Decreased passive muscle stiffness of vastus medialis is associated with poorer quadriceps strength and knee function after anterior cruciate ligament reconstruction

BackgroundMuscle deficits of the quadriceps and hamstrings are common after anterior cruciate ligament reconstruction, and increase the risk of knee reinjury. Muscle stiffness is an important factor for dynamic joint stability. However, the changes in quadriceps and hamstring muscle stiffness and its influence after anterior cruciate ligament reconstruction remain unclear.MethodTwenty-five male subjects with anterior cruciate ligament reconstruction and twenty-one matched healthy subjects participated in this study. The passive muscle stiffness of the quadriceps and hamstrings was assessed by shear modulus using ultrasound shear wave elastography. The isokinetic muscle strengths of the quadriceps and hamstrings were tested. Knee function was evaluated by the International Knee Documentation Committee and Lysholm score. Muscle stiffness was compared between limbs via non-parametric tests. Correlation analysis was used to detect the relationship between muscle stiffness, isokinetic muscle strength and knee functional scores.FindingsThe involved limb exhibited significantly decreased shear modulus in the vastus medialis compared to the dominant limbs(z = −3.585;P = 0.001;ES = 1.13) and non-dominant limbs(z = −3.551;P = 0.002;ES = 1.24) of healthy controls. The shear modulus of ST was also significantly lower in the involved limb when compared with the contralateral limbs(z = −3.996;P < 0.001;ES = 1.33), dominant limbs(z = −4.477;P < 0.001;ES = 1.65) and non-dominant limbs(z = −4.234;P = 0.001;ES = 1.43) of healthy controls. The shear modulus of the vastus medialis was associated with quadriceps peak torque at 60°/s(r = 0.470; p < 0.001) and knee functional score(r = 0.459; p = 0.021).InterpretationThe passive muscle stiffness of the vastus medialis decreased after anterior cruciate ligament reconstruction, which is associated with poorer quadriceps strength and knee function. The effect of modulation of muscle stiffness on improving knee function warrants future investigation.     

Alterations in joint kinematics during walking following hamstring and patellar tendon anterior cruciate ligament reconstruction surgery

Background

Previous research has shown that patients with anterior cruciate ligament reconstruction have altered movement patterns in the reconstructed knee during walking. In the sagittal plane, graft specific changes in knee joint motion have been reported between hamstring and patellar tendon anterior cruciate ligament reconstruction grafts. This study examined the secondary planes of movement during walking in anterior cruciate ligament reconstructed knees to evaluate the influences of graft type (hamstring or patellar tendon) and control condition (control group or contralateral knee).

Methods

In 54 participants (18 patellar tendon graft, 18 hamstring graft and 18 controls) varus–valgus and internal–external rotation was measured during level walking in a gait laboratory at mean of 10 months after surgery. All patients had undergone primary unilateral anterior cruciate ligament reconstruction within 12 months of injury.

Findings

For internal–external rotation there was no difference between the graft types and both patient groups had reduced internal rotation (an external rotation offset) and reduced internal rotation range when compared to the control group and contralateral knee. For 31 of 36 patients, internal rotation values were less than the control group mean. The hamstring group had reduced varus rotation compared to both the patellar tendon and control groups, but not when compared to the contralateral knee.

Interpretation

The results show that there are differences in tibial rotation during walking in anterior cruciate ligament reconstructed knees compared to both the contralateral knee and uninjured control group. These kinematic alterations may relate to the high incidence of knee osteoarthritis observed in this population over time. Reduced varus in the hamstring group may relate to the graft harvest.     

Lesser lower extremity mechanical loading associates with a greater increase in serum cartilage oligomeric matrix protein following walking in individuals with anterior cruciate ligament reconstruction

