Knee Extension Moment Research Articles

Effects of anterior cruciate ligament reconstruction on patellofemoral joint stress and lower extremity biomechanics at 12 weeks post-surgery and at time of return to sport in adolescent females

BackgroundThe purpose of this study was to examine kinematic and kinetic differences associated with patellofemoral pain after anterior cruciate ligament reconstruction between limbs at 12-week post-surgery and at time of return to sport. MethodTwenty-four adolescent females completed 5 consecutive single leg squats on each limb at 12-weeks post-surgery and again during their RTS assessment. Peak knee extension moment, peak hip adduction angle, and patellofemoral joint stress at 45 degrees of knee flexion were calculated. Separate two by two repeated measures ANOVA were performed. FindingsThere was a significant interaction (limb × time) for knee extension moment (p < 0.001). Surgical limb knee extension moment was significantly less than the non-surgical limb at return to sport (p < 0.001). At 12-weeks the surgical limb was significantly less than non-surgical limb (p < 0.001), additionally the surgical limb was significantly greater at time of return to sport than at 12 weeks (p < 0.001). There was a significant main effect of limb for hip adduction angle (p = 0.002). Surgical limb was significantly greater than non-surgical limb (Surgical = 9.84 (SE 1.53) degree, non-surgical = 4.79 (SE 1.01) degree). There was also a main effect of time and limb for patellofemoral joint stress. Return to sport was significantly greater than 12 weeks and the surgical limb was significantly less than non-surgical limb (Surgical = 4.93 (SE 0325) MPa, Nonsurgical = 5.29 (SE 0.30) MPa). InterpretationThe surgical limb of participants following ACL-R demonstrated variables that have been associated with the development of patellofemoral pain.

Effects of BMI on Walking Speed and Gait Biomechanics after Anterior Cruciate Ligament Reconstruction.

History of an anterior cruciate ligament reconstruction (ACLR) and high body mass index (BMI) are strong independent risk factors for knee osteoarthritis (KOA) onset. The combination of these risk factors may further negatively affect joint loading and KOA risk. We sought to determine the combined influence of BMI and ACLR on walking speed and gait biomechanics that are hypothesized to influence KOA onset. Walking speed and gait biomechanics (peak vertical ground reaction force [vGRF], peak vGRF instantaneous loading rate [vGRF-LR], peak knee flexion angle, knee flexion excursion [KFE], peak internal knee extension moment [KEM], and peak internal knee abduction moment [KAM]) were collected in 196 individuals with unilateral ACLR and 106 uninjured controls. KFE was measured throughout stance phase, whereas all other gait biomechanics were analyzed during the first 50% of stance phase. A 2 × 2 ANOVA was performed to evaluate the interaction between BMI and ACLR and main effects for both BMI and ACLR on walking speed and gait biomechanics between four cohorts (high BMI ACLR, normal BMI ACLR, high BMI controls, and normal BMI controls). History of an ACLR and high BMI influenced slower walking speed (F1,298 = 7.34, P = 0.007), and history of an ACLR and normal BMI influenced greater peak vGRF-LR (F1,298 = 6.56, P = 0.011). When evaluating main effects, individuals with an ACLR demonstrated lesser KFE (F1,298 = 7.85, P = 0.005) and lesser peak KEM (F1,298 = 6.31, P = 0.013), and individuals with high BMI demonstrated lesser peak KAM (F1,297 = 5.83, P = 0.016). BMI and history of ACLR together influence walking speed and peak vGRF-LR. History of an ACLR influences KFE and peak KEM, whereas BMI influences peak KAM. BMI may need to be considered when designing interventions aimed at restoring gait biomechanics post-ACLR.

Vibration improves gait biomechanics linked to posttraumatic knee osteoarthritis following anterior cruciate ligament injury.

Anterior cruciate ligament reconstruction (ACLR) incurs a high risk of posttraumatic knee osteoarthritis (PTOA). Aberrant gait biomechanics contribute to PTOA and are attributable in part to quadriceps dysfunction. Vibration improves quadriceps function following ACLR, but its effects on gait biomechanics are unknown. The purpose of this study was to evaluate the effects of whole-body vibration (WBV) and local muscle vibration (LMV) on gait biomechanics in individuals with ACLR. Seventy-five volunteers (time since ACLR 27 ± 16 months) were randomized to WBV, LMV, or Control interventions. Walking biomechanics were assessed prior to and following a single exposure to the interventions. Outcomes included pre-post change scores in the ACLR limb for the peak vertical ground reaction force (vGRF) and its loading rate, peak internal knee extension (KEM) and abduction moments, and peak knee flexion and varus angles. LMV produced a significant decrease in the vGRF loading rate (-3.6 BW/s) that was greater than the changes in the WBV (-0.3 BW/s) and Control (0.5 BW/s) groups. Additionally, WBV produced an increase in the peak KEM (0.27% BW × Ht) that was greater than the change in the Control group (-0.17% BW × Ht) but not the LMV group (0.01% BW × Ht). Lower KEM and greater loading rates have been linked to declines in joint health following ACLR. WBV acutely increased the peak KEM and LMV decreased loading rates. These data suggest that vibration has the potential to mitigate aberrant gait biomechanics, and may represent an effective approach for reducing PTOA risk following ACLR.

