Peak Patellofemoral Joint Stress Research Articles

Effects of Aging on Patellofemoral Joint Stress during Stair Negotiation on Challenging Surfaces

This study examined the effect of age and surface on patellofemoral joint (PFJ) stress magnitude and waveform during stair ascent and descent tasks. A total of 12 young and 12 older adults had knee biomechanics quantified while they ascended and descended stairs on normal, slick, and uneven surfaces. The peak of stance (0–100%) PFJ stress and associated components were submitted to a two-way repeated measures ANOVA, while the PFJ stress waveform was submitted to statistical parametric mapping two-way ANOVA. During stair ascent, older adults exhibited greater PFJ stress waveforms, from 55 to 59% and 74 to 84% of stance (p < 0.001) as well as greater PFJ stress–time integral across stance (p = 0.003), and later peak PFJ stress, than young adults (p = 0.002). When ascending on the uneven surface, participants exhibited smaller PFJ stress from 9 to 24% of stance compared to the normal surface, but greater PFJ stress from 75 to 88% and from 63 to 68% of stance (p < 0.001) as well as greater PFJ stress–time integrals compared to normal and slick surfaces (p < 0.032). During stair descent, older adults exhibited a smaller PFJ contact area range (p = 0.034) and peak knee flexion angle (p = 0.022) than young adults. When descending on the slick surface, participants exhibited smaller PFJ stress from 5 to 18% of stance, but greater stress, from 92 to 98% of stance (both: p < 0.001), compared to the normal surface. Negotiating slick and uneven stairs may produce knee biomechanics that increase PFJ stress, and the larger, later PFJ stress exhibited by older adults may further increase their risk of PFJ pain.

Acute effects of negative heel shoes on perceived pain and knee biomechanical characteristics of runners with patellofemoral pain.

To determine the effects of negative heel shoes on perceived pain and knee biomechanical characteristics of runners with patellofemoral pain (PFP) during running. Sixteen runners with PFP ran in negative (-11mm drops) and positive (5mm drops) heel shoes while visual analog scale (VAS) scores, retroreflective markers, and ground reaction force were acquired by applying a 10-cm VAS, infrared motion capture system, and a three-dimensional force plate. Knee moment, patellofemoral joint stress (PFJS), and other biomechanical parameters during the stance phase were calculated based on inverse dynamics and a biomechanical model of the patellofemoral joint. The foot inclination angle, peak PFJS during the stance phase, patellofemoral joint reaction force, knee extension moment, and quadriceps force at the time of peak PFJS of runners with PFP in negative heel shoes were lower than that in positive heel shoes, no significant difference was found in VAS scores, knee flexion angle, patellofemoral contact area, and quadriceps moment arm at the time of peak PFJS. Compared to positive heel shoes, running in negative heel shoes decreases peak PFJS in runners with PFP, which may decrease patellofemoral joint loading, thus reducing the possibility of further development of PFP. Sports Science Experiment Ethics Committee of Beijing Sport University. 2023095H, April 18, 2023 (prospectively registered).

Increasing Step Frequency Reduces Patellofemoral Joint Stress and Patellar Tendon Force Impulse More at Low Running Speed.

Patellofemoral pain syndrome and patellar tendinopathy are important running-related overuse injuries. This study investigated the interaction of running speed and step frequency alterations on peak and cumulative patellofemoral joint stress (PFJS) and patellar tendon force (PTF) parameters. Twelve healthy individuals completed an incremental running speed protocol on a treadmill at habitual, increased and decreased step frequency. Peak PFJS and PTF, peak rate of PFJS and PTF development, and PFJS and PTF impulse per kilometer (km) were calculated using musculoskeletal modeling. With increasing running speed, peak PFJS ( P < 0.001) and PTF ( P < 0.001) and peak rate of PFJS ( P < 0.001) and PTF ( P < 0.001) development increased, whereas PFJS ( P < 0.001) and PTF ( P < 0.001) impulse per km decreased. While increasing step frequency by 10%, the peak PFJS ( P < 0.001) and PTF ( P < 0.001) and the PFJS ( P < 0.001) and PTF ( P < 0.001) impulse per kilometer decreased. No significant effect of step frequency alteration was found for the peak rate of PFJS ( P = 0.008) and PTF ( P = 0.213) development. A significant interaction effect was found for PFJS ( P < 0.001) and PTF ( P < 0.001) impulse per km, suggesting that step frequency alteration was more effective at low running speed. The effectiveness of step frequency alteration on PFJS and PTF impulse per km is dependent on the running speed. With regard to peak PFJS and PTF, step frequency alteration is equally effective at low and high running speeds. Step frequency alteration was not effective for peak rate of PFJS and PTF development. These findings can assist the optimization of patellofemoral joint and patellar tendon load management strategies.

