We prospectively evaluated 30 hips of 22 patients who had normal knees with a mean age of 53.4 years (range, 38-72 years). In the early postoperative period, genu valgum deformity was observed in all knees. Of 22 patients, 17 complained of severe pain owing to strain in the medial collateral ligament and iliotibial tract. Postoperatively, the ipsilateral extremities of the patients were extended by a mean of 16.5 mm (8-25 mm). Q angles of the patients increased by a mean of 4.4 degrees +/- 2.5 degrees (P < .001). Although the Harris hip scores were improved (40.7-87.8 points), postoperative Lysholm-Gillquist knee scores were significantly reduced (92-76 points, P < .001). Reduction of displaced hips into the anatomical hip center and lengthening the extremity despite shortening procedure may lead to strain at the knee joint iatrogenically, particularly with the mechanical effect of tensor fascia lata, which results with changes in the knee biomechanics.