Effects of Increased Step-Width on Knee Biomechanics During Inclined and Declined Walking.

The purpose of this study was to investigate effects of preferred step width and increased step width modification on knee biomechanics of obese and healthy-weight participants during incline and decline walking. Seven healthy-weight participants and 6 participants who are obese (body mass index ≥ 30) performed 5 walking trials on level ground and a 10° inclined and declined instrumented ramp system at both preferred and wide step-widths. A 2 × 2 (step-width × group) mixed-model analysis of variance was used to examine selected variables. There were significant increases in step-width between the preferred and wide step-width conditions for all 3 walking conditions (all P < .001). An interaction was found for peak knee extension moment (P = .048) and internal knee abduction moment (KAM) (P = .025) in uphill walking. During downhill walking, there were no interaction effects. As step-width increased, KAM was reduced (P = .007). In level walking, there were no interaction effects for peak medial ground reaction force and KAM (P = .007). There was a step-width main effect for KAM (P = .007). As step-width increased, peak medial ground reaction force and peak knee extension moment increased, while KAM decreased for both healthy weight and individuals who are obese. The results suggest that increasing step-width may be a useful strategy for reducing KAM in healthy and young populations.

Clinical outcomes of kinematic alignment versus mechanical alignment in total knee arthroplasty: a systematic review.

Although mechanical alignment (MA) has traditionally been considered the gold standard, the optimal alignment strategy for total knee arthroplasty (TKA) is still debated.Kinematic alignment (KA) aims to restore native alignment by respecting the three axes of rotation of the knee and thereby producing knee motion more akin to the native knee.Designer surgeon case series and case control studies have demonstrated excellent subjective and objective clinical outcomes as well as survivorship for KA TKA with up to 10 years follow up, but these results have not been reproduced in high-quality randomized clinical trials.Gait analyses have demonstrated differences in parameters such as knee adduction, extension and external rotation moments, the relevance of which needs further evaluation.Objective improvements in soft tissue balance using KA have not been shown to result in improvements in patient-reported outcomes measures.Technologies that permit accurate reproduction of implant positioning and objective measurement of soft tissue balance, such as robotic-assisted TKA and compartmental pressure sensors, may play an important role in improving our understanding of the optimum alignment strategy and implant position.Cite this article: EFORT Open Rev 2020;5:486-497. DOI: 10.1302/2058-5241.5.190093

The effect of increasing heel height on lower limb symmetry during the back squat in trained and novice lifters

BackgroundSymmetry during lifting is considered critical for allowing balanced power production and avoidance of injury. This investigation assessed the influence of elevating the heels on bilateral lower limb symmetry during loaded (50% of body weight) high-bar back squats.MethodsTen novice (mass 67.6 ± 12.4 kg, height 1.73 ± 0.10 m) and ten regular weight trainers (mass 66.0 ± 10.7 kg, height 1.71 ± 0.09 m) were assessed while standing on both the flat level floor and on an inclined board. Data collection used infra-red motion capture procedures and two force platforms to record bilateral vertical ground reaction force (GRFvert) and ankle, knee and hip joint kinematic and kinetic data. Paired t-tests and statistical parametric mapping (SPM1D) procedures were used to assess differences in discrete and continuous bilateral symmetry data across conditions.ResultsAlthough discrete joint kinematic and joint moment symmetry data were largely unaffected by raising the heels, the regular weight trainers presented greater bilateral asymmetry in these data than the novices. The one significant finding in these discrete data showed that raising the heels significantly reduced maximum knee extension moment asymmetry (P = 0.02), but in the novice group only. Time-series analyses indicated significant bilateral asymmetries in both GRFvert and knee extension moments mid-way though the eccentric phase for the novice group, with the latter unaffected by heel lift condition. There were no significant bilateral asymmetries in time series data within the regular weight training group.ConclusionsThis investigation highlights that although a degree of bilateral lower limb asymmetry is common in individuals performing back squats, the degree of this symmetry is largely unaffected by raising the heels. Differences in results for discrete and time-series symmetry analyses also highlight a key issue associated with relying solely on discrete data techniques to assess bilateral symmetry during tasks such as the back squat.