BackgroundAberrant mechanical loading during gait is hypothesized to contribute to the development of posttraumatic osteoarthritis following anterior cruciate ligament reconstruction. Our purpose was to determine if peak vertical ground reaction force and instantaneous vertical ground reaction force loading rate associate with the acute change in serum cartilage oligomeric matrix protein following a 20-minute bout of walking.MethodsWe enrolled thirty individuals with a unilateral anterior cruciate ligament reconstruction. Peak vertical ground reaction force and instantaneous vertical ground reaction force loading rate were extracted from the first 50% of the stance phase of gait during a 60-second trial. Blood samples were collected immediately before and after 20 min of treadmill walking at self-selected speed. The change in serum cartilage oligomeric matrix protein from pre- to post-walking was calculated. Stepwise linear regression models were used to determine the association between each outcome of loading and the change in serum cartilage oligomeric matrix protein after accounting for sex, gait speed, time since anterior cruciate ligament reconstruction, graft type, and history of concomitant meniscal procedure (ΔR²).FindingsLesser peak vertical ground reaction force (ΔR² = 0.208; β = −0.561; P = 0.019) and instantaneous vertical ground reaction force loading rate (ΔR² = 0.168; β = −0.519; P = 0.037) on the anterior cruciate ligament reconstructed limb associated with a greater increase in serum cartilage oligomeric matrix protein following 20 min of walking.InterpretationMechanical loading may be a future therapeutic target for altering the acute biochemical response to walking in individuals with an anterior cruciate ligament reconstruction.     

Influence of an unloader brace on lower limb electromyographic activity in individuals with predominant lateral osteoarthritis after anterior cruciate ligament reconstruction

ObjectiveTo determine the immediate effects of a varus unloader knee brace on lower-limb electromyographic activity in individuals with lateral knee osteoarthritis and valgus malalignment after anterior cruciate ligament reconstruction.MethodsElectromyographic data were recorded in 19 individuals with lateral knee osteoarthritis and valgus malalignment after anterior cruciate ligament reconstruction during walking under three conditions: (i) no brace, (ii) unadjusted brace (no varus adjustment), and adjusted brace (varus adjustment). Variables of interest were statistically analyzed using repeated measures analysis of variance.ResultsThere were no significant differences in muscle co-contraction between the three test conditions. The adjusted brace resulted in delayed offset of gluteus maximus (mean difference [95% CI]: 72 ms [24, 119]), and earlier onset of gluteus medius (59 ms [21, 97]) compared to no brace. The adjusted brace delayed onset of lateral gastrocnemius compared to no brace (53 ms [28, 78]) and the unadjusted brace (39 ms [7, 71]) and reduced average activation amplitude of gluteus maximus (−4 mV [−6, −1]) and lateral gastrocnemius (−9 mV [−16, −2]) compared to no brace.ConclusionsThe unloader brace did not produce significant changes in muscle co-contraction in individuals with lateral knee osteoarthritis and valgus malalignment after anterior cruciate ligament reconstruction. Significant changes in gluteal and gastrocnemius muscle activation timing and amplitude were observed, however, it is not clear whether these changes are of clinical importance.     

Effect of muscle loads and torque applied to the tibia on the strain behavior of the anterior cruciate ligament: an in vitro investigation

Background

Very little is known about the effects of applied torque about the long axis of the tibia in combination with muscle loads on anterior cruciate ligament biomechanics. The purpose of this study was to determine the effect of muscle contraction and tibial torques applied about the long axis of the tibia on anterior cruciate ligament strain behavior.

Methods

Six cadaver knee specimens were used to measure the strain behavior of the anterior cruciate ligament. Internal and external axial torques were applied to the tibia when the knee was between 30° and 120° of flexion in combination with the conditions of no muscle load, isolated quadriceps load, and simultaneous quadriceps and hamstring loading.

Findings

The highest anterior cruciate ligament strain values were measured when the muscles were not loaded, when the knee was at 120° of flexion, and when internal tibial torques were applied to the knee. During muscle loading the highest anterior cruciate ligament strain values were measured at 30° of flexion and then the strain values gradually decreased with increase in knee flexion. During co-contraction of the quadriceps and hamstring muscles the anterior cruciate ligament was unstrained or minimally strained at 60°, 90° and 120° of knee flexion.

Interpretation

This study suggests that quadriceps and hamstring muscle co-contraction has a potential role in reducing the anterior cruciate ligament strain values when the knee is in deep flexion. These results can be used to gain insight into anterior cruciate ligament injury mechanisms and to design rehabilitation regimens.     

