A hinge for an orthopedic brace includes: a pivot shaft; a lower leg plate pivoted to the pivot shaft; an upper leg plate; a catch plate having a toothed peripheral edge; and two position adjusting units, each of which includes a rotatable limiting seat, a limiting pin, and a slider body. The rotatable limiting seat defines a housing chamber therein, and is formed with a wall slot. The slider body is slidably disposed in the housing chamber. The limiting pin extends from the slider body through the wall slot for engaging and disengaging the toothed peripheral edge. The catch plate is formed with a guiding groove. The rotatable limiting seat has a tongue protruding into the guiding groove.