Internal Knee Extensor Moment Research Articles

Patellar tendon shortening surgery restores the knee extensor mechanism in flexed knee gait in children with cerebral palsy

BackgroundThis study evaluated a patellar tendon shortening (PTS) surgical procedure that uses an overlapping repair combined with an additional Tycron non-absorbable suture to support the shortening in children with Cerebral Palsy (CP). This study aimed to outline this surgical technique and to evaluate its effectiveness in restoring the knee extensor mechanism. MethodsThe sagittal plane lower limb kinematics, peak knee extensor moment, gait deviation index (GDI), localised movement deviation profile (MDP), temporospatial parameters, passive knee extension ROM, quadriceps lag, and knee extensor strength were calculated pre- and postoperatively. To determine significant differences a robust linear regression model with high breakdown point and high efficiency was fitted to the data. ResultsIn this retrospective cohort study, a total of 41 patients with CP who were treated with unilateral or bilateral PTS in isolation or as part of single event multilevel surgery (SEMLS), with a mean age of 11.1 years were included. The knee extension angle improved at initial contact (p < 0.0001), and during stance phase (p < 0.0001). The peak internal knee extensor moment decreased during early (p = 0.0014) and late stance phase (p < 0.0001). The quadriceps lag decreased (p < 0.0001) and knee extensor strength increased (p < 0.0001). The GDI improved (p < 0.0001), as well as the localised MDP for sagittal angles (p < 0.0001) and moments (p = 0.0001). Walking speed (p = 1.0) remained unchanged, but the cadence decreased (p = 0.024) and step length increased (p = 0.0001). ConclusionsThe knee extension angle and moment during stance phase improved significantly. The children with CP in this study showed improvements in knee extensor strength and quadriceps lag. Thereby it can be concluded that the PTS procedure was able to restore the knee extensor mechanism effectively.

Walking speed does not affect net vastus lateralis fascicle length change on average during weight acceptance

Faster walking speeds increase the demand on quadriceps muscles to produce adequate force to decelerate body mass and control knee flexion. Quadriceps fascicle behavior (i.e., fascicle length changes) influences force generation, which in turn affects mechanical loading of the articular cartilage during walking and the biochemical environment of the knee joint. The fascicle behavior underlying different walking speeds remains unclear but should be characterized to better understand how the quadriceps muscles accommodate faster walking speeds, speeds that often associate with better cartilage health outcomes. Our purpose was to quantify quadriceps muscle net fascicle length change during weight acceptance across a range of walking speeds in the context of more well-documented changes in muscle activity and knee joint moments. We hypothesized that vastus lateralis (VL) fascicles in healthy young adults would produce force with more overall lengthening in early stance at faster walking speeds with concomitant increases in muscle–tendon unit (MTU) lengthening, internal peak knee extensor moment (pKEM), vertical ground reaction force (GRF), and muscle activity. Participants walked for two-minute trials at their preferred speed and at 0.75 m/s and 1.75 m/s. We found that on average, the VL accommodates the greater mechanical demands of walking at faster speeds with greater muscle activity and while resisting muscle lengthening behavior. We infer then that tendon stretch accommodates MTU lengthening in healthy young adults across a range of speeds and suggest these results motivate additional studies aimed at evaluating VL fascicle behavior individuals with known quadriceps strength deficits, inhibition, or heightened risk for developing osteoarthritis.

Total Support Moment Analysis Of The Stop-jump Task In Individuals Following Anterior Cruciate Ligament Reconstruction

