Front-end knocks are one of five parts: a lower arm bush, a ball joint, an anti-roll bar link, a top mount, or a shock that has stopped damping. The drop-link is the cheapest and the commonest, which is why it is worth having someone look before ordering anything.
On the ramp we lever each joint and shake the wheel while the other pair of hands watches. You get a list with the price against each line and you choose. Potholes make this a yearly conversation in this city.