Quantitative cartilage thickness change in radiographically normal knees with and without OA risk factors – data from the OAI

Abstract

Purpose: Quantitative cartilage thickness change, as measured by MRI, has been intensively explored as an imaging biomarker of structural progression in knee OA, and its sensitivity has been reported for various radiographic baseline disease severity strata. However, whether significant femorotibial cartilage change occurs in knees without radiographic knee OA, and whether it differs between knees from persons with and without common risk factors for knee OA, is unknown. The purpose of this work hence was 1) To explore location-independent and region-specific measures of quantitative cartilage thickness change by MRI in knees without any evidence of radiographic knee OA in either knee; 2) To test the hypothesis that knees from persons with common risk factors for knee OA display significantly greater cartilage thinning (and thickening) than knees from persons without risk factors. Methods: In the Osteoarthritis Initiative, a longitudinal cohort study of knee OA, we assessed the right knees of participants without any signs of radiographic knee OA (bilaterally KLG0; centralized readings). Of 755 knees, 77 were from healthy reference OAI participants (no pain, no risk factors for knee OA, 60% female; age 55.4 ± 7.3 y; BMI 24.4 ± 3.2 kg/m2) and 678 from incident cohort participants (various levels of pain and risk factors of knee OA, 57% female; age 59.6 ± 8.8 y; BMI 26.7 ± 4.2 kg/m2). The femoro-tibial cartilages were segmented and subregional thickness change was computed from year 1 and 4 (Y1/Y4) follow-up MRI data, using the sagittal DESS sequence and Chondrometrics software. Thinning (and thickening) scores were computed by summarizing all negative (and positive) subregion changes in each participant (primary analysis). Subregions and ordered values (OV) of subregional change were included as exploratory outcomes. Changes were reported including 95% CIs; statistical comparisons between both groups were made using the unpaired Welch t-test and Cohen D. Results: In KLG0 knees with risk factors (risk cohort), the cartilage thinning score over 3 years exceed the thickening score by approx. 20% and was significantly greater than the thinning score in healthy reference cohort knees. (Fig. 1; Table 1: P = 0.002). Cartilage thickening scores, however, were similar between both Groups (Fig. 1). 9 (of 16) OVs suggested greater thinning in the “risk cohort” compared with the reference cohort (Table 1; Fig. 2), whereas only 2 subregions (cLT; icMF) suggested greater thinning, and 2 regions (iMT, ccMF) less thickening in “risk cohort” than in reference cohort knees (data not shown). Conclusions: Among individuals without radiographic evidence of OA in either knee, knees from persons at higher risk for OA experienced significantly greater cartilage thinning than those from persons without risk factors for knee OA, whilst the observed magnitude of cartilage thickening was similar between groups. Greater thinning in KLG0 knees with risk factors was most prominent in the (central) lateral compartment; yet, location-independent analysis was superior to region-specific analysis in elucidating these subtle between-group differences.Table 13-year cartilage thickness change in KLG0 knees without and with risk factors for knee OA[μm]Healthy kneesRisk kneesP-ValueEffect sizeMeanSD95% CIMeanSD95% CIT-TestCohen's DThinn. Score−634516(−673, −596)−501319(−573, −429)<0.01−0.27Thick. Score529366(501, 556)537308(467, 607)0.83−0.02OV 1−166121(−175, −157)−14291(−163, −122)0.04−0.20OV 2−11685(−122, −109)−9855(−110, −85)0.01−0.22OV 3−8869(−94, −83)−7548(−86, −64)0.03−0.20OV 1614380(137, 149)14474(127, 160)0.970.00 Open table in a new tab