Background Previous studies on ultrasonography in the diagnosis of knee osteoarthritis have described different features seen in painful osteoarthritic knees. We statistically evaluated the diagnostic values of these features as compared to healthy controls.
Methods We prospectively performed ultrasonography on 43 painful osteoarthritic knees of 25 subjects, comparing them with 40 knees of 20 sex and gender-matched healthy subjects, using a linear probe (Shimadzu SDU 1200; 10-5 MHz). Comparisons between the two groups were carried-out using Mann-Whitney U test for continuous variables and Chi-square test or Fisher exact test for relevant categorical variables. Relative risks were also calculated.
Results The mean age of patients was 52.1±5.3 years, 60% women. Abnormal features were found in 100% cases and 27% controls (p<0.0001; RR=3.6, 95% CI: 2.2-6.0). The most relevant features were the presence of joint effusion >2mm (79% Vs 12%; p<0.0001; RR=6.3, 95% CI: 2.7-14.5), joint effusion’s height (10.4 mm Vs 0.8 mm; p<0.0001), the presence of synovial thickening (46.5% Vs 10%; p<0.0001; RR=4.6, 95% CI: 1.7-12.5) and the presence of at least one femoro-tibial osteophyte (100% Vs 12%; p<0.0001; RR=8; 95% CI: 3.5-18.2). Cartilage thickness (inter-condylar: 2.3mm Vs 2.2mm; p=0.233), as well as the presence of a Power Doppler signal (4.6% Vs 0%; p=0.265) did not statistically differ between groups.
Conclusions Joint effusion, synovial thickness and femoro-tibial osteophytes are the most useful features for an ultrasonographic diagnosis for knee osteoarthritis. There is a need to develop an ultrasonographic scoring system for diagnosing knee osteoarthritis and assessing its severity and prognosis.
Disclosure of Interest None Declared
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