Can you have restless leg in only one leg? if so what causes it.

Yes you can: Rls can impact one leg only as you ask, or impact arms instead. Cause not clear but probably related to imbalance brain chemical dopamine. Symptoms become worse as person relaxes & powerful sensation of needing to move legs occurs but w/ only temporary relief. Runs in families, women twice frequency of men, increase symptoms with iron deficiency, disrupts sleep, & is usually treatable.

Yes: It's unusual but can happen. Typically when it is in one limb it is not genetic or due to iron deficiency but some sort of nerve damage.