Kneeling as a risk factor of patellofemoral joint cartilage damage worsening: an exploratory analysis on the Osteoarthritis Initiative

Objectives: To determine whether kneeling activity is associated with the MRI measures of patellofemoral (PF) joint cartilage damage worsening in subjects with/without patella alta (PA). Methods: Baseline and 24-month 3-T MR images and semi-quantitative MRI Osteoarthritis Knee Score (MOAKS) of PF joint of 600 subjects from the FNIH study, a nested study within the Osteoarthritis Initiative (OAI), were extracted. At baseline visit, subjects were asked how many days per week they participated in kneeling activities lasted ≥ 30 min. Insall-Salvati ratio (ISR) (patellar tendon/patellar height) was measured on baseline MRIs by a musculoskeletal radiologist; ISR ≥ 1.3 was considered PA. Regression analysis adjusted for confounding variables was used to assess the impact of kneeling on worsening of MOAKS cartilage over 24 months. The potential moderating effect of PA was evaluated using adjusted regression analysis. Results: Six hundred subjects (58.8% female, years, BMI = 30.7 ± 4.8 kg/m²) were included; 13.7%, 6.2%, and 5.5% of participants reported 1 day, 2–5 days, and ≥ 6 days of kneeling activities per week. A higher frequency of kneeling activity was associated with the increased risk of MOAKS cartilage score worsening (adjusted OR (95% CI): 2.33 (1.08–5.06)). Stratification analysis showed that only ≥ 6 days/week of kneeling activities was associated with the worsening of MOAKS cartilage scores (2.74 (1.03–7.27)). When we included the presence of PA in regression models, the OR (95% CI) for the association between kneeling and PF cartilage damage will decrease to 1.26 (0.78–2.04), suggesting the potential role of PA as the moderator variable. Conclusion: Extensive kneeling activity (≥ 6 days/week) may be associated with the MRI-based worsening of PF cartilage damage, specifically in subjects with an underlying patella alta. Key Points: • Frequent daily kneeling activity is associated with a higher risk of patellofemoral cartilage damage resulting in patellofemoral osteoarthritis. • The cartilage damage associated with extensive kneeling activity may be worse in subjects with an underlying patella alta (i.e., high-riding patella).