Peroneal (adjective)
Pertaining to the fibula or to the part of the leg containing it, the outside (lateral aspect) of the lower leg (that is, what anatomical terminology calls the leg, from knee to foot). from 19th c.
Perineal (adjective)
Referring to the region of the perineum.
“His bicycle seat produced a great deal of perineal discomfort.”
“Many mothers find the use of perineal massage eases their childbirth.”
Wiktionary