History of patellar tendonitis and not riding much before now--sounds like a classic overuse injury. Do you stretch or do any strengthening exercises? I had Patella Femoral Syndrome creep in last summer. Spent time resting per Dr's orders then found www.sports-injury-info.com because the rest didn't work. I realized it was all too coincident that the pain initially started a couple weeks after I stopped doing core exercises. Started up the program and felt immediate improvement and was back to pain free for a bike trip in CO two weeks later. You can check your fit and cleats and braces and such, but if you aren't doing any stretching or strengthening then you may be missing the real problem.