Objectives Obesity is a well-recognised risk factor for osteoarthritis (OA). Our aim is to characterise body mass index (BMI)-associated pathological changes in the osteochondral unit and determine if obesity is the major causal antecedent of early joint replacement in patients with OA.
Methods We analysed the correlation between BMI and the age at which patients undergo total knee replacement (TKR) in 41 023 patients from the Australian Orthopaedic Association National Joint Replacement Registry. We then investigated the effect of BMI on pathological changes of the tibia plateau of knee joint in a representative subset of the registry.
Results 57.58% of patients in Australia who had TKR were obese. Patients with overweight, obese class I & II or obese class III received a TKR 1.89, 4.48 and 8.08 years earlier than patients with normal weight, respectively. Microscopic examination revealed that horizontal fissuring at the osteochondral interface was the major pathological feature of obesity-related OA. The frequency of horizontal fissure was strongly associated with increased BMI in the predominant compartment. An increase in one unit of BMI (1 kg/m2) increased the odds of horizontal fissures by 14.7%. 84.4% of the horizontal fissures were attributable to obesity. Reduced cartilage degradation and alteration of subchondral bone microstructure were also associated with increased BMI.
Conclusions The key pathological feature in OA patients with obesity is horizontal fissuring at the osteochondral unit interface. Obesity is strongly associated with a younger age of first TKR, which may be a result of horizontal fissures.
- knee osteoarthritis
- total knee replacement
- horizontal fissuring
- osteochondral unit
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Handling editor Josef S Smolen
Contributors Conception and design of the study: MZ, CJ, LC and FY. Acquisition of data: LC, FY, PC, EL-B, PV, ML, SG and RCS. Analysis and interpretation of data: LC, MB, GL, TW, MF, and JG. Drafting of article or revising it critically for important intellectual content: LC, JJYZ, GL, YH, JP, CZ, DW, CJ and MZ. Final approval of the version of the article to be published: all authors.
Funding The work is supported by the general funding of the University of Western Australia and International Cooperation and Exchange of the National Natural Science Foundation of China (Grant Number: 81820108020 and 81802214). Lianzhi Chen has received Scholarship for International Research Fees from the University of Western Australia.
Competing interests The conduct of work is supported by the general funding of the University of Western Australia. LC has received Scholarship for International Research Fees from the University of Western Australia. All authors declare no conflicts of interest.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Patient consent for publication Not required.
Ethics approval The Human Research Ethics Committee of the University of Western Australia approved this study.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request. All original datasets (including deidentified participant data) collected for this study will be available upon request to the corresponding author, Minghao Zheng. Registry data can be reused under the approval from the Australian Orthopaedic Association.
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