What is it about?

Understanding and explaining a complex biological system such as the knee joint is often difficult and challenging. To overcome the problem of complexity many scientists simplify or reduce this complexity by disassembling the complex system into their single units. However, the knee joint is not a simple machine put together by bones, muscles and connective tissue. Importantly, clinicians don't treat knees, but a person who has a knee problem. Reductionism has been the basis of most scientific fields, and has led to an impressive range of discoveries and advancements. How can we apply this to enhance our understanding of prevention and treatment of various knee pathologies? In order to understand how the knee joint works, one could dissect the knee and place all soft tissue and bony parts on a counter top. Looking now at the patella and the popliteal artery, does this gives us an idea how the knee joint functions as a whole? It appears that a reductionistic approach is also widely used in ACL research, in particular when aiming for identification of isolated risk factors for ACL injuries. In contrast to reductionism, a complex systems theory is a field of science studying how parts of a system give rise to the collective behaviors of the system, and how the system interacts with its environment in the broadest sense. A complex system approach, that highlights a non-linear interaction between risk factors from different scales (biomechanical, psychological and physiological characteristics). In other words, ACL prevention research should focus on the analysis of the observable regularities arising from the existing and complex interactions among the elements of the web of determinants and not the units (risk factors) themselves].

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Why is it important?

A more complex approach would draw a more realistic picture of the conditions knees are affected from.


We need to think and reconsider the way we do ACL reseach. Simplification is necessary due to logistical and organisational issues, but should not lead to the fact that the results cannot be generalised or can even only applied in a very small group of patients.

Prof. Dr. med. Michael Tobias Hirschmann
Kantonsspital Baselland

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This page is a summary of: Let us rethink research for ACL injuries: a call for a more complex scientific approach, Knee Surgery Sports Traumatology Arthroscopy, March 2018, Springer Science + Business Media, DOI: 10.1007/s00167-018-4886-6.
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