Objective: Inappropriate neural control of the quadriceps femoris muscle group has been implicated in patellofemoral pain syndrome (PFPS) and the methods of biomechanical assessment of PFPS has been developed recently. The aims of the present investigation were to evaluate the effects of therapeutic exercise in the alleviation of PFPS and to develope objective clinical test for PFPS.

Method: We investigated the onset time of the isometric contraction of vastus medialis oblique muscle (VMO) and the vastus lateralis muscle (VL) under four different conditions: knee flexion and extension in weight bearing (standing) and non-weight bearing (sitting on chair) situations. For each condition, onset times of EMG activities and onset times for VMO and VL were determined from five trials of isometric contraction. In addition, we compared knee flexor and extensor torques in control group and subjects with PFPS. To evaluate the effects of the exercise we compared the onset time difference (onset time of VL-onset time of VM) and quadriceps muscle torque at pre- and post- exercise in PFPS groups.

Results: In PFPS group, onset time of VMO during knee extension was significantly longer than the onset time of VL and the knee extensor torque was considerably weaker in comparison with normal group. Although onset time difference was not changed after exercise program, there were significant increase in knee extensor torque in subjects with PFPS.

Conclusion: The role of exercise in the rehabilitation of quadriceps functions is to reduce the pain, to strengthen the knee extensor, and further accurate diagnostic tools and methods for the result of therapeutic exercise in PFPS are needed.

Patellofemoral pain syndrome (PFS) is one of the most common types of anterior knee pain and many studies reported the patellofemoral malalignments (such as high patella, increased sulcus angle and increased congruence angle) as possible causes of the syndrone. In order to confirm this hypothesis, the difference of congruence, sulcus angles and patella height ratio in normal subjects and PFS patients was evaluated. The PFS subjects were selected according to the criterias of anterior knee pain, pain aggravation after the repeated knee flexion and extension motion. A combined knee injury was screened by MRI. We have compared our data to the previous studies of Merchant et al.(1974), Aglietti et al.(1983), and Dowd and Bently(1986). The radiographic studies were done on lateral view, Merchant view, and patella height was measured by Insall-Salvati method and Blackburn-Peel method. The sulcus angle and the congruence angle were measured on a Merchant view.

The results showed that the average patella height of normal group was 1.00⁑0.17 by the Insall test and the patella index was 1.02⁑0.23. There was no statistical difference between normal and patient group of which the patella height was 0.96⁑0.16 by Insall test with patella index of 1.04⁑0.17.

On Merchant view, the congruence angle was ⁣7⁑11 degrees, and the sulcus angle was 135.5⁑6 degrees in PFS patient group, and in normal group the congruence angle was ⁣2⁑14 degrees, and the sulcus angle was 136⁑5. A little statistical variation was noted in both group.

Our results were not much different from previous studies except for the Aglietti's study in congruence angle.

We concluded that the Insall test, patella index, congruence angle and sulcus angle could not help to idetify patellofemoral malalignment of knee joint in PFS patients.