Lower limbs composition and radiographic knee osteoarthritis (RKOA) in Chingford sample—A longitudinal study Orit Blumenfeld a , Frances M.K. Williams b , Deborah J. Hart b , Nigel K. Arden c , Timothy D. Spector b , Gregory Livshits a,b, * a Human Population Biology Research Unit, Department of Anatomy and Anthropology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel b Department of Twin Research and Genetic Epidemiology, King’s College London St. Thomas’ Hospital Campus, London, UK c NIHR Biomedical Research Unit, Botnar Research Center, University of Oxford, Oxford, UK 1. Introduction Knee osteoarthritis (OA) is a common, disabling condition in middle-aged and elderly and its prevalence is predicted to increase substantially over the coming decade (Acheson & Collart, 1975; Garstang & Sittik, 2006). It is characterized by pain, and affects all the structures of the knee joint. The characteristic features include low-grade inflammation, cartilage loss, sub-chondral bone changes and peri-articular soft tissue changes. Important risk factors for radiographic knee OA (RKOA) include age, female sex and obesity (Abbate et al., 2006; Felson, 2004). At least 33% of people over the age of 55 have radiographic evidence of knee OA (Cooper et al., 2000; Felson & Zhang, 1998; Hart, Doyle, & Spector, 1999), and females have more severe RKOA after the menopause (Srikanth et al., 2005). The prevalence of RKOA in adults over the age of 45 years among participants in Framingham study was 19.2% and 27.8% in Johnston County Osteoarthritis project (Lawrence, Felson, Helmick, et al. 2008). Because the proportion of older people in the world population is continually increasing; OA is becoming an increasingly important public health concern. With the increase in obesity and the aging of human population it is essential to understand the relationship between obesity and OA. Longitudinal data have shown that overweight/obesity is a powerful risk factor for the development of knee OA with a clear dose response relationship between excess weight and knee OA (Manek, Hart, Spector, & MacGregor, 2003). Thus 9–13% increased risk of OA occurs with every kilogram increase in body weight (Cicuttini, Baker, & Spector, 1996). Perhaps more surprisingly still, epidemiological studies show this risk to be reversible: a 5.1 kg loss in body mass over 10 years reduced the odds of developing OA by more than 50% (Felson, Zhang, Anthony, Naimark, & Anderson, 1992; Messier, Gutekunst, Davis, & DeVita, 2005). Anthropometric measurements of central adiposity such as BMI, waist circumference and waist–hip ratio (WHR) are often used to assess risk of OA, and all are significantly associated with RKOA (Hart & Spector, 1993). However, such measurements are surrogate measures of adiposity and cannot discriminate adipose from non-adipose mass. Several studies have compared the body composition measures and BMI between individuals with healthy and arthritic knee joints (Toda, Segal, Toda, Kato, & Toda, 2000; Wang et al., 2007). It was found that fat mass, lean mass of the Archives of Gerontology and Geriatrics 56 (2013) 148–154 A R T I C L E I N F O Article history: Received 16 June 2012 Received in revised form 19 September 2012 Accepted 22 September 2012 Available online 18 October 2012 Keywords: RKOA DXA Lean and fat mass Abdominal fat BMI A B S T R A C T Our aim in this longitudinal study was to evaluate to what extent fat and lean tissue mass variations are associated and can predict RKOA in a large sample of British women followed-up over 10 years. Kellgren/ Lawrence (K/L), joint space narrowing (JSN) and osteophyte (OSP) grades were scored from radiographs of both knees in 909 middle-aged women from the Chingford registry. Body composition components were assessed using the dual energy X-ray absorptiometry (DXA) method. In cross-sectional analysis, combined effect of age, BMI and leg tissue composition was required for best fitting model explaining variations of K/L scoring and osteophytes at lateral compartment. To explain medial osteophytes, age and BMI were sufficient to generate the best fitting model. In prediction analysis, leg lean mass was the more powerful predictor of K/L, medial osteophytes than BMI. In conclusion, BMI appears to influence the development of knee OA through both fat and/or lean mass, depending on RKOA phenotype. ß 2012 Elsevier Ireland Ltd. All rights reserved. Abbreviations: BC, body composition; BMI, body mass index; JSN, joint space narrowing; JSN_lt, joint space narrowing, lateral compartment; JSN_md, joint space narrowing, medial compartment; K/L, Kellgren/Lawrence grading scale of osteoar- thritis; LH, likelihood; OA, osteoarthritis; OSP, osteophytes; OSP_lt, osteophytes, lateral compartment; OSP_m, osteophytes, medial compartment; RKOA, radio- graphic knee osteoarthritis. * Corresponding author at: Department of Anatomy and Anthropology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel. Tel.: +972 36409494; fax: +972 36408287. E-mail address: gregl@post.tau.ac.il (G. Livshits). Contents lists available at SciVerse ScienceDirect Archives of Gerontology and Geriatrics jo ur n al ho mep ag e: www .elsevier .c om /lo cate/ar c hg er 0167-4943/$ – see front matter ß 2012 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.archger.2012.09.006