Differences between motion-direction perception and unspecific motion perception in the human knee joint

Perception has commonly been seen as a conscious performance. Thus, regarding proprioception in some publications, it has been proposed that the term is properly used only when subjects are able to report on the direction as well as presence of imposed movements. Consequently, detections of movements without movement-direction perception have not been accepted as perceived, since these detections were regarded as unspecific. Unspecific sensation has been suggested to precede perception. From this "two-state model", it follows that threshold values should be lower for unconscious unspecific perception than for conscious specific perception. The aim of the present study was to test this suggested dichotomy. Proprioception was compared in unspecific detection trials (only the occurrence of a movement had to be detected, not its direction) and direction-specific detection trials (the occurrence of a movement of a specific direction had to be detected). Two types of specific detection trials and two types of unspecific detection trials were studied. Pairs of threshold values were determined, regarding amplitude detection using different angular velocities and regarding velocity detection using different angular displacements, for flexion and extension. Our results showed that, independent of each other, both threshold paradigms (amplitude detection and velocity detection) revealed the same perception characteristics. In specific detection paradigms, the proprioceptive thresholds were two times lower than in unspecific detection paradigms. Thus, movements of a particular type could be detected more easily than movement per se. The suggested "two-state model" might, therefore, not be appropriate in describing proprioceptive perception.     

Nonspecific velocity and amplitude hunting reveals different specific detection performance of flexion and extension movements in the human knee joint

A debate exists in the literature as to what extent perception is conscious. In some publications regarding proprioception, the term proprioception has explicitly only been seen as properly used when subjects were able to report the imposed movement's direction. Detections of movements without movement-direction perception, have been seen as nonspecific. Since a lot of studies discussed this point but never tested it explicitly, we tested it by using nonspecific hunting paradigms (only the occurrence of a movement has to be detected, not its direction) with the following rationale. If the perception performance is really nonspecific, no difference regarding the movement's direction should be found. Thus, if we found a different detection performance regarding flexion and extension by means of a nonspecific paradigm, it would demonstrate that this "nonspecific" perception is already specific. Therefore, we measured the perception characteristics separately for flexion and extension. The perception characteristics have been determined from the amplitude-velocity-relation curve. Two different, nonspecific hunting paradigms, modifications of our previously published specific hunting paradigm, have been used. Thus, we determined pairs of threshold values, regarding amplitude hunting using three different angular velocities (0.1 degrees s(-1), 0.25 degrees s(-1), and 0.5 degrees s(-1)) and regarding velocity hunting using three different angular displacements (0.25 degrees, 0.5 degrees, and 1 degrees) as well, for flexion and extension, respectively. We found that both threshold paradigms (velocity hunting and amplitude hunting) revealed the same perception characteristics for a given movement direction. With an increasing angular velocity, angular displacement threshold values converged toward a common value for flexion and extension (about 0.2 degrees); with an increasing angular displacement, angular velocity threshold values converged toward separate values for flexion (about 0.06 degrees s(-1)) and extension (about 0.1 degrees s(-1)). Thus, our findings demonstrate that detection performance is specific and not bound to conscious perception, since specific thresholds for flexion and extension were revealed with nonspecific hunting paradigms.     

Characterisation of human knee-joint proprioception by means of a signal-detection theory

Human proprioceptive performance of movement detection in joints is currently believed to be based on information from muscle spindles. In previous studies investigating proprioception, we found remarkable differences in threshold values using a conventional movement-detection paradigm and a threshold-hunting paradigm. One reason could be that central processing, the evaluation of the peripheral sensation, was responsible. Therefore, the study was designed to determine, besides the proprioceptive performance, the central processing of movement detection in the knee joint by means of a signal-detection technique (SDT). Only this technique provides parameters such as detectability (d') and the decision criterion (beta), which distinguish between these performances. From the resulting psychometric functions, the threshold (a parameter of classical psychophysics) also was evaluated. This threshold parameter (PCmax), derived from the SDT parameter d', indicates that detection is above threshold when subjects detect only 20-30% of the applied stimuli, as sham stimuli were detected also. The detectability increased with increasing velocity and up to a certain value with increasing amplitude. The threshold for movement detection was lower than 0.25 degree for the three faster angular velocities (0.1 degree s-1, 0.5 degree s-1, 0.6 degree s-1) and lower than 0.75 degree for the slowest velocity (0.05 degree s-1). The decision criterion beta, a measure for central processing which determines acuity, might reflect the central processing output on fusimotor neurones and thus be an indirect measure of the gamma-drive evoked by fusimotor neurones.     

