A study of factors influencing muscle activity about the knee joint

Several factors influencing the myoelectric activity of muscles surrounding the knee joint were studied using fine-wire monopolar electrodes. The muscles studied included the vastus lateralis, vastus intermedius, rectus femoris, vastus medialis, gracilis, sartorius, biceps femoris, semimembranosus, semitendinosus, tensor fasciae latae, medial head of the gastrocnemius, and lateral head of the gastrocnemius. Muscle activity was measured in response to unidirectional loads tending to flex and extend the knee, and to combined loads of flexion-adduction, flexion-abduction, extension-adduction, and extension-abduction. Results indicate that the individual muscle responses are dependent upon the direction, magnitude, and combination of external moments, as well as on the flexion angle of the knee joint. Muscle response appeared to be influenced by certain intrinsic mechanical characteristics of the knee joint that tend to change the moment arms of the muscles as the knee moves. For example, the substantial changes in quadriceps myoelectric activity with knee flexion, with constant load applied, can be related to the movement of the tibial-femoral contact changing the lever arm of the quadriceps mechanism. This study indicates that the mechanics of the knee joint must be taken into consideration while attempting to interpret or predict the load response of muscles crossing the knee joint.     

Effects of sagittal plane prosthetic alignment on standing trans-tibial amputee knee loads

The influence of sagittal plane prosthetic alignment changes on loads applied to the ispilateral knee was investigated using 5 transtibial amputee subjects. The goal was to determine which prosthetic alignment results in the most energy efficient standing and also minimises stresses on knee structures during standing. The electromyogram, the external mechanical loading of the prosthetic leg and the amputees' posture were recorded for a wide range of prosthetic alignments. The EMG of the vastus lateralis and biceps femoris muscles was measured bilaterally; the EMG of the gastrocnemius muscle was measured only on the contralateral side. The distance between the anatomical knee centre and each individual's load line, as determined by the Otto Bock "L.A.S.A.R. Posture" alignment system, was used as a measure of the mechanical load applied to the knee joint. Prosthetic alignment has almost no influence on muscle activity of the contralateral lower limb during static standing. On the other hand, prosthetic alignment has a significant influence on the load applied to the amputee's ipsilateral knee joint. The external knee moments applied to the knee ligaments and knee muscles on the amputated side change systematically in response to different plantar flexion or dorsiflexion angles of the prosthetic ankle-foot. During standing the extensor muscles stabilise the limb by contracting if the load line is located less than 15 mm anterior to the anatomical knee centre. The biceps femoris muscle appears to have little or no protective function against hyperextension during standing even if large external knee extension moments are caused by excessive plantar flexion. Such extreme alignments significantly increase the stresses on knee ligaments and the posterior knee capsule. When prosthetic sagittal plane alignment is altered, the trans-tibial amputee compensates by balancing the upper part of the body over the centre of pressure of the prosthetic foot. Biomechanically optimal alignment of the trans-tibial prosthesis occurs when the individual load line is approximately 15 mm anterior to the anatomical knee centre, permitting a comfortable, energy efficient standing and minimising the mechanical loading on the knee structures.     

Significance of static prosthesis alignment for standing and walking of patients with lower limb amputation

The influence of three alignment parameters of a transtibial prosthesis (sagittal foot position, plantar flexion, mediolateral foot position) on the load and motion of the lower extremity joints was investigated in 13 unilateral transtibial amputees. The aim was to determine whether a correlation exists between static prosthetic alignment and gait pattern that would allow an optimal biomechanical prosthetic alignment. The gait pattern was measured using kinematic, kinetic, and electromyographic methods. Statics was defined using the alignment apparatus L.A.S.A.R. Posture. The electromyogram of the m. vastus lateralis and m. biceps femoris was recorded on both sides. The motion of joints is described by joint angles. External joint moments define the mechanical loads. Alignment has almost no influence on muscle activity and joint mechanics of the contralateral leg. In contrast, prosthetic alignment affects clearly and systematically the load and motion of the knee joint during the stance phase on the ipsilateral side. The sagittal foot position influences the maximal flexion angle in the stance phase. The plantar flexion of the foot affects the temporal structure of knee motion. The mediolateral foot position causes correspondingly different varus and valgus moments acting on the knee. Swing phase motion does not depend on prosthetic alignment. The iEMG of the m. vastus lateralis is reduced. Innervation characteristics of the m. biceps femoris on the prosthetically fitted leg has completely changed. The ischiocrural muscles take over the neuromuscular action of the m. gastrocnemius to compensate for the external knee extension moment during the second part of the stance phase. Prosthetic statics determines if the knee joint is physiologically stressed in a standing posture and during walking. Statics will be correct if the anatomical knee axis of the standing amputee is located about 15 mm posterior to the load line in the sagittal plane. In the frontal plane, the load line touches the lateral patella border and strikes the middle of the foot about 5 cm anterior to the adapter. During walking, attention should be paid to performance of knee flexion in the stance phase.     

