Article

The anterior cruciate ligament-deficient knee: compensatory mechanisms during downhill walking

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Abstract

This investigation sought to identify neuromechanical mechanisms by which a subject with an anterior cruciate ligament (ACL)-deficient knee might cope with the potentially destabilizing joint stresses during both level and downhill walking. Kinematic, kinetic and electromyographic data were collected from 21 subjects with arthroscopically verified ACL-deficient knees and Lysholm scores of 55–100 ( ), as well as from 12 healthy control subjects. Electromyographic data were recorded from the skin surface overlying rectus femoris, biceps femoris and gastrocnemius muscles. A dismountable slope of 6 m length and a gradient of 19% was constructed for downhill walking. Sagittal plane net joint moments and muscle mechanical power at the knee joint were calculated from force platform and videographic records using the inverse dynamics approach. During level walking there were no kinematic nor kinetic differences seen between ACL-deficient subjects and normals. The typical profile of muscle power at the knee contained three peaks during stance: an eccentric peak during early stance (K1); a concentric peak at mid stance (K2); and a second smaller eccentric peak (K3) during late stance. During downhill walking ACL-deficient subjects displayed a significantly smaller K1 compared to normals and their K1:K3 ratio was significantly less than that of normal subjects. Whereas normal subjects showed no hamstring activity during stance in level walking there was continuous activity throughout the stance phase displayed by the ACL-deficient and normal subjects. During downhill walking both the ACL-deficient and normal subjects showed continuous hamstring activity. However, the ACL-deficient subjects showed a significant delay in peak hamstring activity during late swing. Both groups on average displayed gastrocnemius peak activity just on heel strike during downhill walking but the linear envelopes of the ACL-deficient subjects were much more tightly time-locked to this critical event.

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... Considering the magnitude of knee extensor power required and the greater knee flexion adopted on a ramp, it is unlikely that quadriceps avoidance is a possible compensatory strategy as quadriceps muscle force is critical during this task[14]. Two previous studies examining ACL deficient populations during downhill walking have been published[7,16]. Kuster et al.[16]found that ACLD individuals displayed similar knee joint kinematics as uninjured individuals and produced no significant difference in peak quadriceps activity (as measured by rectus femoris EMG). ...
... Two previous studies examining ACL deficient populations during downhill walking have been published[7,16]. Kuster et al.[16]found that ACLD individuals displayed similar knee joint kinematics as uninjured individuals and produced no significant difference in peak quadriceps activity (as measured by rectus femoris EMG). However, the timing of peak gastrocnemius and biceps femoris muscle activity was statistically different. ...
... However, the timing of peak gastrocnemius and biceps femoris muscle activity was statistically different. ACLD individuals delayed peak hamstrings activity and elicited earlier activation of gastrocnemius to coincide with the instant of heel contact, possibly to focus stabilizing muscle forces at the onset of the knee joint loading response[16]. Similar delayed peak hamstring responses have been observed more recently during deceleration landing tasks, again proposed as a strategy to ensure optimal muscle force at the instant of joint loading[11]. ...
Article
Descent of a ramp has been shown to induce large anterior shear forces on the knee joint. Compensatory muscle responses observed in individuals following an anterior cruciate ligament (ACL) injury are believed to be adopted for the purpose of reducing these forces at the knee, in the absence of the mechanical restraint previously provided by the ACL. As such, examining the kinematics and muscle responses of ACL deficient individuals during ramp descent may provide further insight into strategies used by this population to compensate for anterior shear forces at the knee. Eight ACL deficient individuals were studied, in comparison to a healthy CONTROL group (N=8), during the descent of a 20 degrees ramp. Kinematics and electromyography were recorded for the injured lower limb of ACLD and matched limb of healthy control individuals. ACLD individuals produced altered knee kinematics at heel contact only. Knee motion through stance and swing were similar to CONTROL individuals. ACLD individuals produced significantly greater vastus lateralis and gastrocnemius total muscle activity, but decreased total biceps femoris activity. No significant differences were observed for the timing of peak muscle activity or the magnitude at this point between ACLD and CONTROL. Greater total muscle activity of vastus lateralis implies that greater force contributions from this muscle were used by ACLD in comparison to CONTROL in response to the ramp. These observations reinforce that quadriceps avoidance is not used by ACLD individuals to reduce anterior shear forces at the knee joint. Rather, vastus lateralis may be used to reduce internal tibial rotation in extreme loading situations.
... In support of this notion, Reed-Jones and Vallis (2008) observed greater gastrocnemius muscle activity during downhill walking in ACLD individuals, which they attributed to an attempt to compensate for increased joint laxity and to enhance knee stability. In a similar task however, ACLD subjects elicited earlier activation of gastrocnemius to coincide with heel strike without concurrent increases in total muscle activity (Kuster et al., 1995). Comparable findings have recently been observed during level walking (Lindstrom et al., 2010). ...
... Certainly Reed-Jones and Vallis (2008) report earlier activation of gastrocnemius without changes in muscle amplitude in chronic ACLD as compared to acute ACLD subjects during downhill walking, an activity known to increase anterior shear forces on the knee. Similarly, Kuster et al. (1995) found no change during gait in muscle amplitude but definite delayed peak hamstring and earlier peak gastrocnemius activation during heel strike in those with ACLD. They proposed that these temporal changes were in fact compensatory, ensuring optimal muscle force was achieved at the instant of joint loading to guard against the pending anterior drawer forces produced during early stance. ...
