Increasing running step rate reduces patellofemoral joint forces

Altering Knee Abduction Angular Impulse Using Wedged Insoles for Treatment of Patellofemoral Pain in Runners: A Six-Week Randomized Controlled Trial

Objective

Determine if a change in internal knee abduction angular impulse (KAAI) is related to pain reduction for runners with patellofemoral pain (PFP) by comparing lateral and medial wedge insole interventions, and increased KAAI and decreased KAAI groups.

Design

Randomized controlled clinical trial (ClinicalTrials.gov ID# NCT01332110).

Setting

Biomechanics laboratory and community.

Patients

Thirty-six runners with physician-diagnosed PFP enrolled in the trial, and 27 were analyzed.

Interventions

Runners with PFP were randomly assigned to either an experimental 3 mm lateral wedge or control 6 mm medial wedge group. Participants completed a biomechanical gait analysis to quantify KAAIs with their assigned insole, and then used their assigned insole for six-weeks during their regular runs. Usual pain during running was measured at baseline and at six-week follow-up using a visual analog scale. Statistical tests were performed to identify differences between wedge types, differences between biomechanical response types (i.e. increase or decrease KAAI), as well as predictors of pain reduction.

Main Outcome Measures

Percent change in KAAI relative to neutral, and % change in pain over six weeks.

Results

Clinically meaningful reductions in pain (>33%) were measured for both footwear groups; however, no significant differences between footwear groups were found (p = 0.697). When participants were regrouped based on KAAI change (i.e., increase or decrease), again, no significant differences in pain reduction were noted (p = 0.146). Interestingly, when evaluating absolute change in KAAI, a significant relationship between absolute % change in KAAI and % pain reduction was observed (R² = 0.21; p = 0.030), after adjusting for baseline pain levels.

Conclusion

The greater the absolute % change in KAAI during running, the greater the % reduction in pain over six weeks, regardless of wedge type, and whether KAAIs increased or decreased. Lateral and medial wedge insoles were similar in effectiveness for treatment of PFP.

Clinical Relevance

Altering KAAI should be a focus of future PFP research. Lateral wedges should be studied further as an alternative therapy to medial wedges for management of PFP.

Trial Registration

ClinicalTrials.gov NCT01332110

Eight weeks gait retraining in minimalist footwear has no effect on running economy

PURPOSE

To evaluate the effects of an eight week combined minimalist footwear (MFW) and gait-retraining intervention on running economy (RE) and kinematics in conventional footwear runners.

METHODS

Twenty-three trained male runners (age: 43 ± 10 years, stature: 177.2 ± 9.2 cm, body mass: 72.8 ± 10.2 kg, V̇O2max: 56.5 ± 7.0 mL min(-1) kg(-1)) were recruited. Participants were assigned to either an intervention group (n = 13) who gradually increased exposure to MFW and also implemented gait-retraining over an eight week period. RE and kinematics were measured in both MFW and conventional running shoes (CRS) at pre-tests and eight weeks, in a random order. In contrast the control group (n = 10) had no MFW exposure or gait retraining and were only tested in CRS.

RESULTS

The MFW and gait re-training intervention had no effect on RE (p < .001). However, RE was significantly better in MFW (mean difference 2.72%; p = .002) at both pre and post-tests compared to CRS. Step frequency increased as a result of the intervention (+5.7 steps per minute [spm]; p < .001), and was also significantly higher in MFW vs. CRS (+7.5 spm; p < .001).

CONCLUSION

Whilst a better RE in MFW was observed when compared to CRS due to shoe mass, familiarization to MFW with gait-retraining was not found to influence RE.

Influence of step rate and quadriceps load distribution on patellofemoral cartilage contact pressures during running

Interventions used to treat patellofemoral pain in runners are often designed to alter patellofemoral mechanics. This study used a computational model to investigate the influence of two interventions, step rate manipulation and quadriceps strengthening, on patellofemoral contact pressures during running. Running mechanics were analyzed using a lower extremity musculoskeletal model that included a knee with six degree-of-freedom tibiofemoral and patellofemoral joints. An elastic foundation model was used to compute articular contact pressures. The lower extremity model was scaled to anthropometric dimensions of 22 healthy adults, who ran on an instrumented treadmill at 90%, 100% and 110% of their preferred step rate. Numerical optimization was then used to predict the muscle forces, secondary tibiofemoral kinematics and all patellofemoral kinematics that would generate the measured primary hip, knee and ankle joint accelerations. Mean and peak patella contact pressures reached 5.0 and 9.7MPa during the midstance phase of running. Increasing step rate by 10% significantly reduced mean contact pressures by 10.4% and contact area by 7.4%, but had small effects on lateral patellar translation and tilt. Enhancing vastus medialis strength did not substantially affect pressure magnitudes or lateral patellar translation, but did shift contact pressure medially toward the patellar median ridge. Thus, the model suggests that step rate tends to primarily modulate the magnitude of contact pressure and contact area, while vastus medialis strengthening has the potential to alter mediolateral pressure locations. These results are relevant to consider in the design of interventions used to prevent or treat patellofemoral pain in runners.

