I am presently a cyclist, doing about ~50 miles (~80 km) per week.
I am considering getting into duathlons, but I am concerned with injuring myself. I presently weigh 214 pounds (~97 kg), and I don't want to injure my knees, because that would set me back considerably (I'm currently 53 years old). I'd prefer to minimize this risk by putting off running until my knees have less to do.
How much should I lose before expanding into running?