The influence of age on weight-bearing joint reposition sense of the knee

Knee joint-position sensitivity has been shown to decline with increasing age, with much of the research reported in the literature investigating this age effect in non-weight-bearing (NWB) conditions. However, little data is available in the more functional position of weight-bearing conditions. The objective of this study was to identify the influence of age on the accuracy and nature of knee joint-position sense (JPS) in both full weight-bearing (FWB) and partial weight-bearing (PWB) conditions and to determine the effect of lower-extremity dominance on knee JPS. Sixty healthy subjects from three age groups (young: 20-35 years old, middle-aged: 40-55 years, and older: 60-75 years) were assessed. Tests were conducted on both the right and left legs to examine the ability of subjects to correctly reproduce knee angles in an active criterion-active repositioning paradigm. Knee angles were measured in degrees using an electromagnetic tracking device, Polhemus 3Space Fastrak, that detected positions of sensors placed on the test limb. Errors in FWB knee joint repositioning did not increase with age, but significant age-related increases in knee joint-repositioning error were found in PWB. It was found that elderly subjects tended to overshoot the criterion angle more often than subjects from the young and middle-aged groups. Subjects in all three age groups performed better in FWB than in PWB. Differences between the stance-dominant (STD) and skill-dominant (SKD) legs did not reach significance. Results demonstrated that for, normal pain-free individuals, there is no age-related decline in knee JPS in FWB, although an age effect does exist in PWB. This outcome challenges the current view that a generalised decline in knee joint proprioception occurs with age. In addition, lower-limb dominance is not a factor in acuity of knee JPS.     

The precision of proprioceptive position sense

The purpose of this study was to determine the precision of proprioceptive localization of the hand in humans. We derived spatial probability distributions which describe the precision of localization on the basis of three different sources of information: proprioceptive information about the left hand, proprioceptive information about the right hand, and visual information. In the experiment subjects were seated at a table and had to perform three different position-matching tasks. In each task, the position of a target and the position of an indicator were available in a different combination of two of these three sources of information. From the spatial distributions of indicated positions in these three conditions, we derived spatial probability distributions for proprioceptive localization of the two hands and for visual localization. For proprioception we found that localization in the radial direction with respect to the shoulder is more precise than localization in the azimuthal direction. The distributions for proprioceptive localization also suggest that hand positions closer to the shoulder are localized more precisely than positions further away. These patterns can be understood from the geometry of the arm. In addition, the variability in the indicated positions suggests that the shoulder and elbow angles are known to the central nervous system with a precision of 0.6–1.1°. This is a considerably better precision than the values reported in studies on perception of these angles. This implies that joint angles, or quantities equivalent to them, are represented in the central nervous system more precisely than they are consciously perceived. For visual localization we found that localization in the azimuthal direction with respect to the cyclopean eye is more precise than localization in the radial direction. The precision of the perception of visual direction is of the order of 0.2–0.6°. Received: 3 July 1997 / Accepted: 27 March 1998     

The influence of sports practice,dominance and gender on the knee joint position sense

