|Year : 2015 | Volume
| Issue : 2 | Page : 117-122
Preferential vastus medialis oblique activation and its effectiveness in patellofemoral pain syndrome: A review of literature-an update
Anamika Bhatt, Moazzam Hussain Khan
Centre for Physiotherapy and Rehabilitation Sciences, Jamia Millia Islamia, Central University, Jamia Nagar, New Delhi, India
|Date of Web Publication||6-May-2015|
Moazzam Hussain Khan
Central University, Jamia Nagar, New Delhi
To review recent literature regarding evidences for best possible exercises and methods that are proposed for preferential vastus medialis oblique (VMO) activation and effectiveness of preferential VMO activation in patellofemoral pain syndrome (PFPS) patients. The review of recent literature supports preferential VMO activation as one of the efficient management protocols in PFPS patients. Although there is quite heterogeneity in the available research, a majority of research suggests close kinetic chain (CKC) exercises to be more beneficial also the CKC squatting exercise with full maximum voluntary isometric contraction hip adduction has been an exercise quite supported by the recent researches for preferential VMO activation. It can be augmented via other methods like taping, biofeedback, motor imagery, unstable surface to enhance the VMO activation. In accordance with the review of recent literature, preferential VMO activation also has been very well correlated with a reduction in pain, enhancement in function in PFPS patients.
تفعيل العضلة الإنسية المائلة و أثرها في علاج متلازمة الألم الفخذي الرضفي - مراجعة للابحاث المشورة
تمت مراجعة الأبحاث الحديثة لمعرفة أفضل التمارين و الأساليب المقترحة لتنشيط العضلة الإنسية المتسعة المائلة عند المرضي الذين يعانون متلازمة الألم الرضفي الفخذي. بالرجوع الأبحاث الحديثة بشكل خاص يتضح أن تفعيل العضلة الإنسية المتسعة المائلة يعد أحدى طرق العلاج الفعالة في علاج مرضى متلازمة الألم الفخذي الرضفي. وعلى الرغم من عدم تجانس البحوث المنشورة إلاّ أن معظم الأبحاث تشير إلى أن سلسلة من التمارين المغلقة اكثر فائدة كما أن الافادة من ممارسة القرفصاء مع انكماش الورك متساوي الأبعاد تدعمة دراسات حديثة, و يمكن الوصول إلى هذه النتيجة عبر وسائل مساندة أخرى مثل تسجيل اللقطات والاتجاع البيولوجي والسطح غير المستقر. وأثبتت الدراسات الحديثة ارتباط ارتباط تفعيل العضلة الإنسية المائلة بتخفيف الألم لدى مرضى متلازمة الألم الفخذي الرضفي.
Keywords: Maximum voluntary isometric contraction, patellofemoral pain syndrome, vastus medialis oblique
|How to cite this article:|
Bhatt A, Khan MH. Preferential vastus medialis oblique activation and its effectiveness in patellofemoral pain syndrome: A review of literature-an update. Saudi J Sports Med 2015;15:117-22
|How to cite this URL:|
Bhatt A, Khan MH. Preferential vastus medialis oblique activation and its effectiveness in patellofemoral pain syndrome: A review of literature-an update. Saudi J Sports Med [serial online] 2015 [cited 2019 Nov 20];15:117-22. Available from: http://www.sjosm.org/text.asp?2015/15/2/117/156338
| Introduction|| |
"Vastus medialis (VM)," is the most studied muscle out of the four heads of quadriceps and is described in two parts vastus medialis longus (VML) and vastus medialis oblique (VMO).  VMO and vastus lateralis (VL) the two muscles work synergistically to stabilize the patella during dynamic knee extension. VMO is considered clinically significant because it is the only dynamic medial stabilizer of the patella and the only dynamic restraint to the patella's tendency to track laterally.  Therefore VMO is considered to be important for the stability of the patella, thereby opposing the lateral force produced by VL.  The fiber arrangement of VMO makes it ideally suitable to provide a stabilizing force against the normal lateral pull of the other heads of quadriceps.  It has been hypothesized that an imbalance between VMO and VL muscles may be an etiological factor in the development of patellofemoral pain syndrome (PFPS). , So this study aims at reviewing the latest literature regarding methods or exercises proposed in order to preferentially activate VMO and also the role and efficacy of VMO activation in PFPS patients.