Landing Evaluation in Soccer Players with or without Anterior Cruciate Ligament Reconstruction.

The purpose of this study was to evaluate landing biomechanics in soccer players following ACLR during two landing tasks. Eighteen soccer players with an ACLR and 18 sex-matched healthy control soccer players participated in the study. Planned landing included jumping forward and landing on the force-plates, whereas unplanned landing included jumping forward to head a soccer ball and landing on the force-plates. A significant landing×group interaction was found only for knee flexion angles (p=0.002). Follow-up comparisons showed that the ACL group landed with greater knee flexion during planned landing compared with unplanned landing (p<0.001). Significant main effects of landing were found. The unplanned landing showed reduction in hip flexion (p<0.001), hip extension moments (p<0.013), knee extension moments (p<0.001), and peak pressure (p<0.001). A significant main effect for group for gastrocnemius muscle was found showing that the ACL group landed with reduced gastrocnemius activity (p=0.002). Unplanned landing showed greater injury predisposing factors compared with planned landing. The ACL group showed nearly similar landing biomechanics to the control group during both landing tasks. However, the ACL group used a protective landing strategy by reducing gastrocnemius activity.

Chronic nerve health following implantation of femoral nerve cuff electrodes

BackgroundPeripheral nerve stimulation with implanted nerve cuff electrodes can restore standing, stepping and other functions to individuals with spinal cord injury (SCI). We performed the first study to evaluate the clinical electrodiagnostic changes due to electrode implantation acutely, chronic presence on the nerve peri- and post-operatively, and long-term delivery of electrical stimulation.MethodsA man with bilateral lower extremity paralysis secondary to cervical SCI sustained 5 years prior to enrollment received an implanted standing neuroprosthesis including composite flat interface nerve electrodes (C-FINEs) electrodes implanted around the proximal femoral nerves near the inguinal ligaments. Electromyography quantified neurophysiology preoperatively, intraoperatively, and through 1 year postoperatively. Stimulation charge thresholds, evoked knee extension moments, and weight distribution during standing quantified neuroprosthesis function over the same interval.ResultsFemoral compound motor unit action potentials increased 31% in amplitude and 34% in area while evoked knee extension moments increased significantly (p < 0.01) by 79% over 1 year of rehabilitation with standing and quadriceps exercises. Charge thresholds were low and stable, averaging 19.7 nC ± 6.2 (SEM). Changes in saphenous nerve action potentials and needle electromyography suggested minor nerve irritation perioperatively.ConclusionsThis is the first human trial reporting acute and chronic neurophysiologic changes due to application of and stimulation through nerve cuff electrodes. Electrodiagnostics indicated preserved nerve health with strengthened responses following stimulated exercise. Temporary electrodiagnostic changes suggest minor nerve irritation only intra- and peri-operatively, not continuing chronically nor impacting function. These outcomes follow implantation of a neuroprosthesis enabling standing and demonstrate the ability to safely implant electrodes on the proximal femoral nerve close to the inguinal ligament. We demonstrate the electrodiagnostic findings that can be expected from implanting nerve cuff electrodes and their time-course for resolution, potentially applicable to prostheses modulating other peripheral nerves and functions.Trial registrationClinicalTrials.govNCT01923662, retrospectively registered August 15, 2013.

Effects of anterior-posterior shifts in prosthetic alignment on the sit-to-stand movement in people with a unilateral transtibial amputation

The sit-to-stand movement can be challenging for people with a transtibial amputation (TTA). The alignment of the prosthesis may influence the movement strategies people with TTA use to transfer from sit-to-stand by affecting foot placement. The purpose of this study was to determine how shifting the prosthetic foot anterior and posterior relative to the socket affects movement strategies used to transfer from sit-to-stand. To aid in interpretation, we compared movement strategies between people with and without TTA. Nine people with TTA and nine sex-, and age-matched non-amputee controls completed five self-paced sit-to-stand trials. With the posterior alignment, participants with TTA had 1) smaller braking GRF impulse on the prosthetic side and greater impulse on the intact side compared to the anterior alignment, 2) no significant differences between sides, which suggests greater braking impulse symmetry compared to anterior and prescribed alignments, and 3) smaller axial trunk range of motion compared to the prescribed alignment. There were also differences between participants with TTA and controls in braking GRF impulse, knee extension moment, anterior/posterior center of pressure position, and lateral and axial trunk range of motion. Based on these results, shifting the prosthetic foot posterior to the socket may be a useful tool to reduce braking impulse asymmetry and trunk motion in people with TTA during sit-to-stand. Thus, prosthetic alignment can have important implications for the comfort and ability of people with TTA to transfer from sit-to-stand as well as for development of secondary health conditions like low back pain, which is associated with compensatory movements.