BackgroundPhysical activity, muscle fatigue or age have been suggested as factors that positively or negatively influence the knee joint position sense (KJPS). However, conflicting results about the influence of sports practice, limb dominance and gender are found in the literature. This study aimed to assess the influence of sports practice, limb dominance and gender on the KJPS of soccer players and untrained individuals.MethodologySixty subjects participated in this study: 29 soccer players (SPs) and 31 untrained participants (UPs). KJPS was tested in a seated position, for the target angles of 20° and 45° of knee flexion, through an open kinetic chain technique and active repositioning method. Intergroup analysis was performed to compare KJPS between SPs and UPs and between gender, and intragroup analysis was performed to compare proprioceptive acuity between dominant and non-dominant limbs.ResultsKnee repositioning errors were lower in SPs than in the UPs. Repositioning errors of the dominant and non-dominant limb were not significantly different in SPs (P > 0.05), but in UPs the dominant limb showed significantly lower repositioning errors, both for 20° (P = 0.046) and 45° target (P = 0.036). There were no gender differences in the KJPS in both groups (P > 0.05).ConclusionsProprioceptive acuity is higher in trained than in untrained participants. Dominance seems not to influence KJPS of SPs, but in UPs the dominant limb showed a higher accuracy. There were no differences in KJPS related to gender. These results suggest that sports practice, but neither gender nor limb dominance, may positively influence proprioceptive acuity.     

Effect of exercise-induced fatigue on position sense of the knee in the elderly

Previously, data on the effects of muscle fatigue on joint position sense (JPS) have been provided. However, to our knowledge, no studies have been conducted so far to assess the effects of local muscle fatigue on elderly proprioception. Thus, the purpose of the present study was to determine the effects of local muscle fatigue on knee JPS in old-age-subjects. Sixteen male volunteers (mean age ± SD: 69.81 ± 3.92 years) participated in this study. Each subject completed all of the data collection in one morning session; JPS measures were obtained prior to and immediately after the fatigue protocol. JPS was evaluated by the technique of open-kinetic chain and active knee positioning, and was reported using absolute, relative and variable angular errors. The fatigue protocol applied to the lower extremity consisted of 30 maximum concentric repetitions of the knee extensors and flexors muscles on an isokinetic dynamometer at an angular velocity of 120 s⁻¹ (2.09 rad s⁻¹). The results showed that peak torque of knee extensor and flexor muscles was significantly decreased from rest to post exercise-induced fatigue. After local load to the knee muscles, a significant increase of absolute angular error was observed (2.56°). The relative error showed the directional bias in the extension movement. However, the reliability and accuracy of estimating knee angles as showed by the variable error is similar at both times. It can be concluded that exercise-induced local muscle fatigue alters knee JPS in old age adults.     

Changes in head and neck position affect elbow joint position sense

Changes in the position of the head and neck have been shown to introduce a systematic deviation in the end-point error of an upper limb pointing task. Although previous authors have attributed this to alteration of perceived target location, no studies have explored the effect of changes in head and neck position on the perception of limb position. This study investigated whether changes in head and neck position affect a specific component of movement performance, that is, the accuracy of joint position sense (JPS) at the elbow. Elbow JPS was tested with the neck in four positions: neutral, flexion, rotation and combined flexion/rotation. A target angle was presented passively with the neck in neutral, after a rest period; this angle was reproduced actively with the head and neck in one of the test positions. The potential effects of distraction from head movement were controlled for by performing a movement control in which the head and neck were in neutral for the presentation and reproduction of the target angle, but moved into flexion during the rest period. The absolute and variable joint position errors (JPE) were greater when the target angle was reproduced with the neck in the flexion, rotation, and combined flexion/rotation than when the head and neck were in neutral. This study suggests that the reduced accuracy previously seen in pointing tasks with changes in head position may be partly because of errors in the interpretation of arm position.     

The contribution of gravitational torques to limb position sense

Summary An experiment is reported which examined whether gravitational torque acting about a joint is used by the CNS in elbow joint angle matching. Subjects were required to match the joint angles of their two limbs while the external torques acting about each elbow were systematically varied. It was found that when the matching limb was differentially loaded, the error in the produced reference angle corresponded to the directional prediction of a proposed gravitational torque hypothesis. The data suggest that torque sensation is an accessory source of information in limb positioning.This research was partially supported by grants from NATO Scientific Affiars Division, RG82/0227 and US Public Health Service, NS17421 and AG05154 awarded to G. E. Stelmach     

