How old are you? Is it an apophysitis? Is it on the inferior pole of the patella?
Check your muscle lengths, especially rectus fem, iliopsoas,soleus and gastrocs.
Have you tried taping to change the mechanical pull of the patella tendon.
Could it actually be a fat pad irritation, it is highly sensitive, especially chemically (inflammation).
What sport do you play? You may need rest for at least 4-6 weeks as you impliment treatment to try to reduce the chronic inflammation