Article
Changes in hamstring and quadriceps activity are well known in individuals with anterior cruciate ligament deficiency (ACLD) to potentially compensate for knee joint instability. However, few studies have explored gastrocnemius activity or its relationship to knee stability. The purpose of this study was therefore to examine the activation characteristics of medial gastrocnemius (MG) in ACLD subjects and relate any changes to knee joint laxity. Two subject cohorts were assessed: those with unilateral ACLD (n=15) and uninjured control subjects (n=11). Surface EMG of the left and right MG were recorded during a controlled single leg hop on each limb. Onset and offset of MG activation relative to take-off, during flight and landing were calculated as well as muscle activity (RMS). Passive antero-posterior knee laxity was measured with a KT1000 arthrometer during a maximal manual displacement test. Medial gastrocnemius activity on the injured side of ACLD participants demonstrated significantly prolonged activation in preparation to hop, minimal muscle inactivity prior to take-off, and increased duration of overall muscle activity when compared to the uninjured side and control subjects (p<0.05). Significant positive correlations were found between passive knee joint laxity and prolonged activation prior to knee bend. RMS of the muscle signal was not significantly different between limbs. Overall, MG on the ACLD side demonstrated longer activation, with minimal rest during the hop test, which may be an attempt to maintain knee stability. Furthermore, the strong relationship between knee laxity and prolonged muscle activation suggests that individuals with a loss of knee stability are more reliant on active control of the gastrocnemius muscle.
... In addition to physiological variables that change with footwear, there are also several kinetic variables that are affected, such as ground reaction forces and joint moments 9,11,12,46 . These changes in kinetic variables may lead to increased physiological stress, potentially leading to overexertion and falling 7 . ...
... Previous literature has shown that alterations in kinetic variables due to footwear choice, such as ground reaction forces, joint moments, and joint loading, may increase an individual's risk of injury 9,11,12,46 . The extent of these alterations is highly dependent on the task at hand (i.e., level walking, downhill walking) and footwear choice (i.e., barefoot, lightweight shoes, heavy boots). ...
Thesis
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The purpose of this study was to examine the effect of hiking shoes and hiking boots on the biomechanical responses to a stepping task and physiological responses to an inclined walking task. Participants (n = 16) performed six two minute stepping trials at a stepping rate of 72 bpm; three trials in hiking boots and three trials in hiking shoes. Following the stepping task, participants (n = 19) walked at 3.0 mph and 10% grade for five minutes in hiking shoes and hiking boots. Lower limb joint angles and moments were calculated using Visual 3D. Physiological data was averaged over the last three minutes of the inclined walking task to determine mean variables during steady state exercise. Results showed that during the lowering phase of the stepping cycle, ankle ROM and ankle and knee moments were significantly greater in hiking shoes than hiking boots, indicating that no compensatory mechanisms of the knee and hip were implemented due to restricted ankle ROM. Additionally, VO2 and VE were significantly greater in the hiking shoe condition during the inclined walking task. While these variables are statistically significant, they may not be practically significant in an actual hiking scenario, as the magnitudes of differences observed in variables were minimal. Use of either shoe or boot may not result in an increased risk of injury, therefore leaving the choice of footwear up to the hiker’s personal preference.
... Muscle activity was then normalised to the mean amplitude of the EMG signal during a full gait cycle for that subject (MEA). Kuster et al. [12] found a decrease in peak RF muscle activity at heel strike during level walking in the ACL deficient limb. In downhill walking the ACL deficient group displayed peak lateral hamstrings (LH) activity later in the swing phase and less variability in the timing patterns of the gastrocnemius muscles. ...
... Furthermore, subjects who were unable to perform the MVC protocol or who were uncomfortable in performing the protocol were excluded from the study. In discussing a 'normal' altered neuromuscular pattern for ACL injured subjects during gait, the gastrocnemius muscles of the injured leg have shown consistently, alterations when compared with uninjured controls [9,12,17], copers [14] and the contra-lateral limb in this study and [10]. Fleming et al. [29] have shown recently that gastrocnemius activation can increase ACL strain in-vivo. ...
Article
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.
... They were all non-copers, their time since injury was between six to 12 months after ACL rupture and they were right side injured. Previous studies indicated that the time passed since injury may affect compensatory adaptations in ACLD subject [26,27]. In this study, the duration of injury was 8.37 months ( ± 2.34 SD), resulting in more homogenous ACLD subjects. ...
Article
The anterior cruciate ligament (ACL) is not only a mechanical structure for knee joint stability but is also a source of sensory information which could be used in the control of standing posture. It has been shown that the center of pressure (COP) time series during normal standing may be decomposed into two components which are hypothetically governed by different neural mechanisms, namely rambling and trembling. The aim of the present study was to investigate to what extent an injury to the ACL structure would affect these two control mechanisms. In this study the balance of a group of ACL deficient patients during double and single leg standing was examined and compared with that of a group of healthy individuals. We not only calculated the traditional measures of COP, but also decomposed this complex signal to investigate if ACL deficiency would affect the rambling and trembling components differently. The results showed that rambling was not significantly different between the two groups; however the trembling component was significantly greater for the ACL group in both the single leg and the double leg condition. Further, there was also a component (rambling/trembling) by direction (anterior-posterior/mediolateral) interaction for both groups, indicating that the rambling component exhibited differences between directions of sway whereas the trembling component did not. This study provided evidence that the two components of postural control are differently affected by ACL deficiency, and that the rambling component is influenced by direction of sway.