Influence of age on dynamic position sense: evidence using a sequential movement task

Age related changes to the nervous system are well documented. The main objectives of this study were to examine age-associated changes in dynamic position sense and relate these changes to measures of balance and physical function. Two groups of individuals (young <30 years; elderly >60 years) performed an upper extremity movement sequence triggered by a pre-determined target angle during passive rotations of the ankle joint at ten random velocities (10–90° s^–1). Balance was assessed with a series of timed standing tests. Physical function was assessed with the SF 36 questionnaire. Muscle activity was recorded from the ankle dorsiflexors and plantarflexors during the dynamic position tests. Increased error in the elderly group suggested that dynamic position sense declines with age. Moreover, this decline in dynamic position sense was associated with decreased balance and an impaired perception of physical function. The elderly also co-contracted the ankle plantarflexors and dorsiflexors during the proprioceptive testing, perhaps as a strategy to gain up spindle sensitivity. These findings suggest that impaired dynamic position sense of the ankle contributes to alterations in the overall physical function and balance in the elderly. Rehabilitative training methods that improve dynamic position sense of the ankles may improve physical function and balance in the elderly.     

Validity and reliability of smartphones in measuring joint position sense among asymptomatic individuals and patients with knee osteoarthritis: A cross-sectional study

BackgroundQuantifying proprioception deficit in patients with osteoarthritis (OA) may be important in evaluating treatment effectiveness. This study investigated the concurrent and known-groups validity as well as test–retest reliability of a smartphone application in assessing joint position sense (JPS) in asymptomatic individuals and patients with knee OA.MethodsSixty-four knees, from 16 asymptomatic controls and 16 patients with bilateral OA, were assessed twice with a 1-week interval in between. The smartphone Goniometer Pro application and isokinetic dynamometer simultaneously quantified JPS, in terms of absolute repositioning error (RE) angle, during active and passive limb movements at selected angles.ResultsBoth devices showed moderate to almost perfect correlations in measuring JPS; whether active (intra-class correlation coefficient (ICC) >0.87) or passive (ICC >0.97). The mean RE angle differences between the two devices were <0.77° (passive JPS) and <2.76° (active JPS). Both devices were capable of distinguishing patients and asymptomatic controls at 55° and 80°. The smartphone showed moderate test–retest reliability of active JPS measurement (ICC = 0.51) in the two groups, similar to that of the isokinetic dynamometer (ICC = 0.62), but with a high measurement error.ConclusionsSmartphone application is a valid alternative to the isokinetic dynamometer in assessing JPS in patients with knee OA and asymptomatic controls. The two devices could distinguish patients and asymptomatic volunteers during passive JPS measured at 55° and 80°. Both devices have moderate reliability in quantifying active JPS, but reliability results should be considered with caution.     

Limb segment inclination sense in proprioception

Summary Two experiments were performed to determine if proprioceptive signals are perceived more readily in terms of limb segment inclinations to the vertical than as joint angles. Subjects attempted to match arm positions with the upper arms supported at different inclinations. Constant error data showed that, when instructed to match forearm inclinations to the vertical, subjects were very accurate. When required to match elbow joint angles, however, errors were strongly biased in the direction of matching forearm inclinations. The results support a view of proprioception as a system in which afferent signals related to the gravitational torques acting at joints lead to the perception of limb orientation rather than joint angles. Such a system would allow more efficient determination of the relationship of limb segments to external objects than would one based purely on joint angles.This work was supported in part by research awards from the U.S. Public Health Service, AG05154, NS17421 and NATO no 227/82     

The combined effect of muscle contraction history and motor commands on human position sense