Purpose: To examine total support moment in the sagittal plane and individual contribution from each joint during a dynamic sport task to understand the presence of compensatory strategies in a cohort of individuals who have undergone anterior cruciate ligament reconstruction (ACLR) and have been cleared for return-to-sport (RTS) Methods: Twenty-six individuals with unilateral ACLR and RTS clearance participated in the study (20.9 ± 6.6 years; 10.0 ± 1.7 months since surgery). Each participant completed a single-leg and double-leg stop jump task. These tasks were assessed using force plates and a 3D motion analysis system. Bilateral internal hip flexor/extensor, knee flexor/extensor, and ankle plantarflexor/dorsiflexor moments were calculated at peak vertical ground reaction force. The total support moment was calculated by summing these moments for each leg and the individual percent contribution was calculated. Paired t-tests were used to assess between-limb differences for each stop jump task in the following variables of interest: total support moment; hip, knee and ankle joint contributions to the total support moment; hip, knee and ankle moments; and peak vertical ground reaction force. Wilcoxon Signed Rank tests were used to compare variables that were not normally distributed. Statistical significance was set a priori at <0.05. Results: Internal knee extensor moment was lower in the involved limb compared to the uninvolved for both tasks (17.6%, P = 0.022; 18.4%, P = 0.008). The involved limb exhibited 18.2% decrease in knee joint contribution (P = 0.01) and 21.6% increase in ankle joint contribution (P = 0.016) to the total support moment compared to the uninvolved limb in the single-leg stop jump task. No significant between-limb differences were found for the total support moment. Conclusion: Following clearance for RTS, altered knee loading is still observed. These results suggest that compensation for the involved knee is likely due to redistribution of load to the knee of the uninvolved limb or to adjacent joints of the involved limb. A partial shift in joint contribution from the knee to the ankle during the single-leg stop jump task demonstrates intralimb compensation. Further studies are needed to investigate how these adaptations impact the prevalence of subsequent injury and poor joint health.

Force Platforms Can Accurately Predict Knee Kinetics Limb Asymmetry With Sit-to-stands During ACL Rehabilitation

Patients with ACL reconstruction presenting with lowered internal knee extensor moment during sports and mobility tasks exhibit markers of compromised articular cartilage health. Early detection and management of their knee extensor moment deficits during rehabilitation are paramount for risk reduction of future osteoarthritis. However, the technology to obtain knee moment data requires extensive training and financial resources. We seek a more affordable and less technically demanding clinical surrogate. PURPOSE: To determine if data obtained from two force platforms can accurately predict knee extensor moment asymmetry for diagnostic and training purposes early in rehabilitation. METHODS: The study is a retrospective analysis of 14 patients with unilateral ACL reconstruction who underwent motion analysis of a self-paced sit-to-stand from a 48 cm bench. All patients were engaged in rehabilitation at the time of testing. During testing, each foot was positioned on two lengthwise-aligned force platforms. Differences between limbs were tested with paired t-tests. Stepwise linear regression predicted limb symmetry in knee extensor moment with force platform variables of limb symmetry in peak aft forces (e.g. posterior), vertical forces, and differences in the fore-aft position of each leg's center of pressure. RESULTS: Patients presented with significant (p < 0.001) interlimb differences in knee extension moment (mean ± SD: involved = 0.62 ± 0.19 Nm/kg of body mass (BM); uninvolved = 1.06 ± 0.18), vertical ground reaction forces (p < 0.001, inv = 0.56 ± 0.05 BM; uninv = 0.66 ± 0.05), and aft forces (p < 0.001, inv = 0.024 ± 0.016 BM; uninv = 0.056 ± 0.021), and nearly significant for center of pressure position (p = 0.05, involved = 0.230 ± 0.04 m; uninvolved = 0.246 ± 0.026). The regression model explained a substantial portion of limb symmetry in knee extensor moment (R-squared = 0.887, p < 0.001) with all force platform variables contributing to the final model. CONCLUSIONS: The use of force platform parameters can strongly and accurately predict knee extensor moment asymmetry in patients with ACL reconstruction during rehabilitation. This prediction cluster is a promising and affordable alternative that may function as a surrogate measure of abnormal knee moment for retraining and improved clinical reasoning.

Iliotibial Band Autograft Provides the Fastest Recovery of Knee Extensor Mechanism Function in Pediatric Anterior Cruciate Ligament Reconstruction.

