Can I take advil for my knee pain and darvocet for my back pain?

The recent pulling of darvocet does not stop me from taking these pills that I still have left. They work great for my low back pain. I have disc degenerative disease since 1974. So these pills really help calm my back pain down. However I recently started having trouble with my knees. When trying to kneel on either knee I get a burning sensation and horrible pain and cannot put any pressure on them...no kneeling for me. The advil liqui-gels that I have been taking for several days seem to be helping the knee problems, however I'm suffering with a great deal of pain in my low back. Is there anyway I can take advil for my knees and a darvocet for my back? I have been on darvocet since 1994 and trust this med. It works for me!