i have similar knee problems (don't know if it's cartlidge) which, combined with heel striking prevented me from taking up running....it simply hurt too much!
i bought a pair of vff's (vibram five fingers) and started my running career in them. i immediately found that heel striking was very painful, so tried forefoot instead. instantly, the knee pain whilst running stopped. if you do swap to vff's / minimalist / barefoot and don't already run fore/midfoot, your calves will complaint like hell for the first few months, so build the distance up slowly. literally start at ¼mile maximum. your feet need to land pretty much under your hips - don't overstride - or you will probably get calf / achilles injuries (been there, done that) and the cadence needs to be about 180 steps per minute. the high cadence is generally enough to prevent over-striding.
you may be hard pushed to get up to ½ marathon distances in minimalist shoes by may, but they are certainly worth giving a go to see if you get the same pain free knees that i now run with.
cheap ebay chinese 2nds / copies at c£30 a pair are an inexpensive punt to determine if you can get on with them, although they take 2-4 weeks to get delivered.