Kieran graduated from University College Dublin in 1999. In 2004 he completed an MSc in Manipulative Therapy at Curtin University of Technology, Perth, Western Australia. In 2008 O'Sullivan was awarded specialist member status by the Irish Society of Chartered Physiotherapists. His research interests are broadly musculoskeletal pain and injury. He completed his PhD in 2012, which was funded by the Health Research Board. This project investigated the role of sitting behaviour in chronic low back pain, including the use of novel wireless technology to monitor and provide feedback on lumbar posture. From 2016-2019, he moved to Qatar to head up a spinal pain centre at Aspetar orthopaedic and Sports medicine Hospital, a FIFA- and IOC-accredited centre. He is currently involved in several research projects relating to musculoskeletal pain, nationally and internationally. Besides this, he likes to teach his course Changing pain and movement behaviour in chronic low back pain.