Iliotibial band autograft is an increasingly popular option for pediatric anterior cruciate ligament reconstruction (ACLR). The purpose of this study was to compare recovery of knee extensor mechanism function among pediatric patients who underwent ACLR using iliotibial band (IT), hamstring tendon (HT), quadriceps tendon (QT), and patellar tendon (PT) autografts. One hundred forty-five pediatric athletes (76 female; age 15.0, range 7–21 years) with recent (3–18 months) unilateral ACLR performed drop-jump landing and 45° cutting with 3D motion capture. Knee extensor mechanism function (maximum knee flexion angle, maximum internal knee extensor moment, energy absorption at knee) during the loading phase (foot contact to peak knee flexion) was compared among graft types (20 IT, 29 HT, 39 QT, 57 PT) and sides (ACLR or contralateral) using linear mixed models with sex, age, and time since surgery as covariates. Overall, knee flexion was significantly lower on the operated vs. contralateral side for HT, QT, and PT during both tasks (p < 0.03). All graft types exhibited lower knee extensor moments and energy absorption on the operated side during both movements (p ≤ 0.001). Kinetic asymmetry was significantly lower for IT compared with QT and PT during both movements (p ≤ 0.005), and similar patterns were observed for HT vs. QT and PT (p ≤ 0.07). Asymmetry was similar between IT and HT and between QT and PT. This study found that knee extensor mechanism function recovers fastest in pediatric ACLR patients with IT autografts, followed by HT, in comparison to QT and PT, suggesting that IT is a viable option for returning young athletes to play after ACLR.

EFFECT OF AUTOGRAFT TYPE ON RECOVERY OF KNEE EXTENSOR MECHANISM FUNCTION FOLLOWING ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION

Background:While multiple studies have shown clear benefits of autograft over allograft for anterior cruciate ligament reconstruction (ACLR) in young athletes, disagreement remains regarding the optimal autograft choice. Recovery from ACLR may be influenced by autograft type, which can include iliotibial band (IT), hamstring tendon (HT), quadriceps tendon (QT), or patellar tendon (PT) depending on skeletal maturity and surgeon preference.Hypothesis/Purpose:This study compared knee joint function among pediatric athletes with different types of ACLR autografts. We hypothesized that knee extensor function would recover faster for graft types that did not disrupt the knee extensor mechanism (i.e., IT and HT vs. PT and QT).Methods:This retrospective study examined 138 pediatric athletes (73 female; mean age 15.5, SD 2.2, range 8-21 years) who had undergone sports biomechanical testing in our motion analysis laboratory following recent unilateral ACLR (mean 7.7, range 3-18 months post-surgery). All reconstructions used autografts including 20 IT, 26 HT, 37 QT, and 55 PT. Lower extremity sagittal plane kinematics and kinetics were measured during vertical drop jump landing (41 cm height) and 45° cutting. Maximum knee flexion angles, internal knee extensor moments, and energy absorption during the landing phase (initial contact to peak knee flexion) of each movement were compared among graft types and sides (ACLR vs. contralateral) using linear mixed models with sex, age, and time since surgery as covariates.Results:Knee flexion was significantly lower on the operated vs. contralateral side for HT, QT, and PT during drop jump and for QT and PT during cutting (p<0.001). All graft types exhibited lower knee extensor moments and energy absorption on the operated side (p<0.05). This asymmetry was most pronounced for QT and PT and least pronounced for IT (Figure 1.1). Loading on the operated limb decreased from IT to HT to QT and PT, while loading on the contralateral limb increased similarly. Asymmetry of kinetics was significantly lower for IT compared with both QT and PT during both movements (p<0.01). Similar patterns were observed for HT but were not always statistically significant. No differences in asymmetry were observed between IT and HT or between QT and PT.Conclusion:Young athletes with IT and HT autografts exhibit greater engagement of the knee extensors during dynamic loading than peers with PT or QT autografts in the 18 months following ACLR. This may be due to extensor mechanism donor site morbidity associated with PT and QT grafts.Tables/Figures:Figure 1.1:.Comparison of operated (red) and contralateral (blue) limbs by graft type (model predicted average and 95% confidence interval)

Walking Biomechanics Associated With Patellofemoral Pain In Sedentary And Active Emerging Adult Women