Effects of Limb Dominance on Patellofemoral Joint Loading During Gait at 12 Weeks After Anterior Cruciate Ligament Reconstruction.

Background:Patellofemoral joint complications have commonly been reported in long-term outcome studies for anterior cruciate ligament reconstruction (ACLR); however, the biomechanics in the early phases of rehabilitation that could be associated with the development of these abnormalities is unclear. Limb dominance may affect the biomechanics of the knee joint in patients after ACLR.Purpose:To compare knee joint loading between surgical and nonsurgical limbs at 12 weeks postoperatively in patients who underwent ACLR on either their dominant limb (ACL-D) or nondominant limb (ACL-ND).Study Design:Controlled laboratory study.Methods:Included were 54 patients (32 ACL-D and 22 ACL-ND). Peak and integrated patellofemoral joint stress (PFJS), peak patellofemoral joint reaction force (PFJRF), and peak knee extension moment (KEM) were assessed during the stance phase of gait while participants walked on a 10-m runway at a self-selected speed.Results:The surgical limb of the ACL-D group had significantly decreased peak PFJS (P < .001), integrated PFJS (P < .001), peak PFJRF (P < .001), and peak KEM (P < .001) compared to the nonsurgical limb. The surgical limb of the ACL-ND group demonstrated significantly increased peak PFJS (P = .001), integrated PFJS (P = .023), peak PFJRF (P < .001), and peak KEM (P = .001) compared to the nonsurgical limb. For the surgical limb, the ACL-ND group demonstrated significantly greater peak PFJS (P < .001), peak PFJRF (P < .001) , (PFJRF [P<.001]) and peak KEM (P < .001) than the ACL-D group. For the nonsurgical limb, the ACL-D group demonstrated greater peak PFJS (P < .001), integrated PFJS (P = .023), peak PFJRF (P = .003), and peak KEM (P < .001) than the ACL-ND group.Conclusion:Significantly larger knee joint loading on the surgical limb of the ACL-ND group and smaller knee joint loading on the surgical limb of the ACL-D group were observed compared to the contralateral nonsurgical limb, which suggests that limb dominance has a key role in loading at the knee joint during gait.Clinical Relevance:Altered knee joint loading during gait at 12 weeks after ACLR may lead to the development of patellofemoral joint abnormalities.

The effect of heel-to-toe drop of running shoes on patellofemoral joint stress during running

BackgroundTraditional running shoes with heel-to-toe drops is thought to be a contributor to increased patellofemoral joint stress, which is proposed as a mechanism of patellofemoral pain. Research questionIs there an increase in patellofemoral joint stress when running in shoes with drops compared to running in shoes without a drop? MethodsLower limbs kinematics and ground reaction force were collected from eighteen healthy runners during over-ground running in shoes with 15 mm, 10 mm, 5 mm drops, and without a drop. Patellofemoral joint force and stress were calculated from the kinematic and kinetic data using a biomechanical model of the patellofemoral joint. ResultsThe peak patellofemoral joint stress was increased by more than 15% when running in shoes with 15 mm and 10 mm drops compared to running in shoes without a drop (p = 0.003, p = 0.001). The knee flexion angle was significantly increased when running in shoes with 15 mm, 10 mm and 5 mm drops (p = 0.014, p = 0.003, p = 0.002), the knee extension moment (p = 0.009, p = 0.002) and patellofemoral joint force (p = 0.003, p = 0.001) were increased when running in shoes with 15 mm and 10 mm drops, compared to running in shoes without a drop. SignificanceCompared to running in shoes without a drop, running in shoes with drops > 5 mm increase the peak patellofemoral joint stress significantly, which is mainly due to the increased knee extension moment.

