Proprioception in the anterior cruciate deficient knee

Central somatosensory changes associated with improved dynamic balance in subjects with anterior cruciate ligament deficiency

To examine the mechanisms underlying return to pre-injury function in individuals with anterior cruciate ligament deficiency (ACL-D), we grouped 15 individuals (18-50 years of age) with ACL-D by functional status and strength (i.e. copers, non-copers and adapters) and compared measures of proprioception, somatosensory evoked potentials and neuromuscular responses to dynamic testing between groups. Seven subjects without ACL-D provided a comparative sample for dynamic balance testing (DBT). DBT consisted of bilateral EMG recordings of anterior tibialis, medial gastrocnemius, medial hamstrings and quadriceps during toes-down platform rotation. Relative latencies and relative amplitudes were calculated. Somatosensory evoked potential (SEPs) testing was based on identifying the presence or absence of the P27 potential. Proprioception was tested using threshold to detection of passive movement (TDPM). Those with the highest level of function, the copers, had a proprioceptive deficit, loss of P27 and altered postural synergies consisting of earlier and larger hamstring activation. Conversely, those with the lowest functional status, the non-copers, had strength and proprioception deficits, intact SEPs and inconsistent postural synergies. These results suggest that changes in central sensory representation may facilitate altered postural synergies that enable return to pre-injury functional status.

Decrease in anterior knee laxity by electrical stimulation of normal and reconstructed anterior cruciate ligaments

We have investigated the changes in anterior laxity of the knee in response to direct electrical stimulation of eight normal and 45 reconstructed anterior cruciate ligaments (ACLs). In the latter, the mean time from reconstruction was 26.7 months (24 to 32). The ACL was stimulated electrically using a bipolar electrode probe during arthroscopy. Anterior laxity was examined with the knee flexed at 20 degrees under a force of 134 N applied anteriorly to the tibia using the KT-2000 knee arthrometer before, during and after electrical stimulation. Anterior tibial translation in eight normal and 17 ACL-reconstructed knees was significantly decreased during stimulation, compared with that before stimulation. In 28 knees with reconstruction of the ACL, in 22 of which the grafts were found to have detectable somatosensory evoked potentials during stimulation, anterior tibial translation was not decreased. These findings suggest that the ACL-hamstring reflex arc in normal knees may contribute to the functional stability and that this may not be fully restored after some reconstructions of the ACL.

A systematic review of the effect of proprioceptive and balance exercises on people with an injured or reconstructed anterior cruciate ligament

This systematic review investigated the effect of proprioceptive and balance exercise on outcomes following injury and surgical reconstruction of the anterior cruciate ligament (ACL). Five studies of high quality that offered empirical evidence by comparing one rehabilitation program to another were included in this review. There is some evidence that proprioceptive and balance exercise improves outcomes in individuals with ACL-deficient knees. Improvements in joint position sense, muscle strength, perceived knee joint function, and hop testing were reported following proprioceptive and balance exercise. Only one included study investigated proprioceptive exercise following ACL reconstruction. Benefits were noted in the proprioceptive group for measures of strength and proprioception; however, no benefits were noted for any measures of activity. No detrimental effects--such as increased passive joint laxity or decrease in strength--were noted when compared with standard rehabilitation programs for both ACL-deficient and ACL-reconstructed individuals. Further research is required to determine if proprioceptive and balance exercise improves long-term outcomes such as return to sport.

A randomised controlled trial of proprioceptive and balance training after surgical reconstruction of the anterior cruciate ligament

A randomised controlled trial (29 participants) was used to compare a 6-week proprioceptive and balance exercise program with a 6-week strengthening program in the early phases of rehabilitation after anterior cruciate ligament (ACL) reconstruction. Measurements of functional activity were taken by a blinded assessor before the intervention and at the end of the 6 weeks. Results demonstrated that there were no significant differences between groups on hop testing at 6 weeks. For several items in the Cincinnati knee rating system and the patient specific functional scale however, the strengthening group improved more than the proprioceptive and balance group (p < .05). The hypothesis that proprioceptive and balance training would improve functional activity more than strengthening exercises was not supported. There was either no difference between the two forms of exercise or strength training may be more beneficial than proprioceptive and balance training in the early phase of rehabilitation after ACL reconstructive surgery.

[Electromyographic study of stretch reflexes in the normal and prosthetic hip]

PURPOSE OF THE STUDY

Several studies have been devoted to the effect of proprioception on joint function. Modifications in feedback control from the cord have been observed in unstable joints due to capsule and ligament laxity. A few studies have examined the effect of knee and hip arthroplasty on proprioception, but none have established whether stretch reflexes affect function of a prosthetic joint. The purpose of the present study was to demonstrate the electromyographic characteristics of stretch reflexes of the normal hip joint and to compare them with those observed in the prosthetic hip.

MATERIAL AND METHODS

Two groups of patients were studied. The first included eleven subjects free of neurological disorders whose studied limb was healthy. The second group included ten subjects with a total hip prosthesis who had undergone extensive capsulectomy during the arthroplasty. Voluntary muscle contraction was noted in each subject. In addition, electromyographic recordings were made to note response of the ipsilateral and contralateral quadriceps crural and tensor of the fascia lata during changes in joint position. Recordings were made with the subject in the supine position, the limb suspended, hip flexed at 45 degrees and knee extended. Three series of ten recordings were made in random order to measure the latency of muscle response to free fall of the limb, accelerated fall of the relaxed limb, and accelerated fall associated with calibrated contraction of the quadriceps. Mean latency of muscle response was calculated for each trial.

RESULTS

In the conditions of this study, there was no statistically significant difference (p = 0.05) in the reflex time course between natural and prosthetic hips.

DISCUSSION

Changes due to joint replacement and capsulectomy do not appear to affect the stretch reflexes of the hip joint.

Distribution of substance-P nerves inside the infrapatellar fat pad and the adjacent synovial tissue: a neurohistological approach to anterior knee pain syndrome

INTRODUCTION

The purpose of the study was to determine the distribution and number of nerves inside the infrapatellar fat pad and the adjacent synovium, in particular with regards to nociceptive substance-P nerves.

MATERIALS AND METHODS

The infrapatellar fat pad of the knee was resected from 21 patients (4 male, 17 female, mean age 69 years) during the course of standard total knee arthroplasty operations performed in our clinic. The fat pad was dissected into five standardized segments, fixed in formalin and embedded in paraffin. Immunohistochemical techniques using antibodies against S-100 protein and substance-P (SP) were employed to determine and specify the nerves.

RESULTS

Studying all the detectable nerves present in 50 observation fields (200-fold magnification), we found an average of 106 S-100 versus 25 SP nerves (24%) in the synovium and 27 S-100- versus 7 SP nerves (26%) in the interior of the fat pad. The total nerve count was significantly (P < 0.001) higher in the synovium than in the fat pad for both marker types. The number of S-100 nerves was significantly (P < 0.05) higher in the central and lateral segments of the fat pad, while SP nerves were equally distributed throughout all segments of the fat-pad. SP nerves were significantly more frequently associated with blood vessels inside the fat pad (43%, P < 0.05) than in the synovial tissue (28%).

CONCLUSION

The occurrence and distribution of SP nerves inside the infrapatellar fat pad suggest a nociceptive function and a neurohistological role in anterior knee pain syndrome. The data support the hypothesis that a neurogenous infection of the infrapatellar fat pad could contribute to anterior knee pain syndrome.

