Abstract
Background
Some models of knee osteoarthritis (OA) suggest that the properties of knee tissues are adapted in healthy joints, and that OA development is due to a breakdown in the equilibrium among tissue properties. Cartilage thickness and bone density are particularly important properties in this regard because both are related to the mechanical environment. This study tested the hypothesis that locations of thickest cartilage are associated with locations where bone density is the highest in non-OA tibias.
Method
CT-arthrography was performed on six non-OA subjects (2 males; 58± 15 years old). Images were segmented to build 3D models of the bone and cartilage structures. Maps of cartilage thickness were calculated for the medial and lateral subchondral bone areas by measuring the distance between bone and cartilage structures. Bone density maps were calculated based on the intensity of the CT-arthrography signal in the first 3mm of bone. The location of thickest cartilage and most dense bone were measured in the medial and lateral compartments. These locations were then normalised, and paired t-tests and linear regressions were performed to compare the thickness and density locations.
Results
In the medial compartment, the location of highest bone density was significantly more medial than the location of thickest cartilage (p=0.03). Additionally, the location of both features were highly correlated along the anterior-posterior direction (R⁁2=0.92). In the lateral compartment, the location of highest bone density was correlated with the location of thickest cartilage along the medial-lateral direction (R⁁2 =0.64).
Conclusion
This study showed that the location of highest bone density is correlated with the location of thickest cartilage in non-OA tibias, thus supporting the idea that knee tissues are adapted in healthy knees.
