Before you begin, you will need a measuring tape - preferably cloth like the kind a seamstress would use. If you do not have a measuring tape, you can get by with a piece of string and a ruler - first cut a length of string that is 6 inches long, then have another piece of string that is long enough to wrap around your thigh/knee.
Step 1: Measure 6 inches above the middle of your kneecap (patella) and mark the level with a pen or marker:
Step 2: Measure the circumference of your thigh (how long it is around your thigh) at the level you just marked. If you are using a piece of string, simply wrap the string around your thigh at this level, mark it where it overlaps itself, and measure it out with a ruler.
(In this case, the measurement of the person's thigh 6" above the mid-patella is 17 inches - use this to then order the appropriate brace size - in this case, Small - for Legend or Armor braces. If you are very close to the next larger size, then you may consider choosing that one, unless you like your knee brace very snug.)
For the Orthomen Knee Braces, we recommend the following sizes (these are exact Orthomen size recommendations):
Knee Brace Size Chart