A year ago, I hit my knee in a riding accident. About three weeks later, it started to hurt a little and be a bit stiff. This gradually got worse, until in the summer, it was extremely painful. Three weeks ago, I had an arthroscopy, which revealed rough cartlidge behind my knee cap, and hundreds of rice particles. My surgeon told me that my body made these particles, and that it may happen again.
Does anybody know what these particles are, and if they are likely to have been caused by the accident, or is that just coincidence.