An Electromyographic Analysis of the Knee During Functional Activities

Abstract

This study describes the fine-wire electromyographic profile of the normal knee. Twenty-two subjects with no prior history of knee injury volunteered for the study. Each subject had fine-wire electromyographic eval uation of 8 muscles (vastus medialis oblique, vastus lateralis, rectus femoris, semimembranosus, biceps femoris, tibialis anterior, gastrocnemius, and soleus muscles) while performing 7 functional activities. The percentage of maximum manual test for each muscle during each phase of the activities was used to deter mine means and standard deviations for the group. Walking and ramp and stair ascending and descending produced similar electromyographic profiles. Running and cross-cutting demonstrated unique electromyo graphic profiles with an overall higher muscle activity than the previous 5 activities. A quadriceps-hamstrings muscles' coordinated response was identified consis tently in each activity. These findings illustrate the in tegral nature of each of the 8 examined muscles in knee motion. Furthermore, this study demonstrates a coor dinated response of quadriceps-hamstrings muscles in the normal knee and may more thoroughly define the coordinated activity of these 2 antagonist muscle groups. Finally, this study provides a framework within which various knee conditions can be compared and from which specific rehabilitation recommendations can be generated.