Peak knee biomechanics and limb symmetry following unilateral anterior cruciate ligament reconstruction: Associations of walking gait and jump-landing outcomes

BackgroundAberrant walking-gait and jump-landing biomechanics may influence the development of post-traumatic osteoarthritis and increase the risk of a second anterior cruciate ligament injury, respectively. It remains unknown if individuals who demonstrate altered walking-gait biomechanics demonstrate similar altered biomechanics during jump-landing. Our aim was to determine associations in peak knee biomechanics and limb-symmetry indices between walking-gait and jump-landing tasks in individuals with a unilateral anterior cruciate ligament reconstruction.MethodsThirty-five individuals (74% women, 22.1 [3.4] years old, 25 [3.89] kg/m²) with an anterior cruciate ligament reconstruction performed 5-trials of self-selected walking-gait and jump-landing. Peak kinetics and kinematics were extracted from the first 50% of stance phase during walking-gait and first 100 ms following ground contact for jump-landing. Pearson product-moment (r) and Spearman's Rho (ρ) analyses were used to evaluate relationships between outcome measures. Significance was set a priori (P ≤ 0.05).FindingsAll associations between walking-gait and jump-landing for the involved limb, along with the majority of associations for limb-symmetry indices and the uninvolved limb, were negligible and non-statistically significant. There were weak significant associations for instantaneous loading rate (ρ = 0.39, P = 0.02) and peak knee abduction angle (ρ = 0.36, p = 0.03) uninvolved limb, as well as peak abduction displacement limb-symmetry indices (ρ= − 0.39, p = 0.02) between walking-gait and jump-landing.InterpretationNo systematic associations were found between walking-gait and jump-landing biomechanics for either limb or limb-symmetry indices in people with unilateral anterior cruciate ligament reconstruction. Individuals with an anterior cruciate ligament reconstruction who demonstrate high-involved limb loading or asymmetries during jump-landing may not demonstrate similar biomechanics during walking-gait.     

The impact of stochastic resonance electrical stimulation and knee sleeve on impulsive loading and muscle co-contraction during gait in knee osteoarthritis

Background

Increased impulsive loading and muscle co-contraction during gait have been observed in individuals with knee osteoarthritis. Proprioceptive deficits in this population may contribute to these effects. Proprioception has been shown to improve with the combination of stochastic resonance electrical stimulation and a knee sleeve in knee osteoarthritis. Our goal was to determine whether stochastic resonance stimulation combined with a knee sleeve would decrease impulsive loading rates and muscle co-contraction during gait in knee osteoarthritis.

Methods

Gait kinetics, kinematics and muscle activity were assessed during walking in subjects with knee osteoarthritis during three different conditions: no stochastic resonance/no sleeve (control), stochastic resonance at 75% threshold/sleeve, and no stochastic resonance/sleeve. Loading rates were calculated from the ground reaction force. Muscle co-contraction was calculated from the ratio of vastus lateralis to lateral hamstring activity. Differences between conditions were assessed using a repeated measures analysis of variance (P < 0.05).

Findings

The 75% threshold/sleeve and sleeve only conditions resulted in increased knee flexion at contact and reduced loading rates compared to the control condition (P < 0.05). However, these measures did not significantly differ between the 75% threshold/sleeve and sleeve only conditions. Muscle co-contraction was found to decrease with the 75% threshold/sleeve condition compared to the other conditions.

Interpretation

Increased knee flexion and decreased loading rates may be a result of proprioceptive improvements resulting from the sleeve or sleeve/stimulation combination. The stochastic resonance stimulation did not demonstrate an ability to enhance the effects of the sleeve with the exception of reductions in muscle co-contraction.     

Wear patterns on tibial plateau from varus osteoarthritic knees

BACKGROUND: The knowledge of cartilage wear patterns at the medial tibial plateau is important to understand the main causes of arthritis in varus knees. The most important factors influencing knee arthritis in fact seem to be the severity of the degenerative changes determined by the lower limb mechanical axis and the abnormal knee joint kinematics which frequently results from dysfunction of the anterior cruciate ligament. METHODS: We studied the wear patterns of cartilage damage in 70 medial tibial plateaus resected at operation during total knee arthroplasty indicated for varus osteoarthritic knee. Anterior cruciate ligament and medial meniscus integrity was assessed intra-operatively. Calibrated digital images were used to measure the wear patterns with a standard software tool. The medial compartment of the tibial plateau was divided into six zones, and the amount of cartilage and bone destruction in each zone was classified into two grades. FINDINGS: The wear pattern was found to be highly dependent upon knee varus deformity (Mann Whitney P<0.001) and anterior cruciate ligament integrity (Friedman P<0.0005). Anterior cruciate ligament was found intact in 35.7% of the cases. Wear patterns on intact anterior cruciate ligament knees occurred in the central to medial aspect of the tibial plateau. Anterior cruciate ligament deficient knees had significantly larger wear patterns anteriorly and posteriorly in the most medial region of the medial plateau. INTERPRETATION: These observations suggest altered joint mechanics exist in anterior cruciate ligament deficient varus knees, which would worsen cartilage degeneration and osteoarthritis progression.     