Central somatosensory changes and altered muscle synergies in subjects with anterior cruciate ligament deficiency

To clarify the mechanisms of compensation in subjects with anterior cruciate ligament deficiency (ACL-D), we examined proprioception, quadriceps strength, somatosensory evoked potentials (SEPs) and muscle responses during gait in varied combinations of speed and incline. Seventeen subjects with ACL-D were grouped by functional level and report of giving way. Seven subjects without ACL-D served as a control sample for muscle response measures. ACL-D subjects with quadriceps weakness experienced giving way and could not resume sport activities. Those without weakness fell into one of two groups: (1) copers, who had full return to previous activity and no giving way despite proprioceptive loss and altered SEPs, and (2) adapters, who were unable to return to previous activity level and experienced giving way despite neither proprioceptive loss or altered SEPs. The unique muscle pattern in copers during inclined fast walking included larger and earlier hamstring activation. These results suggest that in individuals with ACL-D without a strength deficit, altered SEPs and altered neuromuscular patterns are the factors that enable resumption of pre-injury functional levels. Loss of proprioception may drive the central changes, which in turn drives the development of altered muscle patterns.

Bilateral changes in somatosensory sensibility after unilateral below-knee amputation

OBJECTIVE

To evaluate possible alteration in proprioceptive and cutaneous sensibility in the nonamputated leg of unilateral transtibial amputees.

DESIGN

Cross-sectional study with between-subjects (amputees vs controls) and within-subjects (nonamputated vs amputated leg) comparisons.

SETTING

Canadian rehabilitation hospital research laboratory.

PARTICIPANTS

Two groups of amputees (34 due to traumatic causes, 14 due to vascular causes), recruited more than 1 year after their prosthetic training; and 2 groups (n=34, n=14) of age-matched control subjects.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Threshold of movement detection and touch-pressure perception at the knee and foot levels.

RESULTS

In the traumatic group, the sensory thresholds of the nonamputated leg were significantly higher than the control values in the 2 modalities tested. The movement detection was reduced at the knee and ankle levels, whereas a decrease in touch-pressure sensibility was observed only at the plantar site. As expected, a large proportion of the vascular amputees presented with severe sensory deficits in the nonamputated leg, particularly a loss in touch-pressure perception at the foot. The thresholds of movement detection were similar and correlated at both knees in the 2 groups of amputees. For the touch-pressure thresholds, no significant relationship was found between sides at the knee level.

CONCLUSIONS

Sensory changes observed in the nonamputated leg suggest that central sensory adaptations occur after amputation. For movement detection, they were marked by a matching of perception on both sides of the body. Functional significance of these changes remains to be determined.

Effect of vision on postural sway in anterior cruciate ligament injured knees

Recent clinical studies have investigated postural sway characteristics in anterior cruciate ligament (ACL)-deficient knees, but the relative contributions of vision and ACL remain unclear. In the current study, we measured and compared postural sway during one-leg standing with eyes open and closed to assess the difference between legs with and without ACL injury, and we discuss the contribution of the ligament relative to vision and to postural sway in patients. We examined 32 patients (17 males, 15 females) with ACL injury before surgery from March 2001 through January 2004. None presented obvious dysfunction in the lower limbs or central nervous system. Using a gravicorder, we measured locus length per time (LG) and environmental area (AR) as the factors of postural sway during two-leg and one-leg standing with eyes open or closed. In the ACL-injured knee, the amount of postural sway increased significantly during injured leg standing with eyes closed (LG, P < 0.0001; AR, P < 0.0001), but it did not increase significantly with eyes open. There were no significant differences with respect to sex or general joint laxity. There was no correlation between postural sway and the anterior translation of the tibia measured by arthrometer KT2000 or between the muscle strength around the knee. We concluded that the amount of postural sway in the ACL-injured knee increased significantly on injured leg standing with eyes closed, and that vision appears to be dominant in compensating for the decreased contribution of the injured ACL.

Effect of positioning and bracing on passive position sense of shoulder joint

OBJECTIVE

To examine the effects of positioning and sleeve type bracing on passive position sense of shoulder joints of healthy untrained subjects.

METHOD

A cross over study was carried out on 26 subjects (13 male, 13 female) with a proprioception measurement device. The selected method of testing was passive reproduction of a target angle. Both shoulder joints of all the subjects were evaluated with and without a compressive neoprene sleeve type of brace at two different start positions (45 degrees internal rotation, 75 degrees external rotation) with an angular rotational movement at a constant speed of 0.5 degrees /s. The angular displacements from the target angles at the end of the reproduction tests were recorded as position sense deficit scores.

RESULTS

The overall mean (SD) deficit score (0.99 (0.06)) was significantly (p<0.001) lower with the brace than without, and the overall mean deficit score was significantly (p<0.001) higher at the 45 degrees internal rotation start position than at the 75 degrees external rotation start position. However, there was no significant (p>0.05) interaction between brace application and start position.

CONCLUSION

Terminal limits of range of motion facilitate the position sense of shoulder joints. Compressive brace application improves the passive positioning sense possibly by stimulating cutaneous mechanoreceptors.

Sports-related knee injuries in female athletes: what gives?

Knee injuries occur commonly in sports, limiting field and practice time and performance level. Although injury etiology relates primarily to sports specific activity, female athletes are at higher risk of knee injury than their male counterparts in jumping and cutting sports. Particular pain syndromes such as anterior knee pain and injuries such as noncontact anterior cruciate ligament (ACL) injuries occur at a higher rate in female than male athletes at a similar level of competition. Anterior cruciate ligament injuries can be season or career ending, at times requiring costly surgery and rehabilitation. Beyond real-time pain and functional limitations, previous injury is implicated in knee osteoarthritis occurring later in life. Although anatomical parameters differ between and within the sexes, it is not likely this is the single reason for knee injury rate disparities. Clinicians and researchers have also studied the role of sex hormones and dynamic neuromuscular imbalances in female compared with male athletes in hopes of finding the causes for the increased rate of ACL injury. Understanding gender differences in knee injuries will lead to more effective prevention strategies for women athletes who currently suffer thousands of ACL tears annually. To meet the goal in sports medicine of safely returning an athlete to her sport, our evaluation, assessment, treatments and prevention strategies must reflect not only our knowledge of the structure and innervations of the knee but neuromuscular control in multiple planes and with multiple forces while at play.

Low levels of anterior tibial loading enhance knee extensor reflex response characteristics

We examined whether neuromuscular reflexes were altered with anterior loads applied to the tibio-femoral joint. A ligament testing device was modified by attaching a reflex hammer to a steel mounted frame to illicit a patellar tendon tap, while anterior directed loads displaced the tibia on the femur. Five trials were acquired while anterior-directed loads (20, 50, 100 N; counterbalanced) were applied to the posterior tibia between 20 N pre (20 N(Pre)) and post (20 N(Post)) baseline conditions on two different days. Surface electromyography (sEMG) recorded mean quadriceps (Q) and hamstring (H) reflex time (R(Time)=ms) and reflex amplitude (R(Amp)=%MVIC). A load cell on the anterior tibia measured the timing (KE(Time)=ms) and amplitude (KE(Amp)=N) of the knee extension force, and was used to calculate electromechanical delay (EMD=ms) and peak knee extension moment (KE(Mom)=Nm/kg). Data from 19 recreationally active subjects revealed good to excellent response consistency between test days and between baseline conditions for R(Time), R(Amp), KE(Time) and KE(Amp). With anterior tibial loading, R(Time) was faster at 50 N vs. 20 N(Post), and R(Amp) was greater at 20 N(Pre) vs. 20 N(Post) (Q and H) and at 50 N vs. 100 N (Q only). KE(Mom) was greater at 20 N(Pre) and 50 N vs. 20 N(Post), and EMD was shorter at 50 N vs. 20 N, 20 N(Pre) and 20 N(Post). These results suggest that knee extensor reflex responses are enhanced with low (50 N) but not moderate (100 N) anterior loading of the knee.

