[The role of the quadriceps muscle for the patello-femoral malalignment syndrome].

At knee extension on the Cybex Machine II (Lumex, Co. Ltd.), electromyograms (EMG) from the vastus medialis (M) and the vastus lateralis (L) were picked up by surface electrodes. The L/M ratio was calculated by the integrated value of the EMG and the power spectrum dealt with the frequency analysis of the EMG. There was a correlation between the L/M ratio and Q angle for the normal group, a constant relation for the hypermobile patella group, and an inverse correlation for the group with recurrent subluxation of patella. The vastus medialis (M)-dominant group, intermediate group and the vastus lateralis (L)-dominant group from the value of the L/M ratio was also classified. In the control group, subgroup 2 with clinical signs or their past histories around the knee included relatively more L-dominant than subgroup 1 without clinical signs. In the patello-femoral malalignment group, more cases were L-dominant.