Quantifying varus thrust in knee osteoarthritis using wearable inertial sensors: A proof of concept

BackgroundVarus thrust during walking, visualized as excessive frontal plane knee motion during weight acceptance, is a modifiable risk factor for progression of knee osteoarthritis. However, visual assessment does not capture thrust severity and quantification with optical motion capture is often not feasible. Inertial sensors may provide a convenient alternative to optical motion capture. This proof-of-concept study sought to compare wearable inertial sensors to optical motion capture for the quantification of varus thrust.MethodsTwenty-six participants with medial knee osteoarthritis underwent gait analysis at self-selected and fast speeds. Linear regression with generalized estimating equations assessed associations between peak knee adduction velocity or knee adduction excursion from optical motion capture and peak thigh or shank adduction velocity from two inertial sensors on the lower limb. Relationships between inertial measures and peak external knee adduction moment were assessed as a secondary aim.FindingsBoth thigh and shank inertial sensor measures were associated with the optical motion capture measures for both speeds (P < 0.001 to P = 0.020), with the thigh measures having less variability than the shank. After accounting for age, sex, body mass index, radiographic severity, and limb alignment, thigh adduction velocity was also associated with knee adduction moment at both speeds (both P < 0.001).InterpretationAn inertial sensor placed on the mid-thigh can quantify varus thrust in people with medial knee osteoarthritis without the need for optical motion capture. This single sensor may be useful for risk screening or evaluating the effects of interventions in large samples.     

关节镜下自体腓骨长肌腱和腘绳肌腱重建前交叉韧带的对比研究

目的 比较自体腓骨长肌腱（PLT）与腘绳肌腱（HT）重建前交叉韧带的临床疗效。方法 回顾性分析桂林市中医医院2017年8月－2019年12月收治的56例前交叉韧带损伤患者的临床资料。其中,男26例,女30例,20例行自体PLT重建前交叉韧带（PLT组）,36例行HT重建前交叉韧带（HT组）。在术前及术后6和12个月,对所有患者的手术时间、手术切口长度、合并半月板损伤、受伤时间、体重指数（BMI）等进行分析,并用国际膝关节文献委员会（IKDC）评分、Lysholm评分和Tegner评分对患者膝关节运动功能进行评估。结果 HT组手术时间和手术切口长度均较PLT组长,差异有统计学意义（P < 0.05）;两组患者术后6和12个月IKDC评分、Lysholm评分和Tegner评与术前比较,差异均有统计学意义（P < 0.05）,但术后6和12个月比较,差异均无统计学意义（P > 0.05）。结论 自体PLT重建前交叉韧带较HT重建前交叉韧带用时少、创伤小、更加美观,且操作简单、并发症少,术后疗效确切,可作为移植物替代HT行前交叉韧带断裂重建。     

Long-term gait biomechanics in level,uphill, and downhill conditions following anterior cruciate ligament reconstruction

BackgroundAltered gait biomechanics have been linked to post-traumatic knee osteoarthritis development following anterior cruciate ligament reconstruction surgery, but the persistence of aberrant gait biomechanics after the first year post-surgery is inconsistent in the literature. Gait biomechanics are typically evaluated on a level surface, but this task may not elucidate discrepancies in individuals further removed from surgery due to the simplicity of the task. Graded surfaces are common in real-world ambulation and may exacerbate aberrant gait biomechanics due to greater mechanical demands.MethodsForty-seven individuals post-anterior cruciate ligament reconstruction (4 ± 3 years post-surgery) and forty-seven uninjured controls completed gait analysis under level, uphill, and downhill conditions on an instrumented treadmill. Outcomes included knee flexion displacement and peak knee flexion angle, vertical ground reaction force, and knee extension and abduction moments.FindingsKnee extension moment and knee flexion displacement were lesser in the surgical limb compared to the contralateral during the downhill condition, with lesser knee flexion displacement also observed during the level condition. Additionally, knee extension moment was less symmetrical in the surgical group during both uphill and downhill conditions compared to controls. Knee flexion displacement was less symmetrical in the surgical group during both level and downhill conditions compared to controls.InterpretationGraded surfaces elucidate aberrant gait biomechanics in individuals more than 1 year post-anterior cruciate ligament reconstruction that are not apparent during level walking. These findings suggest that gait assessment on level surfaces may mask existing deficiencies, and warrant emphasizing ambulation of graded surfaces during anterior cruciate ligament rehabilitation.     

