Why does my hand keep going numb? (i have juvenile arthritis too)

Carpal Tunnel Syn. Carpal tunnel syndrome is probably the most common cause. Jra itself doesn't cause numbness, but the swelling associated with jra can cause carpal tunnel syndrome.
Neuropathic? Sounds like you have nerve impingement; possibly from the arthritis...Or from something else. Get with your doctor to determine not only the cause; but the treatment!