There is a knock when the brake is aplied drivers

So you were rolling on the freeway (correct) were you in rush hour traffic.... was there a car in front of you where you had to slow down or were you changing lanes.... Do think you might have accidentally applied the brakes thinking it was the gas pedal

The right rear brake on my Granddaughters car was so worn that the pad jammed when turning backwards stopping any backwards motion. When going forward it did not jam and could be pushed or driven forward. Tell everyone that if you hear scraping noises when applying brakes to get them checked right away.

Lots and lots of things can do this. I would recommend having the knocking sound investigated as the main concern, possibly by a good front-end shop. It could be a c-v joint or bad hub bearing which can allow a wobble in the front brake rotors. This would allow what you call a "judder".

Sometimes rust can form on the brake rotors while the car is parked. This is a weather related problem and if rust is the cause it can wear off to a smooth surface with driving. But a badly pitted rotor will need resurfacing or replacing. It can produce a scuffing sound, but not a knock.

cracked brake rotor or broken brake pad

when car is not started brake is not operative cause needs boosters help and the booster operates with vacuum, produces by the engine. first you need to know what tire(s) are locking, if rear tires are drum type, check if springs are in possition, did you bleed or replace brakes lately? also front brakes, from master cylinder to certaine point is pipe and from there to the caliper is rubber hose, and due to time and use, this hose gets damage inside, and wont let the brake fluid release its pressure after been aplied to stop the car, and front brakes will be applied due to this phenomenon

I just find this (click over this link for zoom)...

Fig. Exploded view of the rear drum brake assembly - LINK
The rear brakes do not require manual adjustment. Adjust the shoes by sharply applying the brake pedal several times while driving the vehicle alternately forwards and backwards. Check the brake operation by making several stops while driving forward. The self-adjusting mechanism will sufficiently adjust the rear brake shoes without any manual tightening at the brake shoe adjuster. If the rear brake shoes are manually adjusted, the additional action of the brake shoe adjuster can cause the brakes to become over-tightened and result in binding or overheated rear brakes.

Hope this helps.

could be the ABS sensor contacting the slotted sensor ring. just behind brake backing plate.

Copy and paste this into your search window: 2002 ford ranger rear brake diagram

You should see four pictures pop up, select the brake parts diagram or the brake picture.

check calliper assembly sliding pins they may need lubing with a bit of grease, check for anti rattle shims if there aply a tni film of sylicone on it face and reinstall

did you check your brake rotor for warpage. even a .010 warp on the rotor will be felt in the steering when aplying the brakes. use a dial indicator to check the warping