It's not clear whether you mean behind the tendon or behind the kneecap itself. There's no cartilage in the tendon.
Patello Femoral Pain Syndrome PFPS is one of the favourite conditions in my practice. It usually responds so quickly to mobilisation of the patella and strengthening exercises, and perhaps a change of diet.
A deficiency of magnesium is the main cause of chondro calcinosis, a build up of crystals of calcium in the cartilage on the underside of the kneecap. Popeye knew the answer: spinach.
I use a gentle mobilising technique, like polishing, which smoothens off those offending crystals and it works remarkably quickly.
Of course I know nothing of your case history, so I can't promise you that every case will repond as outlined above, but I'd certainly give it a try before the knife! Ice it too if it's swollen and inflammed.
But the cartilage doesn't seem to wear away under the kneecap as occurs within the knee itself, that's far more difficult to manage. The patella isn't a weight bearing joint, though the forces between it and the femur on the stairs is considerable. Hence the pain.
If you're obese, get if off, because no treatment, chiropractic or surgery will help for any length of time.
Phone around and look for a chiro who has experience in treating the knee. Some chiros only work with the spine and pelvis which may not bring much relief.
Good luck, let me know how you get on.
PS: It's nice to see that some Americans were taught to write in English! Most of the letters I receive at this site are in such poor grammar and spelling... the letters from Indian and Pakistan are better!