Baseline articular contact stress levels predict incident symptomatic knee osteoarthritis development in the MOST cohort

Abstract

We studied whether contact stress estimates from knee magnetic resonance images (MRI) predict the development of incident symptomatic tibiofemoral osteoarthritis (OA) 15 months later in an at-risk cohort. This nested case-control study was conducted within a cohort of 3,026 adults, age 50 to 79 years. Thirty cases with incident symptomatic tibiofemoral OA by their 15 month follow-up visit were randomly selected and matched with 30 control subjects. Symptomatic tibiofemoral OA was defined as daily knee pain/stiffness and Kellgren-Lawrence Grade > or =2 on weight bearing, fixed-flexion radiographs. Tibiofemoral geometry was segmented on baseline knee MRI, and contact stresses were estimated using discrete element analysis. Linear mixed models for repeated measures were used to examine the association between articular contact stress and case/control status. No significant intergroup differences were found for age, sex, BMI, weight, height, or limb alignment. However, the maximum articular contact stress was 0.54 +/- 0.77 MPa (mean +/- SD) higher in incident OA cases compared to that in control knees (p = 0.0007). The interaction between case-control status and contact stress was significant above 3.20 MPa (p < 0.0001). The presence of differences in estimated contact stress 15 months prior to incidence suggests a biomechanical mechanism for symptomatic tibiofemoral OA and supports the ability to identify risk by subject-specific biomechanical modeling.

Figure 1

Surface registration of tibial and femoral surfaces using a) lateral and b) AP weight-bearing radiographs. The resulting configuration engendered a vertical loading equivalent to 0.3 × body weight, averaged over all knees.

Figure 2

Summary of DEA methods utilized in the study.

Figure 3

The maximum contact stress was 0.54± 0.77 MPa higher in case than in control knees (p=.0007), with a nearly equal number of knees in each group experiencing the maximum contact stress in the medial versus the lateral compartment (M/L proportion = 53.3% and 53.6% for the control and case knees, respectively).

Figure 4

Cumulative area of engagement at each level of contact stress. In addition to absolute disparities evident in the mid to high contact stress range (2.5 to 3.0 MPa), a very pronounced relative increase in the amount of very highly stressed (>3 MPa) cartilage occurred in knees that later developed incident symptomatic tibiofemoral OA. Plotted are mean ± 1 standard deviation values within each group.

Figure 5

Sensitivity and specificity of maximum contact stress for predicting case status.