We present a serious postoperative complication related to the use of femoral nerve block in 4 patients, each of whom fell and sustained further injury. Preoperatively, all patients underwent a 3-in-1 femoral nerve block with 30 to 35 ml of 0.25% levobupivacaine with 1:200 000 epinephrine, with guidance by a nerve stimulator. After the falls, neurological examination of the operated legs revealed reduced 2-point discrimination, pain, and/or light touch sensation. All patients underwent further operation for the fall injury and had delayed full weight bearing. We recommend that, after having a femoral nerve block, patients should undergo enhanced postoperative evaluation Postoperative fall after the use of the 3-in-1 femoral nerve block for knee surgery: a report of four cases of blockade and proprioceptive function to ensure safe neurological function before mobilisation.