Background Patellofemoral OA is very common and is an important contribtor to anterior knee pain and disability. It can co-exist with the tibifemoral OA so most of the studies focussed on tibiofemoral rather than patellofemoral OA. Although there is increasing evidence to demonstrate that tibifemoral BMLs play important roles in tibiofemoral OA; it remains unclear whether patellar BMLs have similar roles.
Objectives To examine whether patellar BMLs are associated with cartilage loss (defects and/or volume loss) and knee pain in older adults.
Methods A total of 904 randomly selected subjects (mean 62.4 years, 49.9% female) were studied. OARSI atlas was used to assess radiographic knee osteophytes and joint space narrowing (JSN). T1- or T2-weighted fat suppressed magnetic resonance imaging (MRI) was used to assess bone marrow lesions (BMLs), cartilage volume and cartilage defects. Knee pain was assessed by self-administered Western Ontario McMaster Osteoarthritis Index (WOMAC) questionnaire.
Results The prevalence of any patellar BMLs was 18.8%. Cross-sectionally, patellar BMLs were positively associated with any BMLs at tibiofemoral compartments (OR: 2.52, 95% CI: 1.78, 3.56), medial and lateral femoral cartilage defects, patellar cartilage defects (OR: 12.99, 95% CI: 8.28, 20.39), and any knee pain when going up/down stairs (OR: 1.67, 95% CI: 1.18, 2.35), but negatively associated with patellar cartilage volume (β: -345.7 mm3, 95% CI: -470.9, -220.4) after adjustments of age, sex, BMI, and rheumatoid arthritis.
Longitudinally, baseline patellar BMLs was associated with increases in any BMLs in tibiofemoral compartment (OR: 2.21, 95% CI: 1.27, 3.85), increases in patellar cartilage defects (OR: 1.75, 95% CI: 1.01, 3.05) and an increase in knee pain when go up/down stairs (OR: 1.67, 95% CI: 1.08, 2.59) over 2.6 years in multivariable analyses. Baseline patellar BMLs were negatively associated with changes in cartilage volume at patellar (β: -2.10%, 95% CI: -3.39%, -0.80%), medial tibial (β: -1.36%, CI: -2.70%, -0.02%) and lateral tibial (-1.21%, -3.39%, -0.80%) sites. The associations with changes in tibial cartilage volume became non-significant after further adjustment for baseline tibial BMLs.
Conclusions Patellar BMLs were consistently associated with increased knee pain when going up/down stairs and patellar cartilage defects, and reduced patellar cartilage volume both cross-sectional and longitudinally, suggesting a local effect of patellar BMLs which may be an important target for the prevention and treatment of patellofemoral OA.
Acknowledgements We especially thank the participants, who made this study possible, and we gratefully acknowledge the role of the staff and volunteers in collecting the data, particularly research nurses Boon C and Boon P. Warren R assessed MR images, and Dr Srikanth V and Dr Cooley H assessed radiographs.This study was supported by the National Health and Medical Research Council of Australia; Arthritis Foundation of Australia; Tasmanian Community Fund; Masonic Centenary Medical Research Foundation; Royal Hobart Hospital Research Foundation; and University of Tasmania Institutional Research Grants Scheme.
J Wang is supported by the China Scholarship Council. G Jones is supported by a National Health and Medical Research Council Practitioner Fellowship. C Ding is supported by an Australian Research Council Future Fellowship.
Disclosure of Interest None declared
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