Neuromuscular function in anterior cruciate ligament reconstructed patients at long-term follow-up

BackgroundThe permanence of neuromuscular adaptations following anterior cruciate ligament reconstruction is not known. The aim of this study was to compare bilateral muscle co-contraction indices, time to peak ground reaction force, and timing of muscle onset between anterior cruciate ligament reconstruction subjects 10–15 years post reconstruction with those of matched uninjured controls during a one-leg hop landing.MethodsNine healthy controls and 9 reconstruction subjects were recruited. Clinical and functional knee exams were administered. Lower limb co-contraction indices, time to peak ground reaction force, and muscle onset times were measured bilaterally. Differences in clinical and functional outcomes were assessed with unpaired t-tests, and mixed model repeated measures were used to examine effects of group, limb and interaction terms in electromyography measures.Findings89% of control knees were clinically “normal”, whereas only 33% of reconstructed knees were “normal”. Anterior cruciate ligament-reconstructed subjects tended to achieve shorter functional hop distances but demonstrated symmetrical lower limb electromyography measures that were no different from those of controls' with the exception that biceps femoris activation was delayed bilaterally prior to ground contact but was greater during the injury risk phase of landing.InterpretationWith the exception of hamstring activation, lower limb electromyography measures were largely similar between ligament-reconstructed and matched control subjects, which was in contrast to the clinical findings. This result brings into question the significance of neuromuscular function at this long-term follow-up but raises new questions regarding the role of symmetry and pre-injury risk.     

Peak knee adduction moment during gait in anterior cruciate ligament reconstructed females

Background

Recent work has shown that anterior cruciate ligament reconstructed patients exhibit an increased peak knee adduction moment during walking gait compared to healthy controls. An increased peak knee adduction moment has been suggested to be a potential mechanism of degeneration for knee osteoarthritis. The few studies in this area have not considered an exclusively female anterior cruciate ligament reconstructed group. This study tested the hypothesis that female anterior cruciate ligament-reconstructed patients would have higher peak knee adduction moments than controls.

Methods

Peak knee adduction moment during walking was compared between a group of anterior cruciate ligament reconstructed females and a group of female activity matched controls over ten 15 m walking trials in a laboratory at a self-selected pace.

Findings

Peak knee adduction moment was lower for the anterior cruciate ligament reconstructed group (N = 17, M = 0.31 Nm/kg·m, SD = 0.08) than for the control group (N = 17, M = 0.41 Nm/kg·m, SD = 0.12; t(32) = 2.483, p = 0.010, one-tailed, eta squared effect size = 0.16).

Interpretation

A group of female anterior cruciate ligament reconstructed subjects did not exhibit a gait characteristic which has been suggested to be associated with knee osteoarthritis development and has been shown to be present in male and mixed sex anterior cruciate ligament reconstructed populations previously.     

The influence of internal and external tibial rotation offsets on knee joint and ligament biomechanics during simulated athletic tasks

BackgroundFollowing anterior cruciate ligament injury and subsequent reconstruction transverse plane tibiofemoral rotation becomes underconstrained and overconstrained, respectively. Conflicting reports exist on how rotations influence loading at the knee. This investigation aimed to determine the mechanical effects of internal and external tibial rotation offsets on knee kinematics and ligament strains during in vitro simulations of in vivo recorded kinematics.MethodA 6-degree-of-freedom robotic manipulator arm was used to articulate 11 cadaveric tibiofemoral joint specimens through simulations of four athletic tasks produced from in vivo recorded kinematics. These simulations were then repeated with 4° tibial rotation offsets applied to the baseline joint orientation.FindingsRotational offsets had a significant effect on peak posterior force for female motion simulations (P < 0.01), peak lateral force for most simulated tasks (P < 0.01), and peak anterior force, internal torque, and flexion torque for sidestep cutting tasks (P ≤ 0.01). Rotational offsets did not exhibit statistically significant effects on peak anterior cruciate ligament strain (P > 0.05) or medial collateral ligament strain (P > 0.05) for any task.InterpretationTransverse plane rotational offsets comparable to those observed in anterior cruciate ligament deficient and reconstructed patients alter knee kinetics without significantly altering anterior cruciate ligament strain. As knee degeneration is attributed to abnormal knee loading profiles, altered transverse plane kinematics may contribute to this. However, altered transverse plane rotations likely play a limited role in anterior cruciate ligament injury risk as physiologic offsets failed to significantly influence anterior cruciate ligament strain during athletic tasks.     

