A deficient anterior cruciate ligament does not lead to quadriceps avoidance gait

Analyses of dynamic co-contraction level in individuals with anterior cruciate ligament injury

BACKGROUND

A complete understanding of neural mechanisms by which ligament receptors may contribute to joint stability is not well established. It has been suggested that these receptors may be involved in a neuromuscular process related to the modulation of dynamic co-contraction, as a means of guaranteeing functional joint stability.

HYPOTHESIS

Individuals with ACL injury have diminished dynamic co-contraction.

STUDY DESIGN

Exploratory, cross-sectional design.

METHODS

Ten subjects with unilateral ACL injury treated conservatively, and ten subjects without history of injury participated in the study. The co-contraction level was assessed through EMG recordings of the vastus lateralis and biceps femoris before and after a perturbation imposed on the subjects during a walking task.

RESULTS

Subjects with ACL injury presented significantly lower co-contraction level pre-perturbation (p = 0.045) and post-perturbation (p = 0.046) than those in the control group.

CONCLUSIONS

The bilateral decrease in muscular co-contraction presented by individuals with ACL injury suggests that ligament and joint receptors may be responsible for a bilateral dynamic increase in muscle and joint stiffness that could result in a greater joint stability.

CLINICAL RELEVANCE

This study analyzed a neuromuscular mechanism that might contribute to the functional stability of the knee joint.

Knee flexion during stair ambulation is altered in individuals with patellofemoral pain

Reduced knee flexion is a logical gait adaptation for individuals with patellofemoral pain (PFP) to lessen the patellofemoral joint reaction force and minimise pain during stair ambulation. This gait adaptation may be related to the co-ordination of individual vasti components.

PURPOSE

This study investigated the amount of stance-phase knee flexion in individuals with (n=48) and without (n=18) PFP using a cross-sectional design. The relationship between stance-phase knee flexion and onset timing of individual vasti activity was also examined.

METHOD

Stance-phase knee flexion was measured in 2-dimensions using a PEAK movement analysis system during stair ascent and descent. Individuals with PFP were separated into those with synchronous onset of the EMG activity of vastus medialis obliquus (VMO) and vastus lateralis (VL), and those where the onset of VMO EMG activity was delayed relative to the VL.

RESULTS

The amount of knee flexion at heel-strike and peak was less in the individuals with PFP compared with the healthy controls. In addition, there were trends towards individuals with PFP who had a delayed EMG onset of VL having reduced knee flexion during stair descent compared with PFP individuals with simultaneous vasti onsets and the control participants.

CONCLUSION

These results indicate that the amount of stance-phase knee flexion is lower in individuals with PFP and that this may be related to onset timing of the vasti.

Comparison of shear forces and ligament loading in the healthy and ACL-deficient knee during gait

The purpose of this study was to predict and explain the pattern of shear force and ligament loading in the ACL-deficient knee during walking, and to compare these results to similar calculations for the healthy knee. Musculoskeletal modeling and computer simulation were combined to calculate ligament forces in the ACL-deficient knee during walking. Joint angles, ground-reaction forces, and the corresponding lower-extremity muscle forces obtained from a whole-body dynamic optimization simulation of walking were input into a second three-dimensional model of the lower extremity that represented the knee as a six degree-of-freedom spatial joint. Anterior tibial translation (ATT) increased throughout the stance phase of gait when the model ACL was removed. The medial collateral ligament (MCL) was the primary restraint to ATT in the ACL-deficient knee. Peak force in the MCL was three times greater in the ACL-deficient knee than in the ACL-intact knee; however, peak force sustained by the MCL in the ACL-deficient knee was limited by the magnitude of the total anterior shear force applied to the tibia. A decrease in anterior tibial shear force was brought about by a decrease in the patellar tendon angle resulting from the increase in ATT. These results suggest that while the MCL acts as the primary restraint to ATT in the ACL-deficient knee, changes in patellar tendon angle reduce total anterior shear force at the knee.

