Table 3

 Prevalence of knee synovitis on ultrasonography in subjects with painful knee OA

Ultrasonographic knee synovitis*p Value†
AbsentPresent
*Knee synovitis was defined as “present” if synovial thickness was ⩾4 mm with diffuse or nodular appearance. †p Values refer to comparisons between subgroups with or without synovitis (Student’s t test for quantitative variables and χ2 test for qualitative variables).
Total number of subjects, No (%)500 (83.3)100 (16.7)
Synovial thickness (mm)<0.0001
    Mean (SD)1.3 (1.5)5.8 (3.0)
    Median (range)1 (0–19)5 (4–29)
Appearance of synovial tissue, No (%)<0.0001
    Absent278 (55.6)0 (0)
    Nodular75 (15.0)56 (56.0)
    Diffuse147 (29.4)44 (44.0)
Maximal effusion depth (mm)<0.0001
    Mean (SD)3.4 (4.5)6.9 (3.9)
    Median (range)2.7 (0–20)6.1 (0–71)