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The influence of cadence and shoes on patellofemoral joint kinetics in runners with patellofemoral pain
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Journal of Science and Medicine in Sport journal homepage: www.elsevier.com/locate/jsams
Original research
The influence of cadence and shoes on patellofemoral joint kinetics in runners with patellofemoral pain Jason Bonacci a,∗ , Michelle Hall b , Aaron Fox a , Natalie Saunders a , Tristan Shipsides c , Bill Vicenzino d a
Centre for Sports Research, School of Exercise and Nutrition Sciences, Deakin University, Australia Centre for Health, Exercise and Sports Medicine, Department of Physiotherapy, University of Melbourne, Australia c Olympic Park Sports Medicine Centre, Australia d University of Queensland, School of Health and Rehabilitation Sciences: Physiotherapy, Australia b
a r t i c l e
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Article history: Received 27 February 2017 Received in revised form 7 July 2017 Accepted 26 September 2017 Available online xxx Keywords: Knee pain Footwear Gait Running Biomechanics
a b s t r a c t Objectives: To determine the effect of a combination of a minimalist shoe and increased cadence on measures of patellofemoral joint loading during running in individuals with patellofemoral pain. Design: Within-participant repeated measures with four conditions presented in random order: (1) control shoe at preferred cadence; (2) control shoe with +10% cadence; (3) minimalist shoe at preferred cadence; (4) minimalist shoe with +10% cadence. Methods: Fifteen recreational runners with patellofemoral pain ran on an instrumented treadmill while three-dimensional motion capture data were acquired. Peak patellofemoral joint stress, joint reaction force, knee extensor moment and knee joint angle during the stance phase of running were calculated. One-way repeated measures ANOVA was used to compare the control condition (1) to the three experimental conditions (2–4). Results: Running in a minimalist shoe at an increased cadence reduced patellofemoral stress and joint reaction force on average by approximately 29% (p < 0.001) compared to the control condition. Running in a minimalist shoe at preferred cadence reduced patellofemoral joint stress by 15% and joint reaction force by 17% (p < 0.001), compared to the control condition. Running in control shoes at an increased cadence reduced patellofemoral joint stress and joint reaction force by 16% and 19% (p < 0.001), respectively, compared to the control condition. Conclusions: In individuals with patellofemoral pain, running in a minimalist shoe at an increased cadence had the greatest reduction in patellofemoral joint loading compared to a control shoe at preferred cadence. This may be an effective intervention to modulate biomechanical factors related to patellofemoral pain. © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.
1. Introduction Patellofemoral pain (PFP) is the most common musculoskeletal complaint in runners.1 PFP is defined as pain around or behind the patella that is aggravated by weight bearing activities that load the patellofemoral joint (PFJ).2 Although the aetiology of PFP is not well understood, there is evidence to implicate the role of excessive PFJ stress in the pathophysiology of PFP.3–5 Repetitive high-frequency loading of the PFJ may exacerbate PFJ symptoms due to an elevated patellar water content6 or subchondral bone metabolic activity.7
∗ Corresponding author. E-mail address: [email protected] (J. Bonacci).
This suggests that it is worthwhile to evaluate strategies that reduce PFJ stress in those with PFP. In healthy individuals, evidence suggests that traditional cushioned footwear can elevate PFJ stress8 while an increased running cadence can reduce PFJ load.9 Running in traditional cushioned footwear can elevate PFJ stress via kinematics changes such as a longer stride length and greater knee flexion during stance that create a larger moment arm of the quadriceps muscles.8 An effective strategy to reduce stride length and knee flexion during stance is to increase running cadence.9,10 A 10% increase in running cadence has also been shown to reduce PFJ reaction force in healthy individuals.9,10 These findings suggest that utilising a less cushioned shoe or running with a higher cadence may be effective strategies to reduce PFJ loading in runners. Combining both
https://doi.org/10.1016/j.jsams.2017.09.593 1440-2440/© 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Bonacci J, et al. The influence of cadence and shoes on patellofemoral joint kinetics in runners with patellofemoral pain. J Sci Med Sport (2017), https://doi.org/10.1016/j.jsams.2017.09.593
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Table 1 Demographic and clinical characteristics of participants, described as mean (SD) or n (%) unless otherwise stated. Characteristics Age (years) Sex (F:M) Height (m) Body mass (kg) Body mass index (kg m−2 ) Anterior knee pain scalea Worst painb Duration of symptoms (months) Number with bilateral knee pain Running volume (km/wk)
n = 15 32.6 (9.6) 12:3 1.71 (0.06) 68.91 (10.99) 23.30 (3.07) 79.67 (6.99) 45.7 (17.3) 49.87 (48.38) Range (2–156) 5 (33%) 15.60 (7.4) Range (10–32)
a Anterior knee pain scale ranges from 0 to 100 points, where higher scores indicate less disability. b Pain measured on 100 mm visual analogue scale; 0 mm = no pain, 100 mm = worst pain imaginable.
the minimalist shoe and reduced step length may yield a greater reduction in knee joint load during running as compared to either minimalist footwear or reduced step length in isolation.11 Although data from healthy individuals support the use of minimalist footwear and gait modification to reduce PFJ load, these observations cannot be generalised to individuals with PFP. Individuals with PFP present with altered running biomechanics compared to healthy controls.12 Those with PFP have also demonstrated dissimilar changes in PFJ stress compared to healthy controls when altering step length during running.13 Taken together, an evaluation of the combined effect of minimalist shoes and gait modification on PFJ stress in individuals with PFP is needed. Given that higher PFJ stress is considered to adversely affect PFP patients,3 the primary aim of this study was to examine the effect of a minimalist shoe and increased running cadence on PFJ stress in individuals with PFP. We hypothesised that the combination of a minimalist shoes and increased cadence would have the greatest reduction in PFJ stress compared to control shoes and preferred cadence. Secondary aims of this study were to evaluate the effect of running in (1) a control shoe and increased cadence; (2) a minimalist shoe with preferred cadence; (3) a minimalist shoe and increased running cadence on PFJ reaction forces, knee extensor moment and knee flexion angle compared to a control shoe and preferred cadence. 2. Methods Fifteen recreational runners people who had clinically diagnosed PFP participated in this study. Descriptive characteristics are presented in Table 1. Participants were predominately female, had moderate level of anterior knee pain and ran on average approximately 16 km per week. The diagnosis of PFP was made based upon previous clinical trials,14,15 whereby participants were initially telephone-screened prior to a physical examination. The inclusion criteria were: (i) aged 18–40 years; (ii) running at least 10 km per week; (iii) non-traumatic retropatellar pain of greater than 6 weeks duration; (iv) aggravated by at least two of: running, hopping, squatting, prolonged sitting or kneeling; (v) pain severity ≥30/100 mm on a visual analogue scale; and (vi) pain on palpation of the patellar facet or during a double leg squat or step down from a 25 cm step. Exclusion criteria were: (i) concomitant injury or pathology of other knee structures (e.g. menisci, ligamentous, patellar tendon, iliotibial band); (ii) a history of lower limb surgery; (iii) pain or injury in the hip, pelvis or lumbar spine; and (iv) any foot condition that precluded use of a minimalist shoe. All participants self-reported a history of running in standard cushioned shoes. Written informed consent was obtained from all
