Trochlear dysplasia is a predisposing factor for recurrent patellar instability. We evaluated the results of an anterior lateral femoral condyle open wedge osteotomy for treating patellar instability. A total of 16 consecutive patients (19 knees) with symptoms of recurrent patellar instability and trochlear dysplasia identified using a true lateral radiograph of the knee underwent an anterior lateral femoral osteotomy. Outcomes were documented at 2 years minimum follow-up using the Lysholm scale, the patellofemoral score, WOMAC score and standard conventional radiographs. In 17 knees, patients reported good improvement in stability (no dislocations) and most patients had a marked improvement in pain and functional scores at follow-up (mean follow-up 51 months). No serious complications occurred. Anterior femoral osteotomy of the lateral condyle appears to be a satisfactory and safe method for treating patients with patellofemoral joint instability caused by trochlea dysplasia. In selected cases this procedure can be used to correct trochlea dysplasia. In our opinion, the key to a successful treatment of patellofemoral instability is to successfully distinguish the anatomic deficiencies and to correct the anatomical abnormality.