The effect of hamstring muscle compensation for anterior laxity in the ACL-deficient knee during gait

Hamstrings vibration reduces tibiofemoral compressive force following anterior cruciate ligament reconstruction

Individuals who have undergone anterior cruciate ligament reconstruction (ACLR) are at greater risk of developing knee osteoarthritis (OA). This elevated risk of knee OA is associated with high tibiofemoral (TF) compressive force, due to a combination of low knee flexion angles and increased co-contraction of the hamstrings and quadriceps during limb loading. Prolonged vibration of the hamstrings fatigues the intrafusal muscle fibers, which reduces autonomic reflexive excitation of the hamstrings and alleviates reciprocal inhibition to the quadriceps. The aim of this study was to examine the effect of prolonged hamstrings vibration on TF compressive force in individuals who have undergone ACL reconstruction. Fourteen participants with unilateral ACLR and 14 participants without knee injury performed a single-leg drop-land task before and after prolonged (20 min) vibration of the hamstrings. Peak TF compressive force, knee flexion angle, and hamstrings/quadriceps co-contraction were calculated during the deceleration phase of the drop-land task before and after vibration. The ACLR group experienced an 18% decrease in TF compressive force, a 32% increase in knee flexion angle, and a 38% decrease in hamstrings/quadriceps co-contraction after hamstrings vibration. There was no difference in any of the parameters in the noninjured group after vibration. These data suggest that acute prolonged hamstrings vibration has the potential to mitigate TF compressive force, which may protect the knee joint in the long term. Clinical significance: The results of this research are expected to lead to improved clinical care for ACLR patients because it holds promise for mitigating altered joint mechanics and perhaps slowing down the onset of posttraumatic knee osteoarthritis.

Influence of hamstring stiffness on anterior tibial translation after anterior cruciate ligament rupture

BACKGROUND

There is a correlation between the hamstring stiffness and the decrease of anterior tibial translation in athletic patients with healthy knees. This observation could question the clinical reliability of the Lachman-Trillat test to detect complete ACL ruptures in patients with an important hamstring stiffness. This study aims to determine if anterior tibial translation is correlated with hamstring stiffness in patients with complete ACL rupture.

METHODS

This is a prospective study including patients with unilateral complete ACL rupture confirmed by MRI. The arthrometer GNRB® was used to measure anterior tibial translation on both knees at 134 N and compute the side-to-side difference. The hamstring stiffness was assessed with the eccentric peak torque using the isokinetic dynamometer CON-TREX. Linear regressions were done between these two parameters on two study groups: one included all patients (GR1), and the other included only isolated ACL injuries without associated lesions (GR2).

RESULTS

Fifty-two patients were included (29 men, 23 women) with an average of 34.9 years old. The mean eccentric peak torque of the hamstrings for pathological knees was 94.9Nm for GR1 and 91.7Nm for GR2. The mean side-to-side difference was 2.42 mm for GR1 and 1.99 mm for GR2. No significant correlations were identified for GR1 (p = 0.66) and GR2 (p = 0.105).

CONCLUSION

No significant linear correlation was found between side-to-side difference measured by GNRB® and hamstring stiffness for pathological knees with complete ACL rupture. These results lead to believe that the Lachman-Trillat clinical test is not influenced by hamstring stiffness.

LEVEL OF EVIDENCE

Prospective study, level of evidence IV.

Muscle dynamics analysis by clustered categories during jogging in patients with anterior cruciate ligament deficiency

BACKGROUND

Patients with anterior cruciate ligament (ACL) deficiency (ACLD) tend to have altered lower extremity dynamics. Little is known about the changes in dynamic function and activation during jogging in patients with ACLD.

METHODS

Twenty patients with an injured ACL before ACL reconstruction (ACLD group) and nine healthy male volunteers (control group) were recruited. Each volunteer repeated the jogging experiment five times. Based on the experimental data measured, a musculoskeletal multibody dynamics model was employed to simulate the tibiofemoral joint dynamics during jogging. Eighteen muscles were used for analysis. The obtained dynamics data were used for clustering and curve difference analysis.

RESULTS

The 18 muscles studied were divided into 3 categories. All the quadriceps, the soleus, the gastrocnemius, and the popliteus were classified as label 1. All the hamstrings were classified as label 2, and the sartorius muscles were classified as label 3. Among them, the classification of the short head of the biceps femoris was significantly different between the two groups (P < 0.001). The force curves of all 18 muscles and the between-group differences were studied according to clustered categories. Most muscle force in label 1 was approaching zero in the terminal stance phase, which was significantly lower than that in the control group (P < 0.05). The muscle force in label 2 had areas with significant differences in the stance phase. Muscle force in label 3 was significantly lower than that in the control group in the pre-swing phase.

CONCLUSIONS

This study showed that there are various changes of muscle function and activation in patients with ACLD. Through clustering and curve analysis, the joint reactions and changes of different muscle forces in the gait cycle between the ACLD and control groups could be further clarified.

Leveraging Multivariable Linear Regression Analysis to Identify Patients with Anterior Cruciate Ligament Deficiency Using a Composite Index of the Knee Flexion and Muscle Force

Patients with anterior cruciate ligament (ACL) deficiency (ACLD) tend to have altered lower extremity kinematics and dynamics. Clinical diagnosis of ACLD requires more objective and convenient evaluation criteria. Twenty-five patients with ACLD before ACL reconstruction and nine healthy volunteers were recruited. Five experimental jogging data sets of each participant were collected and calculated using a musculoskeletal model. The resulting knee flexion and muscle force data were analyzed using a t-test for characteristic points, which were the time points in the gait cycle when the most significant difference between the two groups was observed. The data of the characteristic points were processed with principal component analysis to generate a composite index for multivariable linear regression. The accuracy rate of the regression model in diagnosing patients with ACLD was 81.4%. This study demonstrates that the multivariable linear regression model and composite index can be used to diagnose patients with ACLD. The composite index and characteristic points can be clinically objective and can be used to extract effective information quickly and conveniently.

Apparatus for In Vivo Knee Laxity Assessment Using High-Speed Stereo Radiography

Computational modeling is of growing importance in orthopedics and biomechanics as a tool to understand differences in pathology and predict outcomes from surgical interventions. However, the computational models of the knee have historically relied on in vitro data to create and calibrate model material properties due to the unavailability of accurate in vivo data. This work demonstrates the design and use of a custom device to quantify anterior-posterior (AP) and internal-external (IE) in vivo knee laxity, with an accuracy similar to existing in vitro methods. The device uses high-speed stereo radiography (HSSR) tracking techniques to accurately measure the resulting displacements of the femur, tibia, and patella bones during knee laxity assessment at multiple loads and knee flexion angles. The accuracy of the knee laxity apparatus was determined by comparing laxity data from two cadaveric specimens between the knee laxity apparatus and an existing in vitro robotic knee joint simulator. The accuracy of the knee laxity apparatus was within 1 mm (0.04 in.) for AP and 2.5 deg for IE. Additionally, two living subjects completed knee laxity testing to confirm the laboratory use of the novel apparatus. This work demonstrates the ability to use custom devices in HSSR to collect accurate data, in vivo, for calibration of computational models.

Neuromuscular and biomechanical landing alterations persist in athletes returning to sport after anterior cruciate ligament reconstruction

BACKGROUND

Anterior cruciate ligament reconstructed (ACLR) athletes show increased hamstrings activation and decreased knee flexion moments (KFMs) during single leg landing tasks at time of return-to-sport (RTS). Although these landing alterations seem protective in the short term, they might become undesirable if they persist after RTS. Therefore, the main aim of this study was to investigate whether those landing alterations persist in the months following RTS.

METHODS

Sixteen athletes who had an ACLR performed five unilateral landing tasks at three different time points (at RTS, and at 3 and 6 months after RTS) while KFMs and hamstrings activation were recorded. The following clinical parameters were registered: isokinetic strength of quadriceps and hamstrings, ACL return-to-sport after injury scale (ACL-RSI), Tampa scale of kinesiophobia, self-reported instability and single leg hop distance. A one-way repeated measures analysis of variance (ANOVA) was used to assess whether landing deficits changed over time. Additionally, an explorative analysis was performed to assess whether those athletes whose deficits persisted the most could be identified based on baseline clinical parameters.

RESULTS

The ANOVA showed no differences in landing deficits between sessions, indicating persisting reduced KFMs and increased hamstrings activation in the injured leg compared with the contralateral leg. A significant improvement of the quadriceps concentric strength (at 120°/s), ACL-RSI score and jump distance of the single leg hop was found over time.

CONCLUSIONS

Landing alterations were not resolved 6 months after RTS. Additional interventions may be needed to normalize landing alterations prior to return to sport.

