Magnetic Resonance Imaging Assessment of Subchondral Bone and Soft Tissues in Knee Osteoarthritis

To compare structural knee joint changes in obese patients with knee osteoarthritis (OA) that after an intensive weight loss therapy were randomized to continuous dietetic support, a specialized knee exercise program, or ‘no attention’ for 1 year.

192 obese individuals with knee OA underwent an intensive 16-week weight loss program with subsequent randomization to one of the three treatment groups. Changes in cartilage loss, bone marrow lesions (BMLs), synovitis, and effusion were assessed using semi quantitative assessments of magnetic resonance imaging (MRI) obtained at weeks 0 and 68 applying the BLOKS score.

During the 52 weeks maintenance period the continuous dietary maintenance group support on average gained 1.1 kg (95% CI: −0.3:2.5) body mass, the exercise group gained 6.6 kg (95% CI 5.4:7.8) and the no-attention group gained 4.8 kg (95% CI: 2.9:6.7). There were no statistically significant between-group differences in changes in cartilage loss, synovitis or effusion at the follow-up (analysis of covariance; ANCOVA, P > 0.16), while there was an increased number of medial tibiofemoral BMLs in the exercise group (ANCOVA, P = 0.015) compared to both diet (difference: −0.21 [95%CI −0.40:−0.03]) and “no attention” (difference: −0.26 [95%CI −0.44:−0.07]) groups.

In this 1 year follow-up after weight-loss in obese knee OA patients, we found a potentially increased number of BMLs in the exercise group compared to the diet and no attention groups, with no between-group differences in changes in cartilage loss, synovitis or effusion. These findings should be interpreted with caution for exercise compliance, MRI methodology and follow-up time.

(ClinicalTrials.gov identifier: NCT00655941)

With an increasing prevalence of older and obese citizens, the problems of knee osteoarthritis (KOA) will escalate. Weight loss is recommended for obese KOA patients and in a majority of cases this leads to symptomatic relief. We hypothesized that pre-treatment structural status of the knee joint, assessed by radiographs, 1.5 T magnetic resonance imaging (MRI) and knee-joint alignment, may influence the symptomatic changes following a significant weight reduction.

Patients were recruited from a Department of Rheumatology. Eligibility criteria were age above 50 years, body mass index ≥30 kg/m², primary KOA diagnosed according to the American College of Rheumatology (ACR) criteria and having verified structural damage. Patients underwent a 16 weeks dietary programme with formula products and counselling. MRI and radiographs of the most symptomatic knee were obtained at baseline and assessed for structural damage using the Boston-Leeds Osteoarthritis of the Knee Score, minimum joint space width and Kellgren–Lawrence score. Imaging variables, muscle strength and degree of alignment, were examined as predictors of changes in Knee Osteoarthritis Outcome Score (KOOS) and Outcome Measures in Rheumatoid Arthritis Clinical Trials (OMERACT) - Osteoarthritis Research Society International (OARSI) Responder Criterion.

Structural damage at baseline assessed by imaging, muscle strength or knee-joint alignment showed no statistically significant association to changes in KOOS pain and function in daily living (r ≤ 0.13; P > 0.05) or the OMERACT-OARSI Responder Criterion (OR 0.48–1.68; P-values ≥ 0.13).

Presence of joint damage did not preclude symptomatic relief following a clinically relevant weight loss in older obese patients with KOA. Neither muscle strength nor knee-joint alignment was associated with the degree of symptomatic relief.