Effects Of Toe-in/ Out Toe-in Gait And Lateral Wedge Orthoses On Lower Extremity Joint Kinetics.

PURPOSE: The aim of the current investigation was to examine the effects of both lateral orthoses and toe-in/ toe-out foot progression angles on lower extremity joint loading during walking using a musculoskeletal simulation approach. METHODS: The current investigation examined 15 healthy males, walking in six different conditions (neutral, lateral orthoses, toe-in, lateral toe-in, toe-out and lateral toe-out). Walking kinematics were collected using an eight-camera motion capture system, and kinetics via an embedded piezoelectric force plate. Lower extremity joint loading was explored using a musculoskeletal simulation approach. RESULTS: This investigation showed that peak patellofemoral joint stress was greater in the neutral (3.96 KPa/BW) and lateral orthoses (4.20 KPa/BW) conditions compared to toe-in (3.33 KPa/BW), lateral toe-in (3.43 KPa/BW), toe-out (3.35 KPa/BW) and lateral toe-out (3.53 KPa/BW) and ankle joint impulse larger in the toe-in (1.65BW·s) and toe-out (1.62BW·s) foot progression angle modalities compared to neutral (1.51BW·s) and lateral orthoses (1.53BW·s). Furthermore, it was also shown that medial tibiofemoral impulse was statistically greater in the toe-in (1.20BW·s) and lateral toe-in (1.15BW·s) conditions compared to neutral (1.07BW·s), lateral orthoses (1.07BW·s), toe-out (1.09BW·s) and lateral toe-out (1.05BW·s). CONCLUSIONS: Therefore, the current investigation provides evidence that altering the foot progression angle may attenuate the risk from patellofemoral disorders whilst simultaneously enhancing the risk from degenerative ankle pathologies. Similarly, adopting a toe-in foot progression angle may also increase the risk from medial tibiofemoral degeneration.

The effect of speed on Achilles tendon forces and patellofemoral joint stresses in high-performing endurance runners.

Achilles tendinopathy and patellofemoral pain are common running injuries associated with increased Achilles tendon (AT) forces and patellofemoral joint (PFJ) stresses. This study examined AT forces and PFJ stresses at different running speeds in high-performing endurance runners. Twenty runners ran overground at four running speeds (3.3, 3.9, 4.8, and 5.6m/s). AT forces and PFJ stresses were estimated from kinematic and kinetic data. Repeated measures ANOVA with partial eta squared effect sizes was conducted to assess differences between running speeds. Increased peak AT forces (19.5%; p<0.001) and loading rates (57.3%; p<0.001) from 3.3m/s to 5.6m/s were observed. Cumulative AT loading was greater in the faster speeds compared to the slower speeds. Faster running speeds resulted in increased peak plantar flexor moments, increased peak plantar flexion angles, and a more flexed knee and an anterior center of pressure position at touchdown. Peak PFJ stress was lower in the slowest speed (3.3m/s) compared to the faster running speeds (3.9-5.6m/s; p=0.005). PFJ stress loading rate significantly increased (43.6%; p<0.001). Greater AT loading observed could be associated with strategies such as increased plantar flexor moments and altered lower body position at touchdown which are commonly employed to generate greater ground contact forces. Greater AT and PFJ loading rates were likely due to shorter ground contact times and therefore less time available to reach the peak. Running at faster speeds could increase the risk of developing Achilles tendinopathy and patellofemoral pain or limit recovery from these injuries without sufficient recovery.