Along with afferent information, centrally generated motor command signals may play a role in joint position sense. Isometric muscle contractions can produce a perception of joint displacement in the same direction as the joint would move if unrestrained. Contradictory findings of perceived joint displacement in the opposite direction have been reported. As this only occurs if muscle spindle discharge in the contracting muscle is initially low, it may reflect increased muscle spindle firing from fusimotor activation, rather than central motor command signals. Methodological differences including the muscle contraction task and use of muscle conditioning could underlie the opposing findings. Hence, we tested perceived joint position during two contraction tasks (‘hold force’ and ‘hold position’) at the same joint (wrist) and controlled muscle spindle discharge with thixotropic muscle conditioning. We expected that prior conditioning of the contracting muscle would eliminate any effect of increased fusimotor activation, but not of central motor commands. Muscle conditioning altered perceived wrist position as expected. Further, during muscle contractions, subjects reported wrist positions displaced ~12° in the direction of contraction, despite no change in wrist position. This was similar for ‘hold force’ and ‘hold position’ tasks and occurred despite prior conditioning of the agonist muscle. However, conditioning of the antagonist muscle did reduce the effect of voluntary contraction on position sense. The errors in position sense cannot be explained by fusimotor activation. We propose that central signals combine with afferent signals to determine limb position and that multiple sources of information are weighted according to their reliability.     

兔膝关节解剖学特点及在动物模型的意义

目的　研究兔膝关节血管分布及关节囊附着,为兔膝关节动物模型建立提供解剖学基础。  方法     将20只新西兰大白兔麻醉后,4%多聚甲醛灌注固定。解剖分离兔膝关节的动脉来源及分支、暴露兔膝关节囊的附着点。测量各动脉起始处及其在水平方向上和关节囊附着点距髌骨下极的距离。  结果    分布兔膝关节的各动脉距髌骨下极的距离上、下和左、右约为20 mm和5 mm,关节囊的上、下端和左、右侧的附着点距髌骨下极约为10 mm和4.5 mm。  结论　在制备兔膝关节模型时,髌骨下极可设为参考的基准点,并通过距其距离判断手术安全范围。     

Skin sensory information from the dorsum of the foot and ankle is necessary for kinesthesia at the ankle joint

Previous research has shown that skin is capable of providing kinesthetic cues at particular joints but we are unsure how these cues are used by the central nervous system. The current study attempted to identify the role of skin on the dorsum of the ankle during a joint matching task. A 30 cm patch of skin was anesthetized and matching accuracy in a passive joint matching task was compared before and after skin anesthetization. Goniometers were used to measure ankle angular displacement. Four target angles were used in the matching task, 7° of dorsiflexion, 7°, 14° and 21° of plantarflexion. We hypothesized that, based on the location of skin anesthetized, only the plantarflexion matching tasks would be affected. Absolute error (accuracy) increased significantly for all angles when the skin was anesthetized. Directional error indicated that overall subjects tended to undershoot the target angles, significantly more so for 21° of plantarflexion when the skin was anesthetized. Following anesthetization, variable error (measure of task difficulty) increased significantly at 7° of dorsiflexion and 21° of plantarflexion. These results indicate that the subjects were less accurate and more variable when skin sensation was reduced suggesting that skin information plays an important role in kinesthesia at the ankle.     

A metric for assessing acuity in positioning joints and limbs

In this paper, we present a method for assessing the exactness of sensing and setting the positions of joints and limbs, using a measure we call target resolution. Target resolution, derived from information theory but ultimately based on variance, estimates the fewest number of discrete, equally spaced targets required within a range to provide the maximum possible information transfer from any target set. We argue that target resolution provides better insight into the exactness of position sense than does the usual measure of accuracy based on mean or constant error. Studies have shown that measures of mean error in setting or indicating positions of joints or limbs exhibit lability; they drift and show considerable sensitivity to factors such as previous positions of the limb and learning. We derive the equation for calculating target resolution and give example resolutions for several joints we have tested. Target resolution often gives a quite different impression of proprioceptive exactness than do measures of accuracy based on mean error.     

