Elsevier

Clinical Biomechanics

Volume 15, Issue 8, October 2000, Pages 611-618
Clinical Biomechanics

The influence of orthotic devices and vastus medialis strength and timing on patellofemoral loads during running

https://doi.org/10.1016/S0268-0033(00)00028-0Get rights and content

Abstract

Objective. To use a musculoskeletal model and simulation of running to examine: (1) the influence of two commonly prescribed treatments for patellofemoral pain (vastus medialis oblique strengthening and orthoses) and (2) the functional significance of timing differences between vastus medialis oblique and vastus lateralis on lateral patellofemoral joint loads.

Design. A three-dimensional musculoskeletal model of the lower extremity was used to simulate running at 4 m/s.

Background. Repetitive and excessive joint loading is often associated with overuse injuries that require clinical treatments to reduce pain and restore function. Affecting one in four runners, patellofemoral pain is one of the most common injuries in running. Although conservative treatments have been reported to successfully treat patellofemoral pain, the effectiveness is often based on subjective or empirical data, which have generated disagreement on the most effective treatment.

Methods. Nine subject specific running simulations were generated and experiments were performed by applying the treatments and timing differences to the nominal simulations.

Results. Both treatments significantly reduced the average patellofemoral joint load and the vastus medialis strengthening also significantly reduced the peak patellofemoral joint load. In addition, when the vastus medialis oblique timing was delayed and advanced relative to the vastus lateralis timing, a significant increase and decrease in the joint load was observed, respectively, during the loading response.

Conclusions. Increasing vastus medialis oblique strength yielded more consistent results across subjects than the orthosis in reducing patellofemoral joint loads during running. The effect of orthoses was highly variable and sensitive to the individual subject's running mechanics. Vastus medialis oblique activation timing is an important determinant of lateral patellofemoral joint loading during the impact phase.
Relevance

These findings indicate that a reduction in patellofemoral pain may be achieved through techniques that selectively increase the vastus medialis oblique strength. Therefore, future studies should be directed towards identifying such techniques. Additionally, the functional significance of timing differences between the vastus medialis oblique and vastus lateralis is an important consideration in patellofemoral pain treatment and orthoses may be beneficial for some patients depending on their running mechanics.

Introduction

Running is a popular form of recreation and fitness and is central to many sports. However, running is also associated with a high injury rate for both younger (32%) and older (41%) age populations [1]. Depending on the study cited, the overall yearly incidence rate for running injuries is between 37% and 56% [2] with 42% of these injuries related to the knee and 26% of knee injuries associated with patellofemoral pain (PFP) [3]. PFP includes all disorders associated with discomfort on the anterior side of the knee joint. Two of the more common, conservative PFP treatments are exercise programs and the prescription of orthoses [4]. Although conservative treatments have been reported to be successful, the effectiveness is often based on subjective or empirical data [5]. Therefore, there is considerable disagreement within the scientific community on the mechanisms causing PFP and consequently, it is not clear which treatment is the most effective for specific patients [5], [6], [7]. Further, running mechanics and musculoskeletal properties vary among individuals and may play an important role in the effectiveness of individual treatments.

Studies have suggested that differences in relative muscle forces exerted on the patella between the vastus medialis (VM) and vastus lateralis (VL) contribute to lateral patellar tracking and malalignment, which have been linked to PFP [4], [5], [6], [7]. The lateral tracking and malalignment occurs when the lateral pull of VL is not adequately balanced by pull of the vastus medialis longus (VML) and vastus medialis oblique (VMO). This imbalance can lead to altered patellofemoral contact forces and pressures that may lead to PFP. The VMO is deemed the primary medial patellar stabilizer due to the anatomical differences between the VML and VMO [8]. Therefore, much effort has been directed towards identifying techniques to selectively strengthen the VMO to improve the force balance on the patella [4], [5], [7], although the effectiveness and feasibility of selective VMO strengthening have been widely questioned [6], [7], [9], [10]. Much of the controversy regarding the effectiveness of VMO strengthening is caused by the difficulty of isolating the treatment effect in patients. Electrical stimulation may be the only way to strengthen the VMO selectively [11], but should not be recommended unless its effect on patellofemoral joint mechanics is shown to be significant. Therefore, a theoretical analysis is needed to quantify the effect of VMO strengthening on patellofemoral joint loads to justify further studies seeking to identify techniques to selectively strengthen the VMO.

From a neuromechanical perspective, selective VMO activation can also reduce the lateral dominance of VL by either increasing the intensity of VMO relative to VL, or by initiating VMO activity prior to VL [6]. In patients with PFP, it is speculated that VL is activated earlier than VMO [6], [12] and at a higher relative intensity [13]. But studies examining this dynamic imbalance theory have provided conflicting results [7], [12], [13], [14], [15], [16], and the functional significance of the identified timing differences, on the order of 5 ms, has been questioned [6], [7]. Methodological differences between studies and the inherent difficulty identifying muscle excitation onset and offset make reconciling differences difficult, but these studies suggest a theoretical investigation into the influence of vasti timing and intensity is warranted.