Relationship between anterior cruciate ligament rupture and the posterior tibial and meniscal slopes in professional soccer athletes

OBJECTIVE

Several anatomical parameters have been associated with increased risk of anterior cruciate ligament rupture; however, published studies provide conflicting results. The objectives of this study are to assess whether there is a relationship between anterior cruciate ligament rupture and the lateral and medial posterior tibial slopes, as well as the lateral and medial posterior meniscal slopes and posterior tibial and meniscal delta-slopes.

MATERIALS AND METHODS

A retrospective case-control study was conducted in professional soccer athletes, using images from knee magnetic resonance imaging scans in athletes with clinical and radiological diagnosis of anterior cruciate ligament rupture, and control group, with no signs of ligament rupture.

RESULTS

The lateral and medial posterior tibial slopes, the lateral and medial posterior meniscal slopes, and the posterior tibial and meniscal delta-slopes showed significant differences between the groups (p < 0.05). Multivariate analysis logistic regression revealed that the lateral and medial posterior meniscal slopes proved to be predictors for increased risk of anterior cruciate ligament rupture in professional soccer players.

CONCLUSION

Posterior tibial and meniscal slopes and tibial and meniscal delta-slopes are related to a greater risk of rupture of the anterior cruciate ligament in professional male soccer athletes. The lateral and medial posterior meniscal slopes are predictors for ligament rupture.

Immediate Effect of Anterior Cruciate Ligament Protective Knee Taping on Knee Landing Mechanics and Muscle Activations during Side Hops

Athletic taping is widely used in sports to prevent injury. However, the effect of anterior cruciate ligament (ACL) protective taping on neuromuscular control during dynamic tasks remains unclear. Therefore, this study aimed to investigate the immediate effect of ACL protective taping on landing mechanics and muscle activations during side hops in healthy individuals. Fifteen healthy individuals (11 males and 4 females; age, 23.1 ± 1.4 years; height, 175.1 ± 10.4 cm; weight, 66.3 ± 11.2 kg) volunteered to participate in this study. Landing mechanics and muscle activations were measured while each participant performed single-leg hops side-to-side for ten repetitions with and without taping. An optical motion capture system and two force plates were used to collect the kinematic and kinetic data during the side hops. Surface electromyogram recordings were performed using a wireless electromyography system. Paired t-tests were performed to determine the differences in landing mechanics and muscle activations between the two conditions (taping and non-taping). The level of significance was set at p < 0.05. Compared with the non-taping condition, participants landed with a smaller knee abduction angle, greater knee external rotation angle, and smaller knee extensor moment in the taping condition. Given that greater knee abduction, internal rotation, and knee extension moment are associated with a greater risk of ACL injury, our findings suggest that ACL protective taping can have an immediate effect on dynamic knee stability. Clinicians should consider using ACL protective taping to facilitate the use of favorable landing mechanics for ACL injuries.

The effectiveness of vibration therapy for muscle peak torque and postural control in individuals with anterior cruciate ligament reconstruction: a systematic review and meta-analysis of clinical trials

Objective

This study aimed to review and summarize the existing evidence on the effectiveness of vibration therapy (VT) in comparison with conventional rehabilitation in anterior cruciate ligament (ACL)-reconstructed patients considering muscle peak torque and postural control.

Methods

We searched available online databases for relevant studies published up to February 2020. All randomized clinical trials investigating the effect of VT on quadriceps peak torque, hamstring peak torque, and postural control (closed-eye and open-eye) were included. Overall, 13 clinical trials with a total sample size of 407 participants were included for the meta-analysis. We used the pooled mean difference with random effects model for meta-analyses. We assessed the heterogeneity of the studies using the I² and Cochran’s Q test. Meta-regression analysis was used to assess the source of heterogeneity.

Results

We found that VT significantly improved hamstring peak torque [weighted mean difference (WMD) 12.67, 95% CI 4.51–20.83] and quadriceps peak torque (WMD 0.11, 95% CI −0.06 to 0.29). However, subgroup analysis showed a significant increase in mentioned muscles’ peak torque in studies employing interventions including both local muscle vibration (LMV) and vibration frequency higher than 100 Hz (WMD 20.84, 95% CI 11.75–29.93). With regard to postural control, we observed a significant improvement only in open-eye mediolateral postural control (WMD 0.26, 95% CI −1.26 to 1.77).

Conclusion

This study suggests that VT, especially LMV type with vibration frequency higher than 100 Hz, can be effective in rehabilitation of ACL-reconstructed patients. Although improvement in the peak torque of hamstring and quadriceps muscles was seen, there was no significant improvement in postural control, especially closed-eye, in comparison with conventional rehabilitation.

Level of evidence

1.

Highlights

Vibration therapy can increase hamstring peak torque in individuals with ACL reconstruction.

Local muscle vibration type in comparison with whole-body vibration is recommended for ACL-reconstructed patients.

Vibration frequency higher than 100 Hz is preferred in ACL-reconstructed rehabilitation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10195-021-00589-5.

Differences in Muscle Activities and Kinematics between Forefoot Strike and Rearfoot Strike in the Lower Limb during 180° Turns

BACKGROUND

A forefoot strike (FFS) could be a safer landing technique than a rearfoot strike (RFS) during a cutting motion to prevent anterior cruciate ligament (ACL) injury.

PURPOSE

This study aimed to determine the joint angles, ground reaction force (GRF), and muscle activity levels associated with FFS and RFS landings during 180° turns.

STUDY DESIGN

Cross-sectional study.

METHODS

Fourteen male soccer players from the University of Tsukuba football (soccer) club participated in this study. The FFS consisted of initial contact with the toes on the force plates followed by the rearfoot; meanwhile, the initial contact was performed with the heels on the force plates followed by the forefoot for the RFS. Ankle, knee, and hip joint angles were recorded using a three-dimensional motion capture system. GRFs were measured using a force plate. Gluteus medius (GM), rectus femoris (RF), vastus medialis (VM), vastus lateralis (VL), semitendinosus (ST), biceps femoris (BF), tibialis anterior (TA), and lateral gastrocnemius (GL) activities were measured by electromyography.

RESULTS

The activities of GM, GL, and ST from initial contact to early periods during landing into the ground with the FFS are larger than those with RFS. In addition, the results showed significant differences in lower-limb angles and GRFs between the FFS and RFS.

CONCLUSION

These results suggest that there might be differences in ACL injury risk during a 180° turn between the FFS and the RFS pattern. An investigation into the grounding method that prevents injury is necessary in future studies.

LEVELS OF EVIDENCE

Level 3b.

Knee flexion angle and muscle activations control the stability of an anterior cruciate ligament deficient joint in gait

Anterior cruciate ligament (ACL) is a primary structure and a commonly injured ligament of the knee joint. Some patients with ACL deficiency (ACLD) experience joint instability and require a reconstructive surgery to return to daily routines, some can adapt by limiting their activities while others, called copers, can return to high-level activities with no instability. We investigated the effects of alterations in the knee flexion angle (KFA) and muscle force activations on the stability and biomechanics of ACLD joints at 25, 50, and 75% periods of gait stance. ACLD joint stability is controlled by variations in both KFA and knee muscle forces. For the latter, a parameter called activity index is defined as the ratio of forces in ACL antagonists (quadriceps and gastrocnemii) to those in ACL agonists (hamstrings). Under a greater KFA (2-6° beyond the mean of reported values in healthy subjects), an ACLD joint regains its pre-injury stability levels. The ACLD joint stability also markedly improves at smaller quadriceps and larger hamstrings forces (activity indices of 2.0-3.6 at 25%) at the first half of stance and smaller gastrocnemii and larger hamstrings forces (activity indices of 0.1-1.1 at 50% and 0.1-1.2 at 75%) at the second half of stance. Activity index and KFA are both crucial when assessing the dynamic stability of an ACLD joint. These results are helpful in our understanding of the biomechanics and stability of ACLD joints towards improved prevention and treatment strategies.

Standard RTS criteria effectiveness verification using FMS, Y-balance and TJA in footballers following ACL reconstruction and mild lower limb injuries

The anterior cruciate ligament (ACL) is the most frequently injured knee ligament. In previous studies, it was demonstrated that patients following ACL reconstruction may present motor deficits which may be related to increased risk of injury. The objective of the study was to determine whether players who have passed RTS assessment still have deficits in movement patterns or in neuromuscular control after such a serious injury as ACL rupture and reconstruction,. Sixty-five male football players (age 18-25 years), recruited from regional teams, were divided into three groups: (1) ACL group-subjects after ACL rupture and reconstruction (n = 24); (2) Mild Injury (MI) group-subjects after mild lower limb injuries (n = 21); and (3) Control (C) group-subjects without injuries (n = 20). For all groups, the Y-balance test, Functional Movement Screen (FMS) and Tuck Jump Assessment (TJA) were performed. For the Y-balance test in ACL group for the injured leg, significantly lower values were demonstrated for anterior reach ((ACL) 69.2 ± 5.7% vs. (MI) 74.8 ± 4.5% vs. (C) 74.0 ± 5.6%), at posterior-lateral reach ((ACL) 103.2 ± 6.4% vs. (C) 108.5 ± 6.0%) and composite score ((ACL) 93.9 ± 4.4% vs. (MI) 97.9 ± 4.3%) in comparison to the remaining two groups. In the FMS test, the ACL group had significantly lower composite score (12 ± 4 points) compared to the C group (15 ± 2 points). Also, compared to the remaining groups, subjects following ACL reconstruction demonstrated significantly lower performance in the TJA test related to the following elements: thighs do not reach parallel, thighs not equal side-to-side, foot placement not shoulder width apart, technique declines prior to 10 s and lower extremity valgus at landing. The authors have observed that athletes after ACL reconstruction still have deficits in movement patterns or in neuromuscular control despite passing the RTS and being cleared to perform sports. Creating a set of sufficiently sensitive assessment methods may significantly reduce the potential risk of injury due to the fact that diagnosed and monitored deficits may be treated on an ongoing basis. The authors suggest that individual elements of the Y-balance and TJA tests may be suitable for such specific assessment.

