CHANGE IN ULTRASOUND-BASED KNEE JOINT INFLAMMATORY MARKERS AFTER WEIGHT LOSS IN PATIENTS WITH OSTEOARTHRITIS: A PROSPECTIVE COHORT STUDY

Background Pain and impaired function due to knee OA (KOA) can be reduced with weight loss in obese patients. The role of synovitis in symptom improvement after weight loss is not fully understood. MRI and ultrasound (US) can be used in assessment of inflammation in the KOA. Knee joint synovitis assessed by MRI does not seem to change with weight loss, however, the typical MRI score is semiquantitative, which might be less sensitive to change than a quantitative score. US has a higher resolution than MRI and borders between synovium and surrounding tissues might be clearer allowing for a quantitative score. Changes in US-based synovitis following a weight has not been assessed. Objectives To assess changes in US synovitis in the knee joint after 8 weeks low-calorie weight loss intervention in overweight persons with KOA. Methods prospective cohort study ( NCT02931370 ) including overweight persons (BMI ≥ 27 kg/m 2 ) with KOA. Weight loss was induced by an intensive 8-week diet (1200 kcal/day), participants had symptomatic and radiographically confirmed KOA (KL grade 1-3). At week 0 and 8 all participants filled in the KOOS questionnaire assessing pain, physical function, symptoms, quality of life, and sport/recreation in relation to KOA (0= worst; 100=best). Furthermore, an US examination of the most affected knee was performed assessing the amount of synovial hypertrophy (SH) and effusion in medial and lateral recesses. The US examination was performed in a strictly standardized manner on a high-end US machine. The subsequent image evaluation was done both according to a semiquantitative score from 0 to 3 (0=no SH/effusion and 3=pronounced SH/effusion) and a quantitative scoring system using specific anatomic landmarks to measure the synovial hypertrophy/effusion in millimeter. Statistical analyses were performed on the per protocol population (participants completing diet intervention). Results 135 patients with KOA with a mean age of 60y (SD 9.8), a body weight of 106.0 kg (SD18.5) and mean BMI of 36.4 (SD5.4) completed the weight loss intervention. After the diet intervention mean weight change was -12.8 kg (95%CI -13.3 to -12.4) and the reductions in SH were -0.3mm (95%CI -0.5 to -0.1) (medial recess) and -0.4mm (95%CI -0.6 to -0.1) (lateral recess), and -0.03 (-0.13 to 0.07) (medial recess) and -0.07 (-0.20 to 0.05) using the semi-quantitative system. The mean change in the KOOS subscales range from 15.8 (sport/recreation) to 7.4 (QoL). See Table 1. Table 1. n=135 Baseline Change Mean (SD ) Mean (95%CI ) P Age 60.0 (9.8) - - Females, n (%) 87 (64.4%) - - BMI 36.4 (5.4) -4.4 (-4.5 to -4.3) <.0001 KL-scores; 1 22 (16.3%) - - KL-scores; 2 56 (41.5%) - - KL-scores; 3 57 (42.2%) - - KL-scores; 4 0 (0%) - - Synovial Hypertrophy Medial, mm 3.8 (1.8) -0.3 (-0.5 to -0.1) 0.0198 Lateral, mm 5.3 (2.3) -0.4 (-0.6 to -0.1) 0.0210 Medial, 0-3 1.2 (0.6) -0.03 (-0.13 to 0.07) 0.5584 Lateral, 0-3 1.8 (0.8) -0.07 (-0.20 to 0.05) 0.2311 KOOS, 0-100 Pain 64.1 (16.0) 12 (10.2 to 13.8) <.0001 Function 68.4 (17.3) 14 (12.4 to 15.6) <.0001 Symptoms 68.9 (16.4) 9 (7.2 to 10.8) <.0001 Sports/Recreation 35.9 (24.0) 15.8 (13.2 to 18.3) <.0001 QoL 43.8 (17.5) 7.4 (5.7 to 9.2) <.0001 SD = Standard Deviation; CI = Confidence Interval; BMI = Body Mass Index; KOOS = Knee injury and Osteoarthritis Outcome Score; QoL = Knee-related Quality of Life Conclusion Quantitative measures of SH assessed by US decreased after a significant weight loss over 8-weeks; however, no linear association with weight loss magnitude was seen. A weak correlation between changes in SH in the lateral recess and change in pain was seen. This indicates changes in SH assessed by US examination is associated with a low-calorie diet but seems uncoupled with weight loss magnitude. The weight loss induced changes in synovitis and KOA symptoms seem vaguely related. Disclosure of Interests None declared