I think you'll find both boxers were slipping on the canvas, that's why his leg appeared to buckled. As to the incident, Clottey was trapped in the corner and charge into a crouching Cotto. On contact with Cotto he spun around quickly and lost his footing, falling down forwards. He then went into histrionics so convincing that you would have thought he'd snapped his leg in half, and yet half a minute late he was up and walking on it with no apparent problem. His acting in the last round was digraceful. The soccer comparison is apt. Clottey COULD have won the fight but he gave too many rounds away against a guy with one eye.