Individuals with isolated patellofemoral joint osteoarthritis exhibit higher mechanical loading at the knee during the second half of the stance phase

BACKGROUND

Patellofemoral joint osteoarthritis is a highly prevalent disease and an important source of pain and disability. Nonetheless, biomechanical risk factors associated with this disease remain unclear. The purpose of this study was to compare biomechanical factors that are associated with patellofemoral joint loading during walking between individuals with isolated patellofemoral joint osteoarthritis and no osteoarthritis.

METHODS

MR images of the knee were obtained using a 3D fast-spin echo sequence to identify patellofemoral joint cartilage lesions. Thirty-five subjects with isolated patellofemoral joint osteoarthritis (29 females) and 35 control subjects (21 females) walked at a self-selected speed and as fast as possible. Peak knee flexion moment, flexion moment impulse and peak patellofemoral joint stress during the first and second halves of the stance phase were compared between groups.

FINDINGS

When compared to the controls, individuals with patellofemoral joint osteoarthritis demonstrated significantly higher peak knee flexion moment (P=.03, Eta(2)=.07), higher knee flexion moment impulse (P=.03, Eta(2)=.07) and higher peak patellofemoral joint stress (P=.01, Eta(2)=.10) during the second half of the stance phase. No significant group difference was observed during the first half of the stance phase.

INTERPRETATION

Findings of this study suggest that increased mechanical loading (i.e. knee flexion moment, impulse and patellofemoral joint stress) during the second half of the stance phase is associated with patellofemoral joint osteoarthritis. Prevention and rehabilitation programs for patellofemoral joint osteoarthritis may focus on reducing the loading on the patellofemoral joint, specifically during late stance.

Cumulative loads increase at the knee joint with slow-speed running compared to faster running: a biomechanical study

STUDY DESIGN

Biomechanical cross-sectional study.

OBJECTIVE

To investigate the hypothesis that the cumulative load at the knee during running increases as running speed decreases.

BACKGROUND

The knee joint load per stride decreases as running speed decreases. However, by decreasing running speed, the number of strides per given distance is increased. Running a given distance at a slower speed may increase the cumulative load at the knee joint compared with running the same distance at a higher speed, hence increasing the risk of running-related injuries in the knee.

METHODS

Kinematic and ground reaction force data were collected from 16 recreational runners, during steady-state running with a rearfoot strike pattern at 3 different speeds (mean ± SD): 8.02 ± 0.17 km/h, 11.79 ± 0.21 km/h, and 15.78 ± 0.22 km/h. The cumulative load (cumulative impulse) over a 1000-m distance was calculated at the knee joint on the basis of a standard 3-D inverse-dynamics approach.

RESULTS

Based on a 1000-m running distance, the cumulative load at the knee was significantly higher at a slow running speed than at a high running speed (relative difference, 80%). The mean load per stride at the knee increased significantly across all biomechanical parameters, except impulse, following an increase in running speed.

CONCLUSION

Slow-speed running decreases knee joint loads per stride and increases the cumulative load at the knee joint for a given running distance compared to faster running. The primary reason for the increase in cumulative load at slower speeds is an increase in number of strides needed to cover the same distance.

Effect of Acute Alterations in Foot Strike Patterns during Running on Sagittal Plane Lower Limb Kinematics and Kinetics