Electromyographic analysis of a modified maneuver for quadriceps femoris muscle setting with co-contraction of the hamstrings.

A "quadriceps femoris muscle setting" is isometric quadriceps femoris exercise which can be widely used in early knee rehabilitation. However this exercise cannot obtain enough co-contraction of the hamstrings. Isolated quadriceps femoris contraction in knee extension imposes severe strain to anterior cruciate ligament. We succeeded in developing a simple training maneuver that is effective in obtaining co-contraction of the hamstrings--a modified maneuver for the quadriceps femoris muscle setting with the contralateral lower limb raised (MQS). In this study, we analyzed the effect of this maneuver by EMG quantification. Twenty-eight healthy young adult men performed sequential trials consisting of normal quadriceps femoris muscle setting (NQS) and MQS. Electromyographic activity was recorded from surface electrodes on the gluteus maximus, vastus medialis, rectus femoris, vastus lateralis, semitendinosus and biceps femoris (long head), and normalized to values derived from maximal isometric trials. The % maximal voluntary isometric contraction (%MVIC) of the vastus medialis, vastus lateralis and rectus femoris did not vary in the each maneuver. However, the %MVIC of the hamstrings varied significantly in the MQS. This study suggests that effective co-contraction of the hamstrings can be obtained in MQS by adjusting the load to the raised lower limb.     

Muscle reflexes during gait elicited by electrical stimulation of the posterior cruciate ligament in humans.

We investigated the influence of electrical stimulation of the posterior cruciate ligament (PCL) on the motoneuron pool of the thigh and calf muscle during gait. The study group comprised eight young men without any history of injury to the knee joints. Multistranded teflon-insulated stainless steel wires were inserted into the PCL guided by sonography and in four subjects also into the fat pad of the knee. The PCL was electrically stimulated during gait on a treadmill at heel strike and 100 ms after heel strike. Electromyographic signals were recorded with bipolar surface electrodes placed over the vastus medialis, rectus femoris, vastus lateralis, biceps femoris caput longum, and semitendinosus muscles. The stimuli consisted of four pulses delivered at 200 Hz; the stimulus amplitude was two to three times the sensory threshold. The electrical stimulation of the PCL inhibited the ongoing muscle activity in both the quadriceps and the hamstrings. The latency of the inhibition ranged between 78 and 148 ms in the quadriceps, between 88 and 110 ms in the hamstrings and between 189 and 258 ms in m. gastrocnemius. Stimulation of the fat pad of the knee did not influence the thigh and calf muscle motoneuron pool as evidenced by electromyography. The response elicited from the stimulation of the PCL was not limited to a specific muscle group but depended on ongoing muscle contraction, which suggests that the mechanoreceptors in the PCL are involved in the control of all muscles acting on the knee joint during gait.     

EMG profiles of knee joint musculature during walking: changes induced by anterior cruciate ligament deficiency

