Hello!
Thank you for the query.
The condition which gives diarrhea and leg pain (joints pain) is
Crohns disease. But the joints pain can be present even few years before gastrointestinal symptoms.
So most likely the leg pain and diarrhea are two separate conditions.
The main rule about diarrhea is that if it lasts longer than 48 hours or there is a blood in or you have high fever,
stool test and stool culture test should be done. Most likely this is bacterial infection which needs to be treated with antibiotics.
If its about leg pain, really hard to tell something about it not knowing even the location of pain. It might be
muscular pain, nerve pain. The condition which you should be aware of is veins
thrombosis. The symptoms are swollen, painful calf, warm calf. If any of this symptoms is present, D-dimers level and Dopplers ultrasound should be done.
For other type of pain you should consult orthopedist and
neurologist.
Hope this will help.
Regards.