Running

I can remember the shock of the transition from treadmill running (at least half an hour a day, 4 or 5 days a week) to the road; the treadmill is much more forgiving of bad shoes and poor technique. I found the treadmill much less physically stressful but it still offered opportunities for injury, since it is easier to run on a treadmill when you're tired.

I really think that the treadmill is only good for cardio. It may help you pound out some distance but the experience is nothing like the same number of miles on the road; you don't even have to carry your water/gels/whatever nor (on a more serious note) do you have to remain alert (no obstacles, course or other people on the road). If you're alternating between road and treadmill, then I think at best your technique won't suffer, but you won't gain much.

Is your knee pain from some other cause, Sparky, or from running? If the former, then alternating till your knee firms up is one thing (although I'd consider not running at all or just cutting down on the road running, till you're better). If the latter, then it's possible that something in your technique is the issue, in which case alternating may help you hide that rather than address it.

I had a few knocks skateboarding, biking and a bad landing when doing a parachute jump once. It's always hurt a little, probably for the last 7-8 years. It's not a bad pain at the moment, just an ache. My shins also ache a little bit, but nothing bad. As soon as it stops feeling achey and starts feeling sharp I stop for a few days. I'm not really looking to become a marathon runner or anything, just looking to get fitter, lose a little weight, do some different exercise to cycling and finish a half marathon I've signed up for in October. I don't really want to stop as I'm quite enjoying it in a weird way, but equally I don't want to screw my knees up. I've been to the doctors about it a few times over the years, and even got referred to a physio once. She said the knee was just getting old and I shouldn't do too much. Frankly I think that's just not good enough for a 29-year-old. I want to be active for 4-5 decades more yet - not about to sit on my arse all day because my knee aches sometimes...