participants and ethical approval was granted by the Deakin University Human Ethics Committee. Participants performed 5 min of running on an instrumented treadmill (Bertec, Ohio, USA) in four randomly ordered conditions: (1) control shoe at preferred cadence; (2) control shoe at +10% preferred cadence; (3) minimalist shoe at preferred cadence; and (4) minimalist shoe at +10% preferred cadence. Preferred cadence (steps/min) and foot-strike pattern was determined from sagittal plane video footage (Casio Exilim, Casio, Japan) during the final minute of a 4 min treadmill run in each shoe prior to data collection. A metronome (Seiko DM51, Seiko Instruments Inc, Japan) was used to control cadence during +10% conditions, and trials were only accepted if participants achieved the desired cadence. The control shoe was an Asics Gel-Cumulus 16, with a weight of 345 g, stack height of 31 mm and a 11 mm heel–toe offset. The minimalist shoe was a Vibram Seeya, with a weight of 136 g, stack height of 5 mm and a 0 mm heel–toe offset. A 5 min rest period was provided between conditions for recovery and to change shoes if required. An eight-camera VICON motion analysis system (Oxford Metrics Ltd, Oxford, UK), sampling at 250 Hz was used to capture threedimensional joint kinematics of the lower limb. Ground reaction force (GRF) data were collected at 1500 Hz from the instrumented treadmill in synchrony with the motion capture data. Thirty-two 14 mm retroflective markers were attached to anatomical landmarks in accordance with an established model.16 Markers were placed bilaterally on the iliac crest, anterior and posterior iliac spines, greater trochanter, anterior and lateral thigh and shank, medial and lateral epicondyles of the femur, medial and lateral malleolus, calcaneus and the base of the third and fifth metatarsals. Kinematic and GRF data were processed within Visual 3D software (C-Motion, Rockville, Maryland, USA). Marker trajectories and GRF data were low pass filtered with a 20 Hz cut-off frequency. The cutoff frequency was determined via a residual analysis and visual inspection of the resulting kinematic and GRF data. The net internal knee extension moment was obtained by submitting filtered kinematic and GRF to a conventional Newton-Euler inverse dynamics analysis. Joint moment data was normalised by body mass and reported in units of Nm/kg. Gait events were identified by the use of a 60 N threshold of the vertical GRF. Data were extracted for the affected limb for 20 strides during the final minute of the 5 min run in each condition using a customised MATLAB (Mathworks Inc, Natick, USA) programme. In the case of bilateral symptoms, the most symptomatic leg was used for analysis. Kinetic data related to the PFJ were derived from kinematic and kinetic data using a previously described biomechanical model.17–19 This model has been used to estimate PFJ reaction force (PFJRF) and stress during walking,18 running,8,20 and squatting21 and is sensitive to detect changes in PFJ stress with different footwear22 and knee braces.23 Quadriceps force was calculated for each knee flexion angle by dividing the net knee extensor moment by the effective lever arm for the quadriceps. The quadriceps effective lever arm was determined at each knee flexion angle by fitting a non-linear equation to the data of van Eijden et al.24 The PFJRF was estimated by multiplying the quadriceps force by a constant25 that defines the relationship between PFJRF and knee flexion angle. PFJ stress was estimated by dividing the PFJRF by PFJ contact area. PFJ contact area was estimated by fitting a fourth order polynomial curve to the contact areas for each knee flexion angle as reported previously.26 The output of the model was PFJRF and PFJ stress as a function of knee flexion angle during the stance phase of the gait cycle. The data for each participant were averaged over the 20 strides for each condition and normalised to the stance phase of the gait cycle. Variables of interest included: (1) peak PFJ stress; (2) peak PFJRF; (3) peak knee extensor moment and (4) peak knee flexion angle, which served as the dependent variables. The independent
Please cite this article in press as: Bonacci J, et al. The influence of cadence and shoes on patellofemoral joint kinetics in runners with patellofemoral pain. J Sci Med Sport (2017), https://doi.org/10.1016/j.jsams.2017.09.593
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variable was CONDITION. Statistical analysis was performed using SPSS version 24 (SPSS Inc., Chicago, IL, USA). Using a one-way repeated measures analysis of variance, pre-specified contrasts with Bonferoni correction (pair wise comparisons of interest) for levels within CONDITION were evaluated for each dependent variable. The pairwise comparisons of interest were: (a) control shoe and preferred cadence versus the same shoe and increased cadence; (b) control shoe and preferred cadence versus minimalist shoe and preferred cadence; and (c) control shoe and increased cadence versus minimalist shoe and increased cadence. CONDITION data are presented as individual data plots, as well as means and standard deviations (SD). Point estimates of effect are presented as standardised mean differences (SMD) and 95% confidence intervals (CI) between conditions, with the condition: control shoe and preferred cadence as the reference. SMD >1.2 are considered large, 0.61–1.2 as medium, 0.2–0.6 as small and <0.2 as trivial.27
3. Results A rearfoot strike landing pattern was evident in 14 of the 15 (93%) participants and 12 of the 15 (80%) participants when running at preferred cadence in the control and the minimalist shoe, respectively. The mean (SD) peak knee flexion angle, peak knee extensor moment and peak PFJRF and peak PRFS are presented in Table 2. The individual data plots exhibit the trend of a reduction across conditions for all PFJ measures with the combined minimalist shoe and 10% cadence condition being lower than the interventions applied separately (Fig. 1). Compared to running in the control shoe at preferred cadence, peak PFJ stress was lower running in the control shoe at increased cadence (mean difference: −15.5%, 95% CI: −27.5 to −3%, p = 0.009), running in the minimalist shoe at preferred cadence (mean difference: 15%, 95% CI: −24 to −7%, p < 0.001) and running in the minimalist shoe at increased cadence (mean difference: −27%, 95% CI: −39% to −15%, p < 0.001). The largest reduction in peak PFJ stress was observed running in the minimalist shoe at increased cadence compared to running in control shoe at preferred cadence (Table 2, Fig. 1A). Compared to running in the control shoe at preferred cadence, peak PFJRF was lower running in the control shoe at increased cadence (mean difference: −18.7%, 95% CI: −31.8 to −5.5%, p = 0.004) running in the minimalist shoe at preferred cadence (mean difference: −16.7%, 95% CI: −25.9 to −7.5%, p < 0.001) and running in the minimalist shoe at increased cadence (mean difference: −30.4%, 95% CI: −42.7 to −18.1%, p < 0.001). The largest reduction in peak PFJRF was observed running in the minimalist shoe at increased cadence compared to running in control shoe at preferred cadence (Table 2, Fig. 1B). Compared to running in the control shoe at preferred cadence, peak knee extensor moment was lower running in the control shoe at increased cadence (mean difference: −12.2%, 95% CI −23.6 to −1.6%, p = 0.019), running in the minimalist shoe at preferred cadence (mean difference: −13.0%, 95% CI: −19.5 to −6.5%, p < 0.001) and running in the minimalist shoe at increased cadence (mean difference: −23.6%, 95% CI: −34.1 to −13.0%, p < 0.001). The largest reduction in peak knee extensor moment was observed running in the minimalist shoe at increased cadence compared to running in the control shoe at preferred cadence (Table 2, Fig. 1C). Compared to running in the control shoe at preferred cadence, peak knee flexion angle was lower running in the control shoe at increased cadence (mean difference: −3.6◦ , 95% CI: −5.2 to −2.0◦ , p < 0.001), running in the minimalist shoe at preferred cadence (mean difference: −2.6◦ , 95% CI: −4.2 to −1.0◦ , p = 0.001) and running in the minimalist shoe at increased cadence (mean difference: −5.0◦ , 95% CI −7.6 to −2.4◦ , p < 0.001). The largest reduction in peak
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knee flexion angle was observed running in the minimalist shoe at increased cadence compared to running in control shoe at preferred cadence (Table 2, Fig. 1D).
