Will I get any medicine for pain when I go for the analysis of joint fluid?

Depends. Depends on your doctor and how much pain your in. If you are having alot of pain, they would likely give you some pain meds.
Local anesthetic. For joint fluid, a needle is placed into the joint. Depnding on which joint and the technique used, the may choose to use local anesthetic, or in some cases, topical anesthestics, to decrease pain. But local anesthetic requires an injection also.