Greater Lateral Femorotibial Cartilage Loss in Osteoarthritis Initiative Participants With Incident Total Knee Arthroplasty: A Prospective Cohort Study

Objective. To explore whether baseline to 12-month followup change in femorotibial cartilage thickness differs between subjects who received a total knee arthroplasty (TKA) between 24 and 60 months from those without TKA (non-TKA). Methods. In this prospective cohort study, 531 right knees from Osteoarthritis Initiative participants with definite radiographic knee osteoarthritis (Kellgren/Lawrence [K/L] grades 2-4) were studied. Segmentation was applied to coronal fast low-angle shot magnetic resonance images, to quantitatively determine cartilage thickness in 16 femorotibial subregions. Unadjusted P values (t-tests) and P values adjusted for age, baseline body mass index (BMI), K/L grade, and sex (generalized estimating equation models) were used to evaluate differences in longitudinal 1-year rates of cartilage thickness between TKAs and non-TKAs, with total knee arthroplasty status as fixed effect. Results. Of the 531 participants (mean +/- SD ages 63 +/- 9 years, BMI 30 +/- 4.8 kg/m(2)), 40 received a femorotibial TKA within 4 years. At baseline, TKAs had thinner medial and lateral femorotibial cartilage (215%; P < 0.001) than non-TKAs. Longitudinal cartilage thickness change was significantly greater in TKAs than in non-TKAs in the total femorotibial joint (area under the curve [AUC] 0.64), the lateral compartment (AUC 0.66), both tibiae (AUC >= 0.61), and the first 9 (of 16) ordered values of subregion change (AUC 0.64-0.69). Discrimination was stronger for TKAs that occurred at 24 and 36 months (n=18) than for those at 48 and 60 months (n=22). Conclusion. Knees with incident TKA displayed smaller baseline cartilage thickness and greater lateral as well as location-independent ordered value femorotibial cartilage loss than non-TKAs. Discrimination of cartilage loss was greater for TKAs occurring within 2 years after the measurement than for those occurring later.