Assoc. Prof McMahon is a Consultant Orthopaedic Surgeon with an interest in the management of arthritis and injuries of the hip and knee. Assoc. Prof McMahon’s practice includes hip and knee replacement surgery, including revision hip and knee surgery.

Stephen McMahon's private practice is based in Windsor and he operates at The Avenue Private Hospital.

Assoc. Prof McMahon gained his Royal Australian College of Surgeons Fellowship in 1992 and worked as Senior Joint Replacement Fellow at the Princess Elizabeth Orthopaedic Hospital, Exeter, England, from 1993-1994. When he returned to Melbourne he was appointed as a Consultant Orthopaedic Surgeon at the Monash Medical Centre from 1994-2006.

Assoc. Prof McMahon was one of the first surgeons in Australia to embrace the concept of hip resurfacing. Hip resurfacing is now performed less commonly due in part to the significant advances in hip replacement surgery. Primary and revision hip replacements form the basis of his hip practice. His knee practice includes partial (robotic-assisted), total, and revision joint replacement, arthroscopy, and ACL reconstruction surgery.

In 2009, Assoc. Prof McMahon founded the Malabar Orthopaedic Institute, a not-for-profit charitable body through which he administers his research interests. These interests include the development of new prostheses and instruments, basic science research, and clinical research into arthritis-related conditions. He also supervises an Australian Orthopaedic Association Accredited Fellowship, through which he teaches overseas orthopaedic surgeons who wish to specialize in hip and knee replacement surgery.