Models of behaviors when detecting displacements of joints

This report describes two models of human behavior when detecting displacements of joints that allow one to compare and integrate findings from different proprioception tests in a quantitative way. Results from various tests have led to different and often conflicting conclusions about proprioceptive behaviors and their underlying neural mechanisms. However, it has been impossible to compare data and conclusions in any meaningful way due to lack of a suitable analytical framework to accommodate important differences in procedures used in the various tests. These models can provide one such framework. The models, developed using data from proprioception tests reported in the literature, describe how the amplitude and velocity of joint excursions, and the subject bias expressed as false alarm rate, affect the detectability of displacements of joints. Two models were needed to represent observed behaviors: one based on velocity signals alone (the velocity model) and the other based on both velocity and positional signals (the displacement-velocity model). To simulate the detection-decision process subjects used to determine whether a joint was displaced, we adapted strategies from signal detection theory. The models characterized reported behaviors from disparate proprioception tests remarkably well, requiring only 3 degrees of freedom in the velocity case, and 4 in the displacement-velocity case.     

The ultrastructure of sensory nerve endings in the human knee joint capsule

Summary The ultrastructure of sensory nerve endings in the human knee joint capsule was studied. Three types of nerve endings were found: free nerve endings (FNE), Ruffini corpuscles and Pacini corpuscles.In the joint capsule, FNE are located below the synovial layer and within the fibrous layer near blood vessels. These nerve terminals derive from myelinated A-fibres or from unmyelinated C-fibres. Their structure is almost identical to FNE in human hairy and non-hairy skin.Ruffini corpuscles are present within the fibrous layer and the ligaments of the capsule in three variations: small Ruffini corpuscles without a capsule, small with a connective tissue capsule, and large Ruffini corpuscles with an incomplete perineural capsule. Their afferent axons are myelinated and measure 3–5 m in diameter. Inside the corpuscle, nerve terminals are anchored in the connective tissue belonging to the fibrous layer or to the ligaments respectively. The presence of an incomplete perineural capsule depends on the structure of the surrounding connective tissue. In ligaments with collagenous fibrils oriented in a parallel fashion, the perineural capsule is well-developed and the Ruffini corpuscle resembles a Golgi tendon organ; in areas where the fibrils show no predominant orientation, Ruffini corpuscles lack a capsule.Small Pacini corpuscles are situated within the fibrous layer near the capsular insertion at the meniscus articularis or at the periost. They consist of one or several inner cores and a perineural capsule of 1–2 layers. Larger Pacini corpuscles with one or several inner cores and a perineural capsule consisting of 20–30 layers are found on the outer surface of the fibrous layer.The ultrastructure of these nerve endings is compared with the ultrastructure of articular receptors of various animals and with the ultrastructure of sensory nerve endings in the skin of several mammalian species including man.Supported by the Verein zur Förderung der Erforschung und Bekämpfung rheumatischer Krankheiten e.V. in Bad Bramstedt andby the Deutsche Forschungsgemeinschaft (Sch 587/1-4)     

膝关节矢状断层影像解剖学

目的 为膝关节疾患的影像学诊断提供矢状断层解剖学基础。方法 用成年男尸右膝部标本5例(新鲜3，福尔马林固定2)，按解剖骨性标志画线，其中1例标本先行矢状位MRI扫描，所有标本冻硬后，切制矢状断层解剖标本，每例切5个断层，皆观察其内侧面。结果 观察了构成膝关节的主要结构，交叉韧带、半月板及其周围软组织的形态特征、位置、毗邻及其在连续断层的变化规律，并匹配同一断层之MRI。测量股骨内、外侧髁关节软骨厚为2．3mm和2．4mm，胫骨内、外侧髁关节软骨厚为2．5mm和2．6mm，髌骨关节软骨厚为5．3mm，前交叉韧带长36．1mm，前、后交叉韧带中部矢状径为6．32mm和6．51mm，内、外侧半月板矢状径为42．4mm和33．2mm，内侧半月板前、后部厚度为5．1mm和5．8mm，外侧半月板为6．5mm和7．1mm。结论 膝关节的矢状断层解剖各结构形态、位置及变化规律，对骨科及影像学诊断和治疗有重要的价值。     

Synovial haemangiopericytoma of the knee joint

We report a case of haemangiopericytoma occurring intra-articularly in the synovium of the knee joint. This is a rare tumour which, as far as is known to the authors, has not previously been described in a subsynovial site.