise programme at the gym on the advice of a physio the niggles cleared up but obviously not enough to stop the cartilage wearing out!
I have a similar shoulder problem where it is painful to elevate it. I went to see a physio and was given some exercises to at the gym I go to. 3 of them involve using dumbells and one is press ups with your arms tucked close to your side. It hasn't cured the problem but has eased it significantly.
Well done Wabo, that's a good for a hilly marathon.
Swimming in the sea this time of year is madness! I can appreciate the sense of achievement afterwards though. I'm a 30 + degree temp sea swimmer!