Recent fall while running. diangosis 4 weeks ago with oa (knee). 7.5 mg mobic (meloxicam) daily. now i have swelling 4th toe, right foot and low back pain. related or not?

Possibly: Need complete history, examination and possibly x-rays and blood work.

S/p fall: Could be, depending how you fell, what you are feeling. There could be some pathology associated with the 4th toe and low back pain that may not have been easily identifiable at the time of examination. I would recommend you f/u with your ortho/pcp.

Possibly: Pain in the knee can cause mechanical low back or foot pain due to mechanical reasons. Other conditions like gout must be considered in the differential diagnosis of foot pain.