Bilateral accommodations to anterior cruciate ligament deficiency and surgery

OBJECTIVE To determine bilateral lower extremity joint accommodations during gait in anterior cruciate ligament deficient subjects and uninjured controls.

DESIGN

Gait testing of 10 chronic anterior cruciate ligament deficient subjects prior to and 3 months following reconstructive surgery, and 10 uninjured controls.

BACKGROUND

It is possible that bilateral joint accommodations could occur as a result of anterior cruciate ligament injury and in response to surgical repair. Few studies have investigated bilateral joint accommodations to anterior cruciate ligament injury and there is little consistency in the reported results.

METHODS

Bilateral lower extremity kinematic and kinetic data were collected from 12 walking trials and inverse dynamics calculations were made to estimate bilateral knee and hip joint angle, moment, and power patterns during the stance phase of gait.

RESULTS

Control subjects exhibited asymmetrical hip but symmetrical knee joint moment and power patterns. In contrast, the anterior cruciate ligament deficient subjects exhibited symmetrical hip and asymmetrical knee joint moment and power patterns prior to and following reconstructive surgery.

CONCLUSIONS

Gait asymmetry in healthy subjects should not be considered pathological. In addition, chronic anterior cruciate ligament injury results in joint specific, bilateral lower extremity accommodations in gait mechanics. These accommodations persist 3 months following surgical repair.

Gait patterns before and after anterior cruciate ligament reconstruction

The aim of this study is to determine how selected gait parameters may change as a result of anterior cruciate ligament (ACL) deficiency and following ACL reconstruction. The study was performed on 25 ACL-deficient subjects prior to and 6 weeks, 4 months, 8 months and 12 months after ACL reconstructive surgery by the bone-patellar tendon-bone technique. Gait analysis was performed using the zebris three-dimensional ultrasound-based system with surface electromyograph (zebris Medizintechnik GmbH, Germany). Kinematic data were recorded for the lower limb. The muscles examined include vastus lateralis and medialis, biceps femoris and adductor longus. The results obtained from the injured subjects were compared with those of 51 individuals without ACL damage. The acute ACL-deficient patients exhibited a quadriceps avoidance pattern prior to and 6 weeks after surgery. The quadriceps avoidance phenomenon does not develop in chronic ACL-deficient patients. In the individuals operated on, the spatial-temporal parameters and the knee angle had already regained a normal pattern for the ACL-deficient limb during gait 4 months after surgery. However, the relative ACL movement parameter-which describes the tibial translation into the direction of ACL-and the EMG traces show no significant statistical difference compared with the values of healthy control group just 8 months after surgery. The results suggest that: (1) development of a quadriceps avoidance pattern is less common than previously reported, (2) anterior cruciate ligament deficiency and reconstruction significantly alter the lower extremity gait pattern, (3) the gait parameters shift towards the normal value pattern, and (4) the re-establishment of pre-injury gait patterns--including the normal biphase of muscles--takes at least 8 months to occur.

The clinical significance of electromyography normalisation techniques in subjects with anterior cruciate ligament injury during treadmill walking

This study investigated the clinical interpretation of three electromyographic (EMG) normalisation techniques to detect neuromuscular alterations in patients diagnosed with anterior cruciate ligament knee injury during treadmill walking. The EMG signal was normalised using the mean value during the gait cycles (MEA), the maximum value during the gait cycles (MAX), and a maximum voluntary isometric contraction (MVC) test in 16 male and female subjects. The MAX method detected an increase in total muscle activity in the injured limb rectus femoris (11.6%; P=0.02) while the MVC method detected decreased injured limb gastrocnemius medialis (GM) overall muscle activity (34.4%; P=0.02). The MAX method identified decreased GM activity in three portions of the gait cycle. This study indicates the importance of choosing the appropriate normalisation technique since its choice will change outcome measures and subsequent clinical interpretation.