Kinematic and kinetic gait deviations in males long after anterior cruciate ligament reconstruction

BackgroundBiomechanical deviations long (approx. 5 years) after anterior cruciate ligament reconstruction have not been quantified in males, despite their distinct risk profile as compared to females. These deviations can indicate altered joint loading during chronic, repetitive motions.MethodsCross-sectional study, comparing kinematic and kinetic variables between 15 male anterior cruciate ligament reconstructed patients and 15 healthy controls. During walking and running gait, measurements were taken of impact dynamics, knee and hip sagittal plane angles and moments, and knee varus angles and adduction moments.FindingsComparing affected limbs to control limbs, significantly lower maximum (P = 0.001) and initial (P = 0.003) loading rates were found during running, but not in walking. Hip angles were lower for affected limbs of patients compared to the control group (P = 0.039) in walking, but not during running. Between-limb comparisons showed important differences in symmetry of the affected patients. Maximum force during running was higher in the unaffected limb (P = 0.015), which was linked with a higher loading rate (P = 0.008). Knee flexion angle was reduced by 2° on average for the affected limb during running (P = 0.010), and both walking and running knee and hip moments showed differences. Knee varus angle showed a 1° difference during walking (P < 0.001), but not during running. Knee adduction moment was significantly lower (more valgus) during both walking and running.InterpretationMale anterior cruciate ligament reconstructed patients demonstrate persistent, clinically important gait asymmetries and differences from healthy controls long after surgery in kinematics, kinetics, and impact biomechanics.     

Alterations in patellofemoral kinematics following vastus medialis transection in the anterior cruciate ligament deficient rabbit knee

Background

Anterior cruciate ligament deficiency and quadriceps muscle weakness are considered to be important risk factors for aberrant patellar tracking and subsequent patellofemoral osteoarthritis. However, data from in vivo experiments looking at dynamic patellar joint kinematics and muscle force are scarce. Therefore, the purpose of this study was to evaluate the effects of anterior cruciate ligament transection and loss of vastus medialis force on patellar tracking in the rabbit knee in vivo.

Methods

Eight skeletally mature New Zealand White Rabbits, weighing 6.0 kg (0.6 kg standard deviation) were used. The experimental trials consisted of active, concentric and eccentric movements of the knee joint. Measurements were performed with the intact, the anterior cruciate ligament deficient, and the vastus medialis transected knee. Patellofemoral kinematics (shift, rotation) were quantified from high speed video.

Findings

Following anterior cruciate ligament transection, patellar tracking occurred more laterally, and caused a significant lateral rotation of the patella. The addition of vastus medialis transection did not alter patellar tracking or rotation significantly for any of the force-matched experimental conditions.

Interpretation

The loss of the anterior cruciate ligament results in lateral patellar shift and rotation while the loss of vastus medialis muscle force does not affect patellar tracking or rotation in the anterior cruciate ligament deficient knee. We suggest that the current results should be considered carefully in future interpretations of knee extensor imbalance. More research is needed to describe the contribution of vastus medialis muscle strength to medial patellofemoral stability and confirm these results in the human knee.     

Tibial rotation in anterior cruciate ligament reconstructed knees during single limb hop and drop landings

Background

Alterations in knee joint kinematics have been suggested as a potential mechanism that influences the development of osteoarthritis of the knee after anterior cruciate ligament reconstruction. Whilst previous work has shown changes in internal–external tibial rotation during level walking, many patients aim to return to high impact activities following surgery. This study examined tibial rotation during single limb hop and drop landings in anterior cruciate ligament reconstructed knees compared to a control group, and also evaluated the influence of graft type (hamstring or patellar tendon).

Methods

In 48 participants (17 patellar tendon graft, 18 hamstring graft and 13 controls) internal–external rotation was measured during single limb hop and drop landings in a gait laboratory at mean of 10 months after surgery.

Findings

There was no difference between the two graft types and both patient groups had less internal rotation when compared to the control group. For 60% of patients, internal rotation values were at least 5°  less than the control group mean.

Interpretation

Anterior cruciate ligament reconstructed knees with both hamstring tendon and patellar tendon grafts show altered rotational kinematic patterns during high impact dynamic load activities.     