4. Discussion The aim of this study was to determine the effects of a minimalist shoe and increased cadence on measures of PFJ loading and knee kinematics. Overall, we observed that both minimalist footwear and increased cadence can independently reduce PFJ reaction force and stress compared to running in control footwear at preferred cadence. Importantly, a combination of the minimalist footwear and increased cadence had the largest effect on the measures of PFJ loading assessed in this study. Our hypothesis that a combination of running in a minimalist shoe and increased cadence had the greatest reduction in PFJ stress was supported. In comparison to running in control shoes at preferred cadence, there was a 15% reduction in PFJ stress when running in the minimalist shoe and 16% reduction when running in the control shoe with an increased cadence. Notably, combining both the minimalist shoe and a 10% increase in cadence resulted in a 27% reduction in PFJ stress, which was greater than either the increased cadence or minimalist shoe applied separately. Should a clinician aim to reduce PFJ stress in an individual with PFP, utilising a minimalist shoe plus an increased cadence appears to provide the greatest effect. The reduction in PFJ loading when running in a control shoe at an increased cadence or running in a minimalist shoe is similar to that reported previously in healthy individuals when utilising an increased cadence10 or reduced step length.13 Our finding of a 27% reduction in PFJ stress when combining the minimalist shoe and increased cadence is also similar to the immediate reduction in PFJ stress reported in healthy individuals when changing from a rear foot to forefoot strike (27%).28 Taken together, it appears that any of these gait or shoe interventions are effective for acute reductions in PFJ load. Although an increased cadence results in a greater number of steps to cover any given distance, total stress per mile is still reduced in this condition compared to preferred cadence.13 Similar to previous research in healthy runners8 the predominant influence for the decrease in PFJ stress is likely attributable to the reduction in knee flexion during the stance phase of running. Although a reduction in knee flexion angle may reduce PFJ contact area and elevate PFJ stress, the large reduction in PFJ reaction force in a less flexed position has a greater overall bearing on PFJ stress.29 Importantly, the combination of a minimalist shoe and increased cadence had a greater effect on reducing the knee flexion angle, than either strategy alone. Although we did not quantify the efficacy of these strategies to reduce knee pain, the combination of running in a minimalist shoe at an increased cadence may be a viable treatment option for a runner with PFP. The aetiology of PFP is attributed to overloading,3,4 and individuals with PFP have been shown to exhibit elevated PFJ stress compared to healthy individuals in loaded knee flexed positions5 and during walking.18 Conversely, Wirtz et al.20 reported a small (SMD = 0.47) but non-significant difference in PFJ stress during running between healthy individuals and those with PFP. Although the mechanisms underpinning pain in those with PFP are not well understood, pain may be related to elevated patellar bone metabolic activity in this population6,7 attributable to elevated stress during locomotion. Indeed, wearing a knee brace during walking immediately reduced pain and PFJ stress in individuals with PFP.23 While further research is required to evaluate the effect of load reduction mechanisms on pain, the reduction in PFJ stress in our study was greater than that achieved with bracing which suggests that our findings may be clinically relevant.
Please cite this article in press as: Bonacci J, et al. The influence of cadence and shoes on patellofemoral joint kinetics in runners with patellofemoral pain. J Sci Med Sport (2017), https://doi.org/10.1016/j.jsams.2017.09.593
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Table 2 Mean (SD) measures during the four conditions and standardised mean difference (95% confidence interval) for comparisons of interest. Control shoe
Minimalist shoe
Control shoe and preferred cadence compared to
Preferred cadence
+10% preferred cadence
Preferred cadence
+10% preferred cadence
Control shoe and 10% preferred cadence
Minimal shoe and preferred cadence
Minimal shoe and +10% preferred cadence
Mean (SD)
Mean (SD)
Mean (SD)
Mean (SD)
SMD (95% CI)
SMD (95% CI)
SMD (95% CI)
Peak PFJ stress (MPa)
12.27 (2.92)
10.37 (1.99)
10.39 (1.93)
8.95 (2.32)
Peak PFJRF (N/kg)
43.14 (14.03)
35.08 (9.08)
35.93 (10.56)
30.03 (10.16)
1.08 (0.19)
1.08 (0.22)
0.95 (0.95)
37.03 (6.78)
38.03 (7.03)
35.61 (6.70)
−0.69 (−1.42 to 0.05) −0.68(−1.42 to 0.05) −0.61 (−1.33 to 0.14) −0.50 (−1.21 to 0.24)
−0.61 (−1.34 to 0.12) −0.58 (−1.29 to 0.17) −0.58 (−1.30 to 0.16) −0.35 (−1.06 to 0.38)
−1.04 (−1.81 to −0.28) −1.07 (−1.80 to −0.28) −1.05 (91.78 to −0.26) −0.70 (−1.42 to 0.06)
1.23 (0.29) Peak knee extensor moment (Nm/kg) Peak knee flexion angle 40.62 (7.60) (deg) PFJ: patellofemoral joint. PFJRF: patellofemoral joint reaction force. SD: standard deviation. SMD: standardised mean difference.
Fig. 1. Comparison of mean (SD) in peak patellofemoral stress (MPa) [A], patellofemoral joint reaction force (N/kg) [B], peak knee extensor moment (Nm/kg) [C], peak knee flexion angle (deg) [D] between conditions including individual data.
Strengths of our study include the randomisation of test conditions and homogenous group of patients with PFP. When drawing inferences from our data, several limitations of this study warrant consideration. Our estimates of PFJ loading are based on a simplified non-specific planar model that does not consider individual patella geometry, contact areas and three-dimensional patellar kinematics. Standardised control and minimalist footwear were used in this study and we did not account for participant’s foot type or usual footwear, therefore our findings should be generalised with caution beyond the minimalist footwear used in this study. We only tested a 10% increase in cadence on PFJ loading and it is not known what effect a smaller or larger change in cadence may have during running. The confidence intervals around the mean differences and SMD are reasonably large, which might be due to the sample size or it might be also due to individual variation in response. The clinician employing these strategies as part of a management plan for PFP is advised to consider that there might be differences in the way indi-
vidual patients respond. Further, we only examined changes in PFJ loading during a short running bout at a self-selected velocity. It is unclear if these changes persist over a longer period of running and at different velocities. Finally, we did not evaluate the effect of each intervention on pain, thus we cannot determine if the reduction in PFJ loading observed is associated with a reduction in pain.