Knee joint laxity affects muscle activation patterns in the healthy knee

This study investigated the effects of anterior knee joint laxity on muscle activation patterns prior to and following a lower extremity perturbation. Participants were subjected to a forward and either internal (IR) or external (ER) rotation perturbation of the trunk and thigh on the weight-bearing shank. Pre-activity (%MVIC) before the perturbation, and reflex time (ms) and mean reflex amplitude (%MVIC) following the perturbation were recorded via surface electromyography (sEMG) in the medial and lateral gastrocnemius, hamstring and quadriceps muscles. Twenty-one NCAA DI intercollegiate female athletes with below average anterior knee laxity (3-5 mm) were compared to 21 with above average anterior knee laxity (7-14 mm) as measured by a standard knee arthrometer. Groups differed in reflex timing by muscle (P = 0.013), with females with above average knee laxity (KT((>7 mm))) demonstrating a 16 ms greater delay in biceps femoris reflex timing compared to females with below average knee laxity (KT((<5 mm))). Groups also differed in muscle activation amplitude by response, muscle and direction of rotation (i.e. a 4-way interaction; P = 0.027). The magnitude of change from pre to post perturbation was significantly less in KT((>7 mm)) vs. KT((<5 mm)) for the medial (MG) and lateral (LG) gastrocnemius muscles, primarily due to higher levels of muscle preactivity while awaiting the perturbation (MG = 20% vs. 12% MVIC, P = 0.05; LG = 33% vs. 21% MVIC, P = 0.11). Further, KT((>7 mm)) demonstrated higher activation levels in the biceps femoris than KT((<5 mm)) (47% vs. 27% MVIC; P = 0.025) regardless of response (pre vs. post perturbation) or direction of rotation. These findings suggest females with increased knee laxity may be less sensitive to joint displacement or loading (delayed reflex), and are more reliant on active control of the gastrocnemius and biceps femoris muscles to potentially compensate for reduced passive joint stability.

Proprioception and performance after anterior cruciate ligament rupture

The aim of this study was to investigate the characteristics of proprioception in patients with an anaterior-cruciate-ligament (ACL)-injured knee and to determine whether there is a correlation between proprioception and performance. We studied 32 patients with unilateral isolated ACL ruptures. Proprioception of the knee was evaluated by examining the joint position sense. Functional performance was evaluated with the one-leg hop (OLH) and one-leg vertical jump (OLV) tests. The mean error angle of the joint position sense was 3.6+/-1.5 degrees on the intact side and 5.2+/-1.9 degrees on the injured side. The joint position sense was thus clearly reduced on the injured side (p<0.05). The distance of jumping in the OLH test and the height of jumping in the OLV test was also clearly reduced on the injured side compared with that on the intact side (p<0.01) both with and without visual control. Moreover, we found a significant correlation between proprioception and performance in the ACL-injured knees, and this correlation was more distinct with visual deprivation. In conclusion, decreased proprioception in patients with ACL deficiency reduced their functional ability.

Place des orthèses en pathologie ligamentaire du genou. Revue de la littérature

OBJECTIVE

To review the literature for the benefits of the three different knee braces (prophylactic, rehabilitation, functional) that can be used to treat ligament injuries of the knee. What is their influence on stability? Do they have adverse effects? Is their use justified?

METHODS

We searched the Medline and Embase databases with use of the keywords knee, orthoses, brace, proprioception, stability, rehabilitation, physical therapy, and anterior cruciate ligament for reports published between 1980 and 2003 and selected 93 articles, expert reports or literature reviews.

RESULTS

Anterior tibial displacement can be controlled with mechanical strains (150 N), which are lower than physiological restraints? (400 N). The control of joint position is improved by increasing proprioception. Soft tissue stiffness influences the control of anterior tibial displacement. The beneficial effects observed are mainly subjective. Our analysis of the literature showed limitations and variations in study methodologies.

CONCLUSION

We did not find any justification for use of either prophylactic or rehabilitation braces. Functional braces can improve stability, as reported by the patient, and may be used in some situations.

Effect of Rehabilitation on Hip and Knee Proprioception in Older Adults After Hip Fracture

OBJECTIVE

Impaired proprioception may predispose patients with hip fracture to increased risk of future disability. The purpose of the study was to determine the effect of rehabilitation on proprioceptive changes in both the hip and knee joints of patients after hip fracture.

DESIGN

Data were collected on 30 patients with hip fracture (mean age, 79.6 +/- 6.7 yrs) who attended physical and occupational therapy sessions five times per week during a rehabilitation hospital stay of 24.8 +/- 8.1 days. Proprioception was assessed with an electrogoniometer within 48 hrs of admission to and discharge from the rehabilitation unit. The passive-to-active reproduction of joint angle technique determined absolute angular error in non-weight-bearing positions at 15, 30, and 60 degrees of hip flexion and knee extension in both injured and noninjured sides.

RESULTS

Absolute angular error decreased significantly (P < 0.05) from admission (5.3 +/- 2.6 degrees, 4.1+/- 3.1 degrees) to discharge (3.0 +/- 2.3 degrees, 2.8 +/- 3.1 degrees) in hip flexion and knee extension, respectively, on the injured side. Absolute angular error was significantly less (P < 0.05) at 15 degrees compared with 30 and 60 degrees of hip flexion at admission and discharge on the injured side.

CONCLUSIONS

Hip and knee joint proprioception significantly improved in the injured side after the rehabilitation program. This may be an important outcome regarding future disability in this population.

The effect of local and general fatigue on knee proprioception

PURPOSE

The purpose of this study was to compare the effects of local and general fatigue loads on knee proprioception.

TYPE OF STUDY

Experimental controlled study.

METHODS

Proprioception of the knee joint was evaluated by measuring absolute angular error (AAE) at matching defined index angles before and after 2 different types of fatigue protocols (local load and general load) in 27 healthy male volunteers. Local load was provided with maximum isokinetic knee flexion-extension on the isokinetic dynamometer, and general load was 5 minutes running on a treadmill.

RESULTS

After local load, a significant decrease in peak torque of knee flexors and extensors was found, but no significant change in AAE was seen. In contrast, after general load, a significant increase of AAE was noted without significant muscle weakness.

CONCLUSIONS

The different results in previous studies evaluating the effect of fatigue on knee proprioception may have been affected by the difference of fatigue protocols, whether local or general load. Although local load was intended to produce local fatigue of the knee, which may cause dysfunction of muscle mechanoreceptors, general load may have produced general fatigue and affected other mechanisms in the proprioceptional pathway. The results of the present study suggest that decreased reproduction ability after general load is not due to the loss of peripheral afferent signals, but to other factors, especially deficiency of central processing of proprioceptive signals.

