Ginckel AV, et al. - Baseline data from 594 individuals of the Osteoarthritis Biomarker Consortium Foundation for the National Institutes of Health project were incorporated to examine relationships between engagement in knee bending (stair climbing, kneeling, squatting, heavy lifting, getting in/out of a squatting position) and synovitis prevalence on noncontrast MRI in individuals who were at risk of and with knee osteoarthritis. The predominance of grade ≥ 1 Hoffa synovitis and effusion synovitis was 59% (n = 353) and 62% (n = 366), respectively. Adjusted for confounders, during a single day, kneeling for ≥ 30 minutes was related to grade ≥ 1 Hoffa synovitis prevalence. Individuals involving in this activity ≤ 1 day per week, in comparison with those who did not perform the activity, had greater odds for prevalent Hoffa synovitis. No other important relationships were observed. Sensitivity analyses presented comparable findings. Hence, only prolonged kneeling was related to Hoffa synovitis prevalence in this picked sample with a dominance of grade ≥ 1 Hoffa and/or effusion synovitis on noncontrast MRI. Furthermore, replication in other samples is assured.