Spatial patterns of cartilage loss in the medial femoral condyle in osteoarthritic knees: data from the Osteoarthritis Initiative

Abstract

The objective of this study was to develop a technique for analyzing spatial patterns of cartilage loss in the medial femoral condyle (MF), and to study MF cartilage loss in participants of the Osteoarthritis Initiative. Using a 0.7 mm sagittal double echo at steady state (DESS) sequence, 160 osteoarthritic knees from 80 participants with varying degrees of medial joint space narrowing were imaged at baseline and 1-year follow-up. MF cartilage was segmented and cartilage loss determined. Rate of change varied significantly (P = 0.0067) along the anterior-posterior extension of the MF, with the greatest changes (-45 microm, -2.7%) observed 30-60 degrees posterior to the trochlear notch. The rate was greater in the central MF after excluding peripheral aspects of the MF from analysis. Sensitivity to change was greatest at 45-75 degrees (standardized response mean = -0.32) but was minimally affected by medial-lateral trimming. In conclusion, the greatest sensitivity to change was achieved when analyzing the posterior aspect of the central, weight-bearing MF.

FIG. 1

Sagittal double echo at steady state image of the medial femorotibial joint, showing the medial tibia (MT), the MF condyle, the anterior clipping plane of MF (trochlear notch) through landmark “A”, and the point marked at the posterior end of the femoral condyle (*).

FIG. 2

a: 3D reconstruction of a knee MRI data set showing the anterior clipping plane (red frame), separating the medial femoral condyle cartilage (orange) from the trochlear cartilage (turquoise). b: 3D reconstruction illustrating the regional subdivision of the MF condyle in anatomic relationship with the medial tibia (MT). The figure also shows the anterior clipping plane (gray) through landmark “A” and the sphere (green) that was fitted to the MF. The borders between the subregions not shown are indicated using blue lines. c: 3D reconstruction of MF with medial-lateral trimming showing the central 66.7% of the MF. d: 3D reconstruction of MF with medial-lateral trimming showing the central 33.3% of the MF.

FIG. 3

Analysis of all knees (n = 160). Bar chart showing the average change (μm) in mean cartilage thickness (ThCtAB) over 1 year for the total MF condyle and for subregions of the MF located 0–150° posterior to the trochlear notch. Results are shown for the entire medial-lateral extension (100%) and for the central 66.7% and 33.3% of the MF, respectively.

FIG. 4

Analysis of knees without medial joint space narrowing (mJSN grade 0; n = 73). Bar chart showing the average change (μm) in mean cartilage thickness (ThCtAB) over 1 year for the total MF condyle and for subregions of the MF located 0–150° posterior to the trochlear notch. Results are shown for the entire medial-lateral extension (100%) and for the central 66.7% and 33.3% of the MF, respectively.

FIG. 5

Analysis of knees with medial joint space narrowing (mJSN grade 1; n = 54). Bar chart showing the average change (μm) in mean cartilage thickness (ThCtAB) over 1 year for the total MF condyle and for subregions of the MF located 0–150° posterior to the trochlear notch. Results are shown for the entire medial-lateral extension (100%) and for the central 66.7% and 33.3% of the MF, respectively.

FIG. 6

Analysis of knees with medial joint space narrowing (mJSN grade 2 or 3; n = 33). Bar chart showing the average change (μm) in mean cartilage thickness (ThCtAB) over 1 year for the total MF condyle and for subregions of the MF located 0–150° posterior to the trochlear notch. Results are shown for the entire medial-lateral extension (100%) and for the central 66.7% and 33.3% of the MF, respectively.