Contribution to the pathogenesis of osteochondrosis dissecans: Experimental investigations on the idea of a mechanical overload of the cancellous bone

Abstract The pathogenesis of osteochondrosis dissecans (OD), i.e. the formation of an osteocartilaginous arthrolith, also called aseptic bone necrosis, has been discussed time and again. The formation of the osteochondral fragment which is typical of OD may be attributed to a bland ischemia or to a single or chronic trauma. However, neither of the theories explains the typical location of OD. This study is based on the hypothesis that overload of the subchondral cancellous bone of the femoral condyles through deformation caused by mechanical factors with a slowly progressing fatigue fracture is a decisive factor in the pathogenesis of OD. Recordings made through in vitro measurements of quasi-axial and medio-lateral displacements of knee condyles allowed for consideration of anatomical differences of the individual knee specimens. With a knee flexion of 0° to 120°, condylar measurements showed a maximum of 83 μm of quasi-axial condylar displacements and a maximum of 680 μm of medio-lateral condylar enlargements. Greatly varying deformations in both size and direction were found in the different knee models. This leads to depressions and protuberances during knee flexion, with corresponding alternations of compressive and tensile load of the cancellous bone in the femoral condyles. Compared to the lateral condyle, larger deformations were found in the medial condyle in a quasi-axial direction according to predilected locations of OD. Medio-lateral condylar enlargements may lead to tensile elongations in the size range of the fracture elongation in cancellous bone. Even without considering load peaks, the results of this study point to alternating loads in the femoral condyle and thus support the hypothesis.