5. Conclusion Running with an increased cadence and in a minimalist shoe both reduced PFJ loading in individuals with PFP. Combining the minimalist shoe with an increase in cadence had the greatest reduction effect on PFJ loads. These interventions may provide a simple strategy to unload the PFJ for the purposes of prevention and management of PFP. Further research is required to determine if the strategies evaluated in the current study reduce PFJ related pain.
Please cite this article in press as: Bonacci J, et al. The influence of cadence and shoes on patellofemoral joint kinetics in runners with patellofemoral pain. J Sci Med Sport (2017), https://doi.org/10.1016/j.jsams.2017.09.593
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Practical implications - Minimalist footwear can reduce PFJ loading during running in people with PFP. - Increasing cadence by 10% can reduce PFJ loading during running in people with PFP. - A combination of a minimalist shoe with an increased cadence has a greater effect on reducing PFJ loading than each strategy applied separately. Acknowledgements This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. MH is supported by the Sir Randal Haymanson Research Fellowship from the University of Melbourne. References 1. Taunton JE, Ryan MB, Clement DB et al. A retrospective case-control analysis of 2002 running injuries. Br J Sports Med 2002; 36(2):95–101. 2. Crossley KM, Stefanik JJ, Selfe J et al. Patellofemoral pain consensus statement from the 4th International Patellofemoral Pain Research Retreat, Manchester. Part 1: terminology, definitions, clinical examination, natural history, patellofemoral osteoarthritis and patient-reported outcome measures. Br J Sports Med 2016; 50(14):839–843. 3. Fulkerson JP, Shea KP. Mechanical basis for patellofemoral pain and cartilage breakdown, in Articular cartilage and knee joint function: basic science and athroscopy, Ewing JW, editor, New York, Raven Press, 1990. 4. Willson JD, Davis IS. Lower extremity mechanics of females with and without patellofemoral pain across activities with progressively greater task demands. Clin Biomech 2008; 23(2):203–211. 5. Farrokhi S, Keyak JH, Powers CM. Individuals with patellofemoral pain exhibit greater patellofemoral joint stress: a finite element analysis study. Osteoarthritis Cartilage 2011; 19(3):287–294. 6. Ho KY, Hu HH, Colletti PM et al. Running-induced patellofemoral pain fluctuates with changes in patella water content. Eur J Sport Sci 2014; 14(6):628–634. 7. Draper CE, Fredericson M, Gold GE et al. Patients with patellofemoral pain exhibit elevated bone metabolic activity at the patellofemoral joint. J Orthop Res 2012; 30(2):209–213. 8. Bonacci J, Vicenzino B, Spratford W et al. Take your shoes off to reduce patellofemoral joint stress during running. Br J Sports Med 2014; 48(6):425–428. 9. Heiderscheit BC, Chumanov ES, Michalski MP et al. Effects of step rate manipulation on joint mechanics during running. Med Sci Sports Exerc 2011; 43(2):296–302. 10. Lenhart RL, Thelen DG, Wille CM et al. Increasing running step rate reduces patellofemoral joint forces. Med Sci Sports Exerc 2014; 46(3):557–564.
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11. Firminger CR, Edwards WB. The influence of minimalist footwear and stride length reduction on lower-extremity running mechanics and cumulative loading. J Sci Med Sport 2016; 19(12):975–979. 12. Neal BS, Barton CJ, Gallie R et al. Runners with patellofemoral pain have altered biomechanics which targeted interventions can modify: a systematic review and meta-analysis. Gait Posture 2016; 45:69–82. 13. Willson JD, Sharpee R, Meardon SA et al. Effects of step length on patellofemoral joint stress in female runners with and without patellofemoral pain. Clin Biomech 2014; 29(3):243–247. 14. Collins N, Crossley K, Beller E et al. Foot orthoses and physiotherapy in the treatment of patellofemoral pain syndrome: randomised clinical trial. BMJ 2008; 337:a1735. 15. Mills K, Blanch P, Dev P et al. A randomised control trial of short term efficacy of in-shoe foot orthoses compared with a wait and see policy for anterior knee pain and the role of foot mobility. Br J Sports Med 2012; 46(4):247–252. 16. McLean SG, Su A, van den Bogert AJ. Development and validation of a 3-D model to predict knee joint loading during dynamic movement. J Biomech Eng 2003; 125(6):864–874. 17. Brechter JH, Powers CM. Patellofemoral joint stress during stair ascent and descent in persons with and without patellofemoral pain. Gait Posture 2002; 16(2):115–123. 18. Heino Brechter J, Powers CM. Patellofemoral stress during walking in persons with and without patellofemoral pain. Med Sci Sports Exerc 2002; 34(10):1582–1593. 19. Ward SR, Powers CM. The influence of patella alta on patellofemoral joint stress during normal and fast walking. Clin Biomech 2004; 19(10):1040–1047. 20. Wirtz AD, Willson JD, Kernozek TW et al. Patellofemoral joint stress during running in females with and without patellofemoral pain. Knee 2012; 19(5):703–708. 21. Powers CM, Ho KY, Chen YJ et al. Patellofemoral joint stress during weightbearing and non-weight-bearing quadriceps exercises. J Orthop Sports Phys Ther 2014; 44(5):320–327. 22. Ho KY, Blanchette MG, Powers CM. The influence of heel height on patellofemoral joint kinetics during walking. Gait Posture 2012; 36(2):271–275. 23. Powers CM, Ward SR, Chen YJ et al. The effect of bracing on patellofemoral joint stress during free and fast walking. Am J Sports Med 2004; 32(1):224–231. 24. van Eijden TM, Kouwenhoven E, Verburg J et al. A mathematical model of the patellofemoral joint. J Biomech 1986; 19(3):219–229. 25. van Eijden TM, Weijs WA, Kouwenhoven E et al. Forces acting on the patella during maximal voluntary contraction of the quadriceps femoris muscle at different knee flexion/extension angles. Acta Anat 1987; 129(4):310–314. 26. Powers CM, Lilley JC, Lee TQ. The effects of axial and multi-plane loading of the extensor mechanism on the patellofemoral joint. Clin Biomech 1998; 13(8):616–624. 27. Hopkins WB. A new view of statistics. Internet Society of Sports Sciences. Available from http://www.sportsci.org/resource/stats/index.html. [Cited 27 Feb 2011]. 28. Vannatta CN, Kernozek TW. Patellofemoral joint stress during running with alterations in foot strike pattern. Med Sci Sports Exerc 2015; 47(5):1001–1008. 29. Goudakos IG, Konig C, Schottle PB et al. Regulation of the patellofemoral contact area: an essential mechanism in patellofemoral joint mechanics? J Biomech 2010; 43(16):3237–3239.
