Patellar tendonitis is often the result of over-contracture of the quadriceps muscles. With my patients, I employ a program of PNF stretching (Google it) for the quads and hip flexors (since the rectus femoris is a two-joint muscle). I have had tremendous success with this protocol. Have your training partner or room-mate help you with the stretch in the presence of your chiro so you will be able to do it very often (4-5 times per day is about right).
This all means nothing if you are not positioned properly on your bike. Seek out the best fitter in your area and make an appointment.
It is also important to train for efficiency in pedaling. aberant msucle recruitment patterns are predisposing factors for knee discomfort. Riding the rollers with a high RPM is a good way to balance your muscles.
In the mean time, avoid the big ring, take some short easy spin rides, avoid the training weights for quad strength for a few weeks, and stretch.
Supplementing with a multi-vitamin, magnesium, and fish oil are nutritional considerations every athlete (and human) should consider.