A tear of the anterior cruciate ligament (ACL) disrupts the delicate balance of static stabilizers of the knee, leading to significant alterations in joint kinematics. Little is known about the dynamic compensatory responses of the patient to these kinematic alterations. This lack of quantitative information on the muscle synergy patterns has limited the surgeon's ability to evaluate various operative and rehabilitative techniques. Twelve subjects with documented ACL deficiency for at least 1 year and 15 normal participants were studied. Each subject was asked to walk at free and fast speeds on a 12 m walkway. The right and left foot contact patterns and the linear envelopes from the surface electromyogram (EMG) patterns of the gastrocnemius, medial and lateral hamstrings, rectus femoris, and vastus lateralis were measured. Significant differences were found in the muscle synergy patterns during walking. During the swing-to-stance transition, the ACL-deficient subjects showed significantly less activity in the quadriceps and gastrocnemius muscles and more activity in the biceps femoris than in the normal group. During early swing, the vastus lateralis is more active than normal, and during midstance and terminal stance, the hamstrings appear to be less active than normal subjects. These dynamic compensatory mechanisms suggest that use of the hamstring tendons in reconstructive procedures may alter important compensatory mechanisms about the knee joint. Application of dynamic EMG techniques to the study of reconstructive procedures should provide additional information that will assist the clinician in the rational choice of a surgical procedure.     

Effect of an unrestricted knee-ankle-foot orthosis on the stance phase of gait in healthy persons

Twenty healthy women (mean age: 25 +/- 3.6 years) were studied for postural adaptations produced when walking with unrestricted knee-ankle-foot orthoses. Stride characteristics, motion, floor reaction forces and their torques, and indwelling electromyographic activity of the lower gluteus maximus, as well as the long head of the biceps femoris, vastus lateralis, and soleus muscles were all measured during barefoot and orthosis walking. Wearing a knee-ankle-foot orthosis increased stride length and decreased cadence and stance duration. The subjects walked in slightly more plantar flexion, knee flexion, and hip flexion, while increasing the duration of the corresponding floor reaction torques, resulting in an activity increase of the vastus lateralis, soleus, and biceps femoris muscles. These results, obtained in healthy subjects, show a definite effect of an unrestricted knee-ankle-foot orthosis on gait.     

Selective thigh muscle atrophy in trans-tibial amputees: an ultrasonographic study

In trans-tibial amputees, PTB (patellar tendon bearing) prostheses provide almost physiological mobility of the knee joint in the sagittal plane. Nevertheless, there are characteristic adaptations of the knee joint muscles. Myosonography is a suitable method for depicting muscle atrophy and hypertrophy due to muscle dysfunction. The present study was intended to assess anatomical alterations of thigh muscles in trans-tibial amputees wearing a PTB prothesis. Thicknesses and cross-sectional areas of the quadriceps femoris, sartorius, gracilis, semitendinosus and biceps femoris muscles were determined ultrasonographically on both limbs in 17 amputees with a PTB prothesis. The gait was analysed using an optoelectronical system, force plates and surface electromyography of the vastus lateralis and biceps femoris muscles. Quadriceps femoris and sartorius muscles of the amputated extremity exhibited significant atrophy compared with the contralateral limb (reduction of muscle thickness ranged between 11.7% and 30.4%), whereas the gracilis and hamstring muscles were not significantly affected. Even the quadriceps femoris muscle of the non-amputated limb showed a slight atrophy compared with a reference group. Increased echointensities were found predominantly in the quadriceps muscle on the amputated leg. During gait, electromyographical activity within the amputated limb was reduced in the vastus lateralis and increased in the biceps femoris muscle. Even long-term adaptation to PTB prostheses results in characteristic deviation from normal gait. Atrophy occurs in the ventral thigh muscles, predominantly on the amputated leg, whereas the dorsal thigh muscles are hardly affected, probably due to compensatory hyperactivity. Received: 14 March 2000     

Evaluation of muscle activity just after straight leg raising exercise by using 18FDG-PET

Background

Exercise therapy is one of the recognized treatment methods for knee osteoarthritis (KOA). One such exercise technique, straight leg raising (SLR), is widely known as a home exercise method for strengthening the quadriceps femoris muscle. However, whether this exercise truly strengthens the quadriceps is not known. The objective of the present study was to investigate which lower limb muscle is stimulated and shows increased activity with SLR.