Effects of toe-in/ out toe-in gait and lateral wedge orthoses on lower extremity joint kinetics; an exploration using musculoskeletal simulation and Bayesian contrasts

IntroductionThe aim of the current investigation was to examine the effects of both lateral orthoses and toe-in/ toe-out foot progression angles on lower extremity joint loading during walking using a musculoskeletal simulation approach.MethodsThe current investigation examined 15 healthy males, walking in 6 different conditions (neutral, lateral orthoses, toe-in, lateral toe-in, toe-out and lateral toe-out). Walking kinematics were collected using an eight-camera motion capture system, and kinetics via an embedded piezoelectric force plate. Lower extremity joint loading was explored using a musculoskeletal simulation approach.ResultsThis investigation showed that peak patellofemoral joint stress was greater in the neutral (3.96 kPa/BW) and lateral orthoses (4.20 kPa/BW) conditions compared to toe-in (3.33 kPa/BW), lateral toe-in (3.43 kPa/BW), toe-out (3.35 kPa/BW) and lateral toe-out (3.53 kPa/BW) and ankle joint impulse larger in the toe-in (1.65BW·s) and toe-out (1.62BW·s) foot progression angle modalities compared to neutral (1.51BW·s) and lateral orthoses (1.53BW·s). Furthermore, it was also shown that medial tibiofemoral impulse was statistically greater in the toe-in (1.20BW·s) and lateral toe-in (1.15BW·s) conditions compared to neutral (1.07BW·s), lateral orthoses (1.07BW·s), toe-out (1.09BW·s) and lateral toe-out (1.05BW·s).Conclusions Therefore, the current investigation provides evidence that altering the foot progression angle may attenuate the risk from patellofemoral disorders whilst simultaneously enhancing the risk from degenerative ankle pathologies. Similarly, adopting a toe-in foot progression angle may also increase the risk from medial tibiofemoral degeneration.

Comparisons of trunk and knee mechanics during various speeds of treadmill running between runners with and without patellofemoral pain: a preliminary study.

[Purpose] To determine if runners with patellofemoral pain (PFP) exhibit higher patellofemoral joint (PFJ) stress and trunk extension compared to pain-free runners during treadmill running. [Participants and Methods] Twelve runners (7 with PFP and 5 pain-free) participated in this study. Participants ran at 3 different running conditions: self-selected, fast (120% of self-selected), and slow (80% of self-selected) speeds. Kinematics and kinetics of trunk and lower extremities were obtained. PFJ stress, PFJ reaction force, and PFJ contact area were determined using a biomechanical model. Two-factor ANOVAs with repeated measures were used to compare outcome variables between 3 speeds and between 2 groups. [Results] There was no significant difference in peak PFJ stress between groups across the 3 speeds. Peak PFJ stress was lowest during slow running compared to fast and self-selected running speed conditions across both groups. No significant difference was found in trunk flexion angle, PFJ reaction force, or PFJ contact area between groups across the 3 speeds. [Conclusion] Runners with and without PFP exhibited similar peak PFJ stress and trunk flexion angle during treadmill running. This preliminary work does not support the theory that reduced trunk flexion during running contributes to increased PFJ stress in runners with PFP.

Sex-related Differences In Patellofemoral Joint Stress With Fighting And Approach Load Carriage

PURPOSE: Female Soldiers have 2.2x greater risk for patellofemoral pain (PFP) compared with male Soldiers. Females may experience larger increases in knee loads, versus males, with added load carriage, which is standardized in the military across sexes. Thus, we assessed sex-related differences in patellofemoral joint stress (PFJS) metrics with the addition of fighting (20 kg) and approach (35 kg) load carriage. METHODS: Via motion capture procedures, 34 healthy, well-trained individuals with load carriage experience (17 male(M):26.8 yrs±4.3, 78.9kg±6.8; 17 female(F); 23.8yrs±4.6, 64.3kg±8.1) completed instrumented treadmill trials (1.35 m/s) with and without 20-kg and 35-kg load carriage. Peak PFJS and PFJS loading rate were estimated with a musculoskeletal model and analyzed via repeated measure ANOVAs [Sex(2) x Load(3)]. Standard mean differences (SMD) were calculated on the relative change rate of PFJS metrics in males versus females with added load carriage. RESULTS: Significant Sex X Load interactions (p<0.01) were found for both peak PFJS and PFJS loading rate. While moderate SMDs were found between 0kg and 20kg carriage, large SMDs were found between 0kg and 35kg carriage indicating larger relative increases in PFJS metrics in females versus males. TABLE: Mean and standard deviations for variables.CONCLUSIONS: Females experienced greater relative increases in PFJS metrics with added load carriage compared with males, but only the approach load (35 kg) resulted in large SMDs. Thus, training volume, e.g., march distances, with approach loads should be increased more cautiously in females compared with males whereas fighting loads (20kg) appear less risky and may require minimal adjustments in training volume between sexes. These findings provide insight into why females have a disproportionately higher rate of PFP in the military than the general population.

