Background/Purpose: Plain radiography of knee osteoarthritis (OA) has inherent diagnostic and prognostic limitations, especially in early disease.  Ultrasound (US) examination sheds light on disease activity and inflammatory changes in OA, but there is no uniformity or standard for its routine use in evaluation of OA. Our aim is to identify sonographic features that consistently assess burden of disease and predict future OA progression.

Methods: Knee US was performed on OA patients who were enrolled in a study of biomarkers for radiographic progression. We recorded US images of the more painful knee at baseline and both knees at 24 months.  Each set of US images was scored semiquantitatively (0-3) for osteophyte size, degree of damage to the femoral articular cartilage (FAC), severity of synovitis/effusions, and popliteal cyst size, and these scores were combined to calculate a composite score (0-12). Weight-bearing knee radiographs taken at baseline and 24 months were scored for Kellgren-Lawrence (KL) grade. Linear regression of each set of the 5 US scores and the corresponding KL scores (with 0 and 24 month readings combined) were run to assess how well each of the US measures trended with KL readings. A second analysis compared the 5 mean baseline ultrasound scores for two groups of patients, those with and without KL worsening at 24 months, to identify sonographic predictors of radiographic progression.

Results: US images were obtained on 591 knees from 199 patients at the two time points. There was a significant association between the KL grades and each of the 5 US scores by regression, most significant for osteophytes (R²=0.396) and the composite score (R²=0.334), all with p-values < 0.001 (see Figure 1). In separate t-test analyses of the radiographic progression over 24 months of the more painful knee, the 24 patients whose KL grade worsened (DKL>0) had a higher mean baseline US composite score than those whose KL grade didn’t change (4.25 vs. 3.16, p=0.049).  The 4 sonographic subscores were also higher at baseline in patients who later progressed radiographically, but none reached significance (see Table 1).

Conclusion: US can be used to reliably identify structural and inflammatory changes in knee OA – often earlier or better than plain radiography.   Our cohort also demonstrates that more robust sonographic pathology predicts which patients’ knee OA may be more likely to progress over time. This may be helpful in selecting patients for trials of disease-modifying medications.

Support: R01- AR-052873