... They were all non-copers, their time since injury was between six to 12 months after ACL rupture and they were right side injured. Previous studies indicated that the time passed since injury may affect compensatory adaptations in ACLD subject[26,27]. In this study, the duration of injury was 8.37 months ( ± 2.34 SD), resulting in more homogenous ACLD subjects. Although the results of the present study are congruent with that of a two component model of postural control, additional research is warranted to verify whether rambling and trembling components of the COP does truly distinguish between spinal and supraspinal postural control. ...
Article
Introduction Neck pain is of the common musculoskeletal disorders. Physical maltreatment may have caused disability and socioeconomic repercussions. However, manual therapy techniques are less costly, with least side effects in treatment of neck pain, but there is a lack of evidence about the efficacy of these methods or a comparison of treatment to suggest the best technique. Materials and Methods Thirty subjects with neck pain, aged 18-35 years old, were participated in this study. All individuals were randomly classified into two groups. One group received massage therapy and the other strain-counter strain technique. Participants had three therapy sessions every other day. Pain was assessed via pain numerical rating scale (PNRS) and neck disability index (NDI) questionnaire was used to measure the level of functional disability just before and immediately after each technique. Paired and sample t-tests were used to analyze the data. Results There was a significant improvement in pain intensity and disability level after massage therapy (PNRS = 0.001, NDI = 0) and strain counter-strain (PNRS = 0, NDI = 0.03). Nevertheless, no significant differences were found just after intervention in NDI between both groups (P > 0.05). Differences in NRS between both intervention groups were statistically found (P < 0.05). Conclusion Both massage and Strain-Counter strain alleviate pain and improved function in patients with neck pain, although massage therapy was more effective in these patients. Keywords Neck pain, Massage, Strain-Counter strain technique, Functional disability
... Previous studies indicated that the time elapsed since injury may affect compensatory adaptations of the ACLD subject [7,35]. In this study, the duration of injury was in a narrow range, 8.02 ±2.28 months, resulting in more homogenous ACLD subjects. ...
Article
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Anterior cruciate ligament injury is a debilitating pathology which may alter lower limb coordination pattern in both intact and affected lower extremities during activities of daily living. Emerging evidence supports the notion that kinematic variables may not be a good indicator to differentiate patients with anterior cruciate ligament deficiency during step descent task. The aim of the present study was to examine alterations in kinematics as well as coordination patterns and coordination variability of both limbs of these patients during a single step descent task. Continuous relative phase technique was used to measure coordination pattern and coordination variability between a group of anterior cruciate ligament deficient (n = 23) and a healthy control group (n = 23). A third order polynomial Curve fitting was utilized to provide a curve that best fitted to the data points of coordination pattern and coordination variability of the healthy control group. This was considered as a reference to compare to that of patient group using nonlinear regression analysis. The results of the present study demonstrated an altered coordination pattern of the supporting shank-thigh and the stepping foot-shank couplings in anterior cruciate ligament deficient subjects. It was further noticed that there was an increased coordination variability in foot-shank and shank-thigh couplings of both supporting and stepping legs. There was no significant difference in the hip, knee and ankle joints kinematics in either side of these patients. Anterior cruciate ligament deficient individuals showed altered strategies in both intact and affected legs, with increased coordination variability. Kinematic data did not indicate any significant difference between the two groups. It could be concluded that more sophisticated dynamic approach such as continuous relative phase would uncover discrepancies between the healthy and anterior cruciate ligament deficient individuals.
... The full text of the remaining 17 studies was obtained to determine whether the studies were suitable to review. Four studies were rejected: two studies were excluded, as they did not include a control group [21,26]; and two other studies due to walking on non-flat surface [24,34]. Thirteen studies met the inclusion criteria and were subsequently included for full review. ...
Article
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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.
Chapter
The ultimate goal of a knee ligament reconstruction is to provide the injured knee with a normal function. It should correct the instability and reestablish the normal knee mechanics in order to prevent the articular degeneration process. The ligaments of the knee act as passive restraints to abnormal knee motion. They also provide some dynamic stability by stimulating the neuromuscular system through their sensory innervation.
Article
It was the purpose of the present study to examine the possibility of increased muscle coordination after anterior cruciate ligament (ACL) reconstruction through the wearing of a compression sleeve. Thirty-six patients were studied who had undergone unilateral ACL reconstruction at least 12 months previously. All subjects were required to perform a 10-cm standing drop jump from an elevated platform onto a force plate, to land on one leg, and thereafter maintain a one-legged balance for 25 s. This task was repeated three times without and three times with an elastic compression sleeve worn on the reconstructed limb. For analysis, the task was partitioned into a landing phase (150 ms), an adjusting phase (10s), and a balancing phase (10s). The peak impact loadings were measured in each direction (Fx, Fy, and Fz) during landing, while force-time integrals (intFz, intFy, and intFz) and root mean square (RMS) error of these forces were calculated for the adjusting and balancing phases. The path length and RMS of the center of pressure coordinates (Ax and Ay) were obtained for the adjusting and balancing phases combined. Drop landings with the bandage produced significantly larger (P < 0.001) peak ground reaction forces in the vertical and anteroposterior direction, suggesting increased subject confidence in their knee. Wearing the knee bandage also enabled the patients to reduce all measured parameters in the anteroposterior direction (rmsFx, intFx, rmsAx) during both the adjusting and balancing phases (P < 0.001 ). A significant reduction in the center of pressure path length further indicated an enhanced steadiness during the one-legged stance. It was concluded that a compression sleeve improved the total integration of the balance control system and muscle coordination.
