For select patients with persistent patellofemoral pain, the anteromedial tibial tubercle transfer (Fulkerson osteotomy) provides excellent clinical results. This procedure, indicated for patients with patellar malalignment, has become one of the most popular distal realignment procedures. One potential concern with this technique is the proximity of the posterior vascular structures during bicortical tibial drilling for screw placement. To address this concern, we measured the proximity of these structures in 7 consecutive fresh-frozen cadaveric knees. For each knee, barium was injected into the femoral artery, and anteroposterior (AP) radiographs were taken to document the location of the popliteal vessels. Next, the initial steps of the Fulkerson osteotomy were performed. Then, a lateral release and the tibial osteotomy were performed, the tubercle was advanced into position, and two 9/64-inch extralong drill bits were placed through the tubercle and the posterior tibial cortex. Repeat AP radiographs were obtained, and digital calipers were used to measure the distance from the drill bits to the popliteal vessels. The vascular structure closest to the exit point of the superior drill bit was the bifurcation of the popliteal artery (mean distance, 8.3 mm; SD, 9.3 mm; range, 0.0-21.3 mm), and in 2 knees this structure directly overlay the bifurcation on the AP radiograph; the vascular structure closest to the exit point of the inferior drill bit was the posterior tibial artery (mean distance, 9.0 mm; SD, 8.0 mm; range, 0.0-20.0 mm), and again in 2 knees the drill bit lay directly over the artery on the AP radiograph. Bicortical drilling for screw placement during the anteromedial tibial tubercle transfer procedure may come precariously close to the posterior vascular structures of the knee, so orthopedic surgeons must take extreme caution not to drill past the posterior cortex during this part of the operation.