The purpose of this study was to determine the effect of foot strike patterns and converted foot strike patterns on lower limb kinematics and kinetics at the hip, knee, and ankle during a shod condition. Subjects were videotaped with a high speed camera while running a 5km at self-selected pace on a treadmill to determine natural foot strike pattern on day one. Preferred forefoot group (PFFG, n = 10) and preferred rear foot group (PRFG, n = 11) subjects were identified through slow motion video playback (n = 21, age = 22.8±2.2 years, mass = 73.1±14.5 kg, height 1.75 ± 0.10 m). On day two, subjects performed five overground run trials in both their natural and unnatural strike patterns while motion and force data were collected. Data were collected over two days so that foot strike videos could be analyzed for group placement purposes. Several 2 (Foot Strike Pattern -forefoot strike [FFS], rearfoot strike [RFS]) x 2 (Group - PFFG, PRFG) mixed model ANOVAs (p < 0.05) were run on speed, active peak vertical ground reaction force (VGRF), peak early stance and mid stance sagittal ankle moments, sagittal plane hip and knee moments, ankle dorsiflexion ROM, and sagittal plane hip and knee ROM. There were no significant interactions or between group differences for any of the measured variables. Within subject effects demonstrated that the RFS condition had significantly lower (VGRF) (RFS = 2.58 ± .21 BW, FFS = 2.71 ± 0.23 BW), dorsiflexion moment (RFS = -2.6 1± 0.61 Nm·kg(-1), FFS = -3.09 ± 0.32 Nm·kg(-1)), and dorsiflexion range of motion (RFS = 17.63 ± 3.76°, FFS = 22.10 ± 5.08°). There was also a significantly higher peak plantarflexion moment (RFS = 0.23 ± 0.11 Nm·kg(-1), FFS = 0.01 ± 0.01 Nm·kg(-1)), peak knee moment (RFS = 2.61 ± 0.54 Nm·kg(-1), FFS = 2.39 ± 0.61 Nm·kg(-1)), knee ROM (RFS = 31.72 ± 2.79°, FFS = 29.58 ± 2.97°), and hip ROM (RFS = 42.72 ± 4.03°, FFS = 41.38 ± 3.32°) as compared with the FFS condition. This research suggests that acute changes in foot strike patterns during shod running can create alterations in certain lower limb kinematic and kinetic measures that are not dependent on the preferred foot strike pattern of the individual. This research also challenges the contention that the impact transient spike in the vertical ground reaction force curve is only present during a rear foot strike type of running gait. Key pointsFootstrike pattern changes should be individually considered and implemented based on individual histories/abilitiesForefoot strike patterns increase external dorsiflexion momentsRearfoot strike patterns increase external knee flexion momentsRecreational shod runners are able to mimic habitual mechanics of different foot strike patterns.

Lower limb control and strength in runners with and without patellofemoral pain syndrome

Recreational runners with patellofemoral pain syndrome (PFPS) have been shown to present altered movement kinematics, muscle activations, and ground reaction forces (GRF) during running as well as decreased lower limb strength. However, these variables have never been concurrently evaluated in a specific cohort. Therefore, the aim of this study was to compare lower limb control variables during running in recreational runners with and without PFPS. Lower limb control during treadmill running under typical training conditions (usual shoes, foot strike pattern, and speed) was compared between runners with (n=21) and without (n=20) PFPS using lower limb kinematics, electromyographic (EMG) recordings from representative muscles (gluteus medius/maximus, quadriceps and soleus), and vertical GRF. Isometric muscle strength was also evaluated. When comparing all runners from both groups, no between-group differences were found in variables commonly associated with PFPS such as peak hip adduction, hip internal rotation, contralateral pelvic drop, EMG of gluteal and quadriceps muscles, vertical loading rate, or lower limb strength. However, runners with PFPS showed significantly higher hip adduction at toe-off, lower excursion in hip adduction during late-stance, and longer duration of soleus activation. Sub-analyses were performed for females and for rearfoot strikers (RFS), and revealed that these subgroups accounted for most of between-group differences in hip adduction kinematics. Specifically for RFS with PFPS, lower activation of gluteus medius as well as lower GRF were observed. Our results suggest that deficits reported in runners with PFPS may vary depending on gender and on foot strike pattern.

In-field gait retraining and mobile monitoring to address running biomechanics associated with tibial stress fracture

We sought to determine if an in-field gait retraining program can reduce excessive impact forces and peak hip adduction without adverse changes in knee joint work during running. Thirty healthy at-risk runners who exhibited high-impact forces were randomized to retraining [21.1 (± 1.9) years, 22.1 (± 10.8) km/week] or control groups [21.0 (± 1.3) years, 23.2 (± 8.7) km/week]. Retrainers were cued, via a wireless accelerometer, to increase preferred step rate by 7.5% during eight training sessions performed in-field. Adherence with the prescribed step rate was assessed via mobile monitoring. Three-dimensional gait analysis was performed at baseline, after retraining, and at 1-month post-retraining. Retrainers increased step rate by 8.6% (P < 0.0001), reducing instantaneous vertical load rate (-17.9%, P = 0.003), average vertical load rate (-18.9%, P < 0.0001), peak hip adduction (2.9° ± 4.2 reduction, P = 0.005), eccentric knee joint work per stance phase (-26.9%, P < 0.0001), and per kilometer of running (-21.1%, P < 0.0001). Alterations in gait were maintained at 30 days. In the absence of any feedback, controls maintained their baseline gait parameters. The majority of retrainers were adherent with the prescribed step rate during in-field runs. Thus, in-field gait retraining, cueing a modest increase in step rate, was effective at reducing impact forces, peak hip adduction and eccentric knee joint work.

