View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Cleveland-Marshall College of Law Cleveland State University EngagedScholarship@CSU Mechanical Engineering Faculty Publications Mechanical Engineering Department 10-2000 The nflueI nce of Orthotic Devices and Vastus Medialis Strength and Timing on Patellofemoral Loads During Running R. R. Neptune University of Calgary, [email protected] I. C. Wright University of Calgary Antonie J. van den Bogert Cleveland State University, [email protected] Follow this and additional works at: https://engagedscholarship.csuohio.edu/enme_facpub Part of the Biomechanical Engineering Commons How does access to this work benefit oy u? Let us know! Publisher's Statement NOTICE: this is the author’s version of a work that was accepted for publication in Clinical Biomechanics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Clinical Biomechanics, 15, 8, (10-01-2000); 10.1016/S0268-0033(00)00028-0 Original Citation Neptune, R. R., Wright, I. C., and van den Bogert, A. J., 2000, "The nflueI nce of Orthotic Devices and Vastus Medialis Strength and Timing on Patellofemoral Loads during Running," Clinical Biomechanics, 15(8) pp. 611-618. This Article is brought to you for free and open access by the Mechanical Engineering Department at EngagedScholarship@CSU. It has been accepted for inclusion in Mechanical Engineering Faculty Publications by an authorized administrator of EngagedScholarship@CSU. For more information, please contact [email protected]. The influence of orthotic devices and vastus medialis strength and timing on patellofemoral loads during running R.R. Neptune "', I.e. Wright " A.l. van den Bogert b • Hllmon Performance u'/wra/ory, The Unh'ersily of Calgory. Calgary. A 8, Conar/a T2N I N4 b Departllll!/!/ of Biomedical Engineering. The CIl't'ellmd Clinic FOll/lt/alion, CIeL'eflllld, 01144195, USA 1. Introduction (32%) and older (41%) age populations [I ). Depending on the study citcd, the overall yearly incidence ra le for Running is a popular form of recreation and fitness running injuries is between 37% and 56% [2] with 42% of and is cen tral to many sports. However, running is also these inju ries related to the knee and 26% of knee in­ associated with a high injury rate for both younger juries associated with patellofemoral pain (PFP) [3]. PFP includes all d isorders associated wi th d iscomfort on the anterior side of the knee joint. Two of the more • Corresponding author. Present address: Rehabilitation R&D common, conservative PFP treatments are exercise Center (\53). VA Palo Alto He3lth Care System. 380\ Miranda Avenue. Palo Alto. CA 94304. USA. programs and the prescription of orthoses [4]. Although £-m(li/ (lddress: [email protected] (R.R. Neptune). conservative treatments have been reported to be 612 successful, the efectiveness is often based on subjective between excessive foot pronation and PFP and found a or empirical data [5]. Therefore, there is considerable signifcant association. The mechanism behind the pain disagreement within the scientifc community on the is speculated to be a kinematic coupling between ex­ mechanisms causing PFP and consequently, it is not cessive foot pronation and prolonged tibial rotation [18- clear which treatment is the most efective for specifc 20]. Tiberio [20] used a theoretical model to examine the patients [5-7]. Further, running mechanics and muscu­ relationship between excessive pronation and lateral loskeletal properties vary among individuals and may patellofemoral joint compression. Tiberio [20] suggested play an important role in the efectiveness of individual that during gait, the prolonged tibial rotation prevents treatments. the knee from extending freely. To compensate for this, Studies have suggested that diferences in relative the femur rotates internally relative to the tibia causing muscle forces exerted on the patella between the vastus changes to the patella contact force and pressure pat­ medialis (VM) and vastus lateralis (VL) contribute to terns. This biomechanical explanation was termed lateral patellar tracking and malalignment, which have compensatory internal rotation of the femur, although been linked to PFP [4-7]. The lateral tracking and other studies have provided alternative explanations of malalignment occurs when the lateral pull of VL is not the relationship between excessive foot pronation and adequately balanced by pull of the vastus medialis lon­ PFP [5]. These studies suggest that further research is gus (VML) and vastus medialis oblique (VMO). This needed to understand the biomechanical relationship imbalance can lead