CLINICAL RELEVANCE

To prevent knee injury caused by fatigue-induced proprioceptional decline, muscle endurance training alone is not enough, and neuromuscular training, including central motor programming, is essential.

Proprioception of the shoulder joint after surgical repair for Instability: a long-term follow-up study

BACKGROUND

Proprioceptive capabilities play an important role in stability of the shoulder joint.

HYPOTHESIS

Decreased proprioceptive capabilities can improve by surgical repair of shoulder instability.

STUDY DESIGN

Prospective long-term study.

METHODS

The proprioceptive capabilities of 14 patients with recurrent anterior shoulder instability were examined preoperative and with a minimum follow-up of 5 years postoperative using the angle reproduction test. The patients' data were compared to a healthy control group.

RESULTS

The joint position sense improved significantly in abduction, flexion, and rotation (P <.05). The preoperative difference from the target joint position was 9.3 degrees (SD, 4.6 degrees ) for the summarized positions in abduction, 9.1 degrees (SD, 4.5 degrees ) in flexion, and 10.1 degrees (SD, 5.1 degrees ) in rotation. Postoperatively, it improved to 5.6 degrees (SD, 2.9 degrees ) in abduction, 5.6 degrees (SD, 2.7 degrees ) in flexion, and 5.0 degrees (SD, 1.8 degrees ) in rotation. The joint position sense of the uninvolved contralateral shoulder improved too.

CONCLUSIONS

Five years after surgical repair for shoulder instability, the joint position sense improved significantly, to a level of normal, healthy shoulders.

Biomechanical assessments of lumbar spinal function. how low back pain sufferers differ from normals. implications for outcome measures research. part i: kinematic assessments of lumbar function

OBJECTIVE

To review new and advanced biomechanical assessment techniques for the lumbar spine and illustrate the differences in lumbar function in patients with low back pain and asymtomatic subjects.

DATA SOURCES

The biomedical literature was searched for research and reviews on spinal kinematic differences between low back pain subjects and healthy controls. A data search for articles indexed on MEDLINE until April 2002 was performed.

RESULTS

Kinematic measurements of lumbar function were categorized into 3 areas where low back patients may differ from normals: (1) end range of motion during simple movements; (2) higher order kinematics (displacement, velocity, and acceleration) during complex movement tasks; and (3) spinal proprioception. The assessment of higher order kinematics during complex movement tasks is the most highly researched and the most successful in describing differences between the populations. The use of simple end range of motion appears questionable, while assessing spinal proprioception is the least researched, yet shows potential in highlighting differences between low back sufferers and asymptomatics.

CONCLUSION

Current kinematic biomechanical assessment techniques are capable of identifying functional differences between low back pain populations and controls. The use and validity of the majority of these techniques as outcome measures are currently unknown, yet may be valuable in generating functional diagnoses, evaluating the mechanisms of current therapies, and prescribing specific rehabilitation programs.

Proprioceptive and behavior impairments in individuals with anterior cruciate ligament reconstructed knees

OBJECTIVE

To assess sensory deficits and their effects on proprioceptive and motor function in patients who had undergone unilateral anterior cruciate ligament (ACL) reconstruction.

DESIGN

Four evaluations were conducted: (1) joint position perception of the knee for predetermined angles (0 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees ); (2) threshold for detection of passive knee motion at 0 degrees, 15 degrees, 30 degrees, 45 degrees, and 60 degrees moving into flexion and at 15 degrees, 30 degrees, 45 degrees, and 60 degrees moving into extension; (3) latency onset of hamstring muscles; and (4) postural control during upright double- and single-leg stance.

SETTING

Movement laboratory in Brazil.

PARTICIPANTS

Ten participants who had surgical reconstruction of the ACL (reconstructed group) and 10 participants without knee injury (control group).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Absolute error, angular displacement, hamstring muscles latency, and mean sway amplitude.

RESULTS

Individuals with a reconstructed knee showed decreased joint position perception, a higher threshold for detection of passive knee motion, longer latency of hamstring muscles, and decreased performance in postural control.

CONCLUSIONS

After lesion and ACL reconstruction, sensory and motor behavior changes were still observed. This may be because of the lack of proprioceptive information resulting from the ACL lesion and/or substitution of ACL by the graft.

Functional measurement of knee joint position sense after anterior cruciate ligament reconstruction

OBJECTIVE

To examine for differences in joint position sense (JPS) between knees with reconstructed anterior cruciate ligaments (ACLs) and uninjured knees by using a functional weight-bearing measurement method.

DESIGN

Two-way repeated-measures in a convenience sample.

SETTING

An Australian university rehabilitation laboratory.

PARTICIPANTS

Nine subjects presenting at 12 to 16 months after unilateral ACL reconstruction using the semitendinosus/gracilis graft who were recruited from 2 orthopedic surgeons.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

JPS of the reconstructed and uninjured knees was examined by using the Peak Motus motion measurement system to record target joint angles and to calculate reproduced angles after limb movement into flexion and extension, performed in a weight-bearing position.

RESULTS

There were no significant differences in JPS between reconstructed and uninjured knees (P=.68) or between the flexion and extension tasks (P=.47).

CONCLUSION

There was no deficit in knee JPS 12 to 16 months after ACL reconstruction, as measured by a functional weight-bearing method. Further studies should examine the clinical utility of the method as a way to evaluate functional aspects of knee joint proprioception.

Neuromuscular training and injury prevention in sports

Exercises that help develop neuromuscular control and increase functional joint stability are critical in conditioning and rehabilitation programs designed for injury prevention in sports. Information regarding joint movement and joint position provided by mechanoreceptors in the skin, muscles, tendons, ligaments, and joints combine with input from the vestibular and visual systems to maintain balance. Insufficient neurologic input or improperly processing that input at the spinal, brain stem, or cognitive centers can lead to an inadequate response by the motor system resulting in an injury. Therefore, it is important to include drills that enhance neuromuscular control into traditional training, conditioning, and rehabilitation programs for sports.

Restoration of anterior cruciate ligament-hamstring reflex arc after anterior cruciate ligament reconstruction

It has recently been emphasized that restoration of neuromuscular function contributes to dynamic stability of the anterior cruciate ligament (ACL) reconstructed knee. The existence of an ACL-hamstring reflex arc, one of the protective ligament-muscular pathways, has been revealed in normal human knees. Although reinnervation to the reconstructed ACL has been observed histologically, it remains unclear whether the ACL-hamstring reflex arc is reestablished. This study examined the existence of the ACL-hamstring reflex arc in ACL-reconstructed knees by analyzing the changes in the hamstring EMG elicited by electrical stimulation to the reconstructed ACL. The patellar tendon grafts transplanted as an ACL substitute in three patients were electrically stimulated via a bipolar wire electrode inserted arthroscopically. The surface EMG was monitored from the ipsilateral biceps femoris and semitendinosus. In two of the three patients the significantly increased EMG value of the biceps femoris was detected between 120 and 140 ms after the onset of electrical ACL stimulation. The increased EMG activity detected in the biceps femoris after the stimulation to the patellar tendon graft indicated reestablishment of the ACL-hamstring reflex arc in the ACL-reconstructed knee.