Gait Biomechanics Linked To Post-traumatic Osteoarthritis Following Anterior Cruciate Ligament Reconstruction Are Improved With Vibration

PURPOSE: Anterior cruciate ligament reconstruction (ACLR) incurs a high risk of post-traumatic knee osteoarthritis (PTOA). Aberrant gait biomechanics contribute to PTOA and are attributable in part to quadriceps dysfunction. Vibration improves quadriceps function following ACLR, but its effects on gait biomechanics are unknown. The purpose of this study was to evaluate the effects of whole body vibration (WBV) and local muscle vibration (LMV) on gait biomechanics in individuals with ACLR. METHODS: 75 volunteers with primary unilateral ACLR (72% females; age 21 ± 3 yr; time since ACLR 27 ± 16 mo) were randomized to WBV, LMV, or Control interventions. WBV and LMV were applied 6 x 1 minute (30Hz, 2g). Walking biomechanics were assessed prior to and following the interventions. Outcomes included the peak vertical ground reaction force (vGRF) and its loading rate, peak internal knee extension and valgus moments, and peak knee flexion and varus angles during the first 50% of stance. vGRF magnitude and rate were normalized to body weight (BW) and moments were normalized as % body weight∗height (%BW∗Ht). ACLR limb change scores (post-pre) for each outcome were compared across groups via one-way ANCOVA controlling for gait speed, time since ACLR, and baseline values. RESULTS: Change scores did not differ across groups for peak knee flexion (p = 0.374) or varus (p = 0.801) angles, vGRF (p = 0.656), or internal valgus moment (p = 0.866). However, changes in vGRF loading rate differed across groups (p = 0.024), with a significant decrease in the LMV group (-3.6 BW/s) that was greater than the changes in the WBV (-0.3 BW/s; p = 0.035) and Control (0.5 BW/s; p = 0.010) groups. Additionally, the change in peak internal extension moment differed across groups (p = 0.016), with a significant increase in the WBV group (0.27 %BW∗Ht) that was greater than the change in the Control group (-0.17 %BW∗Ht; p = 0.005) but not the LMV group (0.01 %BW∗Ht; p = 0.101). CONCLUSIONS: Lower knee extension moments and greater loading rates during gait have been linked to declines in joint health following ACLR. WBV acutely increased the peak knee extension moment and LMV decreased loading rates. These data suggest that vibration has the potential to mitigate aberrant gait biomechanics, and may represent an effective approach for mitigating PTOA risk following ACLR.

Greater Matrix Metalloproteinase-3 Concentrations Following ACL Injury Associate With Worse Gait Biomechanics 6-months Post-ACL Reconstruction

Matrix metalloproteinase-3 (MMP-3) is a degenerative enzyme associated with joint tissue breakdown and has been shown to be a potential biomarker of osteoarthritis. It remains unknown if synovial fluid (SF) MMP-3 concentrations following ACL injury influence gait mechanics. PURPOSE: To compare knee flexion angle (KFA) and internal knee extension moment (KEM) during gait 6 months post-ACLR in individuals with the highest concentrations of SF MMP-3 compared to those with the lowest concentrations of SF MMP-3 collected within the first 14 days of injury. METHODS: Thirty-seven individuals with ACL injury scheduled for primary patellar tendon autograft ACLR (57% females, 21±4 yrs, 23.7±2.8 BMI) participated. Individuals were grouped into highest (HQ; n=9) and lowest (LQ; n=10) quartiles based on MMP-3 knee joint SF concentrations sampled 6+4 days after ACL injury. At 6 months post-ACLR, biomechanics were collected using 3-dimensional motion capture during gait performed at a self-selected speed. Functional analyses of variance were conducted to compare KFA and KEM between HQ and LQ groups throughout stance. Groups were considered different at any percentage of stance where the 95% confidence intervals of the mean differences did not cross zero. Peak differences (PD) and corresponding effect sizes (Cohen’s d) within portions of stance demonstrating differences were also calculated. RESULTS: HQ exhibited lesser knee flexion excursion; KFA was lower during 17-24% of stance (PD: 2.1°, d=0.44) and greater during 48-100% of stance (PD: 4.5°, d=0.93). HQ also exhibited lower KEM during 14-30% and 91-100% of stance (PD: 0.72 BW, d=0.67; PD: 0.33 BW, d=1.42) and greater KEM during 45-72% of stance (PD: 0.44, d=0.76) CONCLUSION: Compared to individuals in the lowest quartile of SF MMP-3, those in the highest exhibited a stiffened knee gait strategy. Pre-surgery levels of MMP-3 following ACL injury may serve as a biomarker predicting worse gait mechanics 6 months post-ACLR.