Article
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Previous studies of movement kinematics in patients with a ruptured anterior cruciate ligament (ACL) have focused on changes in angular displacement in a single joint, usually flexion/extension of the knee. In the present study, we investigated the effect of an ACL injury on the overall limb interjoint coordination. We asked healthy and chronic ACL-deficient male subjects to perform eight types of movements: forward squats, backward squats, sideways squats, squats on one leg, going up a step, going down a step, walking three steps, and stepping in place. Depending on the movement concerned, we applied principal component (PC) analysis to 3 or 4 degrees of freedom (DFs): thigh flexion/extension, knee flexion/extension, ankle flexion/extension, thigh abduction/adduction. The first three DFs were investigated in all movements. PC analysis identifies linear combinations of DFs. Movements with a fixed ratio between DFs are thus described by only one PC or synergy. PCs were computed for the entire movement as well as for the period of time when the foot was in contact with the ground. For both the control and the injured groups, two synergies (PC vectors) usually accounted for more than 95% of the DFs' angular excursions. It was possible to describe 95-99% of some movements using only one synergy. Compared to control subjects, injured subjects employed different synergies for going up a step, walking three steps, squatting sideways, and squatting forward, both in the injured and uninjured legs. Those movements may thus be more indicative of injury than other movements. Although ACL-deficiency did not increase asymmetry (angle between the PCs of the same movement performed on the right and the left sides), this result is not conclusive because of the comparatively low number of subjects who participated in the study. However, the finding that synergies in both legs of patients were different from those in control subjects for going up a step and walking three steps suggests that interjoint coordination was affected for both legs, so that the asymmetry index might have been preserved despite the injury. There was also a relationship between the asymmetry index for squatting on one leg, squatting forward, walking three steps and some of the outcomes of the knee injury and osteoarthritis outcome score (pain, symptoms, activities of daily living, sport and recreation function, and knee-related quality of life). This suggests that significant differences in the asymmetry index could be obtained if more severely-injured patients participated in this study. It is possible that subjects compensated for their mechanical deficiencies by modifying muscle activation patterns. Synergies were not only modified in injured subjects, but also rearranged: the percentage of movement explained by the first PC was different for the injured and/or uninjured legs of patients, as compared to the legs of the control group, for going up a step, going down a step, walking three steps, and squatting forward. We concluded that the analysis of interjoint coordination may be efficient in characterizing motor deficits in people with knee injuries.
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The role of lower limb proprioception in the steering control of locomotion is still unclear. The purpose of the current study was to determine whether steering control is altered in individuals with reduced lower limb proprioception. Anterior cruciate ligament deficiency (ACLD) results in a decrease in proprioceptive information from the injured knee joint (Barrack et al. 1989). Therefore the whole body kinematics were recorded for eight unilateral ACLD individuals and eight CONTROL individuals during the descent of a 20 degrees incline ramp followed by either a redirection using a side or cross cutting maneuver or a continuation straight ahead. Onset of head and trunk yaw, mediolateral displacement of a weighted center of mass (COM(HT)) and mediolateral displacement of the swing foot were analyzed to evaluate differences in the steering control. Timing analyses revealed that ACLD individuals delayed the reorientation of body segments compared to CONTROL individuals. In addition, ACLD did not use a typical steering synergy where the head leads whole body reorientation; rather ACLD individuals reoriented the head, trunk and COM(HT) in the new direction at the same time. These results suggest that when lower limb proprioceptive information is reduced, the central nervous system (CNS) may delay whole body reorientation to the new travel direction, perhaps in order to integrate existing sensory information (vision, vestibular and proprioception) with the reduced information from the injured knee joint. This control strategy is maintained when visual information is present or reduced in a low light environment. Additionally, the CNS may move the head and trunk segments as, effectively, one segment to decrease the number of degrees of freedom that must be controlled and increase whole body stability during the turning task.
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Many different methods of evaluating disability after knee ligament injury exist. Most of them differ in design. Some are based on only patients' symptoms. Other include patients' symptoms, activity grading, performance in a test, and clinical findings. The rating in these evaluating systems can be either numerical, as in a score, or binary, with yes/no answers. Comparison between a symptom-related score and a score of more complex design showed that the symptom-related score gave a more differentiated picture of the disability. It was also shown that the binary rating system gave less detailed information than a score and that differences in a binary rating can depend on at what level the symptoms are regarded as "significant." A new activity grading scale, where work and sport activities were graded numerically, was constructed as complement to the functional score. When evaluating knee ligament injuries, stability testing, functional knee score, performance test, and activity grading are all important. However, the relative importance varies during the course of treatment, and therefore they should not all be included in one and the same score.
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Knee specimens were placed in an apparatus which imposed cyclic anterior-posterior or rotatory forces, with various compressive loads applied to the joint. Force-displacement graphs or torque-rotation graphs were automatically plotted, giving the laxity under various conditions. The ligaments, capsule, and menisci provided joint stability under no-load conditions. However, under compressive loads, the conformity of the condylar surfaces was an important factor in stabilizing the knee. The mechanism proposed was the uphill movement of the femur as the femur and the tibia were displaced or twisted relative to one another.
