Relationship of compartment-specific structural knee status at baseline with change in cartilage morphology: a prospective observational study using data from the osteoarthritis initiative

Abstract

Introduction: The aim was to investigate the relationship of cartilage loss (change in medial femorotibial cartilage thickness measured with magnetic resonance imaging (MRI)) with compartment-specific baseline radiographic findings and MRI cartilage morphometry features, and to identify which baseline features can be used for stratification of fast progressors.

Methods: An age and gender stratified subsample of the osteoarthritis (OA) initiative progression subcohort (79 women; 77 men; age 60.9 +/- 9.9 years; body mass index (BMI) 30.3 +/- 4.7) with symptomatic, radiographic OA in at least one knee was studied. Baseline fixed flexion radiographs were read centrally and adjudicated, and cartilage morphometry was performed at baseline and at one year follow-up from coronal FLASH 3 Tesla MR images of the right knee.

Results: Osteophyte status at baseline was not associated with medial cartilage loss. Knees with medial joint space narrowing tended to show higher rates of change than those without, but the relationship was not statistically significant. Knees with medial femoral subchondral bone sclerosis (radiography), medial denuded subchondral bone areas (MRI), and low cartilage thickness (MRI) at baseline displayed significantly higher cartilage loss than those without, both with and without adjusting for age, sex, and BMI. Participants with denuded subchondral bone showed a standardized response mean of up to -0.64 versus -0.33 for the entire subcohort.

Conclusions: The results indicate that radiographic and MRI cartilage morphometry features suggestive of advanced disease appear to be associated with greater cartilage loss. These features may be suited for selecting patients with a higher likelihood of fast progression in studies that attempt to demonstrate the cartilage-preserving effect of disease-modifying osteoarthritis drugs.

Figure 1

Knee magnetic resonance image obtained with fast low angle shot (FLASH) sequences with water excitation. (a) Double oblique coronal image showing the regions of interest used in the current analysis. (b) Same coronal image with the total area of subchondral bone (tAB) being segmented in green, the area of the cartilage surface (AC) in magenta, and the filling between the two surfaces in turquoise. Note the denuded area (tAB not covered by AC) in the medial tibia and the medial femur. (c) Same coronal image with the medial tibial (MT) cartilage marked (segmented) blue, weight-bearing medial femoral cartilage (cMF) marked yellow, the lateral tibial cartilage marked green, and the lateral weight-bearing femoral cartilage marked red. (d) 3D reconstructions of knee cartilage plates from a sagittal data set in a different person: The femoro-tibial cartilages are labeled with the same colors as in (c), the patellar cartilage is labeled magenta and the trochlear (femoral) cartilage in turquoise.

Figure 2

Cartilage plates and subregions used as outcome measures in this study. (a) Inferior view of the weight-bearing (central) part of the medial (cMF) and lateral femoral condyle (cLF). ccMF = central third of cMF (icMF and ecMF = internal and external third of cMF, respectively). (b) Posterior view of the femorotibial joint. MFTC = cMF + MT; cMFTC = ccMF + cMT. (c) Superior view of the medial (MT) and lateraltibia (LT). cMT = central part of MT (iMT, eMT, aMT, and pMT = internal, external, anterior, and posterior parts of MT, respectively).