Short-term effects of a trunk modification program on patellofemoral joint stress in asymptomatic runners

ObjectivesTo evaluate short-term effects of a four-week gait retraining program using visual feedback on trunk flexion angle, patellofemoral joint (PFJ) stress, lower extremity biomechanics and motor skill automaticity. DesignLongitudinal interventional study. SettingsUniversity research laboratory. ParticipantsTwelve asymptomatic recreational runners (seven male and five female). Main outcome measuresTrunk kinematics as well as lower extremity kinematics and kinetics were assessed prior to training at week 1 (baseline) and week 2, 3, 4 and 8 (retention). PFJ stress was computed using a sagittal plane model. A dual-task procedure was performed to examine automaticity. ResultsAt week 8, runners demonstrated 10.1° increase in trunk flexion angle (p < .001) and 17.8% reduction in peak PFJ stress (p < .001) compared to baseline. This is associated with a 16.8% decrease in knee extensor moment and less than 2.5° change in knee flexion angle. Participants also showed 33.3% increase in peak hip extensor moment and small reduction in peak ankle plantar flexor moment. Lastly, runners demonstrated automaticity of the modified skill with a dual-task cost of less than 3%. ConclusionThe gait retraining program is effective to elicit short term changes in trunk position, PFJ stress, and automaticity of the new motor skill.

Twelve-Week Gait Retraining Reduced Patellofemoral Joint Stress during Running in Male Recreational Runners.

Purpose To explore the changes in knee sagittal angle and moment and patellofemoral joint (PFJ) force and stress before and after 12-week gait retraining. Methods A total of 30 healthy male recreational runners were randomized into a control group (n = 15) who ran in their original strike pattern using minimalist shoes or experimental group (n = 15) who ran in a forefoot strike pattern using minimalist shoes during the 12-week gait retraining. The kinematic and kinetic data of the dominant leg of the participants during the 12 km/h running were collected by 3D motion capture systems and 3D force platforms. Besides, the biomechanical property of the PFJ was calculated on the basis of the joint force model and the regression equation of the contact area. Results After the 12-week gait retraining, 78% of the rearfoot strikers turned into forefoot strikers. Peak knee extension moment and peak PFJ stress decreased by 13.8% and 13.3% without altering the running speed, respectively. Meanwhile, no changes in maximum knee flexion angle/extension moment and PFJ force/stress were observed for the control group. Conclusion The 12-week gait retraining effectively reduced the PFJ stress, thereby providing a potential means of reducing the risk of patellofemoral pain syndrome while running.

Patellofemoral Joint Loading During Single-Leg Hopping Exercises.

Single-leg hopping is used to assess a dynamic knee stability. Patellofemoral pain is often experienced during these exercises, and different cadences of jumping are often used in rehabilitation for those with patellofemoral pain. No studies to date have examined patellofemoral joint loading during single-leg hopping exercise with different hopping cadences. To determine if single-leg hopping at 2 different cadences (50 and 100 hops per minute [HPM]) leads to a significant difference in patellofemoral joint loading variables. University research laboratory. Twenty-five healthy college-aged females (age 22.3 [1.8]y, height 171.4 [6.3]cm, weight 67.4 [9.5]kg, Tegner Activity Scale 4.75 [1.75]) participated. Three-dimensional kinematic and kinetic data were measured using a 15-camera motion capture system and force platform. Static optimization was used to calculate muscle forces and then used in a musculoskeletal model to determine patellofemoral joint stress (PFJS), patellofemoral joint reaction force (PFJRF), quadriceps force (QF), and PFJRF loading rate, during the first and last 50% of stance phase. Greater maximal PFJRF occurred at 100HPM, whereas greater PFJRF loading rate occurred at 50HPM. However, overall peak QF and peak PFJS were not different between the 2 cadences. At 50HPM, there was greater PFJS, PFJRF, peak PFJRF loading rate, and peak QF during the first 50% of stance when compared with the last 50%. Training at 50HPM may reduce PFJRF and PFJRF loading rate, but not PFJS or QF. Patellofemoral joint loading variables had significantly higher values during the first half of the stance phase at the 50HPM cadence. This may be important with training individuals with patellofemoral pain.

