DO RATES OF FEMOROTIBIAL CARTILAGE LOSS IN KELLGREN-LAWRENCE 2 AND 3 KNEES DIFFER BETWEEN THOSE WITH MILD-MODERATE VS. SEVERE PATELLOFEMORAL STRUCTURAL DAMAGE?

Abstract

INTRODUCTION

Knees with radiographic disease severity of Kellgren-Lawrence (KL) 2 and 3 are commonly included in disease-modifying (DMOAD) clinical trials of knee osteoarthritis (OA). In an eligibility context, semi-quantitative (sq) MRI assessment has been used to define structural disease severity, rule out diagnoses of exclusion, and possibly define a structural phenotype. The KL system focuses on the femorotibial joint (FTJ) only, with MRI stratification being commonly limited to the FTJ. It is unclear whether sq MRI of the patellofemoral joint (PFJ) should be included for eligibility assessment.

OBJECTIVE

The aim was to assess whether rates of quantitative femorotibial (FT) cartilage loss are increased for knees with semiquantitatively (sq)-defined severe patellofemoral (PF) cartilage damage and/or large bone marrow lesions (BMLs) vs. those without over a period of 24 months.

METHODS

626 knees with Kellgren-Lawrence 2 and 3 from the FNIH and IMI-APPROACH studies were included. MRI assessment was performed using the MRI Osteoarthritis Knee Score (MOAKS) instrument. Medial FT quantitative cartilage thickness loss was derived from baseline and 24-month manual segmentations and was compared between knees with severe vs. mild-moderate PF cartilage damage and between knees with vs. without large PF BMLs. Between-group comparisons were performed using analysis of variance (ANOVA) and were stratified by baseline medial FT cartilage damage severity (defined as mild, moderate, or severe).

RESULTS

410 (65%) knees were categorized as mild, 92 (15%) as moderate, and 124 (20%) as severe medial FT cartilage damage. For almost all categories of FT cartilage damage, the difference in quantitative medial FT cartilage loss was not statistically significant (Table 1). Only for the category of knees with moderate medial FT cartilage damage, statistically higher rates of quantitative medial FT cartilage loss were observed for those with large PF BMLs compared to those without (-0.245 ± 0.304 mm vs. -0.134 ± 0.218 mm) (Table 2).

CONCLUSION

For the large majority of sq-defined FT cartilage damage categories, no statistically significant differences in FT rates of quantitative cartilage loss were detected. Screening for PF cartilage damage and BMLs does not appear to be required in a disease-modifying OA drug trial.