Kinesthetic sense of the shoulder in patients with impingement syndrome

A proprioceptive deficit is an important determinant of disability in various shoulder disorders, such as instability and osteoarthrosis. In 15 patients with impingement syndrome stage II (Neer 1983), who were treated by arthroscopic subacromial decompression, we measured movement sense by determining threshold levels for the perception of motion of the shoulder. The patients were placed in a specially designed chair allowing continuous passive motion of the shoulder joint, while avoiding cutaneous, auditory and visual stimuli. To assess movement detection thresholds, passive abduction movements of the shoulder were performed at a starting angle of 60 degrees, an amplitude of 10 degrees and an angular velocity of 1.3 degrees/s. Before surgery, all patients had higher threshold levels for the perception of motion in their affected shoulders then in the other side. After decompression, proprioception had improved on the decompressed side, but was unchanged on the other side.

Recent advances in the rehabilitation of isolated and combined anterior cruciate ligament injuries

The rehabilitation process begins immediately following ACL injury, with emphasis on reducing swelling and inflammation; improving motion; regaining quadriceps control; allowing immediate weight-bearing; and restoring full passive knee extension and, gradually, flexion. The goal of preoperative rehabilitation is to prepare the patient mentally and physically for surgery. Once the ACL surgery is performed, it is important to alter the rehab program based on the type of graft used and any concomitant procedures performed. This will aid in preventing several postoperative complications, such as loss of motion, patellofemoral pain, graft failure, and muscular weakness. The goal of this article has been to provide an overview of the application and the scientific basis for formulating a rehabilitation protocol following ACL surgery. For an athlete to return to competition, it is imperative that he or she regain muscular strength and neuromuscular control in their injured leg while maintaining static stability. In the past, rehabilitation programs attempted to prepare the athlete for return to sports by using resistance exercise alone. Current rehabilitation programs focus not only on strengthening exercises, but also on proprioceptive and neuromuscular control drills in order to provide a neurologic stimulus so that the athlete can regain the dynamic stability needed in athletic competition. We believe that it is important to use this approach not only possible causes that might predispose the individual to future injury.

Coordination and stability of one-legged hopping patterns in patients with anterior cruciate ligament reconstruction: preliminary results

OBJECTIVES

To investigate whether the intralimb coordination of the lower extremity during one-legged hopping in patients with anterior cruciate ligament reconstruction is different and less stable compared to control subjects.

DESIGN

Measures of coordination dynamics are applied to study the coordination and stability of movement patterns of the knee and ankle in patients and control subjects.

BACKGROUND

Due to several factors, such as loss of proprioceptive function and muscle weakness, the intralimb coordination of the lower extremity might be altered.

METHODS

Seven patients and 13 healthy control subjects were instructed to hop in place on one leg for 10 seconds at a comfortable frequency for each leg separately.

RESULTS AND CONCLUSIONS

The one-legged hopping movement pattern of patients with anterior cruciate ligament reconstruction one-year post-operative is different and less stable compared to healthy subjects, and thus is still impaired.

RELEVANCE

This paper shows that patients, one year after reconstruction of the anterior cruciate ligament, have a different coordination pattern of the lower limb compared to a matched control group. Intersegmental coordination and stability, features that are often observed by eye during a rehabilitation process, are objectified in this study.

Strategies for enhancing proprioception and neuromuscular control of the knee

Proprioception and neuromuscular control of the knee are compromised after ligament injury and must be regained if the athlete is to return to high level sports at a normal injury risk level. The anterior cruciate ligament deficient and reconstructed knee will be used as a model to describe differences in proprioception and neuromuscular control to those of an uninjured knee. The purpose of the current review is threefold. First, the basic science of proprioception and neuromuscular control specific to the knee will be summarized and reviewed. The review will include an overview of terminology, neurophysiology, and the effects of injury on the function of both lower limbs. Second, tools used for assessment and rehabilitation of proprioceptive deficits will be evaluated. Specific rehabilitation procedures that incorporate prophylactic conditioning that focus on transitioning the injured athlete back into sport will be presented. Finally, the literature with respect to gender variation in proprioception and neuromuscular control will be evaluated. The goal of the current review is to provide the clinician and the clinical scientist with sufficient background information for the development of quantitative methods to evaluate a patient's functional capacity and to assist in preventative, preoperative, and postoperative decision-making strategies.

Changes in weight-bearing following injury or surgical reconstruction of the ACL: relationship to quadriceps strength and function

PURPOSE

Changes in weight-bearing an average of 1.5 months after ACL injury (ACLD) and up to 3 months after surgical reconstruction (ACLR) were investigated using a force platform. Correlations between force platform test variables, quadriceps strength and functional self-report scores were also examined.

RESULTS

Each force platform test revealed impaired weight-bearing by either ACLD and/or ACLR subjects. Many variables were correlated to quadriceps strength; therefore, improved strength in ACLR subjects by 6 weeks post-operative negated any weight-bearing impairment. No single force platform variable correlated with the subjects' perception of function.

CONCLUSION

Only the step up/over test provided insight into disability in these patients. Modification of force platform analysis programs may allow for other clinical questions to be answered.

Does wearing a functional knee brace affect hamstring reflex time in subjects with anterior cruciate ligament deficiency during muscle fatigue?

OBJECTIVE

To evaluate the effects of wearing a functional knee brace and muscle fatigue on hamstring reflex time in subjects with anterior cruciate ligament (ACL) deficiency.

DESIGN

Repeated-measures clinical trial.

SETTING

Outpatient physical therapy department.

PARTICIPANTS

Sixteen subjects with ACL deficiency.

INTERVENTION

Subjects tested with and without a functional knee brace before and after an exercise protocol designed to fatigue the knee muscles.

MAIN OUTCOME MEASURE

Latency of hamstring reflex muscle activity after sudden perturbation of the knee.

RESULTS

Wearing a knee brace shortened the hamstring reflex latency regardless of fatigue (F(1,15)=20.62, P<.001). Muscle fatigue lengthened the hamstring reflex time regardless of the bracing condition (F(1,15)=7.57, P<.015).

CONCLUSION

Wearing a functional knee brace facilitated hamstring muscle reflex, but muscle fatigue lengthened the hamstring reflex latency. Subjects with ACL deficiency should not rely on the knee brace to facilitate hamstring reflex for joint protection during prolonged sporting activities when muscles are fatigued.

Cruciate ligament reflexes

The idea of muscular reflexes elicited from sensory nerves of the cruciate ligaments is more than 100 years old, but the existence of such reflexes has not been proven until the recent two decades. First in animal experiments, a muscular excitation could be elicited in the hamstrings when the anterior cruciate ligament (ACL) was pulled, and tension in the ligament caused activity of the gamma motor neurones of the muscles around the knee. Impulses from the sensory nerves in ACL were activated during motion of the knee, in particular overstretching and combined extension and rotation. In humans, proprioception in the knee is decreased after ACL rupture. By mechanical or electrical stimulation of the ACL, an excitation in the hamstrings muscles can be elicited. During muscular activity, stimulation of the ACL or PCL results in a clear inhibition of the ongoing activity, both during static isometric and isokinetic muscle work, and also during dynamic activity (gait). This inhibitory reflex subjectively resembled giving way. The latency of the reflex was short in animals (about 3 ms) and long in humans (60-120 ms), probably caused by differences in the experimental setup and between species. The long latency in humans makes it unlikely that it is a directly protective reflex. Instead it may be involved in the updating of motor programs. Further research may characterize the reflex in details and map its pathways. The existence of this reflex indicate that the cruciate ligaments have an afferent function, which influences knee dynamics.

