JonnyW, glissading is fun, but is really dangerous if you don't have an ice axe to use as a brake. Your knee injury is a light one. People can break an ankle glissading while wearing crampons.
I saw a report last night of people glissading, then losing control (it gets icy lower down). Fortunately the snow softened near the bottom so they were ok.
Do NOT glissade without an ice axe!!!