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In an electromyographic (EMG) study, the coordination in muscles acting on the knee joint was assessed in 14 patients with an arthroscopically verified complete rupture of the anterior cruciate ligament and in 16 controls. EMG and heel-contact signals were recorded while walking on a treadmill at walking gradients from 0 to 25 percent. There was an earlier onset of EMG bursts in the patients, especially in the lateral hamstrings and medial gastrocnemius; and the duration of EMG bursts also tended to be prolonged in the patients. Normalized root mean squares of amplitudes, which correlate with muscle tension, were higher in the gastrocnemius in the patients. EMG profiles, outlining the averaged muscle activity throughout the gait cycle, showed a displacement of peak activity in the hamstrings from the late swing phase into the stance phase, with increasing gradients in both the patients and the controls. Our study indicates that the gastrocnemius muscle contributes to functional stability in the anterior cruciate ligament deficient knee, and more attention should be paid to this muscle.
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Morphologic, physiologic, and clinical evidence for the sensory role of the cruciate ligaments is reviewed. The cruciate ligaments accommodate morphologically different sensory nerve endings (Ruffini endings, Pacinian corpuscles, Golgi tendon organlike endings, and free nerve endings) with different capabilities of providing the central nervous system with information not only about noxious and chemical events but also about characteristics of movements and position-related stretches of these ligaments. A survey of available data reveals that low threshold joint-ligament receptor (i.e., mechanoreceptor) afferents evoke only weak and rare effects in skeletomotor neurons (alpha-motor neurons), while they frequently and powerfully influence fusimotor neurons (gamma-motor neurons). The effects on the gamma-muscle-spindle system in the muscles around the knee are so potent that even stretches of the cruciate ligaments at relatively moderate loads (not noxious) may induce major changes in responses of the muscle spindle afferents. As the activity in the primary muscle spindle afferents modifies the stiffness in the muscles, the cruciate ligament receptors, via the gamma-muscle-spindle system, may participate in the regulation and preprogramming of the muscular stiffness around the knee joint and thereby of the knee joint stiffness. Thus, the sensory system of the cruciate ligaments is able to significantly contribute to the functional stability of the knee joint.
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A new technique was used to measure the resultant forces in the anterior cruciate ligament during a series of loading experiments on seventeen fresh-frozen cadaver specimens. The base of the ligament's tibial attachment was mechanically isolated with a coring cutter, and a specially designed load-transducer was fixed to the bone-plug that contained the ligament's tibial insertion so that the resultant forces were directly measured by the load-cell. Although the magnitudes of values for forces varied considerably between specimens for a given test condition, the patterns of loading with respect to direction of loading and the angle of flexion of the knee were remarkably consistent. Passive extension of the knee generated forces in the ligament only during the last 10 degrees of extension; at 5 degrees of hyperextension, the forces ranged from fifty to 240 newtons (mean, 118 newtons). When a 200-newton pull of the quadriceps tendon was applied to extend a knee slowly against tibial resistance, however, the force in the ligament increased at all angles of flexion of the knee. Internal tibial torque always generated greater forces in the ligament than did external tibial torque; higher forces were recorded as the knee was extended. The greatest forces (133 to 370 newtons) were generated when ten newton-meters of internal tibial torque was applied to a hyperextended knee. Fifteen newton-meters of applied varus moment generated forces of ninety-four to 177 newtons at full extension; fifteen newton-meters of applied valgus moment generated a mean force of fifty-six newtons, which remained unchanged with flexion of the knee. The force during straight anterior translation of the tibia was approximately equal to the anterior force applied to the tibia. The application of 925 newtons of tibiofemoral contact force reduced the mean force in the ligament that was generated by 200 newtons of anterior pull on the tibia by 36 per cent at full extension and 46 per cent at 20 degrees of flexion.
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Sixteen patients who had unilateral deficiency of the anterior cruciate ligament and ten healthy control subjects were analyzed during level walking, jogging, and ascending and descending stairs. Kinematic and kinetic findings for the right and left hips, knees, and ankles of all of the patients and control subjects were recorded during each activity. Substantial differences from normal function were observed for both limbs of the patients during level walking and during jogging. The magnitude of the maximum moment that tended to flex the knee was reduced the most (140 per cent) during level walking. It was reduced less (30 per cent) during jogging, it was not changed while the patient descended stairs, and it was slightly increased while he or she ascended stairs. The reduction in the magnitude of the flexion moment about the knee was interpreted as the patient's effort to reduce or avoid contraction of the quadriceps. Reduction of the flexion moment reduces any contraction of the quadriceps because there must be a mechanical balance between the external moment (due to body weight and the weight and inertia of the segment of the limb) that tends to flex the knee and an internal moment (generated by contraction of the quadriceps) that tends to extend the knee. This so-called quadriceps-avoidance gait was related to the angle of flexion of the knee when the maximum flexion moment occurred during each activity. This angle of flexion was 20 degrees during walking, 40 degrees during jogging, and approximately 60 degrees during stair-climbing.(ABSTRACT TRUNCATED AT 250 WORDS)
Article
The electromyographic activities of six muscles of the thigh were recorded, using bipolar surface electrodes, during active extension of the knee by six healthy men. The signal amplitudes were normalized to those recorded during isometric maximum voluntary contractions. Extension of the knee from 90 to 0 degrees (full extension) was performed at the rate of 10 degrees per second with the leg unimpeded and with weights of 1.8, 3.6, 5.4, or 7.2 kilograms attached to the ankle. The hamstrings were found to coactivate with the quadriceps during the terminal phase of extension. Coactivation of all three hamstrings was found to occur at joint angles of as much as 9 degrees, with the maximum at full extension of the knee and the strength of the signals ranging to as much as 20 per cent. The signals of all of the flexors and extensors increased with increasing loads on the ankle and, with the exception of the rectus femoris at 9 degrees of flexion, they also increased as the knee extended. The results of this study support the hypothesis that the hamstrings function synergistically with the anterior cruciate ligament to prevent the anterior tibial displacement that is produced by active contraction of the quadriceps in the terminal degrees of extension of the knee. This information is important for the physical conditioning of healthy individuals in preparation for athletic endeavors. Furthermore, if coactivation of the hamstrings with the quadriceps is mediated by sensors other than, or in addition to, those of the anterior cruciate ligament, then strengthening of the hamstrings appears to be an important adjunct to rehabilitation programs after repair or reconstruction of that ligament.