Athletes with an ACL reconstruction show a different neuromuscular response to environmental challenges compared to uninjured athletes

BACKGROUND

Evidence suggests that neuromuscular alterations in patients with an anterior cruciate ligament reconstruction (ACLR) are rooted in neurocognitive and proprioceptive deficits. The aim of this study was to assess neuromuscular control of athletes with ACLR under increased cognitive and environmental challenges.

RESEARCH QUESTION

Do athletes with ACLR show a different neuromuscular response to cognitive and environmental challenges relative to controls?

METHODS

Cross-sectional study. Twenty athletes who had an ACLR (age: 23.7 ± 4.3 years, 14 males, time post-surgery: 258.6 ± 54 days) and twenty uninjured controls (age: 21.4 ± 1.5 years, 14 males) performed a stepping down-task in four environmental conditions: no additional challenges, while performing a cognitive dual-task, while undergoing an unpredictable support surface perturbation, and with the cognitive dual-task and unpredictable perturbation combined. Muscle activations of the vastus medialis (VM), vastus lateralis, hamstrings medialis (HM), hamstrings lateralis (HL), gastrocnemius medialis, gastrocnemius lateralis (GL) and gluteus medius were recorded with surface EMG. A three-way ANOVA with main effects for group, dual-task and perturbation was used to compare muscle activations.

RESULTS

Athletes with ACLR show larger HM (ES = 0.45) and HL activation (ES = 1.32) and lower VM activation (ES = 0.72), compared to controls. Athletes with ACLR show a significantly smaller increase in VM (ES = 0.69), VL (ES = 0.53) and GL activation (ES = 0.52) between perturbed and unperturbed tasks compared to controls. Furthermore, under cognitive loading a significantly larger decrease in HM activation (ES = 0.40) and (medial) co-contraction (ES = 0.75) was found in athletes with ACLR compared to controls.

SIGNIFICANCE

Athletes with ACLR show an altered neuromuscular response which might represent an arthrogenic muscle response. They show less additional adaptation to perturbed tasks compared to controls, potentially as result of altered proprioceptive input. Furthermore a larger influence of increased cognitive loading on the neuromuscular control was found in athletes with ACLR, indicating that also neurocognitive limitations may contribute to altered neuromuscular control.

Plantaris tendon: a novel graft for anterolateral ligament reconstruction and additional reinforcement for anterior cruciate ligament autografts in combined reconstructive procedures

The anterolateral ligament is recently recognized as an important structure in restoring rotational stability of the anterior cruciate ligament-deficient knee. Biomechanical and clinical studies confirmed the benefits of concurrent anterior cruciate ligament and anterolateral ligament reconstruction. However, present techniques mostly use hamstring tendons autografts and therefore additionally disrupt the knee biomechanics. The plantaris tendon is a well known and accessible graft and has excellent biomechanical properties for anterolateral ligament reconstruction. The present paper describes a new combined anterior cruciate ligament and anterolateral ligament reconstruction technique using plantaris tendon and semitendinosus tendon.Level of evidence V (Case report).

Single-Joint and Whole-Body Movement Changes in Anterior Cruciate Ligament Athletes Returning to Sport

INTRODUCTION

Athletes returning to sport after anterior cruciate ligament reconstruction (ACLR) demonstrate prolonged changes in landing kinematics, kinetics, and muscle activation, predisposing them for reinjury, knee osteoarthritis, and/or knee instability. So far, researchers have been focusing on how kinematics and kinetics change in every joint separately. However, as the human body operates within a kinetic chain, we will assess whether single-joint changes are associated with whole-body changes.

METHODS

Twenty-one athletes who had an ACLR and 21 uninjured controls performed five unilateral landing tasks, whereas lower limb kinematics, kinetics, and muscle activations of vastus medialis, vastus lateralis, biceps femoris, semitendinosus, semimembranosus, gastrocnemius, and gluteus medius were recorded. Single-joint landing kinematics, kinetics, and muscle activations of the ACL-injured leg were compared with the uninjured leg and compared with the control group. Whole-body changes were assessed by decomposing movements into fundamental components using marker-based principal component analysis (PCA).

RESULTS

We found several single-joint changes in landing kinematics, kinetics, and muscle activations in the athletes with ACLR that were seen across all tasks and therefore of major interest as they are likely to occur during sports as well. Hamstrings activation increased and external knee flexion moments decreased in the ACL-injured leg compared with their uninjured leg. Furthermore, hip adduction moments and knee abduction angles decreased compared with the control group. The PCA could detect changes in whole-body movement, which were task-specific.

CONCLUSIONS

Athletes with ACLR still show protective task-independent single-joint kinematic, kinetic, and muscle activation changes during single-leg landings at the time of return to sport. These single-joint changes were not consistently accompanied by changes in whole-body movements (revealed by marker-based PCA). Whole-body expressions of the single-joint compensations are likely to be affected by the demands of the task.

Long-term arthroscopic assessment of intra-articular allografts for treatment of spontaneous cranial cruciate ligament rupture in the dog

OBJECTIVE

To assess the 12-month survival of intra-articular, decellularized allografts for the treatment of cranial cruciate ligament disease (CCLD) in dogs.

STUDY DESIGN

Prospective case series.

ANIMALS

Twenty client-owned dogs with spontaneous CCL rupture.

METHODS

Affected stifles were treated solely by implantation of an intra-articular, decellularized, deep digital flexor tendon allograft. Functional outcome was evaluated at baseline and at 6 and 12 months after surgery with the Liverpool Osteoarthritis for Dogs questionnaire and force platform gait analysis. At 12 months after surgery, dogs underwent arthroscopy to visually assess the allografts.

RESULTS

Scores on owner questionnaires (improved 62.5%; P = .005) and ground reaction forces (improved 34.4%; P = .017) were improved in all dogs 12 months after surgery. Dogs with an intact graft (IG) were more likely to have a successful outcome compared with dogs with a torn graft (P = .011). According to arthroscopy, 45% of grafts seemed to survive at 12 months after surgery.

CONCLUSION

About half of intra-articular allografts survived 12 months after implantation in CCL-deficient stifles. Dogs with IG had successful outcomes at 12 months after surgery according to assessment by force platform gait analysis.

CLINICAL SIGNIFICANCE

These results preclude immediate clinical application but provide evidence to justify further investigation of intra-articular grafts as a repair option for CLLD.

Relationship between electromyographic activity of knee joint muscles with vertical and posterior ground reaction forces in anterior cruciate ligament reconstructed patients during a single leg vertical drop landing task

The objective of the present study is to examine the relation between activity patterns of knee joint muscles with vertical and posterior ground reaction forces (VGRF and PGRF, respectively) in patients after anterior cruciate ligament reconstruction (ACLR). Twenty males post-ACLR participated in this cross-sectional study. The association between muscle activity with VGRF and PGRF was assessed during a single leg vertical drop-landing task. There were strong negative associations between preparatory VL, VM and MG activity and PGRF (P< 0.05). Strong positive associations were found between reactive VM and LH activity with PGRF (P< 0.05). Preparatory co-activation of VM: MH had significant negative associations with VGRF (P< 0.05) and reactive co-activation of VL:LH had a significant positive relation with PGRF(P< 0.05). Greater preparatory activity and co-activation of knee muscles were associated with lower peak PGRF and VGRF, whereas greater reactive activity and co-activation of knee muscles was associated with greater peak PGRF and VGRF. According to our findings, both activity and co-activation of knee muscles during the preparatory phase were associated with reduced PGRF and VGRF, respectively in ACLR patients; thus, incorporating exercises in order to increase preparatory activity and co-activation of knee joint muscles into rehabilitation programs in ACLR patients seems necessary.

Compensatory strategy for ankle dorsiflexion muscle weakness during gait in patients with drop-foot

BACKGROUND

Pathological movement patterns are characterized by abnormal kinematics, kinetics and muscle activations that alter the distribution of muscle forces during walking.

