On the lateral view, the entry point must be at the anterior tip of the
Blumensaat’s intercondylar roof line. There is no “safe zone” posterior to this
line. Take care not to start the entry point posterior to the Blumensaat’s
line, in order to avoid damage to the cruciate ligaments when reaming.
The x-ray shows the desired 30° flexion of the knee joint. With less flexion
the tibial plateau hinders the guide wire insertion. With more flexion the
articular surface is in danger and the patella is in the way.