The Intensive Diet and Exercise for Arthritis (IDEA) trial: design and rationale

Abstract

Background: Obesity is the most modifiable risk factor, and dietary induced weight loss potentially the best nonpharmacologic intervention to prevent or to slow osteoarthritis (OA) disease progression. We are currently conducting a study to test the hypothesis that intensive weight loss will reduce inflammation and joint loads sufficiently to alter disease progression, either with or without exercise. This article describes the intervention, the empirical evidence to support it, and test-retest reliability data.

Methods/design: This is a prospective, single-blind, randomized controlled trial. The study population consists of 450 overweight and obese (BMI = 27-40.5 kg/m2) older (age > or = 55 yrs) adults with tibiofemoral osteoarthritis. Participants are randomized to one of three 18-month interventions: intensive dietary restriction-plus-exercise; exercise-only; or intensive dietary restriction-only. The primary aims are to compare the effects of these interventions on inflammatory biomarkers and knee joint loads. Secondary aims will examine the effects of these interventions on function, pain, and mobility; the dose response to weight loss on disease progression; if inflammatory biomarkers and knee joint loads are mediators of the interventions; and the association between quadriceps strength and disease progression.

Results: Test-retest reliability results indicated that the ICCs for knee joint load variables were excellent, ranging from 0.86 - 0.98. Knee flexion/extension moments were most affected by BMI, with lower reliability with the highest tertile of BMI. The reliability of the semi-quantitative scoring of the knee joint using MRI exceeded previously reported results, ranging from a low of 0.66 for synovitis to a high of 0.99 for bone marrow lesion size.

Discussion: The IDEA trial has the potential to enhance our understanding of the OA disease process, refine weight loss and exercise recommendations in this prevalent disease, and reduce the burden of disability.

Trial registration: NCT00381290.

Figures

Figure 1

Theoretical model by which intensive dietary restriction plus exercise decreases knee joint loads, improves strength and power, and decreases inflammation leading to a slowing of disease progression, reduced pain, improved function, and less disability.

Figure 2

Participant eligibility and screening.

Figure 3

Test-retest reliability for knee joint loads calculated during gait. (A) Knee flexion/extension moment with an ICC = 0.86, and (B) Knee compressive forces with an ICC = 0.95.

Figure 4

Baseline double oblique coronal MR image acquired using a fat suppressed SPGR sequence with a 1.5 mm slice thickness and 0.31 mm × 0.31 mm in plane resolution. The area of the cartilage surface (AC) and the total subchondral bone area (tAB) are manually segmented in the medial tibia (MT) and weight-bearing medial femur (cMF). The part of the tAB covered by AC is defined as the cartilaginous area of bone (cAB), that not covered by the AC as the denuded area of bone (dAB).

Figure 5

Flow chart visualizing the image analysis and quality control (QC process).

Figure 6

3D visualization of the femorotibial subregions: Top: anterior view with the medial tibia being divided into 5 subregions (red = central, green = external, dark blue = internal, yellow = posterior, and turquoise = anterior subregion. The central subregion is defined by a cylinder and occupies 20% of the total subchondral bone area of medial tibia (MT). The weight bearing femur is divided into three strip-like subregions, each occupying 33.3% of the subchondral bone area (green = central, dark blue = internal, red = external subregion). The total subchondral bone area of the lateral tibia is shown in green and that of the lateral femur in red. Middle: oblique anterior-superior view of the subregions. Bottom: superior view onto the tibial subregions (femur not shown).