Relationship Between Dynamic Limb Symmetry And Subjective Limb Confidence Post ACL Reconstruction In Youth Athletes

Limb symmetry index (LSI) of dynamic movement is used as return to sport criteria for athletes who have undergone an anterior cruciate ligament reconstruction (ACLR). However the relationship between an individual’s perception of confidence and dynamic performance is poorly understood. PURPOSE: To discern a relationship between dynamic limb symmetry during a drop landing (DL) and single leg hop (SLHOP) task with subjective limb confidence in athletes who have had an ACLR. METHODS: 23 subjects (13 female, 10 male; 16±1.4 years) underwent a biomechanical assessment, including a DL and SLHOP task, at around 7±1 months post op ACLR. Subjects were outfitted with a custom marker set and recorded with a 3D camera system while performing tasks on 2 force platforms. To examine dynamic limb symmetry, kinematic variables of peak hip flexion, knee flexion, and ankle dorsiflexion, with kinetic variables of peak hip extension moment, knee extension moment, ankle plantar flexion moment, and vertical ground reaction force (GRFz) were collected and analyzed as an index between the involved and non-involved limb. Subjects completed questionnaires for limb confidence; International Knee Documentation Committee (IKDC)/Pedi-IKDC and Tampa Scale of Kinesiophobia (TSK). The relationship between LSI during DL and SLHOP with the IKDC and TSK scores were tested using a multilinear regression analysis. RESULTS: A significant strong relationship was found between LSI of DL mechanics and IKDC (86±12, r= 0.84, p<0.05). Among predictor variables, peak GRFz (LSI 79±21, p<0.05) was significant in its explanation of IKDC scores. Independent regressions showed significant moderate correlations between IKDC and LSI for peak hip extension moments (LSI 107±24, r= 0.56, p<0.01), knee extension moments (LSI 80±23, r=0.51, p<0.05), and GRFz (r= 0.62, p<0.01). No significant relationships were found for SLHOP and IKDC scores, or with TSK for either dynamic test. CONCLUSIONS: Subjective limb confidence demonstrated a strong relationship with limb symmetry of sagittal plane mechanics with a 1% difference in LSI of GRFz corresponding to a 0.4% difference in IKDC scores during a DL and not SLHOP task. Symmetry in mechanics during a bilateral task may be more reflective of patient confidence in utilizing the affected limb prior to return to sport after ACLR.

Comparison Of Shoe Vs No Shoe On Sagittal Plane Deadlift Biomechanics

Deadlifts are often an integral part of training programs to build posterior chain strength and power, but current research has not examined the performance outcomes when performed with and without shoes from a biomechanical perspective. PURPOSE: To examine the differences in lower extremity sagittal plane joint kinetics and peak vertical ground reaction force (vGRF) of a conventional barbell deadlift with and without shoes. METHODS: Ten subjects (age: 27.9 + 3.8 years) who deadlift twice a week for the past 6 months, were free from injury, and had no history of lower extremity surgery were recruited. Subjects first performed a one repetition max (1RM) test in self-selected footwear according to NSCA guidelines. At least 72 hours later subjects returned for a 3-dimensional analysis of their deadlift at 70% of their 1RM. Subjects performed 1 set of 5 continuous reps of a conventional deadlift in both shoe and barefoot conditions in a randomized order. A 5-minute rest was given between each condition. Visual3D was used to process raw marker and force data, calculate peak sagittal joint moments of the ankle, knee, and hip and to find peak vertical ground reaction force during the concentric phase. A one-way repeated measures MANOVA was performed to statistically test differences between shoe and no shoe conditions in the dependent variables. RESULTS: Average 1RM for males and females was 437.5 + 83.4 lbs. and 224.2 + 37.6 lbs., respectively. No significant differences were found in internal hip extension moments (p=0.444, S=2.99 Nm/kg, B=3.05 Nm/kg), knee extension moments (p=0.151, S=0.92 Nm/kg, B=0.81 Nm/kg), ankle plantar flexion moments (p=0.113, S=1.07 Nm/kg, B=1.01 Nm/kg), and peak vGRF (p=0.295, S=1044.9 N, B=1035.2 N) between shoe and barefoot conditions. CONCLUSION: Anecdotal claims suggest performing a deadlift barefoot enhances stability and increases connection to the ground which would lead to improvement in deadlift performance. The lack of difference seen in sagittal plane kinetics and peak vGRF suggest that deadlift performance is unaffected by footwear choice. Future research should investigate if similar results would be attained when subjects’ deadlift performance is tested at various percentages of the 1RM.

