Pavement/asphalt is actually pretty good for running beginners because the movements are much better controlled (predictable, stable, flat surface) which reduce

Pavement/asphalt is actually pretty good for running beginners because the movements are much better controlled (predictable, stable, flat surface) which reduces sudden moves that can cause injury. But training in an uneven terrain will, over time, strengthen your other muscles and tendons that do not get much workout on pavement. It is important to understand if you want to move to running in uneven terrain you have to reduce your volume initially, pretty considerably, to give time to adjust. As to your problems with inflamed muscles and joints -- I have some experience with this I can share. First is that your aerobic capacity develops much faster than your joints and tendons, especially if you are older. It takes years of regular running to get your joints and tendons to be able to accept daily high mileage running. There is no other way than to start small (say 1-2 miles every other day) and slowly, slowly build it up and react every time you have any problems (by stalling your build up to get time to catch up). Connective tissue reacts best to high, non-repetitive loading. The fastest way to improve your tendons and knees is to start lifting heavy shit. That's why all pro runners are also going to the gym to lift weights. Not because they want to build muscle (you don't want muscle especially in legs because you need to move that mass back and forth) but because it strengthens joints and tendons and makes your legs more resilient to stress. Also, stronger core muscles help maintain good posture throughout long run preventing injuries. Personally, I found walking is an excellent supplement to running. Walking long distances regularly will also strengthen things with less chance for an acute injury. I have even started walking with a loaded backpack (read up on rucking).