Mine are medium, have worn them on a few rides now (probably about 5 one to two hour rides) and they're nice and comfy. I did get some rubbing from the stitching on the top inside corner, but it seems to have gone away now so just a wear in issue I guess. I do lots of pedalling - no big dh sections in this town!

Some measurements as requested:

My height 169cm
Guard length from botoom of pad to top of lower shell 29cm (11.42")
Lower hard shell lenght 26.5cm (10.43")
Bottom to top (overall lenght including knee shell and bottom to top of padding) about 52cm (20.47")
Bottom of knee shell to top of top padding 21.5cm (8.46")

Leg bent: my ankle to top of knee cap is about 40cm (15.75") - measure along front of leg
Inseam about 79cm (31")
Leg bent: floor to top of knee 50cm (19.68") - this one was measured along side of leg

Hope you can make sense of the above measurements and they help.