Functional analysis of the patellar stabilizers

Abstracts

O músculo vasto medial obliquo (VMO) desempenha importante papel na estabilização medial da patela. No entanto, o padrão de recrutamento dos componentes laterais, o músculo vasto lateral longo (VLL) e vasto lateral obliquo (VLO) não está estabelecido. O objetivo deste trabalho foi analisar a atividade eletromiográfica dos músculos VMO, VLL e VLO de 21 indivíduos saudáveis (X=23,3 e DP=2,9), sendo 10 mulheres e 11 homens, sem história clínica de dor ou lesão osteomioarticular. Para tanto foi utilizado um eletromiógrafo NICOLET VIKING II de 8 canais (NICOLET Biomedical Instruments) e eletrodos bipolares de superfície para registrar a atividade elétrica dos músculos VMO, VLL e VLO durante a realização de exercícios isométricos de extensão do joelho a 15º e 90º de flexão. Os dados eletromiográficos foram normalizados pela contração isométrica voluntária máxima de extensão do joelho a 50º de flexão e revelaram que os músculos VLL e VLO apresentam diferença significativa no padrão de recrutamento podendo ser considerados fisiologicamente distintos. O músculo VMO desempenhou juntamente com o VLO um papel recíproco e sincrônico na estabilização patelar e apresentou maior ativação em relação ao músculo VLL nos exercícios isométricos de extensão do joelho a 90º.

Joelho; Músculo; Eletromiografia

ORIGINAL ARTICLE

Functional analysis of the patellar stabilizers

Débora Bevilaqua GrossI^I; Vanessa Monteiro Pedro^II; Fausto Bérzin^III

^IPhD Professor of the Biomechanical Department, Medicine and Rehabilitation of the Locomotors- FMRP – USP

^IIAssociate Professor – IV Professor of the Physiotherapy Department – UFSCar

^IIIChairman of the morphology Department (FOP - UNICAMP)

^{Correspondence}

SUMMARY

The vastus medialis obliquus muscle (VMO) performs an important role in the medial patellar stability . However , the recruitment of the lateral components, the vastus lateralis longus (VLL) and vastus laterallis oblique (VLO) is not established. The main purpose of this work was to investigate the electromyographic (EMG) activity of the VMO, VLL and VLO muscles of twenty one health volunteers (X= 23,3 ± DP 2,9), 10 female and eleven males, without clinical pain symptoms or osteomioarticular injuries EMG NICOLET VIKING II was used with eight channels (NICOLET Biomedical Instruments, and bipolar electrodes surface in order to record the electrical activity of VMO, VLL and VLO muscles during a isometric knee extension at 15º and 90º. The EMG data were normalized by maximum voluntary contraction (MIVC) of the knee flexion at 50º has shown that the VLL and VLO muscles demonstrated significant difference in recruitment pattern and they can be considered physiologically distinct. The VMO and VLO muscles performed synchronic and reciprocal role in the patellar stability and the VMO muscle performed higher activity compared with the VLL muscle in isometric knee extension at 90º.

Key words: Knee, Muscle, Electromyography.

INTRODUCTION

The patellofemoral disorders are the most likely pathology in the knee seen in orthopedics and sports medicine clinics⁽⁶⁾. The patients with patellofemoral pain symptoms are one of the biggest clinical challenges in rehabilitation medicine considering the most recent advances in the diagnoses and treatment of several knees condition⁽²⁵⁾.

One of the most common characteristics in patients with patellofemoral pain is the extensor mechanism disorder, which results in atrophy and strength reduction of vastus medialis muscle and unbalancing of the lateralis and medialis quadriceps components^{(4, 22)}.

The vastus mediallis is divided into two parts, one proximal called vastus mediallis longus (VML) and another distal one, the vastus mediallis obliquus (VMO). These parts show anatomical^(2,11,12,23), functional^(2,13,17), histochemistry⁽²¹⁾ differences and in the pattern of innervations as well^(12,18,20) (Figure 1). In addition, the VLO started also be studied because of clinical surgical importance technique of release lateral, which the releasing decreases the post operation recovery, as compared with the transaction of all vastus lateralis⁽⁷⁾.

The muscles VMO and VLL electromyographic activity have been studied in each opening kinetic chain and in different angles of knee flexion^(3,4,6,15). However, despite Weinstabl et al⁽²³⁾ suggest functional differences between the VLL and VLO muscles, the electrical pattern activity has not been studied yet. Morrish & Woledge⁽¹⁶⁾ compared the electrical pattern activity of the VMO and VLO muscles in normal clinical patients doing exercise of kinetic chain at 20º knee flexion and the authors not found any significant difference between these two muscles with this angle.

