With a prosthetic, One Leg acts exactly like the Lame Hindrance, reducing Pace by 2 and running rolls are now a d4. Without a prosthetic, the character's Pace is 2 and he can never run. He also suffers -2 to Traits that require mobility, such as Climbing and Fighting. A character with one leg also suffers a –2 penalty to his Swimming skill (and Pace).

Savage Worlds Deluxe Edition p. 32