Association of previous injury and speed with running style and stride-to-stride fluctuations

Running-related injuries remain problematic among recreational runners. We evaluated the association between having sustained a recent running-related injury and speed, and the strike index (a measure of footstrike pattern, SI) and spatiotemporal parameters of running. Forty-four previously injured and 46 previously uninjured runners underwent treadmill running at 80%, 90%, 100%, 110%, and 120% of their preferred running speed. Participants wore a pressure insole device to measure SI, temporal parameters, and stride length (S(length)) and stride frequency (S(frequency)) over 2-min intervals. Coefficient of variation and detrended fluctuation analysis provided information on stride-to-stride variability and correlative patterns. Linear mixed models were used to compare differences between groups and changes with speed. Previously injured runners displayed significantly higher stride-to-stride correlations of SI than controls (P = 0.046). As speed increased, SI, contact time (T(contact)), stride time (T(stride)), and duty factor (DF) decreased (P < 0.001), whereas flight time (T(flight)), S(length), and S(frequency) increased (P < 0.001). Stride-to-stride variability decreased significantly for SI, T(contact), T(flight), and DF (P ≤ 0.005), as did correlative patterns for T(contact), T(stride), DF, S(length), and S(frequency) (P ≤ 0.044). Previous running-related injury was associated with less stride-to-stride randomness of footstrike pattern. Overall, runners became more pronounced rearfoot strikers as running speed increased.

Summer training factors and risk of musculoskeletal injury among high school cross-country runners

STUDY DESIGN

Prospective cohort.

OBJECTIVES

To examine the relationship between summer training practices and risk of injury during the first month of a high school interscholastic cross-country season.

BACKGROUND

Several prospective studies have reported a high incidence of injury in adolescent cross-country runners. However, limited reports exist on the role of summer training practices and risk of injury among these runners.

METHODS

Four hundred twenty-one athletes (186 girls, 235 boys) who competed in interscholastic cross-country were followed during a cross-country season. At the start of the season, all participants completed a questionnaire regarding summer training routines. Time-loss, running-related injuries were tracked during the subsequent season. Logistic regression analysis was used to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) for the risk of initial injury during the first month of the season associated with summer training variables.

RESULTS

Sixty-seven runners (15.9%) had a confirmed injury during the first month of the season, with a higher percent among girls (19.4%) than boys (13.2%) (P = .06). Overall, 60.1% of the participants ran during the summer prior to the season, with a significantly higher percent among girls (71.5%) than boys (51.1%) (P<.0001). Overall, no significant association (OR = 0.9; 95% CI: 0.5, 1.5; P = .90) was found between not running sometime during the preceding summer and increased risk of initial injury during the first month of the season. Among only the runners who ran during the summer, after adjusting for sex and prior injury, first-month injuries were more common among those who did not frequently alternate short and long mileage on different days (OR = 3.0; 95% CI: 1.4, 6.4; P = .005), and/or who ran 8 weeks or fewer (OR = 2.7; 95% CI: 1.2, 5.8; P = .01) during their summer training. Running 8 weeks or fewer (P = .03), not frequently alternating mileage on different days (P = .01), and running a higher percentage of time on predominantly hill (P = .001) and irregular terrains (P = .004) were associated with increased risk of injury for girls.

CONCLUSION

These findings suggest that injuries during the first month of the high school cross-country season may be reduced if runners who participate in summer training activities run a greater number of weeks and frequently vary their daily running mileage during the summer. For girls, training programs that reduce mileage on hills and irregular terrains may help to minimize the occurrence of running-related injury.

LEVEL OF EVIDENCE

Prognosis, level 1b-.

Ability of sagittal kinematic variables to estimate ground reaction forces and joint kinetics in running

STUDY DESIGN

Controlled laboratory study, cross-sectional design.

OBJECTIVE

To determine if sagittal kinematic variables can be used to estimate select running kinetics.