Article
The purpose of this investigation was to determine the role the hamstrings group may play in augmenting passive articular mechanisms during activity in which anterior drawer force may detrimentally affect the anterior cruciate ligament (ACL). Nine male subjects performed non-weight-bearing isometric knee extension at 10% increments of maximum voluntary contraction (MVC). Electromyographic (EMG) signals were detected and recorded from the vastus lateralis, vastus medialis oblique, vastus medialis longus, and the long head of the biceps femoris. The EMG signals were rectified and integrated over 1000 ms and normalized to subject-specific values. The data were subjected to a repeated-measures analysis of variance. The results demonstrated that expected significant increases in quadriceps excitation accompanied increases in knee extensor torque. Hamstrings excitation was not found to change significantly (total change = 3.4%). It was concluded that functionally adequate knees do not require posterior drawer force in excess of that provided passively by articular structures.
Article
The objective of this study was to quantify the coacti vation patterns of the knee flexor and extensor muscles as part of continued efforts to identify the role of the antagonist muscles in maintaining joint stability. The simultaneous EMG from the flexor and extensor muscles of the knee were recorded during maximal effort, slow isokinetic contractions (15 deg/sec) on the plane parallel to the ground to eliminate the effect of gravity. The processed EMG from the antagonist mus cle was normalized with respect to its EMG as agonist at maximal effort for each joint angle. The plots of normalized antagonist EMG versus joint angle for each muscle group were shown to relate inversely to their moment arm variations over the joint range of motion. Additional calculations demonstrated that the antago nist exerts nearly constant opposing torque throughout joint range of motion. Comparison of data recorded from normal healthy subjects with that of high perform ance athletes with hypertrophied quadriceps demon strated strong inhibitory effects on the hamstrings coac tivations. Athletes who routinely exercise their ham strings, however, had a coactivation response similar to that of normal subjects. We concluded that coactivation of the antagonist is necessary to aid the ligaments in maintaining joint stability, equalizing the articular surface pressure dis tribution, and regulating the joint's mechanical imped ance. The reduced coactivation pattern of the unexer cised antagonist to a hypertrophied muscle increases the risk of ligamentous damage, as well as demon strates the adaptive properties of the antagonist muscle in response to exercise. It was also concluded that reduced risk of knee injuries in high performance ath letes with muscular imbalance could result from com plementary resistive exercise of the antagonist muscle.
Article
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.
Article
The synergistic action of the ACL and the thigh muscles in maintaining joint stability was studied experimentally. The EMG from the quadriceps and hamstring muscle groups was recorded and analyzed in three separate experimental procedures in which the knee was stressed. The test revealed that direct stress of the ACL has a moderate inhibitory effect on the quadriceps, but simultaneously it directly excites the hamstrings. Similar responses were also obtained in patients with ACL damage during loaded knee extension with tibia subluxation, indicating that an alternative reflex arc unrelated to ACL receptors was available to maintain joint integrity. The antagonist muscles (hamstrings) were clearly demonstrated to assume the role of joint stabilizers in the patient who has a deficient ACL. The importance of an appropriate muscle-conditioning rehabilitation program in such a patient is substantiated.
Article
Eighteen males and two females (mean age, 26.5 years) underwent biomechanical assessment and Cybex eval uation prior to ACL reconstruction. Clinically, all patients had at least a 1+ grade with the Lachman, anterior drawer, and pivot shift tests, the majority being graded as 2+. Footswitch, high speed photography, force plate, and indwelling wire electrode data were collected while each subject performed free and fast walking, running, cutting, and stair climbing activities. During walking, single limb support times did not differ between the subject's involved and uninvolved limbs. Knee joint angles were similar between limbs during walking, running, and stair climbing maneuvers. Dynamic EMG tracings during walking demonstrated similar quadriceps and calf activity between limbs, while greater variation in hamstring firing was evident among subjects. During running, the involved limb had a longer duration of medial hamstring activity compared to the lateral hamstring. No significant differences were seen in either vertical or sagittal shear forces during free walking. During fast walking, higher midstance vertical forces (F2) were present in the involved limb (P < 0.05). During running, the involved limb experienced lower vertical forces (P < 0.05), while both anterior and posterior sagittal shear differences were insignificant. Straight cut maneuvers demonstrated significantly lower lateral shear and ver tical forces in the involved limb (P < 0.05). Lower lateral and sagittal shear forces in the involved limb (P < 0.01 and P < 0.05, respectively), combined with a reduced angle of the cut during the cross-cut maneuver, may be the first means to assess the functional pivot shift phenomenon ever documented. Isokinetic Cybex strength testing demonstrated a mean 14% quadriceps deficit and a mean 4% hamstring deficit in the involved limb. Achieving quadriceps and hamstring torque of 86% and 96%, respectively, was not sufficient to eliminate the subjective need for sur gical reconstruction.