About 50% of emerging adults do not meet the national physical activity recommendations. Risk of injury, like patellofemoral pain (PFP) during walking, may be a barrier to meeting the physical activity recommendations for sedentary emerging adults. PURPOSE: To determine if sedentary emerging adult women had walking biomechanics related to PFP compared to active emerging adult women. METHODS: As part of a larger study, 26 (12 sedentary, 14 active) emerging adult women (age:22(3) years; height: 1.58(0.08) m; mass: 58.4(8.7) kg) participated in the study. Anatomical and tracking retro-reflective markers were placed on body segments to record movement. Participants completed 5 good walking trials at 1.4 m/s (± 5%). Three-dimensional gait analysis was performed using motion capture sampling at 200 Hz and force platforms sampling at 1000Hz. Joint angles were determined using the joint coordinate system and moment was determined using inverse dynamics. The variables of interest were peak knee flexion angle, peak internal knee extensor moment (PKEM), knee abduction and external rotation angles at PKEM, and hip adduction and internal rotation angles at PKEM. Independent t-tests compared variables between sedentary and active emerging adult women. Effect sizes (d) were calculated for each variable. RESULTS: Knee external rotation angle at PKEM was significantly larger in sedentary compared to active emerging adult women (Table 1). There were no other significant differences between the sedentary and active groups for the remaining variables of interest. CONCLUSION: A larger knee external rotation angle at PKEM suggests higher pressure on the lateral patella in the sedentary versus active group. According to the pathomechanical model for PFP, high lateral pressure and associated high cartilage stress is a mechanism for the develop of PFP. Therefore, sedentary women may be more at risk for developing PFP during walking for exercise compared to active women.Table 1:: hip and knee biomechanics during walking in sedentary and active emerging adult women

Unintended Changes in Contralateral Limb as a Result of Acute Gait Modification.

Gait modification using real-time biofeedback is a conservative intervention associated with positive outcomes. Results from systematic reviews corroborate the effectiveness of various strategies employing real-time biofeedback for reducing estimated knee joint load. The effects on the nonmodified limb, however, remain unclear. Biomechanical changes to the nonmodified limb were investigated during unilaterally implemented medial knee thrust, lateral trunk lean, and toe-in foot progression. Nineteen healthy participants were recruited. Ten trials were completed for each gait condition including baseline. Assigned magnitude for each gait modification strategy was individualized based on the mean and SD of the gait parameter during baseline. Visual real-time biofeedback was provided. During medial knee thrust, participants' nonmodified limb presented with increased: first peak medial knee contact force, internal first peak knee extensor moment, as well as knee- and hip-flexion angles at internal first peak knee extensor moment. Observed biomechanical changes are elucidative of the body's attempt to attenuate increased external loads. These findings may carry significant implications for pathological populations. Load redistribution to the nonmodified side may result in unfavorable long-term outcomes particularly in patients with bilateral diagnosis. Future studies should explore acute and chronic changes in the nonmodified limb of individuals with knee osteoarthritis.

Investigation of the Effects of High-Intensity, Intermittent Exercise and Unanticipation on Trunk and Lower Limb Biomechanics During a Side-Cutting Maneuver Using Statistical Parametric Mapping

Whyte, EF, Richter, C, O'Connor, S, and Moran, KA. Investigation of the effects of high-intensity, intermittent exercise and unanticipation on trunk and lower limb biomechanics during a side-cutting maneuver using statistical parametric mapping. J Strength Cond Res 32(6): 1583-1593, 2018-Anterior cruciate ligament (ACL) injuries frequently occur during side-cutting maneuvers when fatigued or reacting to the sporting environment. Trunk and hip biomechanics are proposed to influence ACL loading during these activities. However, the effects of fatigue and unanticipation on the biomechanics of the kinetic chain may be limited by traditional discrete point analysis. We recruited 28 male, varsity, Gaelic footballers (21.7 ± 2.2 years; 178.7 ± 14.6 m; 81.8 ± 11.4 kg) to perform anticipated and unanticipated side-cutting maneuvers before and after a high-intensity, intermittent exercise protocol (HIIP). Statistical parametric mapping (repeated-measures analysis of varience) identified differences in phases of trunk and stance leg biomechanics during weight acceptance. Unanticipation resulted in less trunk flexion (p < 0.001) and greater side flexion away from the direction of cut (p < 0.001). This led to smaller (internal) knee flexor and greater (internal) knee extensor (p = 0.002-0.007), hip adductor (p = 0.005), and hip external rotator (p = 0.007) moments. The HIIP resulted in increased trunk flexion (p < 0.001) and side flexion away from the direction of cut (p = 0.038), resulting in smaller (internal) knee extensor moments (p = 0.006). One interaction effect was noted demonstrating greater hip extensor moments in the unanticipated condition post-HIIP (p = 0.025). Results demonstrate that unanticipation resulted in trunk kinematics considered an ACL injury risk factor. A subsequent increase in frontal and transverse plane hip loading and sagittal plane knee loading was observed, which may increase ACL strain. Conversely, HIIP-induced trunk kinematic alterations resulted in reduced sagittal plane knee and subsequent ACL loading. Therefore, adequate hip and knee control is important during unanticipated side-cutting maneuvers.

