Robert A. Panariello MS, PT, ATC, CSCS
Timothy J. Stump MS, PT, CSCS, USAW
Professional Physical Therapy
Professional Athletic Performance Center
New York, New York
Patellofemoral pathology is a fairly common condition observed in clinical setting. The treatment philosophy of some rehabilitation professionals to resolve this painful condition may include the prescription of exercises in the attempt to isolate the Vastus Medialis Obliquus muscle (VMO). Although this VMO exercise isolation “myth” has been negated at least 20 years ago (1, 2) it continues to presently endure. During this attempt to isolate VMO activity, some designated exercises executed include but are not limited to the following:
• Quad sets
• Terminal open chain knee extension exercises
• Straight leg raises (SLR) with external rotation of the lower extremity
These exercises may or may not be performed with the adjunct application of electric stimulation.
Although these exercises will enhance the strength of the quadriceps muscles, likely assisting in resolving the patient’s knee pathology, this is not due to isolation of the VMO. The case some clinicians formulate for the performance of SLR with external rotation is based on the false premise that by externally rotating the femur will result in further activation of the VMO.
The knee is a hinge joint and during the execution of a SLR, the force of gravity will act in a perpendicular manner between the knee and ground surface. The quadriceps mechanism will now be required to resist the resultant force attempting to flex the knee as this is the only contractile soft tissue structure that is capable of resisting that force. The quadriceps mechanism like any other dynamic structure can only resist this external force via the neural activation of the muscle group. The external rotation of the femur gives rise to the placement of stress on medial collateral ligament (MCL), a static stabilizer of the knee. This treatment philosophy actually removes stress from the very muscle(s) the clinician is attempting to enhance. As an example a patient with a diagnosis of polio, a condition affecting the anterior horn of the femoral nerve or a patient with a quadriceps tendon rupture can still perform a SLR when externally rotating their femur based on the static stabilizing properties of the MCL. Therefore one may inquire why would a clinician who is attempting to activate and enhance the quadriceps muscle group perform the SLR exercise in external rotation.
The Anatomy and Neuroanatomy of the Quadriceps Muscle Group
The quadriceps muscle group is comprised of the rectus femoris, vastus lateralis, vastus intermedius, and vastus medialis. The vastus medialis (VM) is located at the medial aspect of this muscle group and has been reported to consist of two separate components, the proximal vastus medialis longus (VML) and the distal vastus medialis obliquus (VMO) (4). The neuroanatomy of the quadriceps muscle complex reveals an innervation from the femoral nerve. The femoral nerve is comprised of large motor units that innervate all four heads of the quadriceps without individual fine motor unit innervation of the separate muscle heads. Therefore, since the VMO does not have a distinct and separate nerve innervation, it is not possible to “isolate” this muscle from the other quadriceps muscles via a specific exercise performance. The most beneficial way to enhance the VMO is to incorporate the same exercise philosophy used to improve any other muscle or muscle group, the application of unaccustomed stress. The application of unaccustomed yet safe levels of stress is simply known as the “overload principle”. This may be accomplished in two ways; expose the patient to higher levels of unaccustomed resistance or overload them by increasing the velocity of the movement. Both methods will result in a positive adaption of the entire quadriceps muscle group.
Since stress transpires throughout the kinetic chain of the lower extremity during the performance of ADL’s as well as athletic endeavors, the activities prescribed for patellofemoral pathology should also include exercises for both the hip and ankle. “Critical thinking” is a requirement for the approach to the patient’s optimal exercise selection and treatment design. The health care professional’s obligation to provide optimal treatment does not include the application of myths during the patient’s plan of care.
References
1. Cerny K “Vastus medialis oblique/vastus lateralis muscle activity ratios for selected exercises in persons with and without patellofemoral pain syndrome”, Phys Ther (8):672-83, 1995
2. Malone T, Davies G, Walsh WM, “Muscular control of the patella” Clin Sports Med 21(3); 349-362, 2002.
3. Hubbard JK, Sampson HW, Elledge JR, “The Vastus Medialis Oblique Muscle and Its Relationship to Patellofemoral Joint Deterioration in Human Cadavers”, J Ortho Sports Phys Ther 28(6):384-391, 1998.
4. Weinstabl R, Scharf W, and Firbas W, “The extensor apparatus of the knee joint and its peripheral vasti: anatomic investigation and clinical relevance”, Surg and Radiological Anat 11(2): 17-22, 1989
Robert Panariello MS, PT, ATC, CSCS
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