| Anatomy of vastus medialis oblique|| |
The VM is the part of the quadriceps femoris, which originates on the lower part of the intertrochanteric line and the upper third of the medial supracondylar line and has attachments to the medial lip of the linea aspera as it wraps around the femur. The most distal fibers are usually described as a separate part of the muscle, the VMO, due to the oblique orientation of the fibers, as distinct from the more longitudinal orientation of the proximal fibers, which are usually termed the VML.  Three features of the VM have been used to identify the VML and VMO: Fiber angle, the presence or absence of a fascial plane of separation, and the pattern of innervation. Lieb and Perry  reported that the upper fibers were angled 15-18° and the lower fibers 50-55° (with respect to the shaft of the femur), and concluded that the two portions should be regarded as separate entities. A fascial plane of separation between the VML and VMO has been found in several studies. ,,
| PREFRENTIAL VASTUS MEDIALIS OBLIQUE ACTIVATION: IS IT POSSIBLE|| |
It has been proposed that the VMO should be specifically strengthened to increase medial dynamic stabilization of the patella , through exercises that induce a selective training effect on VMO over other quadriceps muscles.  Rehabilitation professionals attempt to restore the VMO-VL muscle balance by emphasizing the VMO activity during exercise  because exercises that simply produce overall strengthening of the entire quadriceps complex may not improve any putative medial lateral muscle imbalance.  Electromyography (EMG) has been used to measure the relative activation levels of VMO and VL during exercises and is represented as absolute individual VMO versus VL activity or as a ratio value for VMO/VL, where greater ratios indicate relatively greater levels of VMO activity, where preferential VMO activation is a VMO/VL ratio >1.  Current literature is flooded with research concerning the best exercises to preferentially activate VMO. Nonetheless, debate remains as to an agreed gold standard exercise and controversy litters the evidence base.
Kushion et al.,  compared four common rehabilitation exercises straight leg raise with neutral and externally rotated hip positions (SLRN, SLRER), and short arc quadriceps with neutral and externally rotated hip positions (SAQN, SAQER) for activating the VMO and VL in males and females both without PFPS. The VMO/VL ratios were not different among the exercises; there was equal activation of VMO and VL. The short arc quad (SAQ) exercises had significantly more overall activation of the VMO and VL muscles than the straight leg raise (SLR) exercises. Ayotte et al.,  quantify EMG amplitude of the VMO and other lower limb muscles during five unilateral weight-bearing exercises. For the VMO, the mean normalized EMG across the five exercises ranged from 66% to 55% maximum voluntary isometric contraction (MVIC). The VMO percent MVIC ranked as follows in descending order: Wall squat, forward step up, mini-squat, retro step up, and lateral step up. Spairani et al.,  assessed the effectiveness of two isometric submaximal contractions (10% and 60% of MVC) in promoting preferential activation of VMO over VML and VL in open and closed kinetic chain (CKC) isometric exercises with the knee joint fixed at 30°, 60° and 90° of flexion. In this study the closed-chain isometric (leg press) and open-chain knee extension exercise produced equal activation of VMO and VL with unchanged VMO: VL ratio at both force levels. Choi et al.,  investigated the effect of combined ankle dorsiflexion and SLR with hip external rotation (SLRER, SLRDFER) on the VMO/VL ratio and found no preferential activation. Balogun et al.,  compared the EMG activities in the VMO and VL muscles during two open-chain exercises combing hip adduction and terminal knee extension and found that that the hip adduction exercise does not produce higher EMG activities in the VMO than VL muscle during the terminal knee extension exercise. Kim and Yoo  examined VMO/VL ratios during lunge exercise using a variety of foot wedge. The EMG activity for the VMO muscle significantly increased in the order of conditions as: Anterior wedge less than no wedge and lateral wedge less than medial wedge and posterior wedge. The VMO/VL ratios under the medial wedge and posterior wedge conditions were significantly increased.
Hyong et al.,  examined preferential VMO activity in squatting at different levels of instability that is on surfaces of hard plate, foam and rubber air disks. The ratio was found to be highest in the most unstable rubber air disks. Marνn and Hazell  examined the effects of using an unstable surface during whole-body vibration (WBV) exercise on leg and trunk muscle activity during a static semi-squat and found performing the half squat in the no vibration unstable surface condition decreased VMO EMG rms activity by 14.5% versus the stable surface condition. The addition of 30 Hz WBV to the unstable surface condition increased EMG rms 7.1% versus the no vibration stable surface condition and 25.3% versus the no vibration unstable surface condition. There were no differences in VL muscle activity across conditions.
