22X Olympia-winning coach Hany Rambod talks about the importance of proper knee positioning for hamstring curls.
When performing hamstring curls, it is important that your knee is aligned with the pivot point of the machine. If you can't adjust the machine properly, you won't have full range of motion and will end up being too short or too tall. You want the pivot point to be right at the knee.
Pro Tip: Slow down the movement and control the weight throughout the full range of motion.