Synergy of medial and lateral hamstrings at three positions of tibial rotation during maximum isometric knee flexion

Rotation of the knee has been used to isolate the strength of the medial and lateral hamstrings during manual testing of the knee flexors. The purpose of this study was to determine if medial and lateral rotation of the knee during manual knee flexor strength testing increased the electromyographic activity of the respective hamstrings. Twenty-three women between 22 and 36 years old with no history of lower extremity injury or disease participated in the study. Indwelling fine wire electrodes were used to record EMG activity of the medial (semitendinosus and semimembranosus) and lateral (long and short heads of the biceps femoris) hamstring muscles during maximally resisted knee flexion with neutral, medial, and lateral rotation of the knee. Repeated measures analysis of variance with post hoc Bonferroni adjustments were used to compare EMG activity across the three tests. EMG activity increased significantly for the target hamstrings during ipsilateral rotation (P<0.05). The semitendinosus had a mean activity of 109% Max. during medial rotation as opposed to 95% Max. during lateral rotation. The semimembranosus averaged 107 and 89% Max. in medial and lateral rotation respectively. Conversely, both the long and short head of the biceps muscle showed significantly higher activity (P<0.05) during lateral compared to medial rotation (110 and 108% compared to 93 and 97%, respectively). Even though the differences are statistically significant they ranged from 2 to 13% only of maximum activity, the clinical importance of this small change in EMG activity is questionable.

Biomechanical changes elicited by an anterior cruciate ligament deficiency during steady rate cycling

OBJECTIVES

To identify any changes to lower limb biomechanics during steady rate cycling as a result of an anterior cruciate ligament deficiency.

DESIGN

Comparative study in which healthy and anterior cruciate ligament injured individuals underwent biomechanical analysis during stationary cycling.

BACKGROUND

Individuals with an anterior cruciate ligament deficiency often exhibit reductions in the magnitude of quadriceps muscle activity and subsequent knee joint extensor moments during walking. It is not known whether these compensations are present during cycling, an exercise frequently used to retrain anterior cruciate ligament injured individuals.

METHODS

Ten healthy and 10 unilateral anterior cruciate ligament deficient individuals participated. All participants were required to cycle for approximately 30 s at each of six different cycling intensities while lower limb EMG, kinetics, and kinematics were collected bilaterally. Before riding, participants performed submaximal isometric contractions to generate normalizing data.

RESULTS

In addition to reduced quadriceps activation and net knee joint extensor moments, the anterior cruciate ligament deficient limbs exhibited decreases in linear impulse of the resultant pedal force, knee joint flexor moments, hip and ankle extensor moments, and muscle activity from gluteus maximus. These decreases were counteracted by an increase in output from the anterior cruciate ligament intact limb.

CONCLUSION

Anterior cruciate ligament injured individuals exhibited a limb attenuation strategy during cycling activities.

RELEVANCE

This study reports lower limb kinetic and electromyographic data from anterior cruciate ligament deficient individuals during stationary cycling, and shows that these individuals exhibit a limb attenuation strategy on the very leg that is undergoing rehabilitation.

Gait perturbation response in chronic anterior cruciate ligament deficiency and repair

OBJECTIVE

To determine how chronic anterior cruciate ligament deficient and surgically repaired subjects react to unexpected forward perturbations during gait as compared to healthy controls.

DESIGN

Gait testing of 10 chronic anterior cruciate ligament deficient subjects prior to and three months following reconstructive surgery, and 10 uninjured controls.

BACKGROUND

The ability of an anterior cruciate ligament injured individual to react and maintain equilibrium during gait perturbations is critical for the prevention of reinjury. No studies have investigated how these individuals respond to unexpected perturbations during normal gait.

METHODS

An unexpected forward perturbation was induced upon heel strike using a force plate capable of translational movement.

RESULTS

Prior to surgery, the anterior cruciate ligament subjects exhibited a greater knee extensor moment in response to the perturbation compared to healthy controls. Following surgery, the anterior cruciate ligament injured subjects exhibited a static knee position and a sustained knee extensor moment throughout stance in response to the perturbation as compared to controls.