The influence of sagittal trunk posture on the magnitude and rate of patellofemoral joint stress during stair ascent in asymptomatic females

Background: Excessive patellofemoral joint stress (PFJS) is thought to be a contributory factor to patellofemoral pain (PFP). Thus, treatment strategies that minimize PFJS rate and magnitude during painful activities like stair ascent may be useful for optimizing outcomes for PFP patients. Sagittal plane trunk posture has been shown to influence PFJS during running although it is unknown if a similar relationship exists during stair ascent. Research Question: Does altering sagittal plane trunk posture affect PFJS rate and/or magnitude during stair ascent? Methods: Twenty asymptomatic females (23.4±2.5 yr; height: 164.4±7.9 cm; mass: 63.0±12.2 kg) performed 5 stair ascent trials (96 steps/min) during 3 conditions: self-selected trunk (SS), flexed trunk (FLX), and extended trunk (EXT). Three-dimensional kinematics (200 Hz) and ground reaction forces (2000 Hz) were collected during each trial. A previously described mathematical model was used to calculate PFJS that included subject-specific and non-subject-specific model inputs. Dependent variables included sagittal plane trunk angle, and the rates and magnitudes of PFJS, patellofemoral joint reaction force (PFJRF), and PFJ contact area during the stance phase of stair ascent. Results: Compared to SS, peak PFJS decreased during FLX (mean difference (MD)=2.6 MPa; p<0.001; 95%CI=2.2 to 2.9; effect size (ES)=5.2) and increased during EXT (MD=-3.3 MPa; p<0.001; 95%CI=-3.9 to -2.6; ES=-3.4). Similarly, PFJS rate decreased during FLX (MD=17.8 MPa/sec; p<0.001; 95%CI=13.6 to 21.9; ES=3.6) and increased during EXT (MD=-14 MPa/sec; 95%CI=-19.4 to -8.7; p<0.001; ES=-2.2). Significance: Sagittal plane trunk posture influences PFJS rate and magnitude during stair ascent in asymptomatic females. Increasing and decreasing forward trunk flexion resulted in decreased and increased PFJS respectively. Future studies should examine the effects of these movement strategy modifications on pain and function in patients with PFP.

Patellofemoral joint stress measured across three different running techniques

BackgroundPatellofemoral pain (PFP) is the most common running-related injury. It has been shown in previous studies that gait retraining may have a beneficial effect on patellofemoral joint stress (PFJS). Research questionIs there a reduction of PFJS across 4 running conditions: 1. runner’s typical rearfoot strike pattern, 2. forefoot landing, 3. step rate increase by 10% and 4. forward trunk lean? MethodsNineteen healthy runners (28.05 ± 5.03 years; 26.58 ± 8.85 km/week, 6.00 ± 4.51 years of running experience) completed one running trial for each condition, at the same subject-specific comfortable speed on a treadmill. Kinetic and kinematic data were collected and measures of hip, knee and ankle joint moments and PFJS were calculated. ResultsCompared to rearfoot strike condition, peak PFJS and PFJS-time integral per step were significantly (P < 0.01) lower during forefoot landing and step rate increase conditions. PFJS per kilometer was significantly reduced for forefoot landing (17.01%; P < 0.01) and increased step rate (12.90%; P = 0.003). Forward trunk lean technique showed no significant differences in peak PFJS (P = 0.187), PFJS-time integral per step (P = 0.815) and PFJS per kilometer (P = 0.077) compared to rearfoot strike pattern. InterpretationThe comparison between techniques revealed greater reductions on PFJS by forefoot landing, followed by 10% step rate increase condition. These changes were the result of different lower limb movement strategies across the 2 running conditions. We conclude that compared to a rearfoot strike pattern, both a forefoot landing and step rate increase result in lower cumulative PFJS joint stress in healthy runners, with the forefoot landing being the most effective. These running technique modifications could be recommended to reduce PFJS loads and may have implications for PFP prevention.

