also: うそく
right foot
Refers specifically to the right foot, as opposed to the leg. Context usually makes the distinction clear.
I sprained my right foot.
right leg
Refers to the entire right leg. In everyday use, 右足 often covers both foot and leg unless specified otherwise.
My right leg is numb and I can't stand up.
He stepped forward, putting his right foot out first.
The soccer player kicked the ball hard with his right foot.
He put his weight on his right leg to keep his balance.
After sitting for a long time, my right foot started to go numb.
Alternate kanji spelling using 脚, which can emphasize 'leg' over 'foot', but both spellings are used for either meaning.