Karl is a Professor of Podiatry and is internationally-known for his research, with a particular interest in investigating musculoskeletal disorders of the foot and ankle. From 2020-2024, he was the Associate Dean, Research and Industry Engagement for the School of Allied Health, Human Services and Sport at La Trobe University.

Karl's main areas of research focus on heel pain (plantar heel pain/plantar fasciitis) and shoe insoles (foot orthoses), although he also has experience investigating other conditions and interventions. He has published 158 peer-reviewed journal articles and 15 book chapters. According to Clarivate Analytics Web of Science, Karl is ranked #1 in the world for total number of publications for the condition ‘plantar heel pain/plantar fasciitis’ and #2 for ‘foot orthoses’ (his two primary research areas). More broadly, he is ranked #3 in the world for the total number of English language scientific-publications relating to the foot (in the combined categories of Orthopedics, Sport Sciences, General Internal Medicine, Rehabilitation and Rheumatology).

Karl is currently involved in several research projects, including: investigations related to musculoskeletal disorders of the foot and ankle (particularly of medical imaging and interventions for plantar heel pain), evaluations of foot orthoses, and studies of patient-reported outcome measurement instruments (PROMs). Karl has supervised 15 PhD, 2 Masters and 24 Honours students to completion, and currently supervises 2 PhD students.

Karl proudly acknowledges the Wurundjeri people of the Kulin nations as the Traditional Custodians of the land and its waterways on which he lives and works.