Evaluating the C-Score from Weight-Bearing CT as a Quantitative Imaging Biomarker for Worsening Knee Osteoarthritis Structure and Pain in the Multicenter Osteoarthritis Study.

Objective

Investigate a novel "C-score" metric of femoral bone shape, derived from weight-bearing-CT (WBCT), as an imaging biomarker for knee osteoarthritis (OA) structural progression and pain worsening in men and women with, and at increased risk for, symptomatic knee OA.

Design

Images were acquired for 649 knees (56.3% females, mean±SD age 63.8±9.6 years, BMI 28.5±5.0 kg/m²). Statistical shape models (SSM) were constructed from segmented distal femurs. C-score was the distance along the femur shape vector from KL0/1 to KL2/3 mean shapes, standardized to 1SD of KL0/1 variation in the SSM. Generalized estimating equations, adjusted for sex, age, >1 knee per participant, and BMI, determined associations between 2-year-worsening of OARSI Joint-Space-Narrowing (JSN) grade in the medial-tibiofemoral compartment and baseline C-score or minimally clinically important worsening (MCIW) of pain (2 points on the WOMAC-pain-subscore).

Results

70 knees had medial-tibiofemoral JSN worsening. In adjusted models, C-score was associated with JSN progression (OR: 1.43 (1.07, 1.92); p=0.01). Baseline C-score was also associated with 2-year MCIW pain (OR: 1.27 (1.00-1.62); p=0.047). The association of C-score with progression of JSN was more pronounced in men, and the association with pain progression was more pronounced in women, but these sex differences were not statistically significant (p >0.05).

Conclusion

In individuals with or at risk of knee OA, higher C-scores are moderately associated with medial-tibiofemoral JSN progression and worsening knee pain over 2-year-follow-up. The C-score is a promising imaging biomarker for knee OA structural progression and pain worsening.