A number of studies in the old literature suggest that VMO may be preferentially activated by performing quadriceps exercises with hip adduction  as the VMO is attached to the adductor longus and magnus tendons and the medial intramuscular septum, with the majority of the fibers arising from the tendon of the adductor magnus,  and with some fibers attaching to the vastus intermedius.  Researchers suggest that the activation of the knee extensors in association with the hip adductors may invoke greater VMO activation needed for patellar stability.  This has been investigated while various knee extensor exercises where some have shown an increase in VMO activity as compared to VL in healthy subjects  while others have reported no effect. 
Peng et al.,  investigated submaximal and vigorous isometric hip adduction on the VMO and VL activity during leg press exercise and they concluded that targeted training using the leg press exercise during the last 45° of knee extension/flexion with vigorous hip adduction may be useful in promoting a greater VMO/VL ratio. Coqueiro et al.,  investigated the effect of hip adduction on the activity of the VMO and vastus lateralis longus (VLL) muscles during semi-squat exercises. The electrical activity of both VMO and VLL muscles was significantly greater during double leg semi-squatting with full isomeric hip adduction (DLSS-HA) exercise than during DLSS in both healthy as well as PFPS individuals. Although there was no preferential VMO muscle activation, the association of hip adduction with a squat exercise promoted a greater balance between the medial and lateral portions of the quadriceps femoris muscle. Irish et al.,  investigated the effect of the tested exercises open-chain leg extension, squat with isometric hip adduction and add a new exercise, that is, lunges on the activation of VMO: VL. Both the double leg squat (LS) and lunge exercises showed a significantly greater VMO: VL ratio than open-chain knee extension exercise which was shown to preferentially activate VL. Murray et al.,  determined the effect of foot position on muscle activation during a functional squatting movement in asymptomatic healthy male and female adults and suggested that altering the foot position during a partial weight squat has little to no effect on the EMG amplitudes of three quadriceps muscles (rectus femoris, VMO, and vastus lateralis oblique. Carlson et al.,  also supported squatting with hip adduction to preferentially activate VMO whereas SLR activated the VL the most. Jang et al.,  investigated the activation of the VMO and VL during squat exercise with various hip adduction loads (conventional squat exercise, maximal load hip adduction squat exercise, 80% hip adduction squat load exercise, 40% hip adduction load squat exercise) using a pressure-biofeedback unit VMO was more active at 80-40% hip adduction loads than in the conventional squat and maximal loading hip adduction squat exercises. Rezazade et al.,  compared EMG activity of the VMO and VLL during squat with isometric hip adduction in athletes with PFPS and healthy athletes and they found significant differences in the activity of VMO, VLL muscles in athletes with PFPS at 45 knee flexion degree. Koh et al.,  investigated the effect of isometric hip adduction and abduction on the muscle activities of VMO and VL during LS, leg squat with isometric hip adduction (LSHD), leg squat with isometric hip abduction (LSHB).The muscle activity of VMO and VL during LSHD were greater than those during LSHB. The VMO: VL ratio was the highest during LSHD.
Garcia et al.,  investigated the efficiency of a muscle strengthening program with electrical stimulation of the VMO muscle in PFPS by surface EMG. The results showed no difference between the onsets of activation and the ratio of onset to peak of muscle activation of the VMO and VL, that is, the motor control did not suffer any changes, however after the muscle stimulation, there were changes in force-generating capacity during the stepping activity.
Previous evidence had supported use of biofeedback like Davin et al.,  had investigated effects of hip rotation on the mean VMO: VL EMG ratio using EMG biofeedback training and showed an increase their VMO: VL ratio in 5 days regardless of hip position, thus supporting the use of EMG biofeedback for the facilitation of VMO muscular recruitment. Kang et al.  examined the effects of CKC exercise using EMG biofeedback 3 times/week for 6 weeks for selective strengthening of the VMO and found significant difference in VMO/VL ratio from group that received just the CKC exercises. Yoon et al.,  examined the effects of visual feedback on the EMG ratios of medial and lateral vastii on the lower extremity joint angles during squat exercises performed by subjects with femoral anteversion and showed an increase in the VMO/VL ratios on dominant side with double LS performed with visual feedback using a laser beam. Azar et al.,  examined the use of motor imagery in the recruitment of actively contracting muscles during traditional squats with the feet parallel and squats with external hip rotation and heels together, also called "pliés." There were no significant differences in VMO EMG amplitudes between the imagery and control groups however there was a clear trend toward higher EMG amplitudes in the imagery group VMO and the squat exercise elicited significantly higher EMG amplitudes than the pliιs exercise.