Please cite this article in press as: Bonacci J, et al. The influence of cadence and shoes on patellofemoral joint kinetics in runners with patellofemoral pain. J Sci Med Sport (2017), https://doi.org/10.1016/j.jsams.2017.09.593
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Contents lists available at ScienceDirect
Journal of Science and Medicine in Sport journal homepage: www.elsevier.com/locate/jsams
Original research
The influence of cadence and shoes on patellofemoral joint kinetics in runners with patellofemoral pain Jason Bonacci a,∗ , Michelle Hall b , Aaron Fox a , Natalie Saunders a , Tristan Shipsides c , Bill Vicenzino d a
Centre for Sports Research, School of Exercise and Nutrition Sciences, Deakin University, Australia Centre for Health, Exercise and Sports Medicine, Department of Physiotherapy, University of Melbourne, Australia c Olympic Park Sports Medicine Centre, Australia d University of Queensland, School of Health and Rehabilitation Sciences: Physiotherapy, Australia b
a r t i c l e
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Article history: Received 27 February 2017 Received in revised form 7 July 2017 Accepted 26 September 2017 Available online xxx Keywords: Knee pain Footwear Gait Running Biomechanics
a b s t r a c t Objectives: To determine the effect of a combination of a minimalist shoe and increased cadence on measures of patellofemoral joint loading during running in individuals with patellofemoral pain. Design: Within-participant repeated measures with four conditions presented in random order: (1) control shoe at preferred cadence; (2) control shoe with +10% cadence; (3) minimalist shoe at preferred cadence; (4) minimalist shoe with +10% cadence. Methods: Fifteen recreational runners with patellofemoral pain ran on an instrumented treadmill while three-dimensional motion capture data were acquired. Peak patellofemoral joint stress, joint reaction force, knee extensor moment and knee joint angle during the stance phase of running were calculated. One-way repeated measures ANOVA was used to compare the control condition (1) to the three experimental conditions (2–4). Results: Running in a minimalist shoe at an increased cadence reduced patellofemoral stress and joint reaction force on average by approximately 29% (p < 0.001) compared to the control condition. Running in a minimalist shoe at preferred cadence reduced patellofemoral joint stress by 15% and joint reaction force by 17% (p < 0.001), compared to the control condition. Running in control shoes at an increased cadence reduced patellofemoral joint stress and joint reaction force by 16% and 19% (p < 0.001), respectively, compared to the control condition. Conclusions: In individuals with patellofemoral pain, running in a minimalist shoe at an increased cadence had the greatest reduction in patellofemoral joint loading compared to a control shoe at preferred cadence. This may be an effective intervention to modulate biomechanical factors related to patellofemoral pain. © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.
1. Introduction Patellofemoral pain (PFP) is the most common musculoskeletal complaint in runners.1 PFP is defined as pain around or behind the patella that is aggravated by weight bearing activities that load the patellofemoral joint (PFJ).2 Although the aetiology of PFP is not well understood, there is evidence to implicate the role of excessive PFJ stress in the pathophysiology of PFP.3–5 Repetitive high-frequency loading of the PFJ may exacerbate PFJ symptoms due to an elevated patellar water content6 or subchondral bone metabolic activity.7
∗ Corresponding author. E-mail address: [email protected] (J. Bonacci).
This suggests that it is worthwhile to evaluate strategies that reduce PFJ stress in those with PFP. In healthy individuals, evidence suggests that traditional cushioned footwear can elevate PFJ stress8 while an increased running cadence can reduce PFJ load.9 Running in traditional cushioned footwear can elevate PFJ stress via kinematics changes such as a longer stride length and greater knee flexion during stance that create a larger moment arm of the quadriceps muscles.8 An effective strategy to reduce stride length and knee flexion during stance is to increase running cadence.9,10 A 10% increase in running cadence has also been shown to reduce PFJ reaction force in healthy individuals.9,10 These findings suggest that utilising a less cushioned shoe or running with a higher cadence may be effective strategies to reduce PFJ loading in runners. Combining both
https://doi.org/10.1016/j.jsams.2017.09.593 1440-2440/© 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Bonacci J, et al. The influence of cadence and shoes on patellofemoral joint kinetics in runners with patellofemoral pain. J Sci Med Sport (2017), https://doi.org/10.1016/j.jsams.2017.09.593
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Table 1 Demographic and clinical characteristics of participants, described as mean (SD) or n (%) unless otherwise stated. Characteristics Age (years) Sex (F:M) Height (m) Body mass (kg) Body mass index (kg m−2 ) Anterior knee pain scalea Worst painb Duration of symptoms (months) Number with bilateral knee pain Running volume (km/wk)
n = 15 32.6 (9.6) 12:3 1.71 (0.06) 68.91 (10.99) 23.30 (3.07) 79.67 (6.99) 45.7 (17.3) 49.87 (48.38) Range (2–156) 5 (33%) 15.60 (7.4) Range (10–32)
a Anterior knee pain scale ranges from 0 to 100 points, where higher scores indicate less disability. b Pain measured on 100 mm visual analogue scale; 0 mm = no pain, 100 mm = worst pain imaginable.
the minimalist shoe and reduced step length may yield a greater reduction in knee joint load during running as compared to either minimalist footwear or reduced step length in isolation.11 Although data from healthy individuals support the use of minimalist footwear and gait modification to reduce PFJ load, these observations cannot be generalised to individuals with PFP. Individuals with PFP present with altered running biomechanics compared to healthy controls.12 Those with PFP have also demonstrated dissimilar changes in PFJ stress compared to healthy controls when altering step length during running.13 Taken together, an evaluation of the combined effect of minimalist shoes and gait modification on PFJ stress in individuals with PFP is needed. Given that higher PFJ stress is considered to adversely affect PFP patients,3 the primary aim of this study was to examine the effect of a minimalist shoe and increased running cadence on PFJ stress in individuals with PFP. We hypothesised that the combination of a minimalist shoes and increased cadence would have the greatest reduction in PFJ stress compared to control shoes and preferred cadence. Secondary aims of this study were to evaluate the effect of running in (1) a control shoe and increased cadence; (2) a minimalist shoe with preferred cadence; (3) a minimalist shoe and increased running cadence on PFJ reaction forces, knee extensor moment and knee flexion angle compared to a control shoe and preferred cadence. 2. Methods Fifteen recreational runners people who had clinically diagnosed PFP participated in this study. Descriptive characteristics are presented in Table 1. Participants were predominately female, had moderate level of anterior knee pain and ran on average approximately 16 km per week. The diagnosis of PFP was made based upon previous clinical trials,14,15 whereby participants were initially telephone-screened prior to a physical examination. The inclusion criteria were: (i) aged 18–40 years; (ii) running at least 10 km per week; (iii) non-traumatic retropatellar pain of greater than 6 weeks duration; (iv) aggravated by at least two of: running, hopping, squatting, prolonged sitting or kneeling; (v) pain severity ≥30/100 mm on a visual analogue scale; and (vi) pain on palpation of the patellar facet or during a double leg squat or step down from a 25 cm step. Exclusion criteria were: (i) concomitant injury or pathology of other knee structures (e.g. menisci, ligamentous, patellar tendon, iliotibial band); (ii) a history of lower limb surgery; (iii) pain or injury in the hip, pelvis or lumbar spine; and (iv) any foot condition that precluded use of a minimalist shoe. All participants self-reported a history of running in standard cushioned shoes. Written informed consent was obtained from all
