Engine knock

Its a sign of early rod bearing or main bearing failure the only option is to change the engine lower bearings and use new bolts both rod an main bearings continue driving could cause serious damage

I respectfully disagree with "Thomas". Since we are unable to hear the knock it is impossible to make a diagnosis via the internet. Is it a knocking or ticking? It could be many things such as valve train (lifter leaking down), piston slap, timing chain related or engine crankshaft related such as rod or main bearing. I would take it to a trusted mechanic for further evaluation.

I respectfully disagree with Bob because he said Knock, he did not ask for what is a ? he said Knock, I am a machinist and if it were me, I would drop the oil pan get some Plastic gauge, use it on your rod caps? how many miles are on it, that is a clue, lets say you have 200K OR MORE, I would lean for sure rods and mains