Rathnam made his debut as a stunt master or stunt man in 1963 and has appeared in 30 films. He has also been credited under the names “Judo” Rathnam and “Rudranggam” Judo Ratnam. He has performed stunts on the films Aaa Re Saathia Aa, Dhire Dhire Prema Hela, Ae Jugara Krushna Sudama, Mahanayak, Nari Nuhen Tu Narayani, Agnee, Katha Deithili Maa Ku, Wrong Number, Rakata Chinhichhi Nijara Kie, Suna Harini, Pua Moro Bhola Shankara, Parampara, Jeevan Ek Sanghursh, Hisabd Kariba Kalia, Jahaku Rakhibe Ananta, and more. In 2006 he retired from film with his final movie Thalainagaram. He authored a book on his memoirs in 2013.