Introduction:​ Overweight and obese individuals are at an increased risk of developing knee osteoarthritis (OA), which severely limits mobility and reduces quality of life. Weight-loss interventions have shown positive effects on knee OA symptoms. However, few long-term follow-up studies have been performed in this population.

Purpose:​ To determine the effectiveness of the IDEA trial on clinical outcomes 2-3 years after study completion. This data could help to improve future weight-loss interventions for adults with knee OA.

Methods:​ Participants in waves 1-5 of the IDEA trial (n = 166) were invited to return to a followup visit 2-3 years after their completion of the study. Pairwise and treatment effect comparisons were performed on the 91 participants who returned for the follow-up visit, relative to their baseline and 18-month (FU18) visit data. Data included anthropometric, mobility, quality of life, and psychosocial measurements.

Results:​ While the D+E group lost 10.6 kg and the D-only group lost 8.9 kg during the IDEA trial, at the conclusion of the IDEA trial participants in the D+E group increased in weight by 5.8 kg, waist circumference by 55.3%, and regressed toward baseline values in pain, function and mobility. The D-only group regained 3.1 kg but slightly increased in waist circumference and regressed in pain and function measures

Conclusions:​ Participants randomized to the IDEA weight-loss groups regained some, but not all, of their weight and this had a negative impact on many clinical outcomes. The D-only group experienced less weight regain than the D+E group, and less regression to baseline values in pain, function, and waist circumference. While the D+E group experienced the greatest improvements in clinical outcomes during the IDEA trial, the regression toward baseline values in all groups resulted in no statistical difference between-groups 2-3 years after trial completion.