A COMPARISON OF ULTRASOUND-DETECTED PATHOLOGIES IN PERSONS WITH AND WITHOUT KNEE OSTEOARTHRITIS AND THE ASSOCIATIONS WITH PAIN

Background: Ultrasound can evaluate osteophytes and synovitis in persons with knee OA. However, albeit the literature demonstrates a positive association between knee pain and synovitis, the instruments used to report pain, the number of patients included, the strengths of associations and the overall quality of the studies varies greatly (1). Objectives: 1) To compare the degree of OA changes by ultrasound among people with and without clinical knee OA according to established classification criteria. 2) Study the associations between ultrasound findings and pain. Methods: We included 286 of 300 participants from the NOR-HAND study, a hospital-based observational cohort after excluding participants with knee prostheses or arthrodesis. The participants reported the levels of knee/hip pain using the Western/Ontario McMaster University index (WOMAC) and marked their painful joints (including the bilateral knees) during the last 24 hours and last 6 weeks on two separate homunculi. An experienced rheumatologist (BSC) examined whether the participants fulfilled the clinical ACR criteria for knee OA or not (n=7 missing). A trained medical student performed the ultrasound examination of the knees using a General Electric (GE) Logic E9 ultrasound machine with a 6-15Mz probe. Both knees were scored for 1) osteophytes in the medial and lateral tibia and femur on 0-3 semi-quantitative scales (0=no, 1=small, 2=medium, and 3=large), and 2) grey-scale synovitis on 0-3 semi-quantitative scales (0=no, 1=mild, 2=moderate, and 3=severe pathology). The highest score of osteophytes and grey-scale synovitis (range: 0-3) and the sum scores of both knees together (range: 0-24 for osteophytes and 0-6 for synovitis) were calculated. We compared the degree of ultrasound pathologies in persons with vs. without clinical knee OA using Chi square tests and Mann-Whitney U test or T test as appropriate. The associations between ultrasound pathologies and pain scores were explored by logistic regression analyses, adjusted for age, sex and BMI. Generalized Estimating Equations were applied to account for two knees belonging to the same person. Results: Knee osteophytes, but not grey-scale synovitis, were more common in persons with vs. without clinical knee OA (median sum score of osteophytes: 2 vs. 0, p<0.001) and were associated with higher levels of WOMAC pain (beta=0.18, 95% confidence interval (CI) 0.03-0.32). The same association to WOMAC pain was not found for synovitis (beta=0.03, 95% CI -0.33-0.40). However, in analyses on joint level, both osteophytes and synovitis were associated with pain in the same joint in both a short (24 hours) and longer term (6 weeks), with stronger associations for more severe ultrasound scores ( Table 1 ). Table 1. Associations between ultrasound pathologies and a) WOMAC pain and b) joint pain in the same joint previous 24 hours and c) previous 6 weeks, adjusted for age, sex and BMI. a) WOMAC pain both kneesBeta (95%CI) b) OR (95% CI) of pain in the same knee joint previous 24 hours c) OR (95% CI) of pain in the same knee joint previous 6 weeks Osteophyte sum score (both knees; range 0-24) 0.18 (0.03-0.32) Highest osteophyte score  -Grade 0 0.0 (ref) 1.00 (ref.) 1.00 (ref.)  -Grade 1 1.13 (-1.3, 2.4) 1.85 (1.20, 2.84) 1.79 (1.19, 2.68)  -Grade 2 0.67 (-0.74, 2.07) 2.77 (1.64, 4.70) 2.98 (1.76, 5.06)  -Grade 3 1.87 (0.04, 3.7) 9.02 (4.04, 20.10) 6.50 (2.95, 14.30) Grey-scale synovitis sum score (both knees; range 0-6) 0.03 (-0.33, 0.40) Highest GS synovitis score  -Grade 0 0.0 (ref) 1.00 (ref.) 1.00 (ref.)  -Grade 1 0.24 (-0.99, 1.47) 1.00 (0.66, 1.53) 0.95 (0.61, 1.47)  -Grade 2 0.27 (-1.33, 1.87) 1.67 (0.96, 2.91) 1.32 (0.78, 2.25)  -Grade 3 0.46 (-1.73, 2.65) 6.63 (2.26, 19.43) 4.32 (1.59, 11.71) Conclusion: Both osteophytes and grey-scale synovitis were associated with pain in the same joint, supporting the validity of ultrasound in knee OA. Grey-scale synovitis was commonly present in people not fulfilling the ACR criteria for clinical knee OA and seems to be less specific for clinical knee OA than osteophytes. REFERENCES: [1]doi 10.1016/j.joca.2016.03.004 Disclosure of Interests: Caroline Dekkerhus: None declared, Alexander Mathiessen: None declared, Caroline Fjellstad: None declared, Barbara Slatwkosky-Christensen: None declared, Hilde Berner Hammer: None declared, Ida K. Haugen Consultant of: Novartis, Grant/research support from: Pfizer Citation: , volume 81, supplement 1, year 2022, page 318Session: New insights into the associations of outcomes and biomarkers in OA (Poster Tours)