HAVANA, Cuba (CNN) -- President Fidel Castro fell, possibly breaking his leg, after giving a graduation speech Wednesday in the central Cuban city of Santa Clara. Sending a buzz through the crowd, the 78-year-old leader appeared to trip as he was walking away from the podium. In an effort to calm the crowd, Castro took the microphone after a few minutes, saying: "Just so that there won't be any speculation, it seems that I broke my knee." He apologized for any concerns he may have caused for those who care about him and then joked how his spill was likely...