I had no prior knee damage or surgeries but had started to feel the force of big air landings on my knees more often, so I made the switch to braces from Thor Force Knee Guards - and what a huge difference. Way more support from these braces. Takes a lot of strain off the knee joint. Size large fit great for my size (5'11" 170lbs) but there's also plenty of adjustability and specific setup instructions are included (check TLD online video too). Great price for the pair considering the higher cost of many other braces. Overall fit & finish is superb. Only complaint is that the white color gets dirty easily.