The effect of ankle foot orthosis alignment on walking in individuals treated for traumatic lower extremity injuries

Limb salvage surgeries are performed to treat a variety of lower limb pathologies and traumatic injuries. Individuals who have undergone limb salvage surgeries may require an ankle foot orthosis (AFO) to compensate for limb impairments and restore walking ability. Understanding the effects of AFO design parameters on gait biomechanics is important to refine AFO prescription criteria. In this study sagittal plane kinematic and kinetic data, muscle activity and alignment preference were examined as individuals treated for traumatic lower extremity injuries (N=12) walked over level ground with Plantarflexed (PF), Neutral, and Dorsiflexed (DF) aligned AFOs. A PF alignment resulted in earlier center of pressure progression (p<0.007) and a resulting decrease in both internal knee extensor moment (p<0.001) and quadriceps and soleus muscle activity (p<0.014) compared to the Neutral and DF alignments without affecting the lower limb support moment. A clear alignment preference was observed, with eight participants preferring the PF over the Neutral and DF alignments. The increase in internal knee extensor moment between the PF and DF alignments in the present study is consistent with previous investigations in other patient populations, suggesting a more DF aligned AFO may affect the knee joint moment similarly across patient populations. The results of this study suggest AFO alignment is an important design parameter that affects ankle and knee joint moments and muscle activity and should be carefully considered during AFO design and clinical fitting.

The effect of high intensity exercise and anticipation on trunk and lower limb biomechanics during a crossover cutting manoeuvre

ABSTRACTWe investigated the effects of high intensity, intermittent exercise (HIIP) and anticipation on trunk, pelvic and lower limb biomechanics during a crossover cutting manoeuvre. Twenty-eight male, varsity athletes performed crossover cutting manoeuvres in anticipated and unanticipated conditions pre- and post-HIIP. Kinematic and kinetic variables were captured using a motion analysis system. Statistical parametric mapping (repeated-measures ANOVA) was used to identify differences in biomechanical patterns. Results demonstrated that both unanticipation and fatigue (HIIP) altered the biomechanics of the crossover cutting manoeuvre, whereas no interactions effects were observed. Unanticipation resulted in less trunk and pelvic side flexion in the direction of cut (d = 0.70 – 0.79). This led to increased hip abductor and external rotator moments and increased knee extensor and valgus moments with small effects (d = 0.24–0.42), potentially increasing ACL strain. The HIIP resulted in trivial to small effects only with a decrease in internal knee rotator and extensor moment and decreased knee power absorption (d = 0.35), reducing potential ACL strain. The effect of trunk and hip control exercises in unanticipated conditions on the crossover cutting manoeuvre should be investigated with a view to refining ACL injury prevention programmes.

Sagittal-Plane Knee Moment During Gait and Knee Cartilage Thickness.

