Performance-based physical functioning in African-American and Caucasian women at midlife: considering body composition, quadriceps strength, and knee osteoarthritis.

In 2000, body composition, x-ray-defined knee osteoarthritis, and self-reported knee pain information from a cross-sectional, community-based study of 211 African-American and 669 Caucasian women in southeast Michigan (mean age, 47 years) was related to performance-based physical functioning measures to characterize development of functional limitations. Body composition was assessed with bioelectrical impedance. Functioning measures were gait assessment, timed walk, timed stair climb with and without videography, and isometric quadriceps strength. Knee osteoarthritis was determined by Kellgren-Lawrence score from radiography, whereas knee pain was self-reported. Almost 31% of mid-aged women walked at functionally inadequate speeds, and over 12% walked at speeds considered typical of frailty in older women. Ten percent of women had skeletal muscle mass levels less than a proposed cutpoint for increased physical disability risk in older adults. Gait measures correlates included increasing age, increasing fat mass (in kilograms), knee joint pain, and reduced quadriceps strength. Stair climbing correlates included skeletal muscle mass (in kilograms) and its change, painful knee osteoarthritis, and reduced quadriceps strength. Race differences in walking measures and stair climbing time diminished when the authors accounted for other factors. Compromised physical functioning began earlier than expected, with indications that approximately 12-31% of women might benefit from interventions to forestall future decline.