Exercise and weight loss in obese older adults with knee osteoarthritis: Apreliminary study

OBJECTIVE: The purposes of this pilot study were to determine if a combined dietary and exercise intervention would result in significant weight loss in older obese adults with knee osteoarthritis, and to compare the effects of exercise plus dietary therapy with exercise alone on gait, strength, kne e pain, biomarkers of cartilage degradation, and physical function. DESIGN: Single-blind, two-arm, randomized clinical trial conducted for 24 w eeks. SETTING: A university health and exercise science center. PARTICIPANTS: Twenty-four community-dwelling obese older adults aged greate r than or equal to 60 years, body mass index greater than or equal to 28, k nee pain, radiographic evidence of knee osteoarthritis, and self-reported p hysical disability. INTERVENTION: Randomization into two groups: exercise and diet (E&D) and ex ercise alone (E). Exercise consisted of a combined weighs training and walk ing program for 1 hour three times per week. The dietary intervention inclu ded weekly sessions with a nutritionist utilizing cognitive-behavior modifi cation to change dietary habits to reach a group goal of an average weight loss of 15 Ib (6.8 kg) over 6 months. MEASUREMENTS: All measurements were conducted at baseline and 3 and 6 month s, except for synovial fluid analysis, which was obtained only at baseline and 6 months. In addition, weight was measured weekly in the E&D group. Phy sical disability and knee pain were measured by self-report and physical pe rformance was measured using the 6-minute walk and stair climb tasks. Biome chanical testing included kinetic and kinematic analysis of gait and isokin etic strength testing. Synovial fluid was analyzed for levels of total prot eoglycan, keratan sulfate, and interleukin-1 beta. RESULTS: Twenty-one of the 24 participants completed the study, with one dr opout in the E&D group and two in the E group. The E&D group lost a mean of 18.8 Ib (8.5 kg) at 6 months compared with 4.0 Ib (1.8 kg) in the E group (P = .01). Significant improvements were noted in both groups in self-repor ted disability and knee pain intensity and frequency as well as in physical performance measures. However, no statistical differences were found betwe en the two groups at 6 months in knee pain scores or self-reported performa nce measures of physical function. There was no difference in knee strength between the groups, with both groups showing modest improvements from base line to 6 months. At 6 months, the E&D group had a significantly greater lo ading rate (P = .03) and maximum braking force (P = .01) during gait. There were no significant between-group differences in the other biomechanical m easures. Synovial fluid samples were obtainable at both baseline and 6 mont hs in eight participants (four per group). The level of keratan sulfate dec reased similarly in both groups from an average baseline of 96.8 +/- 37.1 t o 71.5 +/- 23 ng/mu g total proteoglycan. The level of IL-1 decreased from 25.3 +/- 9.8 at baseline to 8.3 +/- 6.1 pg/mL. The decrease in IL-I correla ted with the change in pain frequency (r = -0.77, P = .043). CONCLUSIONS: Weight loss can be achieved and sustained over a 6-month perio d in a cohort of older obese persons with osteoarthritis of the knee throug h a dietary and exercise intervention. Both exercise and combined weighs lo ss and exercise regimens lead to improvements in pain, disability, and perf ormance. Moreover, the trends in the biomechanical data suggest that exerci se combined with diet may have an additional benefit in improved gait compa red with exercise alone. A larger study is indicated to determine if weight loss provides additional benefits to exercise alone in this patient popula tion.