Kinetic Asymmetry During Squatting And Landing Are Associated In Anterior Cruciate Ligament Reconstructed Patients

High kinetic asymmetry during landing is associated with an increased risk for sustaining a second anterior cruciate ligament (ACL) injury in athletes returning to sport following ACL reconstruction (ACL-R). While previous literature has found that ACL-R patients have more kinetic asymmetry than healthy controls during both landing and bilateral squatting, it is currently unknown if landing asymmetry and squatting asymmetry are related in ACL-R patients. PURPOSE: Determine the relationship between landing kinetic asymmetry and squatting kinetic asymmetry in ACL-R patients. METHODS: 34 ACL-R patients (19 male; 73 ± 16 kg; 174 ± 10 cm; 6.0 ± 1.5 months post-operative) signed informed consent and participated in the study. All participants completed one set of 15 bilateral squats and then ten bilateral stop jump trials, while 3D lower extremity kinematics and kinetics were recorded at 240 Hz and 1920 Hz, respectively. Peak knee extension moment (KEM) and vertical ground reaction force impulse (GRFI) were computed during the descending phase of both tasks. The descending phase was defined between squat initiation and the minimum position of the pelvis during each squat and between initial contact and the minimum position of the pelvis for each stop jump. A limb symmetry index (LSI) was computed for peak KEM and GRFI as the difference between the surgical and non-surgical leg divided by their average during each squat and each stop jump, and then the LSI was averaged across trials. Peak KEM LSI and GRFI LSI were then compared between the stop jump and squat trials using Pearson’s correlations. RESULTS: There was a significant relationship between both stop jump kinetic asymmetry outcomes and both squat kinetic asymmetry outcomes (Table 1). CONCLUSION: Kinetic asymmetry during squatting and bilateral landing are associated in ACL-R patients, which indicates that biofeedback retraining during bilateral squatting could result in improvements in bilateral landing symmetry.

The Relation Between Hamstring:Quadriceps Ratio And Knee Functional Performance During Hopping Tasks

A hamstring to quadriceps strength ratio (H:Q) ≥60% and limb symmetry index (LSI) ≥90% during unilateral assessments of strength and function have been used as return to play (RTP) benchmarks following anterior cruciate ligament reconstruction (ACLR). PURPOSE: Determine the relation between H:Q and single (SH), triple (TH), triple cross-over (CH), and 6 m timed (6H) hopping assessment performance (e.g. distance achieved or time to complete). METHODS: Sixty-four ACLR patients (34 males: 20.92 ± 7.93 y, 1.83 ± .09 m, 88.34 ± 17.36 kg; 30 females: 17.63 ± 2.84 y, 1.67 ± .07 m, 63.32 ± 7.25 kg) 26.01 ± 9.57 wks post-surgery volunteered to participate. Participants completed maximal voluntary isokinetic knee extension and flexion strength testing on the injured leg (IL) and non-injured leg (NIL) through a range of 20° to 90° of knee flexion at 60°·s-1, 180°·s-1, and 300°·s-1. Participants were stratified into groups based on whether they obtained ≥60% H:Q (PASS) or <60% H:Q (FAIL) for each speed. Three trials of each hop test were performed on IL and NIL. The mean hop performance on each leg per test was normalized to participant height. Pearson correlations were used to explore the relation between hopping performance and H:Q. T-tests were used to assess for the effect of group on hopping performance. Significance was set at p < 0.05 RESULTS: Males demonstrated negative correlations for IL between SH and H:Q at 300°·s-1 (r = -.49 [-.71 -.18], p = .003), TH and H:Q at 60°·s1 (r = -.80 [-.80 to -.38], p < .001), and TH and H:Q at 180°·s-1 (r = -.63 [-.76, -.27], p < .001). Males also demonstrated negative correlations for NIL between TH and H:Q at 60°·s-1 (r = -.41 [-.65 to -.08], p = .018) and 180°·s-1 (r = -.42 [-.64, -.05], p = .027). No significant correlations between H:Q and hopping performance were identified in females. At 300°·s-1, FAIL males had greater normalized SH scores for both IL (.78 ± .18 vs. .89 ± .15; p = .04) and NIL (.82 ± .15 vs. .91 ± .14; p = .06). CONCLUSION: These results suggest a negative relation between H:Q and functional performance post-ACLR. H:Q <60% may indicate superior quadriceps strength which leads to a greater internal knee extension moment capacity and improved hopping performance. However, achieving an H:Q above an acceptable threshold may be protective and aid in knee joint translation stability.

