Yes, this could definitely be rheumatic pain.  I have had Rheumatoid Arthritis for 14 years now and deal witht the pain in my knees and especially my feet on a daily basis.  It almost feels like every bnone in the bottom of your foot is broken and virtually impossible to walk on, am I correct?  If this is the case for you, then you need to get to your doctor and get tested.  As far as remedies for this, I am not aware of any.  I do know a few things that might ease your pain though.  Get you a bean bag heating pad.  They are the kind you can throw in the microwave. This heating pad you can mold to the bottom of your foot and hold there with a pillow.  Also get you a pair of slippers that have memory foam in them.  They provide a little extra comfort at the bottom of your foot and really cushion them when you need to get around.  And as far as your knee, you may try a knee brace or a simple ace bandage.  I have to use these constantly as my knees are almost always too swollen to bend.  I hope this helps!  Good luck and best wishes!

Hello

I think it is time you got an xray of your foot.

Just to ensure no structural bone damage.

If you think it is tendon damage an ultra sound image will find any tendon damage.

There are a number of reasons people experience pain in their feet, and since yours has persisted for so long you should probably have a physician evaluate you in person. I've listed a few important questions you should be ready to answer. You may also want to bring the shoes you wear most to your office visit.
When did the pain start and when does it occur?
Is it in one foot or both feet?
What makes the pain worse? (walking, running, not wearing shoes)?
Do any medications lessen the pain?

Good luck!