2000 Ford Escort knocking noise

Depends what kind of knocking sound, does it knock all the time when the engine is running or does it taper off as the engine runs. Does it sound like a tapping sound or a deep knock. If it sounds like a knocking sound when you press the gas pedal under load it could be timing, if it is a tapping sound that quiets down when the engine runs it could be lifters, if it is a constant knocking sound that continues when the engine runs it could be a rod or piston. If its a constant knocking sound you might have to rebuild the engine.