I tried a lot for my old knee Basketball botched by there 30 years (cruciate ligament damn ...) Attention to the choice of the size, it's tricky, measure 10 cm below the knee. I play for 2 L and XL models from Thuasne, and for this one I need the M.
Size Guide:
Between 35 and 37 cm> Size M Between 37 and 40 cm> L Size Between 40 and 43 cm> Size XL
Measure the circumference (cm) to 10 cm below the patella. During measurement, ensure that the knee is slightly bent (about 30 °).