There was a period of time where running in the morning, and then riding my bike in the afternoons on the weekend resulted in a pretty bad case of patellar tendonitis. Still dealing with the fallout from this some 3 years later, but I think I finally have sort of figured out what went wrong, or at least what I need to do to fully rehab things. Likely a result of a toxic mix of muscle imbalance in my legs, stiff muscles, saddle too low on my bike and working out when I should have been implementing RICE.