Mechanoreceptors in the anterior cruciate ligament contribute to the joint position sense

We have investigated the correlation between the number of mechanoreceptors in anterior cruciate ligament (ACL) remnants and the joint position sense just before an ACL reconstruction in 29 patients. The number of mechanoreceptors was evaluated histologically, using the Gairns gold chloride method. Mechanoreceptors were also found in patients who had a long interval between injury and the operation. A joint position sense test was done within 3 days before surgery. We found a positive correlation between the number of mechanoreceptors and accuracy of the joint position sense, suggesting that proprioceptive function of the ACL is related to the number of mechanoreceptors. Therefore, we should consider preserving ACL remnants during ACL reconstruction.

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.

Muscle activation patterns in subjects with and without low back pain

OBJECTIVE

To analyze muscle activation patterns during various footplate perturbations, used as proprioceptive challenges in patients with low back pain (LBP) and in controls.

DESIGN

A prospective and controlled comparative study.

SETTING

Outpatient clinic.

PARTICIPANTS

Twenty subjects with chronic LBP and 20 age- and sex-matched controls.

INTERVENTIONS

The subjects underwent 5 sets of footplate perturbations in 3 directions with 16 perturbations for each set.

MAIN OUTCOME MEASURES

Latency, frequency, and asymmetry of muscle activation of the erector spinae, rectus abdominus, anterior tibialis, and gastrocnemius muscles were measured bilaterally with surface electromyography.

RESULTS

In the toes-up movements, subjects with LBP were significantly less likely to activate their rectus abdominus muscles (P=.02), and they were more likely to exhibit asymmetric muscle activation in the smaller forward movements (odds ratio=4.1, P=.03). The latter result appears to be driven by asymmetric contraction of the erector spinae and rectus abdominus.

CONCLUSIONS

Significantly more subjects with LBP than control subjects exhibited absent firing of trunk muscles during 2 of the 5 footplate perturbations. These results suggest an abnormality of the neuromuscular loop and may represent altered proprioception.

Effect of warming up on knee proprioception before sporting activity

BACKGROUND

It is now generally accepted that the ligamentous structures of the knee not only act as mechanical restraints but also have a neurophysiological role in joint function and protection. A report that knee joint laxity increases with exercise raised the question as to whether there is any compensatory change in joint position appreciation.

OBJECTIVE

To test whether there is a compensatory mechanism for increased ligamentous laxity during normal levels of activity.

METHODS

Joint position appreciation was measured, using a previously reported technique, in the knees of sportsmen at rest and after warm up.

RESULTS

Joint position appreciation was found to be significantly more sensitive after warm up (p = 0.005).

CONCLUSIONS

These findings indicate that joint position appreciation within the knee accommodates physiological changes within the ligaments and muscles after exercise.

Electromechanical delay after ACL reconstruction: an innovative method for investigating central and peripheral contributions

OBJECTIVES

The purpose of this study was to investigate the electromechanical properties of atrophied muscle in patients with anterior cruciate ligament (ACL) reconstruction and to examine the relationship of changes in these properties for a voluntarily elicited maximal isometric contraction and peripherally stimulated twitch contraction.

BACKGROUND

It is not known if, following ACL reconstruction, a prolonged reaction time to a sudden stimulus is due to impaired proprioception in the knee joint, a prolonged processing interval in the central nervous system, or a greater elasticity in the series elastic component of the quadriceps femoris.

METHODS

Seventeen patients were recruited 2 to 3 months following a unilateral ACL reconstruction. Both the involved leg (ACL-invo group) and the uninvolved leg (ACL-uninvo group) were studied. Twenty-two athletes (training group) and 18 control subjects (control group) were also tested. These subjects performed voluntary maximal isometric contraction (MVC) of the quadriceps femoris. Maximal twitch response was also elicited by a supramaximal electrical stimulation to the femoral nerve, and surface electromyograms were recorded from the vastus lateralis in all four groups.

RESULTS

Total reaction time for MVC in the ACL-invo group (250.47 ms) was prolonged compared to that of the control and training groups. Twitch response in the ACL-invo group (25.26 ms) was prolonged compared to that of the other three groups. Premotor time during both MVC and twitch response did not differ among the four groups. Electromechanical delay during MVC (53.62 ms) and the evoked electromechanical delay in twitch response (20.04 ms) were prolonged in the ACL-invo group as compared to the other three groups.

CONCLUSIONS

Prolonged electromechanical delay in twitch response may be due to peripheral physiological disruptions (eg, stiffness of the series elastic component, changes of peripheral muscle fiber-type composition, or a decrease in function of the excitation-contraction coupling process). A prolonged electromechanical delay in twitch response can also explain the prolonged electromechanical delay observed for MVC. These findings suggest that prolonged total reaction time in MVC, when secondary to a visual stimulus in atrophied human quadriceps femoris muscle after ACL reconstruction, may be principally due to prolongation of electromechanical delay produced by peripheral physiological alterations. However, the contribution of premotor time to prolonged total reaction time was not revealed. Our results do not completely eliminate the possibility that central nervous system processing time and other neural factors are involved in the prolongation of reaction time.

[Knee orthosis. First part : evaluation of physiological properties based on a review of the literature]

INTRODUCTION

The aim of this work was to proceed to a literature review to determine the physiological justifications underlying knee orthosis use in medical practice.

METHOD

An analysis of the international literature relating to the years 1980-2000 was carried out with the Medline data bank. We added extra articles focusing on the validity of the protocols used in the different evaluations.

RESULTS

Five hundred and twelve articles were selected and 46 articles of experimental validation were retained. The experimental protocols are divided into in vitro studies and clinical studies carried out in both healthy subject and patients. Only the in vitro experimental data allowed to reach strain values simulating traumatisms of the articular structures. They allowed to define the interest and limits of the orthosis according to articular physiology. Measurements carried out in vivo were effective to characterize the parameters of stability and proprioception and to discriminate between the orthosis. These studies correspond to experimental situations with related constraints that remain far below lesional constraints, focusing on their clinical validity.

CONCLUSION

This work point out many studies focusing on the physiological characterization of the knee orthosis. This evaluation of the orthosis through a single methodology remains difficult and justifies confrontation with clinical trials data.

Inhibition of dynamic thigh muscle contraction 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 muscle during voluntary static and dynamic muscle contraction. The study group comprised nine young men with no history of injury to the knee joints. Multistranded Teflon-insulated stainless-steel wires were inserted into the PCL guided by ultrasound. In three subjects wires were also inserted into the fat pad of the knee. The PCL was electrically stimulated during static, concentric, or eccentric muscle contraction with a constant load of 20% of the maximal voluntary contraction of either the quadriceps or the hamstrings. 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 hamstrings with latencies of 114-150 ms and 99-130 ms, respectively. Stimulation of the fat pad of the knee did not influence the muscle activity. The study suggests that the mechanoreceptors in the PCL are involved in controlling muscle activity during both static and active muscle contractions. The relative long latency of the reflex makes it unlikely that it can serve as a directly protective reflex for the cruciate ligaments.

