Knocking could be from anywhere. Its a matter working through each part pushing and pulling it like in the video a linked earlier. Its a Good video and explains in easy steps.
you can try
find somewhere quite drive at about 5mph
move the steering sharply left to right is the any knocking
Jack a front wheel off the ground
push and pull on the wheel at the 3 o'clock and 6 o'clock position while looking at the arms mounting points with a torch.
engine mounts are easiest to test with brakes on firmly move the car forwards and reverse while watching the engine. Plenty of YouTube demonstrations
and so on