The load moment of force about the knee joint during machine milking and when lifting a 12.8 kg box was quantified using a computerized static sagittal plane body model. Surface electromyography of quadriceps and hamstrings muscles was normalized and expressed as a percentage of an isometric maximum voluntary test contraction. Working with straight knees and the trunk flexed forwards induced extending knee load moments of maximum 55 Nm. Lifting the box with flexed knees gave flexing moments of 50 Nm at the beginning of the lift, irrespective of whether the burden was between or in front of the feet. During machine milking, a level difference between operator and cow of 0.70 m - 1.0 m significantly lowered the knee extending moments. To quantify the force magnitudes acting in the tibio-femoral and patello-femoral joints, a local biomechanical model of the knee was developed using a combination of cadaver knee dissections and lateral knee radiographs of healthy subjects. The moment arm of the knee extensor was significantly shorter for women than for men, which resulted in higher knee joint forces in women if the same moment was produced. A diagram for quantifying patellar forces was worked out. The force magnitudes given by the knee joint biomechanical model correlated well with experimentally forces measured by others. During the parallel squat in powerlifting, the maximum flexing knee load moment was estimated to 335-550 Nm when carrying a 382.5 kg burden and the in vivo force of a complete quadriceps tendon-muscle rupture to between 10,900 and 18,300 N. During isokinetic knee extension, the tibio-femoral compressive force reached peak magnitudes of 9 times body weight and the anteroposterior shear force was close to 1 body weight at knee angles straighter than 60 degrees, indicating that high forces stress the anterior cruciate ligament. A proximal resistance pad position decreased the shear force considerably, and this position is recommended in early rehabilitation after anterior cruciate ligament repairs or reconstructions. The methods presented quantify muscle activity, sagittal knee joint moments and forces, enabling assessments to be made of different work postures, training exercises and joint derangements.
Article
A complete tear of the anterior cruciate ligament represents the initiation of a clinical syndrome characterized by a continuum of functional disability. The authors present here a risk factor checklist, based on statistics drawn from their previous articles, to identify those patients at significant risk for future joint arthrosis. Risk factors are grouped under the categories of activity level, symptoms, clinical laxity, meniscal damage, lower limb alignment, tibiofemoral crepitus, patellofemoral factors, rehabilitation, and patient compliance. They also present their subjective and functional rating system in which six activity levels are related to pain, swelling, and giving way. The functional disability of the anterior cruciate insufficient knee is activity-level related. Thus, activity levels must be rigorously and comprehensively defined for adequate appreciation of the degree of existing disability. The authors also examined the reasons for the conflicting opinions on the functional disability of the anterior cruciate ligament syndrome that exists in the literature. Differences in subjective and objective rating systems; failure to specifically define preinjury and postinjury activity levels and associated symptoms; and different populations as to laxity, giving way episodes, and type of athletic activity (jumping, twisting activities versus light recreational pursuits) are but a few of the important differences that make comparisons between studies often invalid. Long-range treatment guidelines are necessary for management of the acute and chronic anterior cruciate ligament insufficient knee.
Article
The purpose of this study was to assess and describe the status of twenty-four patients with a diagnosed tear of the anterior cruciate ligament who participated in a non-operative program of rehabilitation emphasizing strengthening of the hamstrings. The knees were evaluated by testing stability, strength, and range of motion; by roentgenographic examination; and by the patient's level of participation in sports. The patient's uninjured knee was used for comparison. The results showed a high incidence of anterior instability, but no significant differences in degenerative changes or range of motion. All patients returned to some sports participation, with fourteen (59 per cent) returning to their full preinjury level of participation. Higher levels of sports participation were found in the patients whose hamstrings strength was equal to or more than their quadriceps strength.
Article
We have designed a scoring scale for knee ligament surgery follow-up emphasizing evaluation of symptoms of instability. Instability is defined as "giving way" during activity. Our scoring scale was compared to a slightly modified Larson scale in patients with anteromedial and/or anterolateral instability, posterolateral and straight posterior instability, chondromalacia patellae, and meniscus lesion. The two scales gave basically the same results in patients with meniscus rupture. In patients with unstable knees, the new scale gave a significantly lower total score. Thus, the new scale evaluates functional impairment due to clinical instability better than the modified Larson scale. The total score, with the new scoring scale, corresponded to the patients' own opinion of function and to the presence or absence of signs of instability.