Understanding the factors associated with thicker cartilage in a healthy population is important when developing strategies aimed at minimizing the cartilage thinning associated with knee osteoarthritis progression. Thicker articular cartilage is commonly thought to be healthier cartilage, but whether the sagittal-plane biomechanics important to gait are related to cartilage thickness is unknown. To determine the relationship of a weight-bearing region of the medial femoral condyle's cartilage thickness to sagittal gait biomechanics in healthy individuals. Descriptive laboratory study. Laboratory. Twenty-eight healthy participants (15 women: age = 21.1 ± 2.1 years, height = 1.63 ± 0.07 m, weight = 64.6 ± 9.9 kg; 13 men: age = 22.1 ± 2.9 years, height = 1.79 ± 0.05 m, weight = 75.2 ± 9.6 kg). Tibiofemoral angle (°) was obtained via goniometric assessment, thickness of the medial femoral condyle cartilage (mm) was obtained via ultrasound imaging, and peak internal knee-extensor moment (% body weight · height) was measured during 10 trials of over-ground walking at a self-selected pace. We used linear regression to examine the extent to which peak internal knee-extensor moment predicted cartilage thickness after accounting for tibiofemoral angle and sex. Sex and tibiofemoral angle (12.3° ± 3.2°) were entered in the initial step as control factors (R2 = 0.01, P = .872). In the final step, internal knee-extensor moment (1.5% ± 1.3% body weight · height) was entered, which resulted in greater knee-extensor moment being related to greater cartilage thickness (2.0 ± 0.3 mm; R2Δ = 0.31, PΔ = .003). Individuals who walked with a greater peak internal knee-extensor moment during gait had a cartilage structure that is generally considered beneficial in a healthy population. Our study offers promising findings that a potentially modifiable biomechanical factor is associated with cartilage status in a healthy population. Establishing these baseline relationships in uninjured populations may help us to better understand potential factors related to maladaptive gait patterns that predispose a person to adverse changes in the cartilage environment.

The Shank-to-Vertical-Angle as a parameter to evaluate tuning of Ankle-Foot Orthoses

The effectiveness of an Ankle-Foot Orthosis footwear combination (AFO-FC) may be partly dependent on the alignment of the ground reaction force with respect to lower limb joint rotation centers, reflected by joint angles and moments. Adjusting (i.e. tuning) the AFO-FC's properties could affect this alignment, which may be guided by monitoring the Shank-to-Vertical-Angle. This study aimed to investigate whether the Shank-to-Vertical-Angle during walking responds to variations in heel height and footplate stiffness, and if this would reflect changes in joint angles and net moments in healthy adults. Ten subjects walked on an instrumented treadmill and performed six trials while walking with bilateral rigid Ankle-Foot Orthoses. The AFO-FC heel height was increased, aiming to impose a Shank-to-Vertical-Angle of 5°, 11° and 20°, and combined with a flexible or stiff footplate. For each trial, the Shank-to-Vertical-Angle, joint flexion–extension angles and net joint moments of the right leg at midstance were averaged over 25 gait cycles. The Shank-to-Vertical-Angle significantly increased with increasing heel height (p<0.001), resulting in an increase in knee flexion angle and internal knee extensor moment (p<0.001). The stiff footplate reduced the effect of heel height on the internal knee extensor moment (p=0.030), while the internal ankle plantar flexion moment increased (p=0.035). Effects of heel height and footplate stiffness on the hip joint were limited. Our results support the potential to use the Shank-to-Vertical-Angle as a parameter to evaluate AFO-FC tuning, as it is responsive to changes in heel height and reflects concomitant changes in the lower limb angles and moments.

Muscle Co-contractions Worsen In The ACL Reconstructed Limb When Gait Is Challenged Compared To Normal Gait

PURPOSE: Greater and more symmetrical IKEM predict better functional outcomes after anterior cruciate ligament reconstruction (ACLR). Challenging walking tasks create greater internal knee extensor moments (IKEM) than normal walking after ACLR. Exploring muscle activity during normal and challenging walking could elucidate the underlying muscle responses to increased knee moments. METHODS: Three females (5-12 months post ACLR) who were cleared to return to sports participated. Subjects first completed normal walking followed by walking with a 50% body weight load while towing a sled and wearing a weighted vest. Order of the loaded conditions was randomized. Muscle activity of the medial and lateral quadriceps and hamstrings was measured bilaterally with surface electrodes (Fig 2). Walking speed was controlled. IKEM impulses and muscle activity while generating an IKEM were calculated during the stance phase of the task. Integrated electromyography (EMG) data were normalized to maximal EMG activity during a voluntary isometric contraction (MVIC). RESULTS: Descriptive statistics demonstrate that IKEM impulses and quadriceps activity increased when challenged (vest and sled) compared to normal walking. (Fig 1 and 2) EMG activity was greater in the ACLR limb across tasks, though the confidence intervals were large. (Fig 2) Though the small sample size was not powered to determine statistical significance, the greater magnitude of co-contraction activity in the ACLR limb was apparent for all females across all walking tasks. CONCLUSION: Quadriceps muscle activity increased along with IKEM impulses as expected. The asymmetrical muscle activity and large magnitude of hamstring activity was not expected. High levels of muscle co-contractions to achieve greater IKEM in the ACLR limb in these females is concerning.

