Effect of Diet and Exercise on Knee Pain in Patients With Osteoarthritis and Overweight or Obesity: A Randomized Clinical Trial

Abstract

Importance: Some weight loss and exercise programs that have been successful in academic center-based trials have not been evaluated in community settings.

Objective: To determine whether adaptation of a diet and exercise intervention to community settings resulted in a statistically significant reduction in pain, compared with an attention control group, at 18-month follow-up.

Design, setting, and participants: Assessor-blinded randomized clinical trial conducted in community settings in urban and rural counties in North Carolina. Patients were men and women aged 50 years or older with knee osteoarthritis and overweight or obesity (body mass index ≥27). Enrollment (N = 823) occurred between May 2016 and August 2019, with follow-up ending in April 2021.

Interventions: Patients were randomly assigned to either a diet and exercise intervention (n = 414) or an attention control (n = 409) group for 18 months.

Main outcomes and measures: The primary outcome was the between-group difference in the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) knee pain score (range, 0 [none] to 20 [severe]; minimum clinically important difference, 1.6) over 18 months, tested using a repeated-measures mixed linear model with adjustments for covariates. There were 7 secondary outcomes including body weight.

Results: Among the 823 randomized patients (mean age, 64.6 years; 637 [77%] women), 658 (80%) completed the trial. At 18-month follow-up, the adjusted mean WOMAC pain score was 5.0 in the diet and exercise group (n = 329) compared with 5.5 in the attention control group (n = 316) (adjusted difference, -0.6; 95% CI, -1.0 to -0.1; P = .02). Of 7 secondary outcomes, 5 were significantly better in the intervention group compared with control. The mean change in unadjusted 18-month body weight for patients with available data was -7.7 kg (8%) in the diet and exercise group (n = 289) and -1.7 kg (2%) in the attention control group (n = 273) (mean difference, -6.0 kg; 95% CI, -7.3 kg to -4.7 kg). There were 169 serious adverse events; none were definitely related to the study. There were 729 adverse events; 32 (4%) were definitely related to the study, including 10 body injuries (9 in diet and exercise; 1 in attention control), 7 muscle strains (6 in diet and exercise; 1 in attention control), and 6 trip/fall events (all 6 in diet and exercise).

Conclusions and relevance: Among patients with knee osteoarthritis and overweight or obesity, diet and exercise compared with an attention control led to a statistically significant but small difference in knee pain over 18 months. The magnitude of the difference in pain between groups is of uncertain clinical importance.

Trial registration: ClinicalTrials.gov Identifier: NCT02577549.

Figure 1.. Participant Flow Through the WE-CAN Trial

^aPersons with time conflicts, persons who stated they were not interested, and persons who did not return screening telephone calls. ^bParticipants may have been ineligible for more than 1 reason. ^cParticipants who said they were unable to participate due to personal circumstances in their lives. ^dOther reasons included change in activities due to injury (n = 7), type 1 diabetes (n = 7), staff believed participant was unable or unwilling to change dietary and exercise behaviors (n = 6), contacted study after recruitment closed (n = 5), spouse enrolled in study (n = 4), financial constraints (n = 3), previously enrolled (n = 3), blind (n = 2), unable to speak English (n = 1), community advisory board member (n = 1), and location of center inconvenient (n = 1). ^eOther reasons included desire for compensation (n = 6), staff believed participant was unable or unwilling to change dietary and exercise behaviors (n = 5), planned knee surgery/injection (n = 5), planned on being away for more than 2 months during study period (n = 4), enrolled in another study (n = 3), spouse enrolled in study (n = 1), and double knee replacement (n = 1). ^fSerious adverse events included cancer (n = 1) and severe cardiovascular complications/hospitalization (n = 1). ^gSerious adverse events included cancer (n = 3), motor vehicle collision (n = 1), and cerebral edema (n = 1).

Figure 2.. Unadjusted Mean WOMAC Pain Scores for Patients for Whom Follow-up Data Were Available at 6 Months and/or 18 Months

WOMAC indicates Western Ontario and McMaster Universities Osteoarthritis Index (range, 0 [no pain] to 20 [severe pain]). Box plots are shown for the primary outcome of pain, in which the middle lines represent median values; squares, mean values; and boxes, IQRs. Whiskers extend to the most extreme observed values within 1.5 times the IQR of the nearer quartile, and dots represent observed values outside the range. Unadjusted means are for the diet and exercise and attention control groups across the 18-month intervention period. The within-group minimum clinically important improvement at 18 months is a 20% improvement from baseline or 1.5 points. The between-group minimum clinically important difference is 1.6 points using the half-SD formula.