None here for off road hacking- I just use high viz leg wraps. If I had to ride on roads, then I would probably use knee boots, but then I do own a very sure footed and sturdy native pony. I used to boot all around with either brushing boots and over reach boots for my old TB.
Knee/brushing boots on the front and brushing boots behind.
I'm surprised by how few people use knee boots. People go crazy with fluffy over reach boots, super duper brushing boots and then nothing on the knees, I would never hack my horse out without something on her knees.