Cutting mechanics: relation to performance and anterior cruciate ligament injury risk.

Quick changes of direction during running (cutting) are necessary for successful performance of many sports but are associated with noncontact anterior cruciate ligament (ACL) injuries. Currently, it is not known how biomechanics associated with fast performance of cutting tasks relate to the mechanics associated with increased risk for injury. Without this knowledge, the technique emphasized in injury prevention programs may be at odds with the demands of cutting tasks. The purposes of this study were to 1) identify whole body and/or joint mechanics that are related to completion times of 45° and 90° cuts and, from these variables, 2) determine which variables are predictors of performance (i.e., completion time) and/or ACL injury risk (i.e., peak knee adductor moment). Whole body and joint biomechanics were analyzed during the execution of two sidestep cutting maneuvers (to 45° and 90°) in 25 healthy experienced soccer players. Pearson correlation coefficients and stepwise multiple regression were used to analyze relations between variables. The variables predictive of 45° cut performance included hip extensor moment and hip sagittal plane power generation as well as medial-lateral center-of-mass to center-of-pressure separation distance. This separation distance was also predictive of peak knee adductor moment. During the 90° cut, medial-lateral ground reaction force impulse and hip frontal plane power generation were predictive of performance whereas hip internal rotation and knee extensor moment were predictive of peak knee adductor moment. These relations have important implications for ACL injury prevention programs. Although restricting frontal and transverse plane movement has been emphasized in many programs, these movement recommendations may not be appropriate for cutting tasks performed at greater angles.

Propulsion phase of the single leg triple hop test in women with patellofemoral pain syndrome: a biomechanical study.

Asymmetry in the alignment of the lower limbs during weight-bearing activities is associated with patellofemoral pain syndrome (PFPS), caused by an increase in patellofemoral (PF) joint stress. High neuromuscular demands are placed on the lower limb during the propulsion phase of the single leg triple hop test (SLTHT), which may influence biomechanical behavior. The aim of the present cross-sectional study was to compare kinematic, kinetic and muscle activity in the trunk and lower limb during propulsion in the SLTHT using women with PFPS and pain free controls. The following measurements were made using 20 women with PFPS and 20 controls during propulsion in the SLTHT: kinematics of the trunk, pelvis, hip, and knee; kinetics of the hip, knee and ankle; and muscle activation of the gluteus maximus (GM), gluteus medius (GMed), biceps femoris (BF) and vastus lateralis (VL). Differences between groups were calculated using three separate sets of multivariate analysis of variance for kinematics, kinetics, and electromyographic data. Women with PFPS exhibited ipsilateral trunk lean; greater trunk flexion; greater contralateral pelvic drop; greater hip adduction and internal rotation; greater ankle pronation; greater internal hip abductor and ankle supinator moments; lower internal hip, knee and ankle extensor moments; and greater GM, GMed, BL, and VL muscle activity. The results of the present study are related to abnormal movement patterns in women with PFPS. We speculated that these findings constitute strategies to control a deficient dynamic alignment of the trunk and lower limb and to avoid PF pain. However, the greater BF and VL activity and the extensor pattern found for the hip, knee, and ankle of women with PFPS may contribute to increased PF stress.

CSM 2014 Sports Physical Therapy Section Platform Presentations (Abstracts SPL1–SPL66)

CSM 2014 Sports Physical Therapy Section Platform Presentations (Abstracts SPL1–SPL66)