participants and ethical approval was granted by the Deakin University Human Ethics Committee. Participants performed 5 min of running on an instrumented treadmill (Bertec, Ohio, USA) in four randomly ordered conditions: (1) control shoe at preferred cadence; (2) control shoe at +10% preferred cadence; (3) minimalist shoe at preferred cadence; and (4) minimalist shoe at +10% preferred cadence. Preferred cadence (steps/min) and foot-strike pattern was determined from sagittal plane video footage (Casio Exilim, Casio, Japan) during the final minute of a 4 min treadmill run in each shoe prior to data collection. A metronome (Seiko DM51, Seiko Instruments Inc, Japan) was used to control cadence during +10% conditions, and trials were only accepted if participants achieved the desired cadence. The control shoe was an Asics Gel-Cumulus 16, with a weight of 345 g, stack height of 31 mm and a 11 mm heel–toe offset. The minimalist shoe was a Vibram Seeya, with a weight of 136 g, stack height of 5 mm and a 0 mm heel–toe offset. A 5 min rest period was provided between conditions for recovery and to change shoes if required. An eight-camera VICON motion analysis system (Oxford Metrics Ltd, Oxford, UK), sampling at 250 Hz was used to capture threedimensional joint kinematics of the lower limb. Ground reaction force (GRF) data were collected at 1500 Hz from the instrumented treadmill in synchrony with the motion capture data. Thirty-two 14 mm retroflective markers were attached to anatomical landmarks in accordance with an established model.16 Markers were placed bilaterally on the iliac crest, anterior and posterior iliac spines, greater trochanter, anterior and lateral thigh and shank, medial and lateral epicondyles of the femur, medial and lateral malleolus, calcaneus and the base of the third and fifth metatarsals. Kinematic and GRF data were processed within Visual 3D software (C-Motion, Rockville, Maryland, USA). Marker trajectories and GRF data were low pass filtered with a 20 Hz cut-off frequency. The cutoff frequency was determined via a residual analysis and visual inspection of the resulting kinematic and GRF data. The net internal knee extension moment was obtained by submitting filtered kinematic and GRF to a conventional Newton-Euler inverse dynamics analysis. Joint moment data was normalised by body mass and reported in units of Nm/kg. Gait events were identified by the use of a 60 N threshold of the vertical GRF. Data were extracted for the affected limb for 20 strides during the final minute of the 5 min run in each condition using a customised MATLAB (Mathworks Inc, Natick, USA) programme. In the case of bilateral symptoms, the most symptomatic leg was used for analysis. Kinetic data related to the PFJ were derived from kinematic and kinetic data using a previously described biomechanical model.17–19 This model has been used to estimate PFJ reaction force (PFJRF) and stress during walking,18 running,8,20 and squatting21 and is sensitive to detect changes in PFJ stress with different footwear22 and knee braces.23 Quadriceps force was calculated for each knee flexion angle by dividing the net knee extensor moment by the effective lever arm for the quadriceps. The quadriceps effective lever arm was determined at each knee flexion angle by fitting a non-linear equation to the data of van Eijden et al.24 The PFJRF was estimated by multiplying the quadriceps force by a constant25 that defines the relationship between PFJRF and knee flexion angle. PFJ stress was estimated by dividing the PFJRF by PFJ contact area. PFJ contact area was estimated by fitting a fourth order polynomial curve to the contact areas for each knee flexion angle as reported previously.26 The output of the model was PFJRF and PFJ stress as a function of knee flexion angle during the stance phase of the gait cycle. The data for each participant were averaged over the 20 strides for each condition and normalised to the stance phase of the gait cycle. Variables of interest included: (1) peak PFJ stress; (2) peak PFJRF; (3) peak knee extensor moment and (4) peak knee flexion angle, which served as the dependent variables. The independent
Please cite this article in press as: Bonacci J, et al. The influence of cadence and shoes on patellofemoral joint kinetics in runners with patellofemoral pain. J Sci Med Sport (2017), https://doi.org/10.1016/j.jsams.2017.09.593
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variable was CONDITION. Statistical analysis was performed using SPSS version 24 (SPSS Inc., Chicago, IL, USA). Using a one-way repeated measures analysis of variance, pre-specified contrasts with Bonferoni correction (pair wise comparisons of interest) for levels within CONDITION were evaluated for each dependent variable. The pairwise comparisons of interest were: (a) control shoe and preferred cadence versus the same shoe and increased cadence; (b) control shoe and preferred cadence versus minimalist shoe and preferred cadence; and (c) control shoe and increased cadence versus minimalist shoe and increased cadence. CONDITION data are presented as individual data plots, as well as means and standard deviations (SD). Point estimates of effect are presented as standardised mean differences (SMD) and 95% confidence intervals (CI) between conditions, with the condition: control shoe and preferred cadence as the reference. SMD >1.2 are considered large, 0.61–1.2 as medium, 0.2–0.6 as small and <0.2 as trivial.27
3. Results A rearfoot strike landing pattern was evident in 14 of the 15 (93%) participants and 12 of the 15 (80%) participants when running at preferred cadence in the control and the minimalist shoe, respectively. The mean (SD) peak knee flexion angle, peak knee extensor moment and peak PFJRF and peak PRFS are presented in Table 2. The individual data plots exhibit the trend of a reduction across conditions for all PFJ measures with the combined minimalist shoe and 10% cadence condition being lower than the interventions applied separately (Fig. 1). Compared to running in the control shoe at preferred cadence, peak PFJ stress was lower running in the control shoe at increased cadence (mean difference: −15.5%, 95% CI: −27.5 to −3%, p = 0.009), running in the minimalist shoe at preferred cadence (mean difference: 15%, 95% CI: −24 to −7%, p < 0.001) and running in the minimalist shoe at increased cadence (mean difference: −27%, 95% CI: −39% to −15%, p < 0.001). The largest reduction in peak PFJ stress was observed running in the minimalist shoe at increased cadence compared to running in control shoe at preferred cadence (Table 2, Fig. 1A). Compared to running in the control shoe at preferred cadence, peak PFJRF was lower running in the control shoe at increased cadence (mean difference: −18.7%, 95% CI: −31.8 to −5.5%, p = 0.004) running in the minimalist shoe at preferred cadence (mean difference: −16.7%, 95% CI: −25.9 to −7.5%, p < 0.001) and running in the minimalist shoe at increased cadence (mean difference: −30.4%, 95% CI: −42.7 to −18.1%, p < 0.001). The largest reduction in peak PFJRF was observed running in the minimalist shoe at increased cadence compared to running in control shoe at preferred cadence (Table 2, Fig. 1B). Compared to running in the control shoe at preferred cadence, peak knee extensor moment was lower running in the control shoe at increased cadence (mean difference: −12.2%, 95% CI −23.6 to −1.6%, p = 0.019), running in the minimalist shoe at preferred cadence (mean difference: −13.0%, 95% CI: −19.5 to −6.5%, p < 0.001) and running in the minimalist shoe at increased cadence (mean difference: −23.6%, 95% CI: −34.1 to −13.0%, p < 0.001). The largest reduction in peak knee extensor moment was observed running in the minimalist shoe at increased cadence compared to running in the control shoe at preferred cadence (Table 2, Fig. 1C). Compared to running in the control shoe at preferred cadence, peak knee flexion angle was lower running in the control shoe at increased cadence (mean difference: −3.6◦ , 95% CI: −5.2 to −2.0◦ , p < 0.001), running in the minimalist shoe at preferred cadence (mean difference: −2.6◦ , 95% CI: −4.2 to −1.0◦ , p = 0.001) and running in the minimalist shoe at increased cadence (mean difference: −5.0◦ , 95% CI −7.6 to −2.4◦ , p < 0.001). The largest reduction in peak
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knee flexion angle was observed running in the minimalist shoe at increased cadence compared to running in control shoe at preferred cadence (Table 2, Fig. 1D).