Another conservative treatment for PFP has been the prescription of foot orthoses [4]. Eng and Pierrynowski [17] found that foot orthoses combined with an exercise program can be an effective method to reduce PFP in young females. Bahlsen [18] examined the relationship between excessive foot pronation and PFP and found a significant association. The mechanism behind the pain is speculated to be a kinematic coupling between excessive foot pronation and prolonged tibial rotation [18], [19], [20]. Tiberio [20] used a theoretical model to examine the relationship between excessive pronation and lateral patellofemoral joint compression. Tiberio [20] suggested that during gait, the prolonged tibial rotation prevents the knee from extending freely. To compensate for this, the femur rotates internally relative to the tibia causing changes to the patella contact force and pressure patterns. This biomechanical explanation was termed compensatory internal rotation of the femur, although other studies have provided alternative explanations of the relationship between excessive foot pronation and PFP [5]. These studies suggest that further research is needed to understand the biomechanical relationship between excessive pronation and PFP before the effectiveness of foot orthoses verses exercise programs can be evaluated.

Running is a highly dynamic and complex movement that makes it difficult to predict the effect of these treatments on musculoskeletal loading during movement. Changes in the movement caused by these mechanical treatments (e.g., orthoses, [21]) result in changes in the muscle kinematics and therefore the muscle forces through the intrinsic muscle force, length and velocity relationships. The dynamic interaction within the musculoskeletal system makes such changes difficult to predict and interpret and are often counterintuitive [22]. Thus, the mechanisms behind the changes in patellofemoral joint loading are difficult to identify.

Forward dynamic simulations of running have been developed that allow for the precise identification of muscle forces and joint loading and have contributed to the understanding of mechanisms involved in loading the leg during running (e.g., [23], [24], [25]). These models were, however, limited to the initial impact phase (0–50 ms). Since the etiology and mechanics of PFP and the effectiveness of conservative treatments are not well understood, a theoretical model and simulation approach may contribute to our understanding and provide the information necessary to design effective rehabilitation protocols. Therefore, the goal of this study was to use a three-dimensional forward dynamic simulation of running to investigate the effectiveness of selective VMO strength and activation and the prescription of orthoses on patellofemoral loads.

Section snippets

Musculoskeletal model

A forward dynamic musculoskeletal model was used to produce simulations of heel–toe running. The model was previously described in detail [26] and will be described briefly here. The musculoskeletal model was developed using DADS 8.5 software (CADSI, Coralville, IA, USA) and consisted of rigid segments representing the foot, talus, shank, patella, thigh of the support leg, pelvis, and a rest-of-body segment. The model was dimensioned to represent a male subject with a height of 180 cm and a

Results

The optimization was able to find the muscle controls (excitation onset, offset and magnitude) to reproduce the salient features of the experimentally collected data for the nine subjects. Typical simulation results have been previously reported [26]. The major joint angles and ground reaction forces were almost always within 2 S.D. of the subject’s data, and the muscle stimulation patterns compared well with the collected EMG data.

Typical medio-lateral patellofemoral loading patterns are shown

Discussion

The goal of this work was to examine the influence of two commonly prescribed treatments (vastus medialis strengthening and orthoses) for PFP and the functional significance of timing deficits between VMO and VL on lateral patellofemoral joint forces. The forward dynamic simulation model used in the present study had been shown to closely replicate experimentally collected kinetic, kinematic and EMG data during the same running conditions as the present study [26]. The close agreement between

Acknowledgements

This research was supported by NSERC of Canada, The Whitaker Foundation and Adidas America. We are thankful to Trisha Bellchamber and Phuong Ngo for collecting the experimental data.

References (40)

  • J.W Cutbill et al.

    Anterior knee pain: a review

    Clin J Sports Med

    (1997)
  • M.D Grabiner et al.

    Neuromechanics of the patellofemoral joint

    Med Sci Sports Exerc

    (1994)
  • Powers CM, Landel R, Perry J. Timing and intensity of vastus muscle activity during functional activities in subjects...
  • F.J Lieb et al.

    Quadriceps function. An anatomical and mechanical study using amputated limbs

    J Bone Joint Surg Am

    (1968)
  • J.G Garrick

    Anterior knee pain (chondromalacia patella)

    Phys Sports Med

    (1989)
  • E Mirzabeigi et al.

    Isolation of the vastus medialis oblique muscle during exercise

    Am J Sports Med

    (1999)
  • S Werner et al.

    Electrical stimulation of vastus medialis and stretching of lateral thigh muscles in patients with patello-femoral symptoms

    Knee Surg Sports Traumatol Arthrosc

    (1993)
  • M.L Voight et al.

    Comparative reflex response times of vastus medialis obliquus and vastus lateralis in normal subjects and subjects with extensor mechanism dysfunction. An electromyographic study

    Am J Sports Med

    (1991)
  • P.P Mariani et al.

    An electromyographic investigation of subluxation of the patella

    J Bone Joint Surg Br

    (1979)
  • G.M Karst et al.

    Onset timing of electromyographic activity in the vastus medialis oblique and vastus lateralis muscles in subjects with and without patellofemoral pain syndrome

    Phys Ther

    (1995)
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