BACKGROUND

Excessive loading during running has been implicated in a variety of injuries, yet this information is typically not assessed during a standard clinical examination. Developing a clinically feasible strategy to estimate ground reaction forces and joint kinetics may improve the ability to identify those at an increased risk of injury.

METHODS

Three-dimensional kinematics and ground reaction forces of 45 participants were recorded during treadmill running at self-selected speed. Kinematic variables used to estimate specific kinetic metrics included vertical excursion of the center of mass, foot inclination angle at initial contact, horizontal distance between the center of mass and heel at initial contact, knee flexion angle at initial contact, and peak knee flexion angle during stance. Linear mixed-effects models were fitted to explore the association between the kinetic and kinematic measures, including step rate and sex, with final models created using backward variable selection.

RESULTS

Models were developed to estimate peak knee extensor moment (R(2) = 0.43), energy absorbed at the knee during loading response (R(2) = 0.58), peak patellofemoral joint reaction force (R(2) = 0.55), peak vertical ground reaction force (R(2) = 0.48), braking impulse (R(2) = 0.50), and average vertical loading rate (R(2) = 0.04).

CONCLUSION

Our findings suggest that insights into important running kinetics can be obtained from a subset of sagittal plane kinematics common to a clinical running analysis. Of note, the limb posture at initial contact influenced subsequent loading patterns in stance.

Hip muscle loads during running at various step rates

STUDY DESIGN

Controlled laboratory study, cross-sectional. Objectives To characterize hip muscle forces and powers during running, and to determine how these quantities change when altering step rate for a given running speed.

BACKGROUND

Hip musculature has been implicated in a variety of running-related injuries and, as such, is often the target of rehabilitation interventions, including resistance exercises and gait retraining. The differential contributions of the hip muscles to the task of running are not well understood, and may be important for recognizing the biomechanical mechanisms of running-related injuries and refining current treatment and prevention strategies.

METHODS

Thirty healthy participants ran at their preferred speed at 3 different step rates: 90%, 100%, and 110% of their preferred step rate. Whole-body kinematics and ground reaction forces were recorded. A 3-D musculoskeletal model was used to estimate muscle forces needed to produce the measured joint accelerations. Forces and powers of each muscle were compared across step-rate conditions.

RESULTS

Peak force produced by the gluteus medius during running was substantially greater than that of any other hip muscle, with the majority of muscles displaying a period of negative work immediately preceding positive work. The higher running step rate led to an increase in hip flexor, hamstring, and hip extensor loading during swing, but, conversely, substantially diminished peak force and work during loading response for several hip muscles, including the gluteal muscles and piriformis.

CONCLUSION

Increasing running step rate for a given running speed heightened hamstring and gluteal muscle loading in late swing, while decreasing stance-phase loading in the gluteal muscles and piriformis. These results may enable clinicians to support and refine current treatment strategies, including exercise prescription and gait retraining for running-related injuries.

Sagittal plane trunk posture influences patellofemoral joint stress during running

STUDY DESIGN

Cross-sectional, repeated-measures. Objectives To examine the association between sagittal plane trunk posture and patellofemoral joint (PFJ) stress, and to determine whether modifying sagittal plane trunk posture influences PFJ stress during running.

BACKGROUND

Patellofemoral pain is the most common injury among runners and is thought to be the result of elevated PFJ stress. While sagittal plane trunk posture has been shown to influence tibiofemoral joint mechanics, no study has examined the influence of trunk posture on PFJ kinetics.

METHODS

Twenty-four asymptomatic recreational runners (12 women, 12 men) ran overground at a speed of 3.4 m/s under 3 trunk-posture conditions: self-selected, flexed, and extended. Trunk and knee kinematics, ground reaction forces, and electromyographic signals from selected lower extremity muscles were obtained. A previously described PFJ biomechanical model was used to quantify PFJ stress.

RESULTS

The mean ± SD trunk flexion angles under the self-selected, flexed, and extended running conditions were 7.3° ± 3.6°, 14.1° ± 4.8°, and 4.0° ± 3.9°, respectively. A significant inverse relationship was observed between mean trunk flexion angle and peak PFJ stress during the self-selected condition (r = -0.60, P = .002). Peak PFJ stress was significantly lower in the flexed condition (mean ± SD, 20.2 ± 3.4 MPa; P<.001) and significantly higher in the extended condition (23.1 ± 3.4 MPa; P<.001) compared to the self-selected condition (21.5 ± 3.2 MPa).

CONCLUSION

Sagittal plane trunk posture has a significant influence on PFJ kinetics during running. Incorporation of a forward trunk lean may be an effective strategy to reduce PFJ stress during running.