4. Discussion The aim of this study was to determine the effects of a minimalist shoe and increased cadence on measures of PFJ loading and knee kinematics. Overall, we observed that both minimalist footwear and increased cadence can independently reduce PFJ reaction force and stress compared to running in control footwear at preferred cadence. Importantly, a combination of the minimalist footwear and increased cadence had the largest effect on the measures of PFJ loading assessed in this study. Our hypothesis that a combination of running in a minimalist shoe and increased cadence had the greatest reduction in PFJ stress was supported. In comparison to running in control shoes at preferred cadence, there was a 15% reduction in PFJ stress when running in the minimalist shoe and 16% reduction when running in the control shoe with an increased cadence. Notably, combining both the minimalist shoe and a 10% increase in cadence resulted in a 27% reduction in PFJ stress, which was greater than either the increased cadence or minimalist shoe applied separately. Should a clinician aim to reduce PFJ stress in an individual with PFP, utilising a minimalist shoe plus an increased cadence appears to provide the greatest effect. The reduction in PFJ loading when running in a control shoe at an increased cadence or running in a minimalist shoe is similar to that reported previously in healthy individuals when utilising an increased cadence10 or reduced step length.13 Our finding of a 27% reduction in PFJ stress when combining the minimalist shoe and increased cadence is also similar to the immediate reduction in PFJ stress reported in healthy individuals when changing from a rear foot to forefoot strike (27%).28 Taken together, it appears that any of these gait or shoe interventions are effective for acute reductions in PFJ load. Although an increased cadence results in a greater number of steps to cover any given distance, total stress per mile is still reduced in this condition compared to preferred cadence.13 Similar to previous research in healthy runners8 the predominant influence for the decrease in PFJ stress is likely attributable to the reduction in knee flexion during the stance phase of running. Although a reduction in knee flexion angle may reduce PFJ contact area and elevate PFJ stress, the large reduction in PFJ reaction force in a less flexed position has a greater overall bearing on PFJ stress.29 Importantly, the combination of a minimalist shoe and increased cadence had a greater effect on reducing the knee flexion angle, than either strategy alone. Although we did not quantify the efficacy of these strategies to reduce knee pain, the combination of running in a minimalist shoe at an increased cadence may be a viable treatment option for a runner with PFP. The aetiology of PFP is attributed to overloading,3,4 and individuals with PFP have been shown to exhibit elevated PFJ stress compared to healthy individuals in loaded knee flexed positions5 and during walking.18 Conversely, Wirtz et al.20 reported a small (SMD = 0.47) but non-significant difference in PFJ stress during running between healthy individuals and those with PFP. Although the mechanisms underpinning pain in those with PFP are not well understood, pain may be related to elevated patellar bone metabolic activity in this population6,7 attributable to elevated stress during locomotion. Indeed, wearing a knee brace during walking immediately reduced pain and PFJ stress in individuals with PFP.23 While further research is required to evaluate the effect of load reduction mechanisms on pain, the reduction in PFJ stress in our study was greater than that achieved with bracing which suggests that our findings may be clinically relevant.
Please cite this article in press as: Bonacci J, et al. The influence of cadence and shoes on patellofemoral joint kinetics in runners with patellofemoral pain. J Sci Med Sport (2017), https://doi.org/10.1016/j.jsams.2017.09.593
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Table 2 Mean (SD) measures during the four conditions and standardised mean difference (95% confidence interval) for comparisons of interest. Control shoe
Minimalist shoe
Control shoe and preferred cadence compared to
Preferred cadence
+10% preferred cadence
Preferred cadence
+10% preferred cadence
Control shoe and 10% preferred cadence
Minimal shoe and preferred cadence
Minimal shoe and +10% preferred cadence
Mean (SD)
Mean (SD)
Mean (SD)
Mean (SD)
SMD (95% CI)
SMD (95% CI)
SMD (95% CI)
Peak PFJ stress (MPa)
12.27 (2.92)
10.37 (1.99)
10.39 (1.93)
8.95 (2.32)
Peak PFJRF (N/kg)
43.14 (14.03)
35.08 (9.08)
35.93 (10.56)
30.03 (10.16)
1.08 (0.19)
1.08 (0.22)
0.95 (0.95)
37.03 (6.78)
38.03 (7.03)
35.61 (6.70)
−0.69 (−1.42 to 0.05) −0.68(−1.42 to 0.05) −0.61 (−1.33 to 0.14) −0.50 (−1.21 to 0.24)
−0.61 (−1.34 to 0.12) −0.58 (−1.29 to 0.17) −0.58 (−1.30 to 0.16) −0.35 (−1.06 to 0.38)
−1.04 (−1.81 to −0.28) −1.07 (−1.80 to −0.28) −1.05 (91.78 to −0.26) −0.70 (−1.42 to 0.06)
1.23 (0.29) Peak knee extensor moment (Nm/kg) Peak knee flexion angle 40.62 (7.60) (deg) PFJ: patellofemoral joint. PFJRF: patellofemoral joint reaction force. SD: standard deviation. SMD: standardised mean difference.
Fig. 1. Comparison of mean (SD) in peak patellofemoral stress (MPa) [A], patellofemoral joint reaction force (N/kg) [B], peak knee extensor moment (Nm/kg) [C], peak knee flexion angle (deg) [D] between conditions including individual data.
Strengths of our study include the randomisation of test conditions and homogenous group of patients with PFP. When drawing inferences from our data, several limitations of this study warrant consideration. Our estimates of PFJ loading are based on a simplified non-specific planar model that does not consider individual patella geometry, contact areas and three-dimensional patellar kinematics. Standardised control and minimalist footwear were used in this study and we did not account for participant’s foot type or usual footwear, therefore our findings should be generalised with caution beyond the minimalist footwear used in this study. We only tested a 10% increase in cadence on PFJ loading and it is not known what effect a smaller or larger change in cadence may have during running. The confidence intervals around the mean differences and SMD are reasonably large, which might be due to the sample size or it might be also due to individual variation in response. The clinician employing these strategies as part of a management plan for PFP is advised to consider that there might be differences in the way indi-
vidual patients respond. Further, we only examined changes in PFJ loading during a short running bout at a self-selected velocity. It is unclear if these changes persist over a longer period of running and at different velocities. Finally, we did not evaluate the effect of each intervention on pain, thus we cannot determine if the reduction in PFJ loading observed is associated with a reduction in pain.
