The purpose of this study was to determine if geometry of the articular surfaces of the tibial plateau is associated with non-contact anterior cruciate ligament (ACL) injury. This was a longitudinal cohort study with a nested case-control analysis. Seventyeight subjects who suffered a non-contact ACL tear and a corresponding number of controls matched by age, sex, and sport underwent 3 T MRI of both knees. Surface geometry of the tibial articular cartilage was characterized with polynomial equations and comparisons were made between knees on the same person and between ACL-injured and control subjects. There was no difference in surface geometry between the knees of the control subjects. In contrast, there were significant differences in the surface geometry between the injured and normal knees of the ACL-injured subjects, suggesting that the ACL injury changed the cartilage surface profile. Therefore, comparisons were made between the uninjured knees of the ACL-injured subjects and the corresponding knees of their matched controls and this revealed significant differences in the surface geometry for the medial (p < 0.006) and lateral (p < 0.001) compartments. ACL-injured subjects tended to demonstrate a posterior-inferior directed orientation of the articular surface relative to the long axis of the tibia, while the control subjects were more likely to show a posterior-superior directed orientation. Severe knee injury, such as an anterior cruciate ligament (ACL) disruption, is often immediately disabling and has been associated with the early onset of post-traumatic osteoarthritis regardless of whether surgical or non-surgical treatment is chosen.1,2 This has motivated studies that have focused on identifying the variables associated with increased risk of ACL injury, so that prevention strategies can be developed and those at increased risk can be identified and targeted for intervention.
3During the process of suffering an ACL injury, the geometry of the articular surfaces of the knee is important in controlling the biomechanical response of the tibiofemoral joint and ACL. 4,5 For example, there appears to be a consensus forming in the literature that individuals who are at increased risk of suffering non-contact ACL disruptions have increased posteriorinferior directed slopes of the subchondral bone portion of their tibial plateaus compared to uninjured controls. [6][7][8][9][10][11][12][13][14][15][16] This relationship is important because the magnitude of ACL strain values produced by impulsive loading of the knee during common sportsrelated movements such as jump landings are directly related to the posterior-inferior directed slope of the subchondral bone of the proximal tibia. 4,17,18 Most of what is known about the relationship between the risk of suffering non-contact ACL injury and joint geometry has come from studies of the underlying subchondral bone of the tibia plateau; however, the large inter-segmental forces that are transmitted between the femur and tibia occur across the surface o...