Influence of supervised and nonsupervised training on postural control after an acute anterior cruciate ligament rupture: a three-year longitudinal prospective study

STUDY DESIGN

Prospective randomized longitudinal clinical trial with matched controls.

OBJECTIVES

To investigate the long-term effect of training on postural control and extremity function after an acute anterior cruciate ligament (ACL) injury.

BACKGROUND

ACL injuries may cause severe problems with recurrent giving way of the knee and reduced functional capacity. The effect of an acute ACL injury and the effect of various training programs on postural control, as well as the relation between postural control and extremity function after such an injury, have not been studied longitudinally.

METHODS

Sixty-three consecutive patients, 35 men and 28 women (median age 24 years, quartiles 19-33 years), with an acute nonoperated ACL injury, randomized to neuromuscular supervised or self-monitored training, were examined with stabilometry (amplitude and average speed of center of pressure movements) and a one-leg hop test for distance after 6 weeks (stabilometry only), and after 3, 12, and 36 months, and were compared to a control group.

RESULTS

Regardless of treatment, center of pressure amplitude was persistently higher in both the injured and uninjured legs during the 3-year follow-up, but average speed was less affected or unaffected compared to the control group. The one-leg hop had normalized in the neuromuscular group at the 12-month follow-up, but was shorter in both legs throughout the 3-year period in the self-monitored group. The median value (quartiles) for injured/uninjured legs at 3 months was 150 cm (120-174 cm)/177 cm (140-199 cm), at 12 months was 174 cm (140-200 cm)/180 cm (150-202 cm), and at 36 months was 172 cm (146-200 cm)/178 cm (150-200 cm) in the self-monitored group, compared to the control group (median 186 cm, quartiles 177-216 cm).

CONCLUSIONS

The higher center of pressure amplitude in both legs over the 3-year period indicate persistently impaired postural control in single-limb stance. However, functional performance, as measured with the one-leg hop test, was restored by neuromuscular training, but not by self-monitored training.

Review of knee proprioception and the relation to extremity function after an anterior cruciate ligament rupture

Several tests of human conscious knee proprioception have been described, but there is no consensus or reference standard established. Difficulties remain in the separation of information originating from muscles, tendons, and joints, and the tests cannot discriminate between loss of afferent signals or altered activity in the remaining receptors. There is convincing evidence from several descriptive studies that the afferent information is altered after a knee ligament injury and severely disturbed in some patients with anterior cruciate ligament (ACL) injuries. However, an inherent inferior proprioceptive ability may also exist in some individuals, which makes them vulnerable to injuries. The deficits in proprioception have mostly been studied and related to the consciously registered sense, whereas the extent of possible disturbances of the unconscious or reflectory mechanisms is largely unknown. The latter may, at least from a theoretical point of view, be predominantly contributing to the overall afferent regulation, and a possibility for major defects thus exists, since there is no knowledge of the quantified relation between the conscious and unconscious part. The clinical importance of the altered afferent information has not been evaluated properly, and the role of proprioception that contributes to function has yet to be investigated. A higher physiological sensitivity to detecting a passive joint motion closer to full extension has been found both experimentally and clinically, which may protect the joint due to the close proximity to the limit of joint motion. Proprioception has been found to have a relation to subjective knee function, and patients with symptomatic ACL deficiency seem to have larger deficits than asymptomatic individuals. Little is known about whether training can restore defects in sensory information or by which mechanisms possible compensatory pathways are established. In rehabilitation, each patient must, however, create muscle strength, alertness, and stiffness in harmony with the disturbed mechanics of the knee, which are present both after nonoperative treatment of the ACL and after a reconstruction of the ACL.

Dynamic knee stability: current theory and implications for clinicians and scientists

We will discuss the mechanisms by which dynamic knee stability may be achieved and relate this to issues that interest clinicians and scientists concerned with dynamic knee stability. Emphasis is placed on the neurophysiologic evidence and theory related to neuromuscular control. Specific topics discussed include the ensemble firing of peripheral mechanoreceptors, the potential for muscle stiffness modulation via force and length feedback, postural control synergies, motor programs, and the neural control of gait. Factors related to answering the difficult question of whether or not knee ligament injuries can be prevented during athletic activities are discussed. Prevention programs that train athletes to perform their sport skills in a safe fashion are put forth as the most promising prospect for injury prevention. Methods of assessing neuromuscular function are reviewed critically and the need for future research in this area is emphasized. We conclude with a brief review of the literature regarding neuromuscular training programs.

Effect of fatigue on knee proprioception: implications for dynamic stabilization

The high incidence of injuries that occur later during a session of sports or recreational activities suggests that fatigue may contribute to altered neuromuscular control of the lower limb and an individual's subsequent altered ability to dynamically stabilize the knee joint. One possible mechanism is a fatigue-mediated alteration in proprioception. This paper reviews experimental evidence of fatigue-induced changes in knee joint position sense and movement sense, or kinesthesia. We will discuss the possible physiological mechanisms behind these changes, including the role of joint and muscle receptors in proprioception and neuromuscular control of the knee, and the role of fatigue in changes in afferent output from muscle and joint receptors. We will then explore the implications that alteration in proprioception may have for dynamic stabilization of the knee joint.

Effects of knee bracing on the sensorimotor function of subjects with anterior cruciate ligament reconstruction

The sensorimotor performance of the knee joint in 31 subjects who had undergone unilateral anterior cruciate ligament reconstruction at least 5 months previously was tested under three bracing conditions, 1) the DonJoy Legend brace, 2) a mechanical placebo brace, and 3) no brace, in random order. The accuracy of the subjects' ability to reproduce specified knee joint angles was tested as well as the isokinetic performance of their knee muscles at 60 and 180 deg/sec. The results showed that subjects with the brace or placebo brace performed similarly in reproducing the knee joint positions, but both groups performed better than the subjects without a brace. Isokinetic tests revealed no difference among the three groups in extensor and flexor peak torque production at 60 deg/sec or total work done by the extensors and flexors at 60 and 180 deg/sec. These results suggest that knee bracing can improve the static proprioception of the knee joint, but not the muscle contractile function, in subjects with anterior cruciate ligament reconstruction under isokinetic testing conditions. The finding of similar performances for joint angle reproduction in the brace and placebo brace groups suggests that the apparent improvement in proprioception with knee bracing was not due to the mechanical restraining action of the brace.

The effect of musculoskeletal pain on motor activity and control

Aberrant movement patterns and postures are obvious to clinicians managing patients with musculoskeletal pain. However, some changes in motor function that occur in the presence of pain are less apparent. Clinical and basic science investigations have provided evidence of the effects of nociception on aspects of motor function. Both increases and decreases in muscle activity have been shown, along with alterations in neuronal control mechanisms, proprioception, and local muscle morphology. Various models have been proposed in an attempt to provide an explanation for some of these changes. These include the vicious cycle and pain adaptation models. Recent research has seen the emergence of a new model in which patterns of muscle activation and recruitment are altered in the presence of pain (neuromuscular activation model). These changes seem to particularly affect the ability of muscles to perform synergistic functions related to maintaining joint stability and control. These changes are believed to persist into the period of chronicity. This review shows current knowledge of the effect of musculoskeletal pain on the motor system and presents the various proposed models, in addition to other shown effects not covered by these models. The relevance of these models to both acute and chronic pain is considered. It is apparent that people experiencing musculoskeletal pain exhibit complex motor responses that may show some variation with the time course of the disorder.

