His clinical focus has since 1998 been knee surgery.

He was a substantive consultant orthopaedic surgeon at St. Mary’s Hospital in London (Imperial College) from 2000 to 2004, and was a consultant orthopaedic surgeon and clinical lectuerer at Aarhus University Hospital from 2004 until his present position.

The research of AO was from 1987 to 1999 focused on cancellous bone structure and mechanics. He has authored or coauthored papers, that are now considered classics in the field. The development of methods for quantification of cancellous bone connectivity and anisotropy and their relation to mechanical properties of bone are still highly cited.

Clinically, AO has together with colleagues in Aarhus pioneered a number of surgical treatments in Denmark. Among these are extensor mechanism allograft transplantation, day-case unicompartmental knee replacement and lateral mobile bearing unicompartmental knee replacement.

Since 2014, AO has been responsible for clinical orthopaedic research at the Gentofte unit of Copenhagen University Hospital. The main focus has been on surgeon-assessed indications, patient-reported outcomes, risk-perception, intraoperative bacterial contamination and clinical trials for comparing knee arthroplasty techniques.