Glad to see your Batherapy helped..
  I have a left knee that "blows up" as I call it, and does it everYy couple months..  It happens during the night..so when I wake up in the morning and try to bend it...OOOWCH !
  Usually, topical treatments (things rubbed into the skin) are not very effective, but this time I went to RITE-AID and asked the pharmacist if there was any topical treatment that was any good.
  She showed me one that has just been moved from prescription to over-the-counter status.  It is called DICLOFENAC SODIUM TOPICAL GEL 1%.
  It was pricey, 5.29 oz..cost $21.  It  recommends to rub in a 4.2" strip of the gel for any joint below the waist ... a bit less for upper joints.  It worked quite well overnight for me.