Article
Accelerated rehabilitation after anterior cruciate ligament (ACL) reconstruction has become increasingly popular. Methods employed include immediate extension of the knee and immediate full weight bearing despite the risks presented by a graft pull-out fixation strength of 200-500 N. The purpose of this study was to calculate the tibiofemoral shear forces and the dynamic stabilising factors at the knee joint for the reasonably demanding task of downhill walking, in order to determine whether or not this task presented a postoperative risk to the patient. Kinematic and kinetic data were collected on six male and six female healthy subjects during downhill walking on a ramp with a 19% gradient. Planar net joint moments and mechanical power at the knee joint were calculated for the sagittal view using a force platform and videographic records together with standard inverse dynamics procedures. A two-dimensional knee joint model was then utilised to calculate the tibiofemoral shear and compressive forces, based on the predictions of joint reaction force and net moment at the knee. Linear envelopes of the electromyographic (EMG) activity recorded from the rectus femoris, gastrocnemius and biceps femoris muscles were also obtained. The maximum tibiofemoral shear force occurred at 20% of stance phase and was, on average, 1.2 times body weight (BW) for male subjects and 1.7 times BW for female subjects. The tibiofemoral compressive force was 7 times BW for males and 8.5 times BW for females during downhill walking. The hamstring muscle showed almost continuous activity throughout the whole of the stance phase.(ABSTRACT TRUNCATED AT 250 WORDS)
Article
A computer-based model of the knee was used to study forces in the cruciate ligaments induced by co-contraction of the extensor and flexor muscles, in the absence of external loads. Ligament forces are required whenever the components of the muscle forces parallel to the tibial plateau do not balance. When the extending effect of quadriceps exactly balances the flexing effect of hamstrings, the horizontal components of the two muscle forces also balance only at the critical flexion angle of 22 degrees. The calculations show that co-contraction of the quadriceps and hamstring muscles loads the anterior cruciate ligament from full extension to 22 degrees of flexion and loads the posterior cruciate at higher flexion angles. In these two regions of flexion, the forward pull of the patellar tendon on the tibia is, respectively, greater than or less than the backward pull of hamstrings. Simultaneous quadriceps and gastrocnemius contraction loads the anterior cruciate over the entire flexion range. Simultaneous contraction of all three muscle groups can unload the cruciate ligaments entirely at flexion angles above 22 degrees. These results may help the design of rational regimes of rehabilitation after ligament injury or repair.
Article
Kinematic and kinetic data were collected from 12 healthy subjects whilst they performed both downhill and level walking at a controlled cadence. A ramp of 6 m length and a gradient of -19% was used for downhill walking and this incorporated the same force platform that was used for level walking. Planar net joint moments and mechanical power at the ankle, knee, and hip joints were calculated for the sagittal view using force platform and video records based on standard inverse dynamics procedures. On the basis of differences in ankle, knee, and hip joint kinematics the ankle joint was seen to compensate for the gradient at push off and during the swing, the knee joint from early stance through until early swing phase, and the hip joint from early swing through until the early stance phase. The major differences in joint moments and muscle mechanical power were seen in the knee and ankle joint. Whereas peak moments and muscle power were much higher for downhill walking in the knee joint, these measures were significantly smaller at the ankle joint. Hip joint moments and muscle power estimates were only slightly larger for downhill walking. These data explain well the problems that patients with patellofemoral pathology and anterior cruciate ligament (ACL) deficiency encounter with downhill walking, and the muscle soreness experienced by mountain trekkers. RELEVANCE: Biomechanical estimates of musculoskeletal loadings in gait are invariably derived from laboratory studies of walking over a level surface. In this study comparisons were made between downhill and level walking in order to appreciate more fully the increased loadings on the lower extremity under more stressful but not atypical conditions. The data so derived provide the necessary basis for the prediction of loadings on specific muscle/joint structures and can serve as a foundation for exercise prescription with patients recovering from injury or orthopaedic surgery.
Article
A technique has been developed for performing pattern analysis of electromyographic (EMG) activities generated during locomotion. It was found that the shapes of the EMG linear envelopes (LE) are mainly determined by their phase spectra; their magnitude spectra are much less important. Autoregressive (AR) parametric models and discrete Fourier transform (DFT) approaches were tested and compared. The latter proved to be a better way to describe the EMG LEs. Feature extraction and clustering were performed by performing a DFT of EMG LEs, extracting part of the phase and magnitude spectra as features, and using the percent powers to weigh the corresponding harmonics. The approach was applied to the clustering analysis of EMG LEs of normal and anterior cruciate ligaments (ACL) injured subjects during walking.
The coordination of the knee-muscles in some voluntary movements and in the gait in cases with and without knee joint injuries Electromyographic study of the anterior cruciate ligament -hamstrings synergy during isometric knee extension
  • Ca-Lss68 S Nordstrand
Ca-lss68 S, Nordstrand A. The coordination of the knee-muscles in some voluntary movements and in the gait in cases with and without knee joint injuries. Acta Chir &and 1968; 134: 42336. Grabiner MD, Campbell KR, Hawthorne DL, Hawkings DA. Electromyographic study of the anterior cruciate ligament -hamstrings synergy during isometric knee extension. J Orthop Res 1989; 7: 152-5
Downhill walking: a stressful task for the anterior cruciate
  • Kuster Mi
  • S Sakurai
  • Ga Wood
  • Blatter
Kuster MI Sakurai S, Wood GA, Blatter G. Downhill walking: a stressful task for the anterior cruciate
The coordination of the knee-muscles in some voluntary movements and in the gait in cases with and without knee joint injuries
  • Carlssöö
Electromyographic study of the anterior cruciate ligament — hamstrings synergy during isometric knee extension.
  • Grabiner MD
  • Campbell KR
  • Hawthorne DL
  • Hawkings DA
Anterior-cruciate-insufficient knees treated with physiotherapy
  • Friden