Mr Johnson has been a consultant at Stepping Hill Hospital, Stockport since 2001 where he practices in knee and trauma surgery. He also treats children with knee injuries and has an interest in recurrent patella dislocation. As well as providing a clinical service, he is currently the Clinical Director of the Trauma and Orthopaedic Department at Stepping Hill Hospital.
He also leads an active research unit and supervises on the Knee Fellowship training scheme. He is a Member of the British Orthopaedic Association, the British Association for Surgery of the Knee and the British Orthopaedic Research Society.