Patellofemoral joint stress during incline and decline running

ObjectivesTo compare patellofemoral joint (PFJ) stress between level, incline, and decline running. DesignExperimental study. SettingUniversity laboratory. ParticipantsTwenty recreational runners. Main outcome measuresKinematics and kinetics of the trunk and lower extremity were obtained under 3 treadmill conditions: level, 6° incline, and 6° decline. PFJ stress, PFJ reaction force, and PFJ contact area were determined using a biomechanical model. One-way ANOVAs with repeated measures and post-hoc analyses were used to compare outcome variables across the 3 conditions. ResultsPeak PFJ stress and PFJ stress-time integral (cumulative PFJ stress over the stance phase) during decline running were significantly higher than during level and incline running. There was no difference in peak PFJ stress and PFJ stress-time integral between level and incline running. The increased peak PFJ stress during decline running was related to increased PFJ reaction force, resulting from a decrease in trunk flexion angle. ConclusionsRunning on a decline treadmill resulted in higher peak PFJ stress and stress-time integral. Peak PFJ stress and PFJ stress-time integral were similar during level and incline running. Results from this study may be used to prevent excessive PFJ stress during decline running, by targeting a postural strategy utilizing increased trunk flexion.

Local associations between knee cartilage T1ρ and T2 relaxation times and patellofemoral joint stress during walking: A voxel-based relaxometry analysis

BackgroundThis study aimed to utilize voxel-based relaxometry (VBR) to examine local correlations between patellofemoral joint (PFJ) stress during gait and PFJ cartilage relaxation times. MethodsEighty-three subjects with and without PFJ osteoarthritis (OA) underwent knee magnetic resonance (MR) images using fast spin-echo, T1ρ and T2 relaxation time sequences. Patellar and trochlear cartilage relaxation times were computed for each voxel. Peak PFJ stress was computed during the stance phase from three-dimensional gait analysis. Statistical Parametric Mapping was used to perform VBR analyses. Pearson partial correlations were used to evaluate the associations between peak PFJ stress and cartilage relaxation times while controlling for age, sex, and body mass index. ResultsA higher percentage of the trochlear cartilage (15.9–29.1%) showed significant positive correlations between PFJ stress and T1ρ and T2 than the patellar cartilage (7.4–13.6%). Average correlation coefficient (R) of the voxels showing significant positive correlations ranged from 0.27 to 0.29. Subcompartment analysis revealed a higher percentage of lateral compartment cartilage (trochlea: 30.2–34.7%, patella: 8.1–14.8%) showed significant correlations between peak PFJ stress and T1ρ and T2 than the medial compartment cartilage (trochlea: 7.1–27.2%, patella: 5.5–5.9%). Subgroup analysis showed that larger percentages of PFJ cartilage demonstrated significant positive correlations with PFJ stress in subjects with PFJ OA than those without PFJ OA. ConclusionsThe findings of this study suggest that peak PFJ stress has a greater influence on the biochemical composition of the trochlear than the patellar cartilage, and the lateral than the medial PFJ compartment.

The influence of cadence and shoes on patellofemoral joint kinetics in runners with patellofemoral pain

ObjectivesTo 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. DesignWithin-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. MethodsFifteen 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). ResultsRunning 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. ConclusionsIn 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.

