We intend to provide more objective data for diagnosis of the patellofemoral pain syndrome by analyzing the positional changes of the patella radiologically.

In 42 normal knees and in 91 knees of patients with the patellofemoral pain syndrome, the following 6 parameters were analyzed using a 30 degree flexion lateral view and a Merchant axial view: 1) the Insall and Salvati method, 2) the Blackburne and Peel method, 3) the Saille method, 4) the depth of the trochlea, 5) the sulcus angle, 6) and the congruence angle.

Using the Blackburne and Peel method of assessing the height of patella, the ratio was 0.86 in the control group, in contrast to 0.92 in the patellofemoral pain syndrome group (P<0.05). The average value of the congruence angle was 2.9 in the control group, while it was -9.2 in patellofemoral pain syndrome group (P<0.05). The other parameters showed no statistical significance.

This indicates that the patella alta by the Blackburne and Peel method and the increase of congruence angle are useful in the diagnosis of the patellofemoral pain syndrome.