The curvature of the lumbar spine and the risk of developing either osteoporosis (OP) or osteoarthritis (OA) are influenced by many common factors. The aim of this study is to determine whether lumbar lordosis is different between patients with either disease and healthy persons. A cross-sectional, blinded, controlled design was implemented. One hundred and twelve postmenopausal women were evaluated for bone mineral density as well as undergoing spinal radiography. Lordosis measurement was performed with Cobb's method. The sample was divided in four groups: patients with OP (n = 34, L1-L5 = 40.7 degrees, L1-S1 = 54.1 degrees), patients with OA (n = 29, L1-L5 = 38 degrees, L1-S1 = 52.3 degrees), patients with both diseases (n = 20, L1-L5 = 41.8 degrees, L1-S1 = 52.3 degrees) and controls (n = 29, L1-L5 = 38.6 degrees, L1-S1 = 51.8 degrees). For all participants age, height, weight, body mass index, physical activity level and basal metabolic rate were measured and recorded. The results revealed that although the four groups have significant constitutional differences, lumbar lordosis was comparable between them. The reasons for the lack of association are discussed.