Could be the CV joints (inspect the inner and outer boots for damage), inspect outer tie rods, ball joints, struts and control arm bushings.
More than likely the CV boots are leaking/out of grease. Sometimes a rock or tree limb hits the rubber boot(s) and causes a tear. The grease leaks out and water gets in and will cause rust on the CV joint, when you turn this wear will manifest itself as " clicking" or knocking. It will eventually fail. You can replace the boot, but I have found it much easier to buy a remanufactured axle with new boots.