to altered patellofemoral contact between excessive pronation and PFP before the efec­ forces and pressures that may lead to PFP. The VMO is tiveness of foot orthoses verses exercise programs can be deemed the primary medial patellar stabilizer due to the evaluated. anatomical diferences between the VML and VMO [8]. Running is a highly dynamic and complex movement Therefore, much efort has been directed towards iden­ that makes it difcult to predict the efect of these tifying techniques to selectively strengthen the VMO to treatments on musculoskeletal loading during move­ improve the force balance on the patella [4,5,7], al­ ment. Changes in the movement caused by these me­ though the efectiveness and feasibility of selective VMO chanical treatments (e.g., orthoses, [21]) result in strengthening have been widely questioned [6,7,9,10]. changes in the muscle kinematics and therefore the Much of the controversy regarding the efectiveness of muscle forces through the intrinsic muscle force, length VMO strengthening is caused by the difculty of iso­ and velocity relationships. The dynamic interaction lating the treatment efect in patients. Electrical stimu­ within the musculoskeletal system makes such changes lation may be the only way to strengthen the VMO difcult to predict and interpret and are often counter­ selectively [11], but should not be recommended unless intuitive [22]. Thus, the mechanisms behind the changes its efect on patellofemoral joint mechanics is shown to in patellofemoral joint loading are difcult to identify. be signifcant. Therefore, a theoretical analysis is needed Forward dynamic simulations of running have been to quantify the efect of VMO strengthening on patel­ developed that allow for the precise identifcation of lofemoral joint loads to justify further studies seeking to muscle forces and joint loading and have contributed to identify techniques to selectively strengthen the VMO. the understanding of mechanisms involved in loading From a neuromechanical perspective, selective VMO the leg during running (e.g., [23-25]). These models activation can also reduce the lateral dominance of VL were, however, limited to the initial impact phase (0- by either increasing the intensity of VMO relative to VL, 50 ms). Since the etiology and mechanics of PFP and the or by initiating VMO activity prior to VL [6]. In patients efectiveness of conservative treatments are not well with PFP, it is speculated that VL is activated earlier understood, a theoretical model and simulation ap­ than VMO [6,12] and at a higher relative intensity [13]. proach may contribute to our understanding and pro­ But studies examining this dynamic imbalance theory vide the information necessary to design efective have provided conficting results [7,12-16], and the rehabilitation protocols. Therefore, the goal of this functional signifcance of the identifed timing difer­ study was to use a three­dimensional forward dynamic ences, on the order of 5 ms, has been questioned [6,7]. simulation of running to investigate the efectiveness of Methodological diferences between studies and the in­ selective VMO strength and activation and the pre­ herent difculty identifying muscle excitation onset and scription of orthoses on patellofemoral loads. ofset make reconciling diferences difcult, but these studies suggest a theoretical investigation into the in­ fuence of vasti timing and intensity is warranted. 2. Methods Another conservative treatment for PFP has been the prescription of foot orthoses [4]. Eng and Pierrynowski 2.1. Musculoskeletal model [17] found that foot orthoses combined with an exercise program can be an efective method to reduce PFP in A forward dynamic musculoskeletal model was used young females. Bahlsen [18] examined the relationship to produce simulations of heel-toe running. The model 613 was previously described in detail [26] and will be de­ scribed briefy here. The musculoskeletal model was developed using DADS 8.5 software (CADSI, Coral­ ville, IA, USA) and consisted of rigid segments repre­ senting the foot, talus, shank, patella, thigh of the support leg, pelvis, and a rest­of­body segment. The model was dimensioned to represent a male subject with a height of 180 cm and a mass of 75 kg. Musculoskeletal geometry was based on the work of Delp [27] and seg­ ment masses and inertial properties were determined using regression equations [28,29]. The joint models were based on existing literature [27] and further developed to allow three­dimensional movements at the knee. The hip joint was modeled as a spherical joint while rotations about the subtalar