Knee mechanics during landing in anterior cruciate ligament patients: A longitudinal study from pre- to 12 months post-reconstruction

Background

Patients with a history of anterior cruciate ligament rupture are at elevated risk of developing knee osteoarthritis. Altered knee kinematics and kinetics during functional activities have been viewed as risk factors for cartilage breakdown and, therefore, one of the primary goals of anterior cruciate ligament reconstruction is to restore knee joint function.

Methods

Patients' (n = 18) knee mechanics while performing a single leg hop for distance were calculated for both legs using a soft-tissue artifact optimized rigid lower-body model at the pre-reconstruction state and six and twelve months after anterior cruciate ligament reconstruction.

Findings

Independent of the analyzed time point the involved leg showed a lower external flexion and adduction moment at the knee, and an increased anterior translation and external rotational offset of the shank with respect to the thigh compared to the uninvolved leg. There were no differences for any of the analyzed knee kinematic and kinetic parameters within the control subject group.

Interpretation

The identified kinematic changes can cause a shift in the normal load-bearing regions of the knee and may support the view that the risk of developing knee osteoarthritis in an anterior cruciate ligament ruptured joint while performing activities involving frequent landing and stopping actions is less likely to be associated with the knee adduction moment and is rather due to kinematic changes. Anterior cruciate ligament reconstruction surgery failed to restore normal knee kinematics during landing, potentially explaining the persistent risk for the development of knee osteoarthritis in patients who have returned to sports following reconstruction surgery.     

Reducing anterior tibial translation by applying functional electrical stimulation in dynamic knee extension exercises: Quantitative results acquired via marker tracking

BackgroundPain that accompanies anterior cruciate ligament deficiency during dynamic knee extension exercises is usually caused by excessive anterior tibial translation, which can be restricted if the anterior cruciate ligament was intact.MethodsA functional electrical stimulator is incorporated with a training device to induce hamstring contractions during certain degrees of knee extension to replicate effects similar to those generated by an intact anterior cruciate ligament and to reduce anterior tibial translation. By using a camera that tracks markers placed on bony prominences of the femur and tibia, the anterior tibial translations corresponding to various settings were determined by customized image processing procedures.FindingsIn the electrical stimulation sessions, the knee extensions with electrical stimulation feedback induced significantly (n = 6, P < .05) less anterior tibial translation over the range of 20 to 50° when compared to those using the standard isokinetic shank restraint. Likewise, the knee extensions with an anti-shear device that blocks tibia displacement mechanically also induced significantly (n = 6, P < .05) less anterior tibial translation, but over a different range of knee extension (30 to 70°).InterpretationDespite the fact that both the electrical stimulator and the anti-shear device assisted in reducing anterior tibial translation, the tendency of the curves generated with the functional electrical stimulation was generally more similar to those generated when using the standard isokinetic shank restraint.     

Activity progression for anterior cruciate ligament injured individuals

Background

Functional exercises are important in the rehabilitation of anterior cruciate ligament deficient and reconstructed individuals but movement compensations and incomplete recovery persist. This study aimed to identify how tasks pose different challenges; and evaluate if different activities challenge patient groups differently compared to controls.

Methods

Motion and force data were collected during distance hop, squatting and gait for 20 anterior cruciate ligament deficient, 21 reconstructed and 21 controls.

Findings

Knee range of motion was greatest during squatting, intermediate during hopping and smallest during gait (P < 0.01). Peak internal knee extensor moments were greatest during distance hop (P < 0.01). The mean value of peak knee moments was reduced in squatting and gait (P < 0.01) compared to hop. Peak internal extensor moments were significantly larger during squatting than gait and peak external adductor moments during gait compared to squatting (P < 0.01). Fluency was highest during squatting (P < 0.01). All patients demonstrated good recovery of gait but anterior cruciate ligament deficient adopted a strategy of increased fluency (P < 0.01). During squatting knee range of motion and peak internal knee extensor moment were reduced in all patients (P < 0.01). Both anterior cruciate ligament groups hopped a shorter distance (P < 0.01) and had reduced knee range of motion (P < 0.025). Anterior cruciate ligament reconstructed had reduced fluency (P < 0.01).

Interpretation

Distance hop was most challenging; squatting and gait were of similar difficulty but challenged patients in different ways. Despite squatting being an early, less challenging exercise, numerous compensation strategies were identified, indicating that this may be more challenging than gait.