AIM

The objective of this study was to identify what compensatory strategy is evident in muscle force distribution in patients with drop-foot, in response to weakness in the dorsiflexor muscles.

METHODS

A sample of 10 patients with drop-foot were evaluated by a computerized gait analysis system and compared to a group of 10 healthy subjects. Muscle-actuated simulations of normal and drop-foot walking were performed using OpenSim software. A musculoskeletal model with 43 muscles acting on one lower extremity was used in order to perform the simulations. In order to evaluate the difference between muscle force curves in the healthy and the drop-foot populations, an integrals of each muscle curve were computed.

RESULTS

The group of patients with drop-foot exhibited an increased force integral for all muscle groups, except for the ankle evertors. The highest increases were observed for hip adductors (112%), hip extensors (88%), knee and hip flexors (83% and 50%, respectively) and for the plantarflexor (47%). These results were mainly influenced by the following muscles: flexor digitorum and hallucius, tibialis posterior and semitendinosus. The force integral for these muscles increased by more than 200% in the drop-foot group as compared to the control group. In addition, significant changes (>100%) were noted for the posterior thigh muscle group (semitendinosus, biceps femoris long and short head), which are responsible for bending the knee joint and straightening the hip joint.

CONCLUSIONS

It was proved that the loss in muscle force in individual muscle groups of the ankle joint are compensated for by the increased force and activity in other muscles acting on this joint and another muscles in neighbouring joints. The results may have important implications for physiotherapy treatments.

Can altered neuromuscular coordination restore soft tissue loading patterns in anterior cruciate ligament and menisci deficient knees during walking?

Injuries to the anterior cruciate ligament (ACL) and menisci commonly lead to early onset osteoarthritis. Treatments that can restore normative cartilage loading patterns may mitigate the risk of osteoarthritis, though it is unclear whether such a goal is achievable through conservative rehabilitation. We used musculoskeletal simulation to predict cartilage and ligament loading patterns during walking in intact, ACL deficient, menisci deficient, and ACL-menisci deficient knees. Stochastic simulations with varying coordination strategies were then used to test whether neuromuscular control could be modulated to restore normative knee mechanics in the pathologic conditions. During early stance, a 3 mm increase in anterior tibial translation was predicted in the ACL deficient knee. Mean cartilage contact pressure increased by 18% and 24% on the medial and lateral plateaus, respectively, in the menisci deficient knee. Variations in neuromuscular coordination were insufficient to restore normative cartilage contact patterns in either the ACL or menisci deficient knees. Elevated cartilage contact pressures in the pathologic knees were observed in regions where cartilage wear patterns have previously been reported. These results suggest that altered cartilage tissue loading during gait may contribute to region-specific degeneration patterns, and that varying neuromuscular coordination in isolation is unlikely to restore normative knee mechanics.

Activation of biceps femoris long head reduces tibiofemoral anterior shear force and tibial internal rotation torque in healthy subjects

The anterior cruciate ligament (ACL) provides resistance to tibial internal rotation torque and anterior shear at the knee. ACL deficiency results in knee instability. Optimisation of muscle contraction through functional electrical stimulation (FES) offers the prospect of mitigating the destabilising effects of ACL deficiency. The hypothesis of this study is that activation of the biceps femoris long head (BFLH) reduces the tibial internal rotation torque and the anterior shear force at the knee. Gait data of twelve healthy subjects were measured with and without the application of FES and taken as inputs to a computational musculoskeletal model. The model was used to investigate the optimum levels of BFLH activation during FES gait in reducing the anterior shear force to zero. This study found that FES significantly reduced the tibial internal rotation torque at the knee during the stance phase of gait (p = 0.0322) and the computational musculoskeletal modelling revealed that a mean BFLH activation of 20.8% (±8.4%) could reduce the anterior shear force to zero. At the time frame when the anterior shear force was zero, the internal rotation torque was reduced by 0.023 ± 0.0167 Nm/BW, with a mean 188% reduction across subjects (p = 0.0002). In conclusion, activation of the BFLH is able to reduce the tibial internal rotation torque and the anterior shear force at the knee in healthy control subjects. This should be tested on ACL deficient subject to consider its effect in mitigating instability due to ligament deficiency. In future clinical practice, activating the BFLH may be used to protect ACL reconstructions during post-operative rehabilitation, assist with residual instabilities post reconstruction, and reduce the need for ACL reconstruction surgery in some cases.

Influence of Medial Hamstring Tendon Harvest on Knee Flexor Strength after Anterior Cruciate Ligament Reconstruction

Background

The advantages of hamstring tendon autografts for anterior cruciate ligament reconstruction are well known; however, concerns have arisen regarding the influence of hamstring tendon harvest on postoperative weakness in knee flexion.

Purpose

To evaluate the influence of hamstring tendon harvest on knee flexion strength in patients undergoing anterior cruciate ligament reconstruction.

Study Design

Prospective randomized study.

Methods

Ninety patients were randomly assigned at surgery to undergo anterior cruciate ligament reconstruction with either a semitendinosus tendon autograft or a semitendinosus and gracilis tendon autograft. Quadriceps and hamstring muscle strength was tested before surgery and at 6, 12, and 18 months after surgery.

Results

There was no significant difference in clinical results between the groups and neither group showed a significant decrease in isokinetic hamstring muscle strength. However, when the subjects’ knees were at positions of 70° or more of flexion, both isokinetic and isometric measurements revealed a significant decrease in hamstring muscle strength in both groups. The strength in the group with semitendinosus and gracilis tendons was considerably less than that in the group with semitendinosus tendon alone at 18 months.

Conclusions

Tendon harvest causes significant weakness of hamstring muscle strength at high knee flexion angles, but such weakness can be minimized if the gracilis tendon is preserved.

Knee muscle activity during gait in patients with anterior cruciate ligament injury: a systematic review of electromyographic studies

PURPOSE

This review compared knee muscle activity between ACL-deficient (ACLD) patients and healthy controls during gait, to find out whether the available electromyography (EMG) studies support Quadriceps (Q-ceps) inhibition or hamstring facilitation during gait in ACLD patients.

METHOD

A systematic review was conducted to retrieve the EMG studies of knee muscles during gait in ACLD patients. Cochrane library, PubMed, Medline, Ovid, CINAHL and Science Direct databases were searched entries from 1995 through October 2014 using the terms "anterior cruciate ligament" OR "ACL", "electromyography" Or "EMG" "gait" Or "walking". Articles that assessed subjects with ACL rupture that used surface EMG to assess the knee muscle activity were included. The quality of the included papers was assessed using the Critical Appraisal Skills Programme tool for observational studies.

RESULT

In total, 13 studies met the inclusion criteria. Seven studies consistently found no significant difference in magnitude of activity or timing of Q-ceps muscle between the chronic ACLD patients and control subjects. Two studies on acute ACLD patients and three studies on ACLD patients with unstable knee found the significantly reduced Q-ceps activity compared to control subjects. Six studies showed the significantly greater hamstring activity, and three studies found prolonged duration of activity in ACLD patients compared to the control subjects.

CONCLUSION

This review highlighted that the results of the studies are in favour of increased hamstring muscular activity. However, decreased Q-ceps activation exists in the acute stage and in ACLD patients that experience knee instability (non-copers).

LEVEL OF EVIDENCE

III.

Increasing hip and knee flexion during a drop-jump task reduces tibiofemoral shear and compressive forces: implications for ACL injury prevention training

Although most ACL injury prevention programmes encourage greater hip and knee flexion during landing, it remains unknown how this technique influences tibiofemoral joint forces. We examined whether a landing strategy utilising greater hip and knee flexion decreases tibiofemoral anterior shear and compression. Twelve healthy women (25.9 ± 3.5 years) performed a drop-jump task before and after a training session (10-15 min) that emphasised greater hip and knee flexion. Peak tibiofemoral anterior shear and compressive forces were calculated using an electromyography (EMG)-driven knee model that incorporated joint kinematics, EMG and participant-specific muscle volumes and patella tendon orientation measured using magnetic resonance imaging (MRI). Participants demonstrated a decrease in peak anterior tibial shear forces (11.1 ± 3.3 vs. 9.6 ± 2.7 N · kg^-1; P = 0.008) and peak tibiofemoral compressive forces (68.4 ± 7.6 vs. 62.0 ± 5.5 N · kg^-1; P = 0.015) post-training. The decreased peak anterior tibial shear was accompanied by a decrease in the quadriceps anterior shear force, while the decreased peak compressive force was accompanied by decreased ground reaction force and hamstring forces. Our data provide justification for injury prevention programmes that encourage greater hip and knee flexion during landing to reduce tibiofemoral joint loading.