Quantitative study of the quadriceps muscles and trochlear groove geometry related to instability of the patellofemoral joint

This was a quantitative study of the major anatomical structures associated with instability of the patellofemoral joint: the quadriceps muscles and the femoral trochlear groove. The attachments of the muscles to the patella, their lines of action, and their relative sizes (physiological cross-sectional areas) were found. On the basis of the physiological cross-sectional areas, it was estimated that the central muscles—the rectus femoris and vastus intermedius—contributed 35% of the quadriceps strength, with 40% from the vastus lateralis and 25% from the vastus medialis. The vastus lateralis had the most variable results, with the ratio of the lateralis to the medialis ranging from 0.90 to 2.18; this may be associated with patellar instability. Both the long and oblique parts of the vastus medialis were more oblique than the corresponding parts of the vastus lateralis. Photographic “skyline” views of the trochlear groove produced data on the sulcus angle and ratio of depth to width. The data showed that the trochlear groove did not deepen in the area contacted by the patella with progressive knee flexion (p > 0.53). contrary to popular belief. These data are useful for objective analysis of patellofemoral stability and related surgical interventions.     

Hamstrings cocontraction reduces internal rotation, anterior translation, and anterior cruciate ligament load in weight-bearing flexion.

Strengthening of the hamstrings is often recommended following injury and reconstruction of the anterior cruciate ligament. It has been suggested that hamstrings activity stabilizes the knee and reduces anterior cruciate ligament load during weight-bearing flexion; however, the effects of hamstrings cocontraction on the kinematics and mechanics of the normal knee have not been assessed at physiological load levels. The aim of this study was to determine whether the addition of hamstrings force affects knee rotations, translations, and joint and quadriceps force during flexion with loads at physiological levels applied to the muscles and joints. Eight cadaveric knee specimens were tested with a servohydraulic mechanism capable of applying controlled dynamic loads to simulate quadriceps and hamstrings muscle forces throughout a physiological range of motion. A constant vertical load of physiologic magnitude was applied to the hip, and quadriceps force was varied to maintain equilibrium throughout flexion. Two conditions were tested: no hamstrings force and a constant hamstrings force equivalent to the vertical load. Hamstrings force significantly reduced internal rotation (p<0.0001) and anterior translation (p<0.0001), increased quadriceps force (p<0.0001) and normal resultant force on the tibia (p<0.0001), and reversed the direction of the shear force on the tibia (p<0.0001). These results suggest that hamstrings strengthening following anterior cruciate ligament injury may benefit anterior cruciate ligament-deficient and reconstructed knees by reducing the load in the ligament; however, they also imply that this comes at the expense of efficiency and higher patellofemoral and joint forces.     

Musculoskeletal loading in the symptomatic and asymptomatic knees of middle‐aged osteoarthritis patients

This study quantified the contributions by muscles, gravity, and inertia to the tibiofemoral compartment forces in the symptomatic (SYM) and asymptomatic (ASYM) limbs of varus mal‐aligned medial knee osteoarthritis (OA) patients, and compared the results with healthy controls (CON). Muscle forces and tibiofemoral compartment loads were calculated using gait data from 39 OA patients and 15 controls aged 49 ± 7 years. Patients exhibited lower knee flexion angle, higher hip abduction, and knee adduction angles, lower internal knee flexion torque but higher external knee adduction moment. Muscle forces were highest in CON except hamstrings, which was highest in SYM. ASYM muscle forces were lowest for biceps femoris short head and gastrocnemius but otherwise intermediate between SYM and CON. In all subjects, vasti, hamstrings, gastrocnemius, soleus, gluteus medius, gluteus maximus, and gravity were the largest contributors to medial compartment force (MCF). Inertial contributions were negligible. Highest MCF was found in SYM throughout stance. Small increases in contributions from hamstrings, gluteus maximus, gastrocnemius, and gravity at the first peak; soleus and rectus femoris at the second peak; and soleus, gluteus maximus, gluteus medius, and gravity during mid‐stance summed to produce significantly higher total MCF. Compared to CON, the ASYM limb exhibited similar peak MCF but higher mid‐stance MCF. In patients, diminished non‐knee‐spanning muscle forces did not produce correspondingly diminished MCF contributions due to the influence of mal‐alignment. Our findings emphasize consideration of muscle function, lower‐limb alignment, and mid‐stance loads in developing interventions for OA, and inclusion of the asymptomatic limb in clinical assessments. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:321–330, 2017.