EFFECT OF HEEL LIFTS ON PATELLOFEMORAL JOINT STRESS DURING RUNNING

Patellofemoral pain is a debilitating injury for many recreational runners. Excessive patellofemoral joint stress may be the underlying source of pain and interventions often focus on ways to reduce patellofemoral joint stress. Heel lifts have been used as an intervention within Achilles tendon rehabilitation programs and to address leg length discrepancies. The purpose of this study was to examine the effect of running with heel lifts on patellofemoral joint stress, patellofemoral stress impulse, quadriceps force, step length, cadence, and other related kinematic and spatiotemporal variables. A repeated-measures research design. Sixteen healthy female runners completed five running trials in a controlled laboratory setting with and without 11mm heel lifts inserted in a standard running shoe. Kinetic and kinematic data were used in combination with a static optimization technique to estimate individual muscle forces. These data were inserted into a patellofemoral joint model which was used to estimate patellofemoral joint stress and other variables during running. When running with heel lifts, peak patellofemoral joint stress and patellofemoral stress impulse were reduced by a 4.2% (p=0.049) and 9.3% (p=0.002). Initial center of pressure was shifted anteriorly 9.1% when running with heel lifts (p<0.001) despite all runners utilizing a heel strike pattern. Dorsiflexion at initial contact was reduced 28% (p=0.016) when heel lifts were donned. No differences in step length and cadence (p>0.05) were shown between conditions. Heel lift use resulted in decreased patellofemoral joint stress and impulse without associated changes in step length or frequency, or other variables shown to influence patellofemoral joint stress. The center of pressure at initial contact was also more anterior using heel lifts. The use of heel lifts may have therapeutic benefits for runners with patellofemoral pain if the primary goal is to reduce patellofemoral joint stress. 3b.

Elevated Knee Joint Kinetics and Reduced Ankle Kinetics Are Present During Jogging and Hopping After Achilles Tendon Ruptures

Background: Deficits in plantarflexor function are common after an Achilles tendon rupture. These deficits may result in an altered distribution of joint loads during lower extremity tasks. Hypothesis: We hypothesized that, regardless of treatment, the Achilles tendon–ruptured limb would exhibit deficits in ankle kinematics and joint power while exhibiting elevated knee joint power and patellofemoral joint loads during walking, jogging, and hopping. We further hypothesized that this loading pattern would be most evident during jogging and hopping. Study Design: Controlled laboratory study. Methods: Thirty-four participants (17 participants treated surgically, 17 treated nonsurgically) were tested at a mean 6.1 ± 2.0 years after an Achilles tendon rupture. Lower extremity kinematics and kinetics were assessed while participants completed walking, jogging, and single-legged hopping trials. Patellofemoral joint stress was calculated via a musculoskeletal model. Data were analyzed via mixed-model repeated analyses of variance (α = .05) and the limb symmetry index (LSI). Results: No differences (P ≥ .05) were found between the surgical and nonsurgical groups. In both groups, large side-to-side deficits in the plantarflexion angle at toeoff (LSI: 53.5%-73.9%) were noted during walking, jogging, and hopping in the involved limb. Side-to-side deficits in the angular velocity were only present during jogging (LSI: 93.5%) and hopping (LSI: 92.5%). This pattern was accompanied by large deficits in eccentric (LSI: 80.8%-94.7%) and concentric (LSI: 82.2%-84.7%) ankle joint powers in the involved limb during all tasks. Interestingly, only jogging and hopping demonstrated greater knee joint loads when compared with the uninvolved limb. Concentric knee power was greater during jogging (LSI: 117.2%) and hopping (LSI: 115.9%) compared with the uninvolved limb. Similarly, peak patellofemoral joint stress was greater in the involved limb during jogging (LSI: 107.5%) and hopping (LSI: 107.1%), while only hopping had a greater loading rate of patellofemoral joint stress (LSI: 110.9%). Conclusion: Considerable side-to-side deficits in plantarflexor function were observed during walking, jogging, and hopping in patients after an Achilles tendon rupture. As a possible compensation, increased knee joint loads were present but only during jogging and hopping. Clinical Relevance: These data suggest that after an Achilles tendon rupture, patients may be susceptible to greater mechanical loading of the knee during sporting tasks, regardless of surgical or nonsurgical treatment.