EMG activity of the vastus medialis oblique and the vastus lateralis in their role in patellar alignment

Using instramuscular electrodes the integrated electomyographic activity of the vastus medialis oblique and the vastus lateralis was examined in twenty normal females. The activity was recorded during the last thirty degrees of distal segment stabilized knee extension, when patellar sublixation commonly occurs. The electromyogrphic activity was normalized and expressed as a percentage of a maximal isometric contraction. Both muscles exhibited low levels of activity with no significant differences between the two. This study provides a quantitative method to assess whether muscular imbalance is present in patients with patellar subluxation.