Date of Award


Document Type

Scholarly Project

Degree Name

Master of Physical Therapy (MPT)


Physical Therapy

First Advisor

Susan H.N. Jeno


Electromyography; Knee Injuries -- rehabilitation


Knee pathology is a common clinical complaint that may result in diminished function of the affected lower extremity, ultimately leading to atrophy of the vastus medialis oblique (VMO) muscle. The VMO contributes a great deal to the medial tracking mechanism of the patella which is crucial for normal biomechanical function of the knee joint. Effective strengthening of the VMO is a challenging task in physical therapy clinics. The purpose of this study was to determine if it is possible to enhance the muscle activity of the VMO with the addition of an adductor contraction.

Thirty-one subjects between the ages of 18 and 50 years with no history of debilitating trauma to the right knee were recruited to participate in this study. All subjects were recruited from the University of North Dakota and Center Court Fitness Club. Electromyography (EMG) was used to record muscle activity during each exercise trial. Pre-gelled, self-adhesive EMG electrodes were placed on the subject's right leg over the motor points of the following muscles: 1) Rectus Femoris, 2) Vastus Lateralis, 3) Vastus Medialis, and 4) Adductor Longus. After attachment of electrodes, each subject warmed-up on a cycle ergometer prior to performing 3 exercise trials. The trials included an isometric contraction of knee extension, an isometric contraction of hip adduction, and then a combined isometric contraction of knee extension with hip adduction. All trials were performed on the Kin-Kom isokinetic equipment at a preset angle of 50° of knee flexion.

The rectified EMG data were analyzed utilizing a Noraxon Telemyo 8 telemetry unit. The data were digitized and then analyzed using a simple T-test with a .05 confidence interval. The results of this study have demonstrated there is an increase in overall muscle activity of the VMO. This would suggest that utilizing hip adduction in conjunction with knee extension does facilitate an increased contraction of the VMO.

The results of this study have very important clinical applications. Being able to better elicit a muscle contraction of the VMO can be very valuable in early rehabilitation of the knee. When aiming to gain back stabilizing muscle forces following pathology, focus is on the VM.o due to the large part it plays in knee function. If the VMO can be elicited earlier, this will allow for an accelerated rehabilitation pace, which ultimately will save the patient time and money.