When the pad is on the leg with your skates on, the player's knee should fit perfectly into the middle of the knee cradle while the knee is slightly bent.
When sizing a set of leg pads for someone who is growing it is important to allow for the most growing room possible. However, It's equally important that the pad is not too cumbersome. Bulky pads cause limited movement.
To properly account for growing room, the player should be able to get his or her knee to touch at least the bottom third of the knee cradle while the knee is slightly bent. If the knee doesn't reach while bent, the pad is too big.
An easy way to properly estimate the most appropriate size for a goalie's leg pads is to take the following measurements:
Be sure and record these measurements. It will serve as an important reference when searching for the right pair of pads. Providing these measurements (A, B, C, and D) to a sales associate will help in assuring that the goalie's is getting the right gear for his size.