CONCLUSIONS

These data suggest that chronic anterior cruciate ligament deficient subjects rely heavily on knee extensor musculature to prevent collapse in response to an unexpected perturbation. This same reactive response was more pronounced 3 months following surgery.

RELEVANCE

The results suggest that, prior to and following surgery, chronic anterior cruciate ligament injured subjects respond differently than healthy controls to an unexpected perturbation during gait. Anterior cruciate ligament injured or repaired subjects do not reduce or avoid vigorous contraction of the quadriceps muscles when responding to gait perturbations.

A clinically applicable EMG-force model to quantify active stabilization of the knee after a lesion of the anterior cruciate ligament

OBJECTIVES

To investigate whether a simple electromyography-force (EMG-force) model can be used to measure different levels of co-contraction about the knee for healthy subjects and patients with an anterior cruciate ligament deficiency.

DESIGN

To evaluate an EMG-to-force processing model, two groups of subjects, with and without deficiency of the anterior cruciate ligament, participated in experiments in which surface EMG, kinematics and kinetics about the knee were recorded during isokinetic and functional movements.

BACKGROUND

Clinical and biomechanical evidence supports the hypothesis that higher level of co-contraction of quadriceps and hamstrings provide an active stabilization of the knee to compensate for the lost anterior cruciate ligament. To quantify the level of co-contraction, the contribution of both agonist and antagonist muscles to the net joint moment must be known.

METHODS

Surface EMG levels were calibrated to moment by means of a limited number of isokinetic contractions about the knee. With these calibration values, an estimate of the muscle moments during a vertical jump were obtained and compared with the net joint moment, calculated with inverse dynamics. Also co-contraction indices were determined.

RESULTS

The EMG-force model provided a fair estimate of the net joint moment. The co-contraction index in anterior cruciate ligament deficient subjects was significantly higher (mean 0.54 (SD, 0.04)) compared to healthy subjects (mean 0.25 (SD, 0.07)).

CONCLUSIONS

Although the EMG-to-force processing model is not perfectly accurate, it is appropriate within a clinical context.

RELEVANCE

Previous research supports the hypothesis that subjects with an anterior cruciate ligament deficiency compensate the loss of passive stability by developing higher co-activation levels of the knee muscles, i.e. active stabilization. Quantifying co-contraction may serve as a valuable parameter to evaluate clinical interventions and rehabilitation processes. The EMG-force model presented in this study appears to be a useful instrument for this purpose.

Consequences of a ligament injury on neuromuscular function and relevance to rehabilitation - using the anterior cruciate ligament-injured knee as model

The purpose of this article is to survey current knowledge concerning the consequences of a ligament injury on neuromuscular function and its relevance to rehabilitation, in relation to clinical practice. Although it deals with the ACL-injured knee, these views may also apply to other joints. The effects of a ligament injury on neuromuscular function are first considered - i.e., proprioception, postural control, muscle strength, functional performance, movement and activation pattern, central mechanisms, motor control and learning. The treatment and effects of rehabilitation on neuromuscular function are then discussed. The survey is concluded by discussing the clinical significance.

Gait mechanics in chronic ACL deficiency and subsequent repair

OBJECTIVE

To determine how normal gait patterns may change as a result of chronic anterior cruciate ligament deficiency and subsequent reconstructive surgery.

DESIGN

Gait testing of 10 chronic anterior cruciate ligament deficient subjects prior to and 3 months following reconstructive surgery, and 10 uninjured controls.

BACKGROUND

There is controversy whether persons with chronic anterior cruciate ligament deficiency develop a "quadriceps avoidance" pattern and how anterior cruciate ligament reconstructive surgery influences gait mechanics in these same individuals.

METHODS

Gait analysis was employed to determine kinematic, kinetic, and muscle Electromyographic data.

