A. Ferreira1, S. Lack2, B. Taborda1, M. Pazzinatto3, F. Azevedo1, D. De Oliveira Silva3
1Sao Paulo State University, Department of Physiotherapy, Presidente Prudente, Brazil, 2Queen Mary University of London, Centre for Sports and Exercise Medicine, London, United Kingdom, 3La Trobe University, La Trobe Sport and Exercise Medicine Research Centre Human Services and Sport, Melbourne, Australia
Background: Patellofemoral pain (PFP) is a common cause of knee pain in young adults. Young adults with PFP have higher body mass index (BMI) compared with non-injured people. Increased levels of pro-inflammatory cytokines by adipose tissue was previously reported in overweight populations, which may lead to sensitization of peripheral nociceptors and central nociceptive pathways (i.e., local and widespread pressure hyperalgesia). However, the association between body composition measures and pressure hyperalgesia has never been explored in young adults with PFP. A better understanding of how body fat, lean mass and BMI are associated with the pain experience in this population is likely to help guide both health care practitioners and researchers to improve the management of PFP (e.g. there is no trial targeting weight loss in PFP).
Purpose: To explore the association between body composition measures (body fat, lean mass and BMI) with local, spread and widespread pressure hyperalgesia in young adults with PFP.
Methods: A cross-sectional study was conducted with 114 young adults with PFP (62% women; mean (SD) age: 24.0 (4.7) years; BMI: 25.2 (4.7) kg/m2). The study was approved by the University Ethics Committee (number: 1.484.129), all participants provided consent. Demographics and self-reported pain (0-100mm Visual Analog Scale) were obtained. Body fat and lean mass were measured using bioelectrical impedance. Pressure hyperalgesia was measured using a handheld algometer (pressure pain threshold) at three sites: center of patella of painful knee (local), ipsilateral tibialis anterior (spread), and contralateral upper limb (widespread). Statistical analysis: (i) partial correlation coefficients were used to determine the association between body fat, lean mass and BMI with local, spread and widespread pressure hyperalgesia; (ii) all variables found to be significantly correlated (p < 0.05) were inserted into hierarchical regression models to determine the unique association between each measure of body composition (independent variables) with each measure of pressure hyperalgesia (dependent variables). All analyses were adjusted for sex, bilateral pain, and duration of symptoms.
Results: Body fat and lean mass were associated with all measures of pressure hyperalgesia (r = -0.30 to -0.42, p<0.01; r = 0.35 to 0.51, p<0.01, respectively). BMI was not associated with any measures of pressure hyperalgesia (p>0.05). Body fat explained 9%, 15% and 17% of the variance in local, spread and widespread pressure hyperalgesia, respectively. Lean mass explained 14%, 17% and 26% of the variance in local, spread and widespread pressure hyperalgesia, respectively.
Conclusion(s): Higher body fat and lower lean mass, but not BMI, were associated with local, spread and widespread pressure hyperalgesia in young adults with PFP. These findings suggest that the mechanism driven pain sensitization in this population may not simply be via loading of the joint, but mainly by the systemic effect occurring as a consequence of increase in adiposity. Further research is warranted to explore this hypothesis.
Implications: Young adults with PFP might benefit from a more detailed assessment of body composition (i.e. body fat and lean mass) during the management of this condition as it seems to have an impact on the pain experience.
Funding, acknowledgements: The present work was supported by the Sao Paulo Research Foundation - FAPESP (scholarship nº 2018/17106-0).
Keywords: knee pain, body composition, hyperalgesia
Topic: Musculoskeletal: lower limb
Did this work require ethics approval? Yes
Institution: Sao Paulo State University - UNESP
Committee: São Paulo State University Human Ethics Committee
Ethics number: 1484129
All authors, affiliations and abstracts have been published as submitted.