Activity progression for anterior cruciate ligament injured individuals

BackgroundFunctional exercises are important in the rehabilitation of anterior cruciate ligament deficient and reconstructed individuals but movement compensations and incomplete recovery persist. This study aimed to identify how tasks pose different challenges; and evaluate if different activities challenge patient groups differently compared to controls. MethodsMotion and force data were collected during distance hop, squatting and gait for 20 anterior cruciate ligament deficient, 21 reconstructed and 21 controls. FindingsKnee range of motion was greatest during squatting, intermediate during hopping and smallest during gait (P<0.01). Peak internal knee extensor moments were greatest during distance hop (P<0.01). The mean value of peak knee moments was reduced in squatting and gait (P<0.01) compared to hop. Peak internal extensor moments were significantly larger during squatting than gait and peak external adductor moments during gait compared to squatting (P<0.01). Fluency was highest during squatting (P<0.01). All patients demonstrated good recovery of gait but anterior cruciate ligament deficient adopted a strategy of increased fluency (P<0.01). During squatting knee range of motion and peak internal knee extensor moment were reduced in all patients (P<0.01). Both anterior cruciate ligament groups hopped a shorter distance (P<0.01) and had reduced knee range of motion (P<0.025). Anterior cruciate ligament reconstructed had reduced fluency (P<0.01). InterpretationDistance hop was most challenging; squatting and gait were of similar difficulty but challenged patients in different ways. Despite squatting being an early, less challenging exercise, numerous compensation strategies were identified, indicating that this may be more challenging than gait.

The Effects of a Home-Based Instructional Program Aimed at Improving Frontal Plane Knee Biomechanics During a Jump-Landing Task

Randomized controlled trial. To determine the effects of instruction to improve frontal plane knee biomechanics during a jump-landing task. Technique training is a common component of knee injury-prevention programs. In developing programs that minimize time commitment and increase the likelihood of adoption by target groups, there is a need to evaluate individual program components. A total of 26 female recreational athletes (average age, 21.2 years), who presented with medial knee displacement during a jump-landing task, completed the study protocol. Participants were randomly placed into 1 of 2 groups, an experimental or control group. The experimental group received instructions aimed at improving knee abduction during jump landings. The control group received a sham training. Prior to training, baseline kinematics and kinetics (peak knee abduction angle, peak internal knee adductor moment, knee flexion excursion, peak internal knee extensor moment, and peak vertical ground reaction force) were obtained from participants while performing a basketball rebound task. Immediate (5 minutes postinstruction) and delayed (15-20 minutes postinstruction) retention tests were performed within the instructional session. Two additional retention tests were performed following home-based training (1 and 2 weeks following the initial training). The initial instructional session resulted in greater knee flexion excursion (9°) and a 20% reduction in the peak internal knee adductor moment in the experimental group. Following home-based training, the experimental group continued to exhibit increased knee flexion excursion, along with decreased peak vertical ground reaction forces. No biomechanical changes were observed in the control group for any of the retention tests when compared to baseline. The jump-training instructions employed in the current study resulted in kinematic and kinetic changes in the sagittal plane as opposed to the frontal plane. Prevention, level 2b-.

Gait and Neuromuscular Asymmetries after Acute Anterior Cruciate Ligament Rupture

The decreased internal knee extensor moment is a significant gait asymmetry among patients with anterior cruciate ligament (ACL) deficiency, yet the muscular strategy driving this altered moment for the injured limb is unclear. This study aimed to determine whether patients with ACL deficiency and characteristic knee instability would demonstrate normal extensor and increased flexor muscle force to generate a decreased internal extensor moment (i.e., use a hamstring facilitation strategy). Gait analysis was performed on 31 athletes with acute ACL rupture who exhibited characteristic knee instability after injury. Peak internal knee extensor moment was calculated using inverse dynamics, and muscle forces were estimated using an electromyography-driven modeling approach. Comparisons were made between the injured and contralateral limbs. As expected, patients demonstrated decreased peak knee flexion (P = 0.028) and internal knee extensor moment (P = 0.0004) for their injured limb but exhibited neither an isolated decrease in extensor force (quadriceps avoidance) nor an isolated increase in flexor force (hamstring facilitation) at peak knee moment. Instead, they exhibited decreased muscle force from both flexor (P = 0.0001) and extensor (P = 0.0103) groups. This strategy of decreased muscle force may be explained in part by muscle weakness that frequently accompanies ACL injury or by apprehension, low confidence, and fear of further injury. This is the first study to estimate muscle forces in the ACL-deficient knee using an electromyography-driven approach. These results affirm the existence of neuromuscular asymmetries in the individuals with ACL deficiency and characteristic knee instability.