     

Quadriceps torque and integrated electromyography*

Using surface electromyography, the myoelectric activity and torque of the quadriceps muscles were recorded under isometric conditions. The purpose of the study was to identify the optimal angle of knee flexion for normalization purposes. Additionally, the behavior of the quadriceps as the knee was flexed was investigated. It was found that the subject's sex may affect the angle at which maximal torque and integrated electromyography (lemg) occurs. Maximal torque and lemg occurred at 50 degrees for males and 70 degrees for females. This may have an effect on the normalization procedure when the quadriceps is studied dynamically. The location of maximal myoelectric activity of the quadriceps should influence our treatment of patellofemoral disorders when patellar biomechanics are considered. J Orthop Sports Phys Ther 1985;6(6):309-314.     

The gastrocnemius muscle is an antagonist of the anterior cruciate ligament.

Since the proximal tendon of the gastrocnemius muscle wraps around the posterior aspect of the tibia, its contraction could potentially strain the anterior cruciate ligament (ACL) by pushing the tibia anteriorly. However, the relationship between contraction of the gastrocnemius muscle and ACL strain has not been studied in vivo. The objectives of this study were to evaluate the ACL strain response due to isolated contractions of the gastrocnemius muscle and to determine how these strains are affected by cocontraction with the hamstrings and quadriceps muscles. Six subjects with normal ACLs participated in the study; they underwent spinal anesthesia to ensure that their leg musculature was relaxed. Transcutaneous electrical muscle stimulation (TEMS) was used to induce contractions of the gastrocnemius, quadriceps and hamstrings muscles while the strains in the anteromedial bundle of the ACL were measured using a differential variable reluctance transducer. The ACL strain values produced by contraction of the gastrocnemius muscle were dependent on the magnitude of the ankle torque and knee flexion angle. Strains of 2.8% and 3.5% were produced at 5 degrees and 15 degrees of knee flexion, respectively. The ACL was not strained at 30 degrees and 45 degrees. Changes in ankle angle did not significantly affect these strain values. Co-contraction of the gastrocnemius and quadriceps muscles produced ACL strain values that were greater than those produced by isolated activation of either muscle group when the knee was at 15 degrees and 30 degrees. Co-contraction of the gastrocnemius and hamstrings muscles produced strains that were higher than those produced by the isolated contraction of the hamstrings muscles. At 15 degrees and 30 degrees of knee flexion. the co-contraction strain values were less than those produced by stimulation of the gastrocnemius muscle alone. This study verified that the gastrocnemius muscle is an antagonist of the ACL. Since the gastrocnemius is a flexor of the knee, this finding may have important clinical ramifications in ACL rehabilitation since flexor torques are generally thought to be protective of a healing ACL graft.     

In situ forces of the anterior and posterior cruciate ligaments in high knee flexion: an in vitro investigation.

The function of the anterior and posterior cruciate ligaments (ACL and PCL) in the first 120 degrees of flexion has been reported extensively, but little is known of their behavior at higher flexion angles. The aim of this investigation was to study the effects of muscle loads on the in situ forces in both ligaments at high knee flexion (>120 degrees). Eighteen fresh-frozen human knee specimens were tested on a robotic testing system from full extension to 150 degrees of flexion in response to quadriceps (400 N), hamstrings (200 N), and combined quadriceps and hamstrings (400 N/200 N) loads. The in situ forces in the ACL and PCL were measured using the principle of superposition. The force in the ACL peaked at 30 degrees of flexion (71.7 +/- 27.9 N in response to the quadriceps load, 52.3 +/- 24.4 N in response to the combined muscle load, 32.3 +/- 20.9 N in response to the hamstrings load). At 150 degrees, the ACL force was approximately 30 N in response to the quadriceps load and 20 N in response to the combined muscle load and isolated hamstring load. The PCL force peaked at 90 degrees (34.0 +/- 15.3 N in response to the quadriceps load, 88.6 +/- 23.7 N in response to the combined muscle load, 99.8 +/- 24.0 N in response to the hamstrings load) and decreased to around 35 N at 150 degrees in response to each of the loads. These results demonstrate that the ACL and PCL carried significantly less load at high flexion in response to the simulated muscle loads compared to the peak loads they carried in response to the same muscle loads at other flexion angles. The data could provide a reference point for the investigation of non-weight bearing flexion and extension knee exercises in high flexion. Furthermore, these data could be useful in designing total knee implants to achieve high flexion.     