Patella taping also has been supported by various studies to be used for preferential VMO activation. ,,, The use of tape became popular following McConnell's original publication,  which proposed that pulling the patella medially with tape (medialglide) will correct the patella position, stretch the tight lateral structures, increase the activity of the VMO muscle, decrease pain and thus allow the patient to begin strengthening exercises of the quadriceps.
Christou [ 42] showed patellar taping differentially affected the activity of the vastii muscles for healthy women and women with PFPS. Specifically, in women with PFPS, application of tape in any direction increased the activity of the VMO and decreased the activity of the VL and patellofemoral pain declined equally. Lee and Cho  examine the effect of McConnell taping to patients with PFPS on the change of the muscle activity of vastus medialis and vastus lateralis during squatting. The muscle activity of vastus medialis and muscle activity ratio of vastus medialis to vastus lateralis increased in McConnell taping compared to no-taping. Lee et al.,  studied effects of Kinesio tape on EMG activity of VMO and VL in PFPS individuals and concluded that during stair ascent and decent pain in PFPS was alleviated, MVIC increased however the EMG activity of VMO and VL decreased to a significant degree.
| Vastus medialis oblique strengthening effectiveness in patellofemoral pain syndrome|| |
Patellofemoral pain syndrome is a common complaint in the sporting and general populations, especially when repetitive lower-limb loading is involved.  PFPS is defined as anterior or retropatellar pain in the absence of other pathology. Clinically the condition presents as diffuse pain exacerbated by activities such as stair climbing, prolonged sitting, squatting, and kneeling. Despite the prevalence of PFPS, its etiology is not well-understood. The most commonly accepted hypothesis is abnormal lateral tracking of the patella.  Commonly, treatment aims to restore the equilibrium of the patellar tracking system.  Routine clinical practice addresses this aim by attempts to selectively activate VMO.
Studies have provided evidence of an imbalance in the activation of the timing of VMO and VL in people with PFPS. ,, The ratio of VMO: VL has a theoretical ideal of 1:1,  and research has shown this ratio to be as low as 0.54:1 in people with PFPS.  Any disturbance in the VMO: VL ratio, owing to a decreased medial pull, may lead to patella mal tracking , and consequently inflammation, pain, premature cartilage degeneration, and ultimately PFPS.  Reduced strength of VMO or abnormal relationship in the timing of activation pattern of the VMO and VL can alter the dynamics of patellofemoral joint and therefore predisposes PFPS. The existing evidence base supports preferential VMO strengthening as a successful method of preventing and reducing PFPS. ,
The finding of an alteration in the relative timing of VMO compared with VL after treatment provides a mechanism, which may explain the efficacy of physical therapy treatment of PFPS. Additionally, it provides support for frequently used physical therapy treatment programs that aim to improve VMO timing through specific retraining of this muscle. A number of clinical trials have been published that have evaluated the efficacy of physical therapy treatment. A number of possibilities exist including part or the entire treatment program VMO retraining with biofeedback, home exercise program, taping, etc. [ 5] Retraining of the VMO and general quadriceps strengthening could improve both quadriceps strength and EMG onset timing of VMO and VL activity.  Song et al.,  performed leg press exercises, with one group combining the exercise with hip adduction in an 8 weeks program in an attempt to further activate the VMO in patients with PFPS and showed that there was VMO hypertrophy and reduction in knee pain and improvement in knee function. Mrityunjay and Chhabra  found out that strengthening of which of the two, quadriceps generalized or specifically VMO, has a better effect on Q-angle and patellar shift. Results revealed that after 4 weeks of VMO strengthening had a greater effect on the Q-angle and patellar shift than static quadriceps exercises. Paoloni et al.,  found short period of patellar taping followed by an exercise program results in long-lasting pain control in PFPS associated with muscular dysfunction as VMO/VL muscular coordination in patients returned to normal. Syme et al.,  compared the effects, with emphasis on retraining the VMO component of the quadriceps femoris muscle or general strengthening of the quadriceps femoris muscles on pain, function and quality of life in patients with PFPS. They concluded exercises involving selective activation of the VMO early in the rehabilitation process, however, clinicians should not overly focus on selective activation and quadriceps strengthening should also be inculcated especially in chronic cases.
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