Considering the importance of understanding the involved factors in patellofemoral this disorder and the poor knowledge about the role of the medially and laterallis components of the quadriceps in the patella stability, the main purpose of this study was figure out the electrical VMO, VLL, and VLO muscles activities with the flexion knee extension exercise in a kinetic at 15º and 90º of the knee flexion.

MATERIAL AN METHODS

The vastus medialis obliquus (VMO),vastus lateralis obliquus (VLO) and vastus lateralis longus (VLL) were evaluated by the use of electromyography in 21 volunteers, ten female and 11 male, aged from 19 to 28 (X=23,3±2.9) had no previous surgery, pain or osteomyarticular injury in the lower limbs. The study was led with the 196/96 resolution of the Health National Council.

EQUIPAMENT

Electromyography records were obtained by bipolar surface electrodes with 11mm diameter and detection surface of 2mm connected to the electromyography Viking II of eight channels (Nicolet Biomedical Instruments). The calibration of the equipment ranged from 200 to 500µV, the division and speed of the beam displacement was of 200ms/division. The filters were fixed with amplitude of 10 Hz low frequency and 10KHz high frequency.

PROCEDURES

The electrodes were fixed on the skin, previously trichotomized and hygienized with alcohol at 70%, in order to reduce the impedance and eliminate any unexpected interferences. Before the electrodes fixation they had been greased with gel and fixed to the skin at longitudinal direction from the muscular fibers with microspores scotch tape (3M of Brazil). The distance between the centers of each electrode was of 2cm. An earthed connected electrode was greased with gel and fixed to the anterior tibia tuberosity.

To install the electrodes in different parts of the quadriceps muscle, a line was traced from the antero superior iliac spine (ASIS) to the center of patella, as a pattern of the inclination angle of the measurement of each portion⁽¹⁾. The pair of electrodes on the VMO was placed on the belly of the muscle at an inclination of 55º⁽¹²⁾. The VLL electrodes were placed at 15cm from the superior and lateral edge of patella at an inclination of 13.6º. The VLO shows its superficial part located around 2,2 cm of the lateralis epicondyle, with a superficial length of about 8.9cm. To insert the electrodes on this muscle, the femoral lateralis epicondyle was located and the beginning and center of the VLO belly muscle at an inclination of 50,4º⁽¹⁾ (Figure 2).

POSITIONS AND EXERCISES

The knee isometric extension exercises at15º, 50ºand 90º angles of knee flexion were performed on an extensor flexor table, which allowed the limb mechanical fixation of different knee flexion angle, leading to a maximum voluntary isometric contraction (MVIC) in each exercise performance. The volunteer remained sat with the trunk and hips flexioned at 90º and stabilized with two belts: an auxiliary and a pelvic one.

The exercise performance order was random and before the beginning of each test, the familiarization with the exercises was done. The time performance of each contraction was of 5 seconds with a break of 60 seconds between each repetition and ten minutes between the set of exercises. The electromyographic data were normalized considering the MVIC of the knee extension at 50º of the knee flexion according to Hanten & Schulthies⁽⁸⁾.

Comparing the muscles at the different angles studied, analyses of variance test was used.

RESULTS

The comparison among VMO, VLL and VLO muscles showed that isometric extension exercise at 15 º knee flexion there is difference in activation pattern of these muscles (p=0.06). On the other hand , the performance of the same exercises at 90º of knee flexion, the VMO and VLO muscles showed the same behaviour and were significantly more active than the VLL muscle (p=0,02) (Table 1).

The comparison among the angles, only the VLL muscle showed a distinct activation pattern, that is, higher activity at the extension exercise at 15º than at 90º (p=0,04). On the other hand the angle variation did not make any difference in the VMO and VLO muscles (Table 1)

DISCUSSION

One of the purposes of this study was to verify if the VLL and VLO showed differences in their function, and the results revealed different recruiting pattern in these muscles, besides the anatomical differences⁽¹⁾ they also showed distinct activation pattern.

During the isometric extension exercises of knee at 15ºflexion, these muscles did not show any remarkable difference among them, differently from VLO, which remained with the same recruitment pattern independent of the knee flexion angle, the VLL is significantly more active during the knee flexion at 15º than at 90º. Although the difference was not so significant, Boucher et al.⁽³⁾, also observed more VLL activity at 15º than 90º. Either, Escamilla et al.⁽⁶⁾ also reported more activity of the VLL muscle at last knee extension degree.

Cerny⁽⁴⁾, associated this higher VLL activity at 15º as a mechanical disadvantage due to the increase of the gravity and the lever of the quadriceps muscle, besides the decrease of the muscle length.