Muscle activation at the human knee during isometric flexion-extension and varus-valgus loads

We examined the role of muscles in counteracting static loads in the transverse plane at the knee to determine if (a) knee muscles are activated to counteract isometric varus or valgus loads, (b) muscle activity during varus and valgus loads changes with the angle of knee flexion, and (c) the direction of a muscle's activation can be predicted by its moment arm orientations. For seven subjects, muscle activity was recorded during isometric tasks using surface and intramuscular electrodes from 10 muscles that span the knee. A six-degree-of-freedom load cell was rigidly attached to each subjects lower leg just above the ankle, and the subjects were instructed to push against the load cell so as to produce moments in the flexion-extension-varus-valgus plane at the knee. Moments in this plane were all of equal magnitude and varied in direction the full 360° in 20° increments. Most muscles were not activated to stabilize the knee against varus-valgus loads, but the sartorius, gracilis, and tensor fasciae latae showed substantial electromyographic activation in these directions. The load directions where muscles were principally active were observed to be dependent on joint angle for some muscles. In particular, the principal directions of activation for these three muscles changed as the angle of knee flexion changed. Similarly, a muscle's moment arm orientation was a good predictor of direction of activation for some muscles and a poor one for others. These results suggest that different muscles may play different roles in providing joint stability and that these roles are complex functions of muscle moment arm orientations, joint angles, external load directions possibly and other undetermined parameters.     

Gender differences in patellofemoral joint biomechanics

Patellofemoral pain is associated with patellar malalignment and quadriceps weakness which are seen more commonly in women. The objective of the current study was to determine the effects of gender, vastus medialis strength, and tibial rotation on patellofemoral joint biomechanics. Twelve fresh-frozen knees from cadavers were tested using a custom knee jig. Anatomic multiplane loading of the extensor mechanism was used with varying vastus medialis loads. Patellofemoral contact area and pressure were measured using pressure sensitive film at knee flexion angles of 0 degrees, 30 degrees, 60 degrees, and 90 degrees with the tibia in neutral and 15 degrees internal and external tibial rotation. Patellofemoral joint contact areas in specimens from men were larger at knee flexion angles greater than 30 degrees. A significant increase in mean patellofemoral contact pressures was seen for specimens from women when compared with specimens from men at 0 degrees and 30 degrees knee flexion. The knees from women also showed a greater change in contact pressures to varying vastus medialis load at knee flexion angles of 0 degrees, 30 degrees, and 60 degrees. The results of the current study indicate that there are gender differences in patellofemoral contact areas and pressures. These differences may help explain the increased incidence of patellofemoral disorders in women.     

Evaluation of the muscles around the knee in rabbits whose anterior cruciate and/or medial collateral ligaments were dissected

Introduction The biological response of the muscles around the knee in chronic ligamentous instability was investigated in an animal study.Materials and methods There were four groups of 6- to 9-month-old adult New Zealand albino rabbits (2500–3300 g). The animals were divided into groups according to the ligament that was surgically sectioned: group A anterior cruciate ligament (ACL), group B medial collateral ligament (MCL), group C both ACL and MCL, and group D served as the control group undergoing no surgical intervention. Three months after surgery, biopsy specimens of the vastus lateralis, rectus femoris, biceps femoris, extensor digitorum longus, and gastrocnemius muscles of the rabbits were obtained. Electron-microscopic cross-sections of the biopsy specimens were evaluated using the new predetermined atrophy parameters.Results Atrophy was found in the biopsy specimens of the quadriceps muscles in groups A and C (p<0.005). Unimportant changes were seen in the hamstrings, extensor digitorum longus, and gastrocnemius muscles (p>0.05). Only in the group undergoing MCL dissection were no changes observed in the muscles (p>0.05).Conclusion It is concluded that ACL lesions affect the biomechanics of the knee negatively and this situation causes atrophy, especially in the quadriceps muscle. An MCL lesion alone does not cause an important problem in the surrounding musculature, probably because of its spontaneous healing capacity. New criteria for assessment of atrophy in the muscles employing electron-microscopic evaluation are suggested.