Knee Kinetics Of Patients With Different Types Of Total Knee Arthroplasty Implants During Downhill Walking

Ramping walking is a common daily activity that is often incorporated in rehabilitation for total knee arthroplasty (TKA) patients. However, no studies have investigated knee biomechanics of patients with total knee arthroplasty (TKA), and comparisons between posterior stabilized (PS), cruciate retaining (CR) and bi-cruciate stabilized (BCS) TKA implants during ramp walking. PURPOSE: To examine the differences in knee biomechanics between patients with the three different types of TKA implants and healthy controls during downhill walking on a 10° ramp. METHODS: Five BCS, 10 CR, 10 PS TKA patients and 10 healthy controls performed five downhill walking trials at their self-selected pace, on a 10° instrumented ramp mounted through rigid contact surface structures mounted onto two force platforms (AMTI). Three-dimensional kinematic data (240 Hz, Vicon) were collected in conjunction with ground reaction force data (1200 Hz). A 2 × 4 (limb × group) mixed design ANOVA was used to examine selected knee joint kinematic and kinetic variables. RESULTS: In downhill walking, a significant limb effect was found in peak loading-response (p=0.005) and push-off knee extension moment (KEM, p=0.015). Peak loading-response KEMs were smaller (p=0.006) in replaced limbs (0.94 Nm/kg) than non-replaced limbs (0.97 Nm/kg). Similar findings were seen in peak push-off (p=0.015) KEMs. Peak loading-response knee abduction moment (KAbM) were mostly similar between the replaced limbs of three TKA groups and healthy controls in downhill walking. Peak loading-response KAbMs were smaller in non-replaced limbs of BCS (-0.34 Nm/kg, p=0.018) and PS (-0.37 Nm/kg, p=0.001) patients compared to that in their non-replaced limbs (BCS: -0.53 Nm/kg & PS: -0.49 Nm/kg). CONCLUSION: The results from this study showed that during downhill walking, peak KEMs were lower in replaced limbs than non-replaced limbs for all TKR patients, suggesting a deficit in knee extensor strength regardless of TKA designs. Post-surgery rehabilitation should focus on eccentric strength training of quadriceps for their replaced knees to reduce the asymmetry in knee movement and loading. BCS and PS patients may need additional attention in strengthening of quadriceps and hamstrings of the replaced limbs.

Changes In Gait Biomechanics Between Level And Downhill Walking Do Not Differ Between Those With Anterior Cruciate Ligament Reconstruction And Controls

Conflicting evidence exists regarding the presence of aberrant gait biomechanics after the first year post-anterior cruciate ligament reconstruction. Overground walking may not elucidate differences in those further removed from surgery due to the unexacting nature of the task. Deleterious gait biomechanics following ACLR are partly attributable to quadriceps dysfunction. Downhill walking may exacerbate aberrant gait biomechanics, as this task places greater demands on the quadriceps compared to level walking. PURPOSE: To compare gait biomechanics between individuals with ACLR and healthy controls during level and downhill walking conditions. METHODS: 24 individuals more than 1 year removed from primary ACLR (83% female, age= 21 ± 3 yr, time since ACLR 44 ± 26 mo, BMI= 23 ± 3 kg/m2) and 24 healthy controls (79% female, age= 21 ± 1 yr, BMI= 24 ± 3 kg/m2) completed both level and downhill (10°grade) gait biomechanics assessments on an instrumented split-belt treadmill at their preferred walking speed. Peak variables were evaluated over the first 50% of stance including the vertical ground reaction force (vGRF), internal knee abduction moment, internal knee extension moment, knee flexion angle, and knee abduction angle. Moments were normalized to %body weight∗height (%BW∗Ht) and vGRF was normalized to %body weight. Dependent variables were compared across groups and conditions via two-way repeated measures ANCOVA controlling for gait speed. RESULTS: There were no significant condition∗group interaction effects nor group main effects for any outcomes. However, there were significant condition main effects for peak internal knee extension moment (p = 0.020, level to downhill mean increase of 0.042 %BW∗Ht) and peak knee flexion angle (p = 0.018, level to downhill mean increase of 13.2&#176;). CONCLUSIONS: Downhill walking necessitates a larger internal extension moment and knee flexion angle compared to level gait. Our results suggest that changes in gait biomechanics between level and downhill conditions do not differ between individuals with ACLR > 1 year post reconstruction and controls. These results suggest that aberrant gait biomechanics may be mitigated over time in those with ACLR.

