Dave, I have been riding dirt for 30 years now, and I could tell about 5 years or so ago that things were starting to get wore out in the knee area. Between the bikes and lots of running (been in the Army 23 years now) it was too much. Finally, summer 99 did the ACL/MCL rupture in the left knee. After about 4 months of rehab (and the Army kicking in and buying the CTi2 braces) I was able to pick it back up again. I believe I am as pscyhologically dependent on these things now, as much as physically! The one or two times I have fooloishly ridden since with out wearing them, I was sore the next day, not only from any twisting action but also impact absorption. I could not imagine riding competivley without them (over 40 expert) and only wish I had invested in them sooner!