Tendonitis is the worst! I had it in my knee last year, before I started riding my bike. It was actually the reason I started riding, less impact on it than doing step aerobics. I went to the orthopedic dr. and he sent me to a phys. therapist who gave me a bunch of exercizes to do. I think the exercizes, and the biking has really helped the problem. Just be sure not to push too hard of gears because that makes it worse.

Hope you're feeling better soon!