It could be a "CV" joint, wheel bearing, ball joint, strut or any of a number of loose parts. It depends on the type of knocking and how it sounds. In any case, it should be repaired as soon as possible to avoid the possibility of a dangerous condition.
No
A hole in the muffler would cause a knocking sound in your muffler. A loose exhaust pipe can also cause a knocking noise.
possibly hitting the front bumper
Worn Ball Joint
Perhaps a worn CV joint (usually more of a clicking sound when turning), but there are many components in the front end of a motor vehicle that could cause a knocking (or similar) sound, including suspension components, brakes, steering components and bearings. Worn tie rods, by the way, do not normally cause a knocking sound, but result in very loose feeling steering and noticeable drift, especially at highway speeds. A knocking sound is more likely to be an engine problem, such as pre-ignition. If you are not accustomed to diagnosing these sounds, you will best best off to see a qualified mechanic, or a friend who is more familiar with the front-end components of a motor vehicle.
Yes
you re rear axle i just replaced mine it probably the front pinion bearing
a dog
A seized gear can cause a knocking sound on a 1987 Nissan 5 speed transmission. A blown gasket can also cause this sound.
My 2000 Grand Prix would have a low-speed knocking noise coming from the drivers side as the CV axle was failing. The loss of lubrication in the CV Boots allows the joint to make a knocking/tapping sound at a low speed. If the knocking is coming from the engine compartment, then it could be an entirely different problem.
If it's knocking it's probably a rod going out - if it's ticking it could just be the valves - Rodeos are notorious for value noise...
Could be a worn CV joint