for the left knee. It is meant as an offloader, but you should really consult the Donjoy website whether this is meant for you - I am not a medical practitioner so please don't ask me. I'm guessing, but would fit someone 5'7"ish to 5'9", probably 225 lbs (i.e. with a larger thigh). I'm 195 lbs 5'9" and it is too large for my thigh.