Engine knocking

If it is a crankshaft connecting rod knocking, then that means one or more of the connecting rod bearings has worn down probably due to a lack of motor oil and the excess space in between the crankshaft and connecting rod now creates a knocking noise.
You would need to replace one of all of them connecting rod bearings, make sure the crankshaft was not ruined and also find out why it happened, whether the engine oil pressure is low, etc. So just in case, replace the oil pump as well.
If it is an ignition knock then it could just need to run higher octane gas and make sure the knock sensor is working.
Usually the rod knock can be heard at idle but the ignition knock will knock when reving the engine up under load, like when in gear going up a hill.