New England Patriots rookie RB Sony Michel underwent a procedure on his knee after injuring it in Wednesday’s training camp practice. Per reports, the procedure is to drain the knee. Draining the knee usually insinuates that there was fluid accumulation. Most common cause of this is either an injury (meniscus, ligament) or arthritis. In this situation I am skeptical that acute arthritis flare would cause this swelling (especially at his age). This likely means that he either had a ligament injury or a meniscus injury. Meniscal Injury is the most likely scenario. An orthopedic surgeon would go in an ‘clean up’ acute debris and smooth out the edges. Usually the player is back in their feet the same day but takes at least 10-14 days to ramp up activity again.