Lower Limb Asymmetry After Anterior Cruciate Ligament Reconstruction in Adolescent Athletes: A Systematic Review and Meta-Analysis.

To identify reported (1) common biomechanical asymmetries in the literature after anterior cruciate ligament (ACL) reconstruction in adolescents during landing and (2) timescales for asymmetry to persist postsurgery. We identified sources by searching the CINAHL, PubMed, Scopus, and SPORTDiscus electronic databases using the following search terms: asymmetry OR symmetry AND landing AND biomechanics OR kinematics OR kinetics. We screened the titles and abstracts of 85 articles using our inclusion criteria. A total of 13 articles were selected for further analysis. Three reviewers independently assessed the methodologic quality of each study. We extracted the effect sizes directly from studies or calculated them for biomechanical variables assessing asymmetry between limbs of participants with ACL reconstruction. We conducted meta-analyses on variables that were assessed in multiple studies for both double- and single-limb landings. Asymmetry was more commonly identified in kinetic than kinematic variables. Anterior cruciate ligament reconstruction appeared to have a large effect on asymmetry between limbs for peak vertical ground reaction force, peak knee-extension moment, and loading rate during double-limb landings, as well as mean knee-extension moment and knee energy absorption during both double- and single-limb landings. Our findings suggested that return-to-sport criteria after ACL reconstruction should incorporate analysis of the asymmetry in loading experienced by each limb rather than movement patterns alone.

Shoe collar height and heel counter-stiffness for shoe cushioning and joint stability in landing

ABSTRACT This study examined the effects of shoe collar-height and counter-stiffness on ground reaction force (GRF), ankle and knee mechanics in landing. Eighteen university basketball players performed drop landing when wearing shoes in different collar height (high vs. low) and counter-stiffness (stiffer vs. less stiff). Biomechanical variables were measured with force platform and motion capturing systems. Two-way repeated measures ANOVA was performed with α = 0.05. Wearing high collar shoes exhibited smaller peak ankle dorsiflexion and total sagittal RoM, peak knee extension moment, but larger peak knee varus moment than the low collar shoes. Stiffer counter-stiffness shoes related to smaller ankle inversion at touchdown and total coronal RoM, but larger peak knee flexion and increased total ankle and knee sagittal RoM than the less stiff counter-stiffness. Furthermore, wearing stiffer counter-stiffness shoes increased forefoot GRF peak at high collar condition, while no significant differences between counter-stiffness at low collar condition. These results suggest that although higher collar height and/or stiffness heel counter used can reduce ankle motion in coronal plane, it would increase the motion and loading at knee joint, which is susceptible to knee injuries. These findings could be insightful for training and footwear development in basketball.

A Pilot Study of Musculoskeletal Abnormalities in Patients in Recovery from a Unilateral Rupture-Repaired Achilles Tendon

The purpose of this study was to compare the inter-limb joint kinematics, joint moments, muscle forces, and joint reaction forces in patients after an Achilles tendon rupture (ATR) via subject-specific musculoskeletal modeling. Six patients recovering from a surgically repaired unilateral ATR were included in this study. The bilateral Achilles tendon (AT) lengths were evaluated using ultrasound imaging. The three-dimensional marker trajectories, ground reaction forces, and surface electromyography (sEMG) were collected on both sides during self-selected speed during walking, jogging and running. Subject-specific musculoskeletal models were developed to compute joint kinematics, joint moments, muscle forces and joint reaction forces. AT lengths were significantly longer in the involved side. The side-to-side triceps surae muscle strength deficits were combined with decreased plantarflexion angles and moments in the injured leg during walking, jogging and running. However, the increased knee extensor femur muscle forces were associated with greater knee extension degrees and moments in the involved limb during all tasks. Greater knee joint moments and joint reaction forces versus decreased ankle joint moments and joint reaction forces in the involved side indicate elevated knee joint loads compared with reduced ankle joint loads that are present during normal activities after an ATR. In the frontal plane, increased subtalar eversion angles and eversion moments in the involved side were demonstrated only during jogging and running, which were regarded as an indicator for greater medial knee joint loading. It seems after an ATR, the elongated AT accompanied by decreased plantarflexion degrees and calf muscle strength deficits indicates ankle joint function impairment in the injured leg. In addition, increased knee extensor muscle strength and knee joint loads may be a possible compensatory mechanism for decreased ankle function. These data suggest patients after an ATR may suffer from increased knee overuse injury risk.