Effects of denervation of the hip joint on results of clinical observations and instrumented gait analysis in dogs with sodium urate crystal-induced synovitis

OBJECTIVE To evaluate the effects of selective hip joint denervation on gait abnormalities and signs of hip joint pain in dogs. ANIMALS 6 healthy adult hound-type dogs. PROCEDURES Minimally invasive denervation was performed on the right hip joint of each dog. Two weeks later, sodium urate was injected into the right hip joint to induce synovitis. Dogs were evaluated clinically and by use of instrumented gait analysis before and 2 weeks after minimally invasive denervation and 4, 8, and 24 hours after induction of synovitis. Dogs were euthanized, and necropsy and histologic examination were performed. RESULTS No kinetic or kinematic gait modifications were detected 2 weeks after minimally invasive denervation. Denervation did not eliminate signs of pain and lameness associated with sodium urate-induced synovitis. Results of histologic examination confirmed that denervation was an effective method for transecting the innervation of the craniolateral and caudolateral aspects of the hip joint capsule. CONCLUSIONS AND CLINICAL RELEVANCE In this study, minimally invasive denervation did not result in gait modifications in dogs. Denervation did not abolish the signs of pain and lameness associated with generalized induced synovitis of the hip joint. Further studies are required before conclusions can be drawn regarding the clinical usefulness of hip joint denervation for dogs with hip dysplasia.

Variations in medial-lateral hamstring force and force ratio influence tibiofemoral kinematics

A change in hamstring strength and activation is typically seen after injuries or invasive surgeries such as anterior cruciate reconstruction or total knee replacement. While many studies have investigated the influence of isometric increases in hamstring load on knee joint kinematics, few have quantified the change in kinematics due to a variation in medial to lateral hamstring force ratio. This study examined the changes in knee joint kinematics on eight cadaveric knees during an open-chain deep knee bend for six different loading configurations: five loaded hamstring configurations that varied the ratio of a total load of 175 N between the semimembranosus and biceps femoris and one with no loads on the hamstring. The anterior-posterior translation of the medial and lateral femoral condyles' lowest points along proximal-distal axis of the tibia, the axial rotation of the tibia, and the quadriceps load were measured at each flexion angle. Unloading the hamstring shifted the medial and lateral lowest points posteriorly and increased tibial internal rotation. The influence of unloading hamstrings on quadriceps load was small in early flexion and increased with knee flexion. The loading configuration with the highest lateral hamstrings force resulted in the most posterior translation of the medial lowest point, most anterior translation of the lateral lowest point, and the highest tibial external rotation of the five loading configurations. As the medial hamstring force ratio increased, the medial lowest point shifted anteriorly, the lateral lowest point shifted posteriorly, and the tibia rotated more internally. The results of this study, demonstrate that variation in medial-lateral hamstrings force and force ratio influence tibiofemoral transverse kinematics and quadriceps loads required to extend the knee. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1707-1715, 2016.

Prophylactic knee bracing alters lower-limb muscle forces during a double-leg drop landing

Anterior cruciate ligament (ACL) injury can be a painful, debilitating and costly consequence of participating in sporting activities. Prophylactic knee bracing aims to reduce the number and severity of ACL injury, which commonly occurs during landing maneuvers and is more prevalent in female athletes, but a consensus on the effectiveness of prophylactic knee braces has not been established. The lower-limb muscles are believed to play an important role in stabilizing the knee joint. The purpose of this study was to investigate the changes in lower-limb muscle function with prophylactic knee bracing in male and female athletes during landing. Fifteen recreational athletes performed double-leg drop landing tasks from 0.30m and 0.60m with and without a prophylactic knee brace. Motion analysis data were used to create subject-specific musculoskeletal models in OpenSim. Static optimization was performed to calculate the lower-limb muscle forces. A linear mixed model determined that the hamstrings and vasti muscles produced significantly greater flexion and extension torques, respectively, and greater peak muscle forces with bracing. No differences in the timings of peak muscle forces were observed. These findings suggest that prophylactic knee bracing may help to provide stability to the knee joint by increasing the active stiffness of the hamstrings and vasti muscles later in the landing phase rather than by altering the timing of muscle forces. Further studies are necessary to quantify whether prophylactic knee bracing can reduce the load placed on the ACL during intense dynamic movements.

Hamstring Activity in the Anterior Cruciate Ligament Injured Patient: Injury Implications and Comparison With Quadriceps Activity

PURPOSE

To investigate the potential causes of diminished knee extension after acute anterior cruciate ligament (ACL) injury using both surface electromyography (sEMG) analysis of the quadriceps and hamstrings, and gait analysis to assess muscle action and tone.

METHODS

Consecutive patients with an acute ACL tear underwent sEMG and gait analysis within 2 weeks of injury, before ACL reconstruction. Standard motion analysis techniques were used and sEMG data were collected simultaneously with gait data. T-tests were used to determine differences between the ACL-deficient and control subjects in knee flexion angles, peak external knee joint moments, and total time that a muscle was activated ("on") during gait. External knee moments were expressed as a percentage of body weight times height.

RESULTS

Ten patients (mean age 24 ± 4 years) were included at a mean 10.2 days between injury and analysis; 10 uninjured, matched control subjects were included for comparison. There were significant increases in minimum flexion angle at heel strike (5.92 ± 3.39 v -3.49 ± 4.55, P < .001) and midstance (14.1 ± 6.23 v 1.20 ± 4.21, P < .001) in the injured limb compared with controls. There were significantly lower maximum external extension moments at heel strike (-0.99 ± 0.46 v -2.94 ± 0.60, P < .001) and during the second half of stance in the injured limb compared with controls (-0.56 ± 1.14 v -3.54 ± 1.31, P < .001). The rectus femoris was "on" significantly less during gait in the injured leg compared with controls (49.1 ± 7.76% v 61.0 ± 14.8%, P = .044). There were no significant differences in hamstring activity "on" time during gait (P > .05).

CONCLUSIONS

In patients with acute ACL injury, the ACL-deficient limb does not reach as much extension as controls. Although the rectus femoris is "on" for shorter periods during the gait cycle, there is no difference in hamstring time on during gait. This information may help clinicians better understand muscle function and gait patterns in the acute time period after ACL injury.

LEVEL OF EVIDENCE

Level III, case control study.

Muscle co-contraction during gait in individuals with articular cartilage defects in the knee

Increased muscle co-contraction during gait is common in individuals with knee pathology, and worrisome as it is known to amplify tibiofemoral compressive forces. While knees with articular cartilage defects (ACD) are more vulnerable to compressive forces, muscle co-contraction has never been reported in this population. The purpose of this study was to evaluate the extent to which individuals with ACDs in the knee demonstrate elevated quadriceps to hamstrings muscle co-contraction on the involved limb during gait compared to the uninvolved limb and to healthy controls. We also explored the impact of participant characteristics and knee impairments on co-contraction. Twenty-nine individuals with full-thickness knee ACDs (ACD group) and 19 healthy adults (control group) participated in this study. Participants performed five gait trials at self-selected speed, during which activity of the quadriceps and hamstrings muscles were collected with surface electromyography. Three-dimensional motion capture was used to define phases of gait. Quadriceps strength and self-reported outcomes were also assessed in the same session. There were no differences in quadriceps: hamstrings co-contraction between the ACD and control groups, or between the involved and uninvolved limb for the ACD group. For both ACD and control groups, co-contraction was highest in early stance and lowest in late stance. Quadriceps strength was consistently the strongest predictor of muscle co-contraction in both the ACD and the control groups, with individuals with lower strength demonstrating greater co-contraction. Further study is needed to understand the effect of increased muscle co-contraction on joint compressive forces in the presence of varied quadriceps strength.

Mechanical loading of knee articular cartilage induced by muscle contraction can be assessed by measuring electrical potentials at the surface of the knee

Electroarthrography (EAG) consists of recording electrical potentials on the knee surface that originate from streaming potentials within articular cartilage while the joint is undergoing compressive loading. The aim was to investigate how the contraction of specific leg muscles affects the contact force of the knee joint and, in turn, the EAG values. For six normal subjects, voluntary isometric muscle contractions were repeatedly conducted to activate four leg muscle groups while the subject was lying on his back. Two EAG signals were recorded on the medial and lateral sides of the knee, as well as four EMG signals (gastrocnemius, hamstring, quadriceps, tensor fascia latae), and the signal from a force plate fixed against the foot according to the direction of the force. The EAG and force signals were very well correlated: the median of the correlation coefficients between an EAG signal and the corresponding force signal during each loading cycle was 0.91, and 86% of the correlation coefficients were statistically significant (p<5%). Isolated muscle contraction was possible for the gastrocnemius and hamstring, but not always for the quadriceps and tensor fascia latae. Using the clinical loading protocol which consists of a one-legged stance, the quadriceps and hamstring EMGs showed minimal activity; loading cycles with increased EAG amplitude were associated with higher EMG activity from the gastrocnemius, which is involved in antero-posterior balance. These results document the role of the EAG as a "sensor" of the knee contact force and contribute to the development of clinical loading protocols with improved reproducibility.

