Arterial tortuosity in the femoropopliteal region during knee flexion: a magnetic resonance angiographic study.

Dynamic changes in curvature are expected in the femoropopliteal region during knee flexion. The location of the artery dorsal to the axis of movement implicates a relative length excess that may influence local morphology. To study arterial morphology in vivo, magnetic resonance angiography was performed in 22 healthy volunteers (aged 23-68 y). The curvature of the femoral vessels was studied and quantified in stretched and flexed positions. During knee flexion the vessel followed the movement of the leg and in the sagittal plane one curve was visible distal to the adductor hiatus. Three or more small curves were seen proximal to the knee joint in all volunteers. In the group aged under 30 y these minor curves were located proximal to the adductor hiatus as if the artery curls up in Hunter's canal. In the group aged over 45 y one or more curves were located distal to the adductor hiatus in the popliteal fossa. In volunteers aged 60 y and older some of these curves did not disappear during knee extension. In older individuals, natural elongation and loss of arterial elasticity will contribute to the formation of these curves. Impairment of the free gliding mechanism of the femoral vessels in the adductor canal could explain the differences in location of these minor curves between younger and older subjects. It is concluded that morphological changes in the femoral artery occur during knee flexion and that this tortuosity is age dependent. This may influence local haemodynamics and therefore possibly contribute to atherogenesis.