If i have a joint replacement, how long does physical therapy usually last?

Not too long: Joint replacements shouldn't really require much (if any) physical therapy. Most of my patients who have had new knees and hips (once the surgical / anesthesia aftershock wears off in a few days) are "up and running". Physical therapy should not have much call in these cases of having new joints. Basically your joints have just magically gotten younger. New joints don't need therapy.

Individualized: Those who need therapy may need it for weeks or months. The goal is make sure that once you have a replacement joint that the range of motion is maximized and your gait is normalized. The time needed is determined between you, your orthopaedic surgeon and the therapist.