Intra-Articular Knee Contact Force Estimation During Walking Using Force-Reaction Elements and Subject-Specific Joint Model2

Joint contact forces measured with instrumented knee implants have not only revealed general patterns of joint loading but also showed individual variations that could be due to differences in anatomy and joint kinematics. Musculoskeletal human models for dynamic simulation have been utilized to understand body kinetics including joint moments, muscle tension, and knee contact forces. The objectives of this study were to develop a knee contact model which can predict knee contact forces using an inverse dynamics-based optimization solver and to investigate the effect of joint constraints on knee contact force prediction. A knee contact model was developed to include 32 reaction force elements on the surface of a tibial insert of a total knee replacement (TKR), which was embedded in a full-body musculoskeletal model. Various external measurements including motion data and external force data during walking trials of a subject with an instrumented knee implant were provided from the Sixth Grand Challenge Competition to Predict in vivo Knee Loads. Knee contact forces in the medial and lateral portions of the instrumented knee implant were also provided for the same walking trials. A knee contact model with a hinge joint and normal alignment could predict knee contact forces with root mean square errors (RMSEs) of 165 N and 288 N for the medial and lateral portions of the knee, respectively, and coefficients of determination (R2) of 0.70 and −0.63. When the degrees-of-freedom (DOF) of the knee and locations of leg markers were adjusted to account for the valgus lower-limb alignment of the subject, RMSE values improved to 144 N and 179 N, and R2 values improved to 0.77 and 0.37, respectively. The proposed knee contact model with subject-specific joint model could predict in vivo knee contact forces with reasonable accuracy. This model may contribute to the development and improvement of knee arthroplasty.

Sagittal kinematics of mobile unicompartmental knee replacement in anterior cruciate ligament deficient knees

BACKGROUND

There is a greater risk of tibial component loosening when mobile unicompartmental knee replacement is performed in anterior cruciate ligament deficient knees. We previously reported on a cohort of anterior cruciate ligament deficient patients (n=46) who had undergone surgery, but no difference was found in implant survivorship at a mean 5-year follow-up. The purpose of this study was to examine the kinematic behaviour of a subcohort of these patients.

METHODS

The kinematic behaviour of anterior cruciate deficient knees (n=16) after mobile unicompartmental knee replacement was compared to matched intact knees (n=16). Sagittal plane knee fluoroscopy was taken while patients performed step-up and forward lunge exercises. The patellar tendon angle, knee flexion angle and implant position was calculated for each video frame.

FINDINGS

The patellar tendon angle was 5° lower in the deficient group, indicating greater anterior tibial translation compared to the intact group between 30 and 40° of flexion. Large variability, particularly from 40-60° of flexion, was observed in the bearing position of the deficient group, which may represent different coping mechanisms. The deficient group took 38% longer to perform the exercises.

INTERPRETATION

Kinematic differences were found between the deficient and intact knees after mobile unicompartmental knee replacement; but these kinematic changes do not seem to affect the medium-term clinical outcome. Whether these altered knee kinematics will have a clinical impact is as yet undetermined, but more long-term outcome data is required before mobile unicompartmental knee replacement can be recommended for an anterior cruciate ligament deficient patient.

Electromechanical delay of the knee flexor muscles after anterior cruciate ligament reconstruction using semitendinosus tendon

The purpose of the study was to evaluate whether using only the semitendinosus as a tripled short graft would affect the electromechanical delay (EMD) of the knee flexors. EMD was evaluated in volunteers (N = 15) after they had undergone surgery for anterior cruciate ligament (ACL) reconstruction where the semitendinosus tendon alone was used as a graft. The results were compared with the intact leg and healthy controls (N = 15). After warming up, each subject performed four maximally explosive isometric contractions on an isokinetic dynamometer. Torques were measured by the dynamometer, while the electrical activity of the semitendinosus and biceps femoris muscles was detected using surface electromyography. EMD was found to be significantly increased (p = 0.001) in patients who had undergone ACL reconstruction compared to the controls. On the contrary, no significant differences (p = 0.235) were found for the biceps femoris muscle between the two groups. Similar results were found when the study group was compared with the intact leg group (p = 0.027 for semitendinosus and p = 0.859 for biceps femoris). Harvesting the semitendinosus tendon increases the EMD for the semitendinosus muscle but does not influence the EMD outcomes for the biceps femoris muscle.

17β-Estradiol Induced Effects on Anterior Cruciate Ligament Laxness and Neuromuscular Activation Patterns in Female Runners

BACKGROUND

We investigate the effects of 17β-Estradiol across phases of menstrual cycle on the laxness of the anterior cruciate ligament (ACL) and the neuromuscular control patterns around the knee joint in female runners.

METHODS

Twelve healthy female runners who reported normal menstrual cycles for the previous 6 months were tested twice across one complete menstrual cycle for serum levels of 17β-estradiol, and knee joint laxity (KJL). Electromyographic (EMG) activity of the quadriceps and hamstrings muscles was also recorded during running on a treadmill. The changes in the EMG activity, KJL, and hormonal concentrations were recorded for each subject during the follicular and the ovulatory phases across the menstrual cycle.

RESULTS

An observed increase in KJL in response to peak estradiol during the ovulatory phase was associated with increased preactivity of the hamstring muscle before foot impact (p<0.001). A consistent pattern was also observed in the firing of the quadriceps muscle recruitment pattern throughout the follicular phase associated with decreased hamstring recruitment pattern during weight acceptance phase of running (p=0.02). Additionally, a low ratio of medial to lateral quadriceps recruitment was associated with a significant reduction of the quadriceps to hamstring co-contraction ratio during the follicular phase.

CONCLUSIONS

Changes in KJL during the menstrual cycle in response to 17β-estradiol fluctuations changes the neuromuscular control around the knee during running. Female runners utilize different neuromuscular control strategies during different phases of the menstrual cycle, which may contribute to increased ACL injury risk.

Preactivation of the quadriceps muscle could limit cranial tibial translation in a cranial cruciate ligament deficient canine stifle

Cranial cruciate ligament (CrCL) deficiency is the leading cause of lameness of the canine stifle. Application of tension in the quadriceps muscle could trigger cranial tibial translation in case of CrCL rupture. We replaced the quadriceps muscle and the gastrocnemius muscle by load cells and turn-buckles. First, eight canine limbs were placed in a servo-hydraulic testing machine, which applied 50% of body weight (BW). In a second phase, the CrCL was transected, and the limbs were tested in a similar manner. In a third phase, a quadriceps pretension of 15% BW was applied and limbs were again tested in a similar manner. Cranial tibial translation was significantly decreased in CrCL deficient stifles (p < 0.05) when quadriceps pretension was applied. These findings indicate that quadriceps pretension could play a role in the stability of a CrCL deficient stifle and should then be considered in rehabilitation programs and conservative treatment of CrCL rupture in dogs.

Quadriceps/hamstrings co-activation increases early after total knee arthroplasty

Quadriceps and hamstrings weakness and co-activation are present following total knee arthroplasty (TKA) and may impair functional performance. How surgery and post-operative rehabilitation influence muscle activation during walking early after surgery is unclear.

PURPOSE

Examine muscle strength and activation during walking before and one and 6-months post-TKA.

METHODS

Ten patients (n=6 female; age: 64.7 ± 7.9 years; body mass index[BMI]:29.2 ± 2.5 kg/m(2)) and 10 healthy adults (n=6 female; age: 60.6 ± 7.4 years; BMI: 25.5 ± 4.0 kg/m(2)) participated. The patients underwent bilateral quadriceps and hamstrings strength testing and assessment of quadriceps/hamstrings co-activation and on/off timing using surface electromyography during a six-minute walk test (6MW). Groups, limbs, and changes with TKA surgery were compared.

RESULTS

Patients reported greater 6MW knee pain pre- versus post-TKA and compared to controls (P<0.05). Patients had weaker surgical limb hamstrings (P<0.05) and bilateral quadriceps (P<0.05) strength than controls pre- and post-TKA. Before and 1-month post-TKA, patients had side-to-side differences in quadriceps and hamstrings strength (P<0.05). Controls walked farther than patients (P<0.01). Patients demonstrated greater surgical limb co-activation pre-operatively than controls (P<0.05). Co-activation was higher bilaterally one-month post-TKA compared to controls (P<0.05). Patients turned off their quadriceps later during stance than controls before and 1-month post-TKA (P<0.05).

CONCLUSIONS

Muscle strength, co-activation, and timing differed between patients and controls before and early after surgery. Rehabilitation to improve strength and muscle activation seems imperative to restore proper muscle firing patterns early after surgery.

Voluntary enhanced cocontraction of hamstring muscles during open kinetic chain leg extension exercise: its potential unloading effect on the anterior cruciate ligament

BACKGROUND

A number of research studies provide evidence that hamstring cocontraction during open kinetic chain knee extension exercises enhances tibiofemoral (TF) stability and reduces the strain on the anterior cruciate ligament.

