Measure the circumference of your knee joint with your leg out straight, keeping your muscles relaxed. Measure around the centre of your kneecap (at the patella), and around the thickest part of your calf. If your calf is more than 4cm (1.6in) larger than your knee, then you may wish to size up to ensure a good fit.
If you are new to wearing knee sleeves we recommend going with the recommended fit instead of sizing down, especially if you fall on size medium or smaller.