Flexion of the knee increases the distance between the popliteal artery and the proximal tibia: MRI measurements in 15 volunteers.

We determined which angle of flexion best prevents popliteal artery injury during knee surgery. We took MRIs of the knee in the lateral position with the knee in 0 degrees, 45 degrees, 90 degrees, and 120 degrees of flexion in 15 volunteers. The shortest distance between the posterior cortex of the tibia and the popliteal artery was measured at various levels from the knee joint to 60 mm distally. At the level of the joint and 15 mm distally, the distance between the tibia and artery increased with increasing knee flexion. More distally, no significant difference was noted with increasing flexion. Flexion of the knee may minimize injury to the popliteal artery in procedures between the level of the joint and 15 mm distal to the joint.