5. Conclusion Running with an increased cadence and in a minimalist shoe both reduced PFJ loading in individuals with PFP. Combining the minimalist shoe with an increase in cadence had the greatest reduction effect on PFJ loads. These interventions may provide a simple strategy to unload the PFJ for the purposes of prevention and management of PFP. Further research is required to determine if the strategies evaluated in the current study reduce PFJ related pain.
Please cite this article in press as: Bonacci J, et al. The influence of cadence and shoes on patellofemoral joint kinetics in runners with patellofemoral pain. J Sci Med Sport (2017), https://doi.org/10.1016/j.jsams.2017.09.593
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Practical implications - Minimalist footwear can reduce PFJ loading during running in people with PFP. - Increasing cadence by 10% can reduce PFJ loading during running in people with PFP. - A combination of a minimalist shoe with an increased cadence has a greater effect on reducing PFJ loading than each strategy applied separately. Acknowledgements This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. MH is supported by the Sir Randal Haymanson Research Fellowship from the University of Melbourne. References 1. Taunton JE, Ryan MB, Clement DB et al. A retrospective case-control analysis of 2002 running injuries. Br J Sports Med 2002; 36(2):95–101. 2. Crossley KM, Stefanik JJ, Selfe J et al. Patellofemoral pain consensus statement from the 4th International Patellofemoral Pain Research Retreat, Manchester. Part 1: terminology, definitions, clinical examination, natural history, patellofemoral osteoarthritis and patient-reported outcome measures. Br J Sports Med 2016; 50(14):839–843. 3. Fulkerson JP, Shea KP. Mechanical basis for patellofemoral pain and cartilage breakdown, in Articular cartilage and knee joint function: basic science and athroscopy, Ewing JW, editor, New York, Raven Press, 1990. 4. Willson JD, Davis IS. Lower extremity mechanics of females with and without patellofemoral pain across activities with progressively greater task demands. Clin Biomech 2008; 23(2):203–211. 5. Farrokhi S, Keyak JH, Powers CM. Individuals with patellofemoral pain exhibit greater patellofemoral joint stress: a finite element analysis study. Osteoarthritis Cartilage 2011; 19(3):287–294. 6. Ho KY, Hu HH, Colletti PM et al. Running-induced patellofemoral pain fluctuates with changes in patella water content. Eur J Sport Sci 2014; 14(6):628–634. 7. Draper CE, Fredericson M, Gold GE et al. Patients with patellofemoral pain exhibit elevated bone metabolic activity at the patellofemoral joint. J Orthop Res 2012; 30(2):209–213. 8. Bonacci J, Vicenzino B, Spratford W et al. Take your shoes off to reduce patellofemoral joint stress during running. Br J Sports Med 2014; 48(6):425–428. 9. Heiderscheit BC, Chumanov ES, Michalski MP et al. Effects of step rate manipulation on joint mechanics during running. Med Sci Sports Exerc 2011; 43(2):296–302. 10. Lenhart RL, Thelen DG, Wille CM et al. Increasing running step rate reduces patellofemoral joint forces. Med Sci Sports Exerc 2014; 46(3):557–564.
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11. Firminger CR, Edwards WB. The influence of minimalist footwear and stride length reduction on lower-extremity running mechanics and cumulative loading. J Sci Med Sport 2016; 19(12):975–979. 12. Neal BS, Barton CJ, Gallie R et al. Runners with patellofemoral pain have altered biomechanics which targeted interventions can modify: a systematic review and meta-analysis. Gait Posture 2016; 45:69–82. 13. Willson JD, Sharpee R, Meardon SA et al. Effects of step length on patellofemoral joint stress in female runners with and without patellofemoral pain. Clin Biomech 2014; 29(3):243–247. 14. Collins N, Crossley K, Beller E et al. Foot orthoses and physiotherapy in the treatment of patellofemoral pain syndrome: randomised clinical trial. BMJ 2008; 337:a1735. 15. Mills K, Blanch P, Dev P et al. A randomised control trial of short term efficacy of in-shoe foot orthoses compared with a wait and see policy for anterior knee pain and the role of foot mobility. Br J Sports Med 2012; 46(4):247–252. 16. McLean SG, Su A, van den Bogert AJ. Development and validation of a 3-D model to predict knee joint loading during dynamic movement. J Biomech Eng 2003; 125(6):864–874. 17. Brechter JH, Powers CM. Patellofemoral joint stress during stair ascent and descent in persons with and without patellofemoral pain. Gait Posture 2002; 16(2):115–123. 18. Heino Brechter J, Powers CM. Patellofemoral stress during walking in persons with and without patellofemoral pain. Med Sci Sports Exerc 2002; 34(10):1582–1593. 19. Ward SR, Powers CM. The influence of patella alta on patellofemoral joint stress during normal and fast walking. Clin Biomech 2004; 19(10):1040–1047. 20. Wirtz AD, Willson JD, Kernozek TW et al. Patellofemoral joint stress during running in females with and without patellofemoral pain. Knee 2012; 19(5):703–708. 21. Powers CM, Ho KY, Chen YJ et al. Patellofemoral joint stress during weightbearing and non-weight-bearing quadriceps exercises. J Orthop Sports Phys Ther 2014; 44(5):320–327. 22. Ho KY, Blanchette MG, Powers CM. The influence of heel height on patellofemoral joint kinetics during walking. Gait Posture 2012; 36(2):271–275. 23. Powers CM, Ward SR, Chen YJ et al. The effect of bracing on patellofemoral joint stress during free and fast walking. Am J Sports Med 2004; 32(1):224–231. 24. van Eijden TM, Kouwenhoven E, Verburg J et al. A mathematical model of the patellofemoral joint. J Biomech 1986; 19(3):219–229. 25. van Eijden TM, Weijs WA, Kouwenhoven E et al. Forces acting on the patella during maximal voluntary contraction of the quadriceps femoris muscle at different knee flexion/extension angles. Acta Anat 1987; 129(4):310–314. 26. Powers CM, Lilley JC, Lee TQ. The effects of axial and multi-plane loading of the extensor mechanism on the patellofemoral joint. Clin Biomech 1998; 13(8):616–624. 27. Hopkins WB. A new view of statistics. Internet Society of Sports Sciences. Available from http://www.sportsci.org/resource/stats/index.html. [Cited 27 Feb 2011]. 28. Vannatta CN, Kernozek TW. Patellofemoral joint stress during running with alterations in foot strike pattern. Med Sci Sports Exerc 2015; 47(5):1001–1008. 29. Goudakos IG, Konig C, Schottle PB et al. Regulation of the patellofemoral contact area: an essential mechanism in patellofemoral joint mechanics? J Biomech 2010; 43(16):3237–3239.
Please cite this article in press as: Bonacci J, et al. The influence of cadence and shoes on patellofemoral joint kinetics in runners with patellofemoral pain. J Sci Med Sport (2017), https://doi.org/10.1016/j.jsams.2017.09.593