PURPOSE

To determine the possible increase in hamstring muscle coactivation caused by a voluntary cocontraction effort during open kinetic chain leg-extension exercises, and to assess whether an intentional hamstring cocontraction can completely suppress the anterior TF shear force during these exercises.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Knee kinematics as well as electromyographic activity in the semitendinosus (ST), semimembranosus (SM), biceps femoris (BF), and quadriceps femoris muscles were measured in 20 healthy men during isotonic leg extension exercises with resistance (R) ranging from 10% to 80% of the 1-repetition maximum (1RM). The same exercises were also performed while the participants attempted to enhance hamstring coactivation through a voluntary cocontraction effort. The data served as input parameters for a model to calculate the shear and compressive TF forces in leg extension exercises for any set of coactivation patterns of the different hamstring muscles.

RESULTS

For R≤ 40% 1RM, the peak coactivation levels obtained with intentional cocontraction (l) were significantly higher (P < 10(-3)) than those obtained without intentional cocontraction (l 0). For each hamstring muscle, maximum level l was reached at R = 30% 1RM, corresponding to 9.2%, 10.5%, and 24.5% maximum voluntary isometric contraction (MVIC) for the BF, ST, and SM, respectively, whereas the ratio l/l 0 reached its maximum at R = 20% 1RM and was approximately 2, 3, and 4 for the BF, SM, and ST, respectively. The voluntary enhanced coactivation level l obtained for R≤ 30% 1RM completely suppressed the anterior TF shear force developed by the quadriceps during the exercise.

CONCLUSION

In leg extension exercises with resistance R≤ 40% 1RM, coactivation of the BF, SM, and ST can be significantly enhanced (up to 2, 3, and 4 times, respectively) by a voluntary hamstring cocontraction effort. The enhanced coactivation levels obtained for R≤ 30% 1RM can completely suppress the anterior TF shear force developed by the quadriceps during the exercise.

CLINICAL RELEVANCE

This laboratory study suggests that leg extension exercise with intentional hamstring cocontraction may have the potential to be a safe and effective quadriceps-strengthening intervention in the early stages of rehabilitation programs for anterior cruciate ligament injury or reconstruction recovery. Further studies, including clinical trials, are needed to investigate the relevance of this therapeutic exercise in clinical practice.

Functional performance tests as indicators of returning to sports after anterior cruciate ligament reconstruction

BACKGROUND

There is a lack of standardized objective criteria to accurately assess the ability of a patient to progress through the end stages of rehabilitation and safely return to their previous level of athletic activity after anterior cruciate ligament (ACL) reconstruction.

PURPOSE

To determine objective factors involved in returning to sports following ACL reconstruction.

METHODS

Based on our inclusion criteria of a minimum 2-year follow-up, pre-injury sports activity level of Tegner 5 or greater, we retrospectively evaluated 67 patients who underwent ACL reconstruction. The patients were divided into "return-to-sports" (n=51) and "non-return" groups (n=16) by surveying participants using a questionnaire. Comparisons between the two groups were made using pre-operative and post-operative International Knee Documentation Committee questionnaires (IKDC), Lysholm score, and KT-2000 arthrometer. Flexor and extensor muscle strength, and functional performance tests (one-leg-hop test, co-contraction, shuttle run, and carioca tests) were used for assessment.

RESULTS

Overall clinical results, including IKDC score, Lysholm score, and KT-2000 arthrometer, improved in all patients post-operatively and no significant difference was seen between the two groups (P>0.05). Although there was no significant difference in flexor or extensor deficits, one-leg-hop test, or shuttle run test, "return-to-sports" group obtained significantly better scores in the co-contraction and carioca tests (P<0.05).

CONCLUSIONS

Tests that assess rotational stability showed statistically significant differences between the two groups. Further prospective studies with larger cohort are needed to determine the factors associated with returning to sports after ACL reconstruction.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.

Anterior cruciate ligament-deficient patients with passive knee joint laxity have a decreased range of anterior-posterior motion during active movements

BACKGROUND

Although instability of the knee joint is known to modify gait patterns, the amount that patients compensate for joint laxity during active movements remains unknown.

PURPOSE

By developing a novel technique to allow the assessment of tibiofemoral kinematics, this study aimed to elucidate the role of passive joint laxity on active tibiofemoral kinematics during walking.

STUDY DESIGN

Controlled laboratory study.

METHODS

Using motion capture, together with combinations of advanced techniques for assessing skeletal kinematics (including the symmetrical axis of rotation approach [SARA], symmetrical center of rotation estimation [SCoRE], and optimal common shape technique [OCST]), a novel noninvasive approach to evaluate dynamic tibiofemoral motion was demonstrated as both reproducible and repeatable. Passive and active anterior-posterior translations of the tibiofemoral joint were then examined in 13 patients with anterior cruciate ligament (ACL) ruptures that were confirmed by magnetic resonance imaging and compared with those in their healthy contralateral limbs.

RESULTS

Passive tibial anterior translation was significantly greater in the ACL-ruptured knees than in the contralateral healthy controls. However, the femora of the ACL-ruptured knees generally remained more posterior (~3 mm) relative to the tibia within a gait cycle of walking compared with the healthy limbs. Surprisingly, the mean range of tibiofemoral anterior-posterior translation over an entire gait cycle was significantly lower in ACL-ruptured knees than in the healthy joints (P = .026). A positive correlation was detected between passive laxity and active joint mobility, but with a consistent reduction in the range of tibiofemoral anterior-posterior translation of approximately 3 mm in the ACL-deficient knees.

CONCLUSION

It seems that either active stabilization of tibiofemoral kinematics or anterior subluxation of the tibia reduces joint translation in lax knees. This implies that either a muscular overcompensation mechanism or a physical limitation due to secondary passive stabilizers occurs within the joint and thus produces a situation that has a reduced range of active motion compared with knees with physiological stability.

CLINICAL RELEVANCE

The reduced range of active tibiofemoral translation suggests overloading of the passive structures in passively lax knees, either through excessive muscular action or joint subluxation, and could provide a plausible mechanism for explaining posttraumatic degeneration of cartilage in the joint.

Secondary gait deviations in patients with and without neurological involvement: a systematic review

Pathologies that lead to biomechanical restrictions in human gait interfere with the tightly regulated muscle activation patterns that control the external moments. In order to maintain proper function, secondary mechanisms are required. The aims of this systematic review were (1) to identify secondary mechanisms in pathologic gait that have been described throughout the scientific literature by means of instrumented gait analysis, (2) to distinguish between active compensatory mechanisms and passive physical effects and (3) to identify common compensatory mechanisms that appear to be independent from the underlying disease. A comprehensive literature search revealed 4080 citations for review, whereof 148 studies entered the full-text review. Thirty-six studies were included and the quality of these studies was assessed by two independent reviewers (kappa=0.83). The quality of the included studies showed large variation and several methodological issues were identified. Five studies were further identified describing only passive physical effects, leaving a total of 31 studies reporting on compensations. The qualitative analysis revealed common compensations that appeared to be independent from the underlying pathology. In clinical practice, distinguishing primary from secondary gait deviations can be considered highly important since unnecessary treatment may be avoided. However, given the introduction of general principles of compensatory mechanisms and the fact that certain presumed "compensations" were identified as simple passive physical effects, secondary gait deviations have to be further investigated. Computer simulation studies are valuable, especially in respect of the distinction between compensations and physical effects. Furthermore, the need for a uniform terminology was highlighted.

The application of musculoskeletal modeling to investigate gender bias in non-contact ACL injury rate during single-leg landings

The central tenet of this study was to develop, validate and apply various individualised 3D musculoskeletal models of the human body for application to single-leg landings over increasing vertical heights and horizontal distances. While contributing to an understanding of whether gender differences explain the higher rate of non-contact anterior cruciate ligament (ACL) injuries among females, this study also correlated various musculoskeletal variables significantly impacted by gender, height and/or distance and their interactions with two ACL injury-risk predictor variables; peak vertical ground reaction force (VGRF) and peak proximal tibia anterior shear force (PTASF). Kinematic, kinetic and electromyography data of three male and three female subjects were measured. Results revealed no significant gender differences in the musculoskeletal variables tested except peak VGRF (p = 0.039) and hip axial compressive force (p = 0.032). The quadriceps and the gastrocnemius muscle forces had significant correlations with peak PTASF (r = 0.85, p < 0.05 and r = - 0.88, p < 0.05, respectively). Furthermore, hamstring muscle force was significantly correlated with peak VGRF (r = - 0.90, p < 0.05). The ankle flexion angle was significantly correlated with peak PTASF (r = - 0.82, p < 0.05). Our findings indicate that compared to males, females did not exhibit significantly different muscle forces, or ankle, knee and hip flexion angles during single-leg landings that would explain the gender bias in non-contact ACL injury rate. Our results also suggest that higher quadriceps muscle force increases the risk, while higher hamstring and gastrocnemius muscle forces as well as ankle flexion angle reduce the risk of non-contact ACL injury.