RESULTS

Prior to surgery, no anterior cruciate ligament deficient subject exhibited a quadriceps avoidance pattern. Following surgery, the subjects exhibited a significantly greater knee extensor moment during early stance as compared to the control group. Prior to and following surgery, anterior cruciate ligament deficient subjects demonstrated a significantly greater hip extensor moment possibly to reduce anterior tibial translation. CONCLUSIONS; These data suggest that (1) development of a quadriceps avoidance pattern is less common than previously reported, (2) anterior cruciate ligament deficient subjects accommodate through alterations of hip joint mechanics, (3) surgical repair significantly alters lower extremity gait patterns, and (4) re-establishment of pre-injury gait patterns takes longer than 3 months to occur.

RELEVANCE

The results suggest that chronic anterior cruciate ligament deficient subjects do not exhibit a quadriceps avoidance gait pattern. Surgical intervention significantly alters lower extremity gait mechanics in a population that has accommodated to anterior cruciate ligament deficiency.

Giving way event during a combined stepping and crossover cutting task in an individual with anterior cruciate ligament deficiency

STUDY DESIGN

Case study.

OBJECTIVE

To compare knee kinematics and moments of nongiving way trials to a giving way trial during a combined stepping and crossover cutting activity.

BACKGROUND

The knee kinematics and moments associated with giving way episodes suggest motor control strategies that lead to instability and recovery of stability during movement.

METHODS AND MEASURES

A 27-year-old woman with anterior cruciate ligament deficiency reported giving way while performing a combined stepping and crossover cutting activity. A motion analysis system recorded motion of the pelvis, femur, tibia, and foot using 3 infrared emitting diodes placed on each segment at 60 Hz. Force plate recordings at 300 Hz were combined with limb inertial properties and position data to estimate net knee joint moments. The stance time, foot progression angle, and cutting angle were also included to evaluate performance between trials.

RESULTS

Knee internal rotation during the giving way trial increased 3.2 degrees at 54% of stance relative to the nongiving way trials. Knee flexion during the giving way trial increased to 33.1 degrees at 66% of stance, and the knee moment switched from a nominal flexor moment to a knee extensor moment at 64% of stance. The knee abductor moment and external rotation moment during the giving way trial deviated in early stance.

CONCLUSIONS

The observed response to the giving way event suggests that increasing knee flexion may enhance knee stability for this subject. The transverse and frontal plane moments appear important in contributing to the giving way event. Further research that assists clinicians in understanding how interventions can impact control of movements in these planes is necessary.

Quadriceps Activation during Knee Extension Exercises in Patients with ACL Pathologies

This study assessed muscle inhibition in patients with chronic anterior cruciate ligament (ACL) deficiency or ACL reconstruction. A series of protocols were tested for their effectiveness in increasing activity of the individual knee extensor muscles and decreasing muscle inhibition of the whole quadriceps group. Quadriceps muscle inhibition was measured by superimposing an electrical twitch onto the quadriceps muscle during a maximal voluntary knee extension. The level of activation of the individual knee extensor and knee flexor muscles was assessed via electromyography (EMG). Patients with ACL pathologies showed strength deficits and muscle inhibition in the knee extensors of the involved leg and the contralateral leg. Muscle inhibition was statistically significantly greater in ACL-deficient patients compared to ACL-reconstructed patients. When a knee extension was performed in combination with a hip extension, there was a significant increase,p< 0.05, in activation of the vastus medialis and vastus lateralis muscles compared to isolated knee extension. The use of an anti-shear device, designed to help stabilize the ACL-deficient knee, resulted in increased inhibition in the quadriceps muscle. Furthermore, a relatively more complete activation of the vasti compared to the rectus femoris was achieved during a fatiguing isometric contraction. Based on the results of this study, it is concluded that performing knee extension in combination with hip extension, or performing fatiguing knee extensor contractions, may be more effective in fully activating the vasti muscles than an isolated knee extensor contraction. Training interventions are needed to establish whether these exercise protocols are more effective than traditional rehabilitation approaches in decreasing muscle inhibition and achieving better functional recovery, including equal muscle strength in the injured and the contralateral leg.