Chelsea forward Diego Costa has joined social networking site Twitter. The controversial Spanish international, who joined Chelsea from Atletico Madrid in the summer, has been involved in a number of unsavoury on-the-field incidents this season. The 26-year-old has netted 17 goals for the London outfit, however, with his form a big contributor to the team’s success. On Wednesday, Chelsea’s official Twitter account welcomed their striker to the networking site, with Costa operating under the tag @diegocosta.