I had very serious patalla tendonitis, heres what I did with great success. First off, I would treat this in 2 stages, first recovery mode, then after recovery. Before I go further, this was MY stagety, see a doctor first and do what YOU think is right. First off, do not stop hiking, the body learns to adapt and overcome, I trained my body many years ago to climb and hike, and I do both through any injuries I encounter, I am lucky to have an extremely high pain threashhold which allows me to do this.
For hiking, get a neoprene knee brace, this will support your tendons and generate heat which will keep your tendon loose and warm. Poles, use them always, these take weight off your legs, any weight off your knees is very helpfull. Take advil before, during and after a hike, personally at the beggining stages I took 4, 4 times a day, then tapered down to 3, then down to 2.
I am not an advocate of PT but thats, me many people swear by it. Becarefull stetching you dont want to stain your tendons by stetching them, personally, I dont stetch, only for rock climbing.
Thats about it, your doctor will say dont hike, I found a sports doctor, they are used to treating athletes that work through there injurys.
At your age your body should be very resistant, hike, hike and hike, avoid running descents.
Oh one more thing, I talked my doctor into giving cortazone shots, into my knee, some are reluctant to apply them, but they get the ball rolling quite well.
This is what I did, like I said before, it might or might not be right for you. I do not like doctors, I believe the body is adapt at self healing, many urbanites live at the doctors and take what they say as gold, I do not, I think they over treat everything and milk the insurance company at your expense, they make a fortune on PT, so they prescibe it always and keep you hooked. Buy a bike and ride alot, its much less abusive then running, I would cannot afford to waste my knees running but I bike alot, it stetches and works your knees without overlee stessing them.