my 2000 ford explorer engine knocking.
 

Hey everyone i have a 2000 ford explorer eddie baur edition with the 5.0 v8 engine and today i was driving around 70 mph and all of a sudden the engine started making a loud knocking noise and lost power so i had to get home so i drove it around 40 mph. I am wondering what can be the causes of the knocking noise. the truck has 125,000 miles on it and i never had a real problem till now. I want to findout the problem and see what options i have on fixing it.
thank you
enrico