Here are the most likely culprits:
* Ball Joints: Worn ball joints are a common cause. They allow for articulation in the suspension, and when worn, they can create play that becomes noticeable under load (like braking).
* Tie Rod Ends: Similar to ball joints, worn tie rod ends can cause knocking or clunking, especially when the suspension is stressed.
* Control Arm Bushings: These bushings are rubber components that allow the control arms to pivot. Worn bushings allow excessive movement, leading to knocking.
* Shocks/Struts: While less likely to *knock* specifically, severely worn shocks or struts can allow for excessive movement and bottoming out, which could contribute to a noise that sounds like a knock.
* Steering linkage components: A worn or loose component in the steering linkage could be amplified by brake application.
It's crucial to have this inspected by a mechanic. Driving with a worn suspension is dangerous, as it can affect your steering and braking control. Attempting to diagnose and fix this yourself without proper tools and knowledge could be risky.
The mechanic will need to inspect the front suspension components to pinpoint the exact source of the noise. They'll likely perform a thorough inspection of the ball joints, tie rod ends, control arm bushings, shocks/struts, and steering linkage.
