The subject of this paper is the complication of loss of dorsiflexion power and loss of sensation on the dorsum of the foot as a consequence of osteotomy in the proximal part of the tibia. Most recent articles on tibial osteotomy for genu valgum or varum deal with adult patients, the procedure being done principally for degenerative arthritis of the knee 2,3,4,5 The complications which have been reported in adults are few. The single specifically vascular complication reported is laceration of the anterior tibial artery and this did not cause any ischemic problem postoperatively 2 The literature concerning a complication of this type of osteotomy in children also is scant 1,6, and none has suggested that the etiology of the conuplication was either compression or traction on the vessels. It should be recognized that osteotomy of the proximal part of the tibia in the child is potentially more liable to this complication than the same procedure in the adult. This statement is based on the anatomical facts that in the child the osteotomy must be done more distally in the metaphysis to avoid damaging the proximal tibial epiphysis. The placement of the osteotomy and the subsequent correction at that level can stretch or compress the anterior tibial artery because of its location close to the tibia at that level. In the course of evaluating tibial osteotomies performed to correct bow-leg or knock-knee deformities, several instances of immediate postoperative onset of this complication were encountered. The symptoms and signs were severe intractable pain and weakness or loss of dorsiflexion of the foot and, secondarily, sensory loss in the foot and impaired circulation ofthe extremity operated on. In several instances a reduction in the degree of correction obtained at surgery caused inumcdiatc relief ofall symptoms and improvement ofcirculation to the limb. An etiological explanation involving acute ischemia produced by trauma to the anterior tibial artery seems to explain the symptom complex most satisfactorily. We suggest that compromise of the blood supply produces the sensory and motor alterations which most often have incorrectly been attributed to peroneal-nerve palsy. We will present evidence in support of this etiologic concept in a situation that is nuore common than is generally realized.