Effect of weight maintenance on symptoms of knee osteoarthritis in obese patients: a twelve-month randomized controlled trial

Abstract

Objective: To compare results of obese patients with knee osteoarthritis (OA) who, after an intensive weight loss regimen, received 1 year of either dietary support (D), a knee-exercise program (E), or "no attention" (C; control group).

Methods: We conducted a randomized, 2-phase, parallel-group trial. A total of 192 obese participants with knee OA were enrolled; the mean age was 62.5 years and 81% were women with a mean entry weight of 103.2 kg. In phase 1, all participants were randomly assigned to 1 of 3 groups and began a dietary regimen of 400-810 and 1,250 kcal/day for 16 weeks (2 8-week phases) to achieve a major weight loss. Phase 2 consisted of 52 weeks' maintenance in either group D, E, or C. Outcomes were changes from randomization in pain on a 100-mm visual analog scale, weight, and response according to the Outcome Measures in Rheumatology-Osteoarthritis Research Society International criteria.

Results: Mean weight loss for phase 1 was 12.8 kg. After 1 year on maintenance therapy, the D group sustained a lower weight (11.0 kg, 95% confidence interval [95% CI] 9.0, 12.8 kg) than those in the E (6.2, 95% CI 4.4, 8.1 kg) and C (8.2, 95% CI 6.4, 10.1 kg) groups (P = 0.002 by analysis of covariance [ANCOVA]). Adherence was low in the E group. All groups had statistically significant pain reduction (D: 6.1; E: 5.6; and C: 5.5 mm) with no difference between groups (P = 0.98 by ANCOVA). In each group 32 (50%), 26 (41%), and 33 (52%) participants responded to treatment in the D, E, and C groups, respectively, with no statistically significant difference in the number of responders (P = 0.41).

Conclusion: A significant weight reduction with a 1-year maintenance program improves knee OA symptoms irrespective of maintenance program.

Trial registration: ClinicalTrials.gov NCT00655941.

Figure 1

Study flow diagram of enrollment, randomization, and followup. Ineligibility at screening was mostly due to young age or too low body mass index for participation. ITT = intent-to-treat; VLED = very low energy diet; LED = low energy diet; TKA = total knee arthroplasty.

Figure 2

Changes in body weight over time were explored using a repeated-measures analysis of covariance (via PROC MIXED): a factor for group, a factor for time, and a factor for the interaction between them. The outcome at baseline was applied as covariate. Values are least squares (LS) means and error bars indicate SE of the LS means.