Mr. Mark O'Sullivan is Melbourne born and completed his basic medical training at Melbourne University. Orthopaedic training was also through the Victorian training program and was completed in 1990.

After completing his basic orthopaedic training he spent 2 years in the United States obtaining a Fellowship in Paediatric Orthopaedic Surgery. On returning home to Melbourne in 1992 he commenced work at the Royal Children’s Hospital and the Western Hospital in Footscray, He has now worked at the Royal Children’s Hospital for 20 years. He is a senior surgeon at the Royal Children's Hospital with a role in the management of elective and trauma surgery. He is particularly involved in the management of hip and knee conditions and the treatment of bone and soft tissue tumors. He has teaching commitments with the registrars, Fellows, and medical students that rotate through the hospital.

Mark has always had a strong interest in sporting injuries. His work also encompasses knee and hip surgery in adults and children. Most of this work is performed arthroscopically. He has particular interests in the management of acute knee injuries including ACL reconstruction, the management of meniscal injuries, and patellar realignment surgery. He has been involved in the management of difficult hip conditions for 20 years using a combination of femoral and pelvic osteotomies and more recently hip arthroscopy to improve the outlook of these hip problems. Mark has joined with several of the surgeons from Melbourne Orthopaedic Group to form the Hip Preservation Group in an effort to manage the more difficult of these hip conditions.

The other major area of Mark’s practice is the management of bone and soft tissue tumors.

Mark is a member of the Australian Orthopaedic Association, and the Australian Paediatric Orthopaedic Association and is a Fellow of the Royal Australasian College of Surgeons.

Mark is a keen sportsman, playing competitive tennis from an early age, skiing in winter, and playing golf whenever possible. He has two teenage children who keep him occupied in his spare hours. His hobbies include painting and sculpting.