According to Bouncher et al.⁽³⁾, the VLL muscle while working in MICV at 15º flexion, is more involved in the knee extension than the patella stability. This also shows the VLL fibers alignment that tends to tractionate patella promoting the extension, differently from the VLO which spirally and inclination fibers in relation to femoral dyaphisis promotes⁽¹⁾ the patella alignment associated to the VMO. In addition, the VLL muscle shows a greater muscular body⁽²⁴⁾ with a higher traction component than the VLO, therefore, more available to alterations in its length. On the other hand at (MIVC) 15º, both are in the shortening position spite of the anatomical differences, the fibers structure and disposition seem not promoting important alterations in relation of the length tension.

The comes out of this work suggest when doing the exercise at the last extension degrees, besides not activate preferably the VMO, the action of the VLL is preferred, contributing to the patellar balancing.

About the VLO muscle electrical activity , the only work referring to the VLO electromyographical study, is the one by Morrish & Woledge⁽¹⁶⁾, who also studied the VMO at 20º degree knee flexion in an opening kinetic chain and no important differences in these muscles activity, nearly synchronic were found, suggesting a reciprocal activity at the patella control.

According to Javadpour et al.⁽¹¹⁾ the traction balancing of the VMO and VLO is fundamental considering its muscular factor which determines patella position, as the opening kinetic chain exercise of the leg extension isolating the quadriceps contraction. The data from this study showed that VMO and VLO muscles have the same behaviour suggesting a synchronic role of stability and an antagonist stability of the patella in normal people.

On the other hand the strength vector made by the VLO muscle, very associated with the iliotibial tract and lateralis retinaculum⁽¹⁾ may be able to alter the patella normal balancing, promoting an excessive tension in these structures could generate clinical pain and patella disorder.

Considering the VMO muscle being more active during the last extension degrees it is well known^(6,13,17), what subsided the use of these exercises in this traditional treatment. Equally, the concept of the strength of patellofemoral reaction increases according to knee flexion and decrease as long as reaching the final extension proposed by Hungerford & Barry⁽¹⁰⁾, contributed to the exercises protocol to these patients that were based on exercises done at the last extension degrees.

This work data showed the VMO muscle is not the most active at the last degrees., which is in accordance to Boucher et al.⁽³⁾, Doucete & Child⁽⁵⁾, Herrington & Payton⁽⁹⁾, who did not find difference in VMO muscle activity at different angles of knee flexion in normal patients.

Spite of the increase of the activity in CIVM at 90º VMO and VLO muscles not be significant in relation to 15º of knee flexion, the results showed the difference between these two muscles and the VLL muscle increasing as much as the knee flexion angle increases.

Furthermore, according to Boucher et al.⁽³⁾, at 90º, the compressive strength is maximized and the shearing strength is minimized facilitating not only VMO muscle activity, but also increasing the articular contact facilitating articular nutrition.

For the VMO selective muscle training, it is not only the Arch of movement what is searched where it shows more activity, but also offer higher stability, better compressive strength higher activation in relation to the lateralis components.

The strength exercise of the VMO muscle at the last degrees extension until now has been proclaimed to these patients treatment. However, it is essential to this muscle, besides being more active, the VMO muscle show an advantage of activation if compared to VLL and VLO.

At the last knee extension degrees there is even less articular contact, therefore higher and instability Stickup et al.⁽¹⁹⁾, showed that at the last degrees of the extension exercises done in opening kinetic chain, there is also higher patellofemoral stress, as the particular contact angle is smaller, nevertheless the compressive strength, despite being smaller is distributed in a small contact area, increasing the stress. Otherwise, the 90º knee flexion, shows a higher strength of the stress, but the articular contact and the patellofemoral is higher as well., consequently the authors showed the patellofemoral decreases due to the increase of the knee flexion angle.

Therefore, the isometric contraction exercise of the knee extension flexion at 90º can be proscribed to the rehabilitation program which is indicate VMO strength exercise.

CONCLUSION

The VLL and VLO muscles showed difference in the activity pattern, which could be considered physiologically distinct. Besides, the VLO muscle as the VMO also active, independent of the knee flexion angle, suggesting these muscles performance in reciprocal and synchronic patella stability. The isometric exercises of the knee extension at 90º higher activation of the VMO muscle was obsereved during in relation to lateral components, with important difference in relation to VLL muscle.

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Work performed at the Electromyography Laboratory of Morphology Department of Dentistry College of Piracicaba (FOP) – UNICAM

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Publication Dates

• Publication in this collection
  16 June 2004
• Date of issue
  June 2004

History

• Accepted
  09 Apr 2004
• Received
  17 Sept 2003