Greater muscle co-contraction results in increased tibiofemoral compressive forces in females who have undergone anterior cruciate ligament reconstruction

Individuals who have undergone ACL reconstruction (ACLR) have been shown to have a higher risk of developing knee osteoarthritis (OA). The elevated risk of knee OA may be associated with increased tibiofemoral compressive forces. The primary purpose of this study was to examine whether females with ACLR demonstrate greater tibiofemoral compressive forces, as well as greater muscle co-contraction and decreased knee flexion during a single-leg drop-land task when compared to healthy females. Ten females with ACLR and 10 healthy females (control group) participated. Each participant underwent two data collection sessions: (1) MRI assessment and (2) biomechanical analysis (EMG, kinematics, and kinetics) during a single-leg drop-land task. Joint kinematics, EMG, and MRI-measured muscle volumes and patella tendon orientation were used as input variables into a MRI-based EMG-driven knee model to quantify the peak tibiofemoral compressive forces during landing. Peak tibiofemoral compressive forces were significantly higher in the ACLR group when compared to the control group (97.3 ± 8.0 vs. 88.8 ± 9.8 N · kg(-1)). The ACLR group also demonstrated significantly greater muscle co-contraction as well as less knee flexion than the control group. Our findings support the premise that individuals with ACLR demonstrate increased tibiofemoral compression as well as greater muscle co-contraction and decreased knee flexion during a drop-land task. Future studies are needed to examine whether correcting abnormal neuromuscular strategies and reducing tibiofemoral compressive forces following ACLR can slow the progression of joint degeneration in this population.

Limited benefit of hamstrings forces for the anterior cruciate ligament-deficient knee: an in vitro study

The hamstrings are considered stabilizers of the anterior cruciate ligament-deficient knee; however, anterior cruciate ligament injury primarily influences tibiofemoral kinematics near full extension, where the hamstrings have the least influence on kinematics. Ten knees were tested at multiple flexion angles in vitro to directly compare the influence of anterior cruciate ligament injury and hamstrings activation on tibiofemoral kinematics. Tibiofemoral kinematics were measured for three testing conditions: (1) anterior cruciate ligament intact, with forces applied through the quadriceps muscles (596 N), (2) anterior cruciate ligament cut, with forces applied through the quadriceps, and (3) anterior cruciate ligament cut, with forces applied through the quadriceps and hamstrings (200 N). Based on repeated measures comparisons performed at each flexion angle, cutting the anterior cruciate ligament significantly (p < 0.05) increased tibial anterior translation, medial translation, and internal rotation at 0 degrees and 15 degrees of flexion by approximately 2.5 mm, 1 mm, and 2 degrees, respectively. Internal rotation also increased significantly at 30 degrees. With the anterior cruciate ligament cut, loading the hamstrings significantly decreased anterior translation, medial translation, and internal rotation at 45 degrees, by approximately 2 mm, 2 mm, and 4 degrees, respectively. Loading the hamstrings caused kinematic changes in the opposite direction of the anterior cruciate ligament injury, but the changes occurred at deeper flexion angles than those at which anterior cruciate ligament injury influenced tibiofemoral kinematics.

Antagonist muscle moment is increased in ACL deficient subjects during maximal dynamic knee extension

INTRODUCTION

Coactivation of the hamstring muscles during dynamic knee extension may compensate for increased knee joint laxity in anterior cruciate ligament (ACL) deficient subjects. This study examined if antagonist muscle coactivation during maximal dynamic knee extension was elevated in subjects with anterior cruciate ligament (ACL) deficiency compared to age-matched healthy controls.

METHODS

Electromyography (EMG) and net knee joint moments were recorded during maximal concentric quadriceps and eccentric hamstring contractions, performed in an isokinetic dynamometer (ROM: 90-10°, angular speed: 30°/s). Hamstring antagonist EMG recorded during concentric quadriceps contraction was converted into antagonist moment based on the EMG-moment relationship observed during eccentric agonist contractions.

RESULTS

The magnitude of antagonist hamstring EMG was 65.5% higher in ACL deficient subjects compared to healthy controls (p<0.05). Likewise, antagonist hamstring moment expressed in percentage of the measured net extension moment was elevated in ACL deficient subjects (56 ± 8 to 30 ± 6%) compared to controls (36 ± 5 to 19 ± 2%) at 20-50° of knee flexion (0°=full extension) (p<0.05).

DISCUSSION

The results showed a marked increase in hamstring coactivation towards more extended joint positions. Notably, this progressive rise in coactivation was greater in ACL deficient subjects, which may reflect a compensatory strategy to provide stability to the knee joint in the anterior-posterior plane during isolated knee extension. The present study encourages further investigations of hamstring coactivation in ACL deficient subjects.

Relationships among tendon regeneration on MRI, flexor strength, and functional performance after anterior cruciate ligament reconstruction with hamstring autograft

BACKGROUND

There are numerous reports on hamstring tendon regeneration after harvest for anterior cruciate ligament (ACL) reconstruction. However, few studies have evaluated the relationships among the magnetic resonance imaging (MRI) findings of hamstring regeneration, muscle strength, and functional results.

PURPOSE

This study evaluates the correlations among the hamstring regeneration on MRI, flexor strength, and functional performance after hamstring tendon harvesting in ACL reconstruction.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

We enrolled 45 patients who underwent primary ACL reconstruction using hamstring tendon autografts and in whom flexor strength, functional performance, and preoperative and postoperative MRI results were evaluated at least 2 years postoperatively. Isokinetic flexion strength was tested in the standard and prone positions. We evaluated the differences in flexor strength and functional performance according to the number of regenerated tendons. The correlation between the MRI findings (the number of regenerated hamstring tendons and proximal shift of the musculotendinous junction) and the functional performance and flexor strength was analyzed.

RESULTS

The patients were divided into 3 groups according to the regeneration of the hamstring tendons on MRI: both semitendinosus and gracilis tendons regenerated (group SG), only 1 tendon regenerated (group O), and no tendon regenerated (group N). Significant differences were found in the flexor deficit between group N and groups SG and O on the standard and prone position isokinetic tests. There was a significant correlation (ρ = -.472) between the number of regenerated hamstring tendons and the carioca test result. The proximal shift significantly correlated with the flexor deficit in the prone position isokinetic test (semitendinosus, r = .449; gracilis, r = .366).

CONCLUSION

Hamstring tendons regenerated after harvest for ACL reconstruction in a high proportion of the patients. The flexor strength with both the standard and prone position isokinetic tests differed in the 3 groups. The number of regenerated hamstring tendons was significantly correlated with performance on the carioca test. Proximal shifting of the musculotendinous junction was significantly correlated with flexor deficit on the hyperflexion isokinetic test.

The effects of hamstring harvesting on outcomes in anterior cruciate ligament-reconstructed patients: a comparative study between hamstring-harvested and -unharvested patients

PURPOSE

The purpose of this study was to evaluate the effects of hamstring harvesting in patients after anterior cruciate ligament (ACL) reconstruction by comparing groups with and without hamstring harvesting.

METHODS

We evaluated the effect of hamstring harvesting in 73 consecutive patients who underwent ACL reconstruction: 39 patients whose hamstrings were harvested for autografts (group H) were compared with 34 patients who received allografts during the same time period (group C [control]). The cases and controls were compared by analyzing the following variables: age, height, weight, mean follow-up period, type of tissue used, and meniscal surgery. Outcomes were assessed by the Lysholm knee score, Tegner activity score, and KT-2000 side-to-side difference (MEDmetric, San Diego, CA), as well as functional performance tests. The flexor deficit and isokinetic peak torque for knee flexion were measured in the sitting position (0° to 90°), and the flexion torque at 90° was measured in the prone position (60° to 120°).

RESULTS

Although significant knee flexion weakness after ACL reconstruction was observed, a significantly greater knee flexor deficit was found in autograft patients than in allograft patients (P < .001). No differences were found between groups in terms of clinical and functional results regardless of hamstring harvesting. The performance of both study groups in all 4 functional tests were significantly correlated with flexor deficit in the sitting position (P < .05) but not in hyperflexion. Significant flexor deficits in both normal and hyperflexed positions were noted in both groups when compared with the unaffected knee (group H, P < .001; group C, P = .002).

CONCLUSIONS

These results indicate significant knee flexion weakness compared with the unaffected knee after ACL reconstruction regardless of hamstring harvesting. Moreover, the greater increase in knee flexor deficit in the hamstring-harvested group compared with the allograft group was statistically significant. However, clinical and functional outcomes were similar between the groups.

LEVEL OF EVIDENCE

Level III, case-control study.