The cat, named Babygirl, will undergo surgery Wednesday near Pittsburgh to remove the extra leg and the crippled rear left leg to which it is attached.
Babygirl will be fine with just three legs, said Linda Hughes, cat care supervisor at the Washington Area Humane Society, which is caring for the cat.
"She gets around on three legs right now," Hughes said. "She is very healthy and she should make a full recovery."
The cost of the $1,600 surgery will be paid for by donations.
After surgery, the humane society will place Babygirl in foster care over the weekend or early next week.
"She'll do much better in a nice comfortable warm home ... than being in a kennel cage," Hughes said.
The humane society also will review applications from about 50 people who want to adopt the cat, Hughes said.
A woman brought babygirl to the Washington Area Humane Society on Jan. 19.