Anterior cruciate ligament function after tibial eminence fracture in skeletally mature patients

We compared anterior cruciate ligament function in skeletally mature patients after treatment of tibial eminence fractures with that of patients in two other groups: patients who had anterior cruciate ligament deficiency and patients who had undergone anterior cruciate ligament reconstruction using bone-patellar tendon-bone autografts. The Lysholm questionnaire was used to evaluate symptoms and KT-1000 arthrometry was used to determine objective knee laxity at an average follow-up of 5.2 years. Knee joint proprioception was assessed with a new method designed to test joint position sense. The Lysholm score for the tibial eminence group was 94 +/- 7. Only the patients in the anterior cruciate ligament-deficient group demonstrated statistically significantly increased laxity and inferior proprioception when the injured leg was compared with the uninjured leg. Both laxity and proprioception were statistically inferior for the anterior cruciate ligament-deficient group when compared with both the treated tibial eminence fracture group and the anterior cruciate ligament-reconstructed group. No statistically significant difference was observed between the anterior cruciate ligament-reconstructed and treated tibial eminence fracture groups. Correlation was observed between laxity and proprioception when all patients were analyzed. The results demonstrate that appropriate treatment of tibial eminence fractures restores stability and proprioception to the knee.

Postural control after anterior cruciate ligament reconstruction and functional rehabilitation

Total sagittal knee laxity and postural control in the sagittal and frontal planes were measured in 25 patients at a mean of 36 months (range, 27 to 44) after anterior cruciate ligament reconstruction and in a control group consisting of 20 uninjured age- and activity-matched subjects. Body sway was measured in the sagittal plane on a stable and on a sway-referenced force plate in single-legged stance, double-legged stance, or both, with the eyes open and closed. Postural reactions to perturbations in the sagittal and frontal planes were recorded in the single-legged stance with the eyes open. Total sagittal plane laxity was significantly greater in the anterior cruciate ligament-reconstructed knee (11.2 mm; range, 6 to 15) than in the uninjured knee (8.9 mm; range, 6 to 12) or in the control group (6.0 mm; range, 5 to 8). In spite of this, the patients, in comparison with the controls, exhibited normal postural control except in two variables-the reaction time and the latency between the start of force movement to maximal sway in the sagittal plane perturbations. This supports the hypothesis that rehabilitation, with proprioceptive and agility training, is an important component in restoring the functional stability in the anterior cruciate ligament-reconstructed knee.

Reflex extension loss after anterior cruciate ligament reconstruction due to femoral "high noon" graft placement

We describe a rare case of a painful reflex extension loss due to femoral malplacement of an anterior cruciate ligament (ACL) graft in a female high-level athlete. The graft was placed on the femoral site in the "high noon" position combined with a slight medial tibial tunnel placement. The resulting anterior-posterior cruciate ligament impingement near extension caused a persistent functional extension deficit of 20 degrees. Under anesthesia, the extension loss diminished, and thus it was hypothesized that the ACL-PCL impingement during extension activates a proprioceptive reflex leading to a functional extension loss while the patient is awake. After sacrifice of the graft and subsequent replacement of the ACL, full range of motion was achieved within 2 months. After a 3-year postinjury history of 3 arthroscopies and 2 ACL reconstructions, the athlete reached her preinjury activity level again. This rare cause of a reflex extension loss due to femoral high noon graft placement has not been described previously and should be included as a differential diagnosis when evaluating patients with an extension deficit after ACL reconstruction.

Direct evidence of the anterior cruciate ligament-hamstring reflex arc in humans

It has been emphasized that the anterior cruciate ligament plays an important role in the proprioceptive feedback system. The anterior cruciate ligament-hamstring reflex has been revealed in animal experiments, but it has not been established in humans. The purpose of this study was to demonstrate direct evidence of the anterior cruciate ligament-hamstring reflex arc. Nine knees in nine healthy subjects were investigated. The anterior cruciate ligament was stimulated by the use of wire electrodes inserted using an arthroscopic technique. Electromyographic signals from the biceps femoris and the semitendinosus muscles were recorded with surface electrodes. The change in electromyographic activity was analyzed after electrical stimulation in the normal knee condition, and again after intraarticular sensation had been interrupted with a local anesthetic. After electrical stimulation, subjects demonstrated increased electromyographic activity of the hamstring muscles in the normal knee condition. This response indicates the existence of an anterior cruciate ligament-hamstring reflex arc. Conversely, there was no change in activity for the hamstring muscle in the anesthetized knee because the afferent impulse from the neural elements of the anterior cruciate ligament had been removed.

Analysis of retrieved polymer fiber based replacements for the ACL

The present retrospective analysis of 117 surgically excised anterior cruciate ligament (ACL) prostheses was designed to elucidate the etiology and mechanisms of failure of synthetic ligamentous prostheses. They were harvested from young and active patients (26 +/- 7 yrs) at various orthopaedic centers in France between 1983 and 1993. The average duration of implantation of augmentation and replacement prostheses were 21.5 +/- 12.6 and 33.2 +/- 25.3 months, respectively. The principal causes for their excision were ruptures and synovitis. Each ACL prosthesis was examined macroscopically, histologically, and, after tissue removal, by scanning electron microscopy (SEM) to determine the model, manufacturer, surgical technique used at implantation, the extent of healing, the site of rupture, and the morphology of the damaged fibers. Fourteen types of ACL prostheses were analysed, each fabricated using a different combination of polymers, fibers and textile constructions. Consequently, they generated a variety of healing characteristics and mechanical responses in vivo. SEM observations revealed that abrasion of the textile fibers as a result of yarn-on-yarn and/or yarn-on-bone contact was a common phenomenon to almost all models, and was the primary cause of prosthetic failure. Healing inside the synthetic ACL was poorly organized, incomplete and unpredictable as the extent of collagenous infiltration into the textile structure did not increase with the duration of implantation. In fact, the collagenous infiltration into certain models appeared to be more detrimental than beneficial since it caused deterioration and fraying of the textile structure rather than serving as a reinforcing matrix around the prosthesis. In conclusion, the present study shows that three mechanisms may be involved in the failure of ACL prostheses: (1) inadequate fiber abrasion resistance against osseous surfaces; (2) flexural and rotational fatigue of the fibers, and (3) loss of integrity of the textile structure due to unpredictable tissue infiltration during healing.

Proprioceptive improvement in knees with anterior cruciate ligament reconstruction

The correlation between the prospective course of proprioceptive improvement and knee stability after anterior cruciate ligament reconstruction was investigated in 38 patients. Proprioception, on the basis of the patient's capacity to reposition the limb accurately, was evaluated at 3-month intervals for 24 months after hamstring graft anterior cruciate ligament surgery. Knee stability was evaluated concurrently with a KT-2000 knee arthrometer. Thirty patients experienced improvement in postoperative position sense in at least one of the examinations, although eight patients had no improvement at any time. Of the 30 patients who had improvement, 28 maintained improved position sense from 18 months to the final followup. Thirty patients maintained significantly better knee stability for a postoperative period of at least 24 months. These results indicated that a minimum of 18 months after anterior cruciate ligament reconstruction may be needed for complete restoration of the proprioceptive function in knees, although the mean position sense in all patients gradually improved from 9 months. Improvement in postoperative knee stability may have facilitated recovery of proprioception.