Proprioception in the anterior cruciate deficient knee

Comparison of joint position sense after total knee arthroplasty

A comparison of joint position sense, determined by reproducibility of index angles and their subsequent change, was performed in 55 knees that had undergoing a semiconstrained total knee arthroplasty. Knees were stratified into groups that represented arthroplasties performed with or without posterior cruciate ligament retention, with or without resurfacing of the patella, and with or without cement for fixation. There was no significant difference in joint position sense among all the arthroplasty groups. Likewise, there was no difference in joint position sense between any of the arthroplasty groups and an age-matched control group of 32 knees in 32 patients who had not previously undergoing a total knee arthroplasty. Knee arthroplasty does not affect joint position sense.

Is knee joint proprioception worse in the arthritic knee versus the unaffected knee in unilateral knee osteoarthritis?

OBJECTIVE

Neuromuscular joint protection requires proprioceptive input and motor output. Impairment of proprioception in knee osteoarthritis (OA) may contribute to, and/or result from, the disease. If this impairment was exclusively a local result of OA, a between-knee difference would be expected in patients with unilateral OA (UOA). To explore causal directions, 2 hypotheses were tested: 1) proprioception is worse in UOA patients versus elderly controls; 2) proprioception is worse in the arthritic knee versus the unaffected knee in UOA patients.

METHODS

Twenty-eight UOA patients (Kellgren-Lawrence grade > or =2 in 1 knee and <2 in the other knee) and 29 elderly controls were enrolled. The unaffected knee of each UOA patient and both knees of the elderly controls were required to meet symptom, examination, and radiographic criteria. Proprioception (detection threshold of joint displacement after slow, passive, automated knee motion), body mass index, pain, functional status, range of motion, and laxity were measured.

RESULTS

UOA patients had worse proprioception than did elderly controls, in either knee. A between-knee difference was not found in UOA patients.

CONCLUSION

Impaired proprioception is not exclusively a local result of disease in knee OA. The relative importance of impaired proprioception in the development and progression of knee OA will require longitudinal study.

The effects of joint position and direction of joint motion on proprioceptive sensibility in anterior cruciate ligament-deficient athletes

We studied a group of anterior cruciate ligament-deficient athletes to identify whether joint position and direction of joint motion have a significant effect on proprioception. Twenty-nine anterior cruciate ligament-deficient athletes were tested for their threshold to detect passive motion at both 15 degrees and 45 degrees moving into the directions of both flexion and extension. The single-legged hop test was used to identify function in the deficient limb. Results demonstrated statistically significant deficits in threshold to detect passive motion for the deficient limb at 15 degrees moving into extension. For the deficient limb, threshold to detect passive motion was significantly more sensitive moving into extension than flexion at a starting angle of 15 degrees; at a starting angle of 15 degrees moving into extension threshold was significantly more sensitive than at a starting angle of 45 degrees moving into extension. We conclude that in deficient limbs proprioception is significantly more sensitive in the end ranges of knee extension (15 degrees) and is significantly more sensitive moving into the direction of extension. To effectively restore reflex stabilization of the lower limb we recommend a rehabilitation program emphasizing performance-based, weightbearing, closed kinetic chain exercise for the muscle groups that act on the knee joint.

Serial kinematic analysis of the canine hindlimb joints after deafferentation and anterior cruciate ligament transection

OBJECTIVE AND DESIGN

Transection of the anterior cruciate ligament 2 weeks after ipsilateral hindlimb deafferentation leads to osteoarthritis of the knee joint within 3 weeks. We analyzed the gait of six dogs that underwent this procedure in order to identify kinematic changes that could account for this rapid joint degeneration. All animals were video taped, 1, 3, 6, 9 and 13 weeks after surgery while they trotted on a treadmill.

RESULTS

In each dog, extension of the hip, knee and ankle joints of the unstable limb was increased, and the yield phase of the unstable knee was delayed or attenuated. When killed, five of six