In reply to bobstones:
hmm mine went pop in an erm... sledging incident, had it x-rayed which didn't show anything
I think the advice was just the usual "rest it"
it did hurt for some time though
so, I was laying on my back on my brother in laws metal framed sledge with straight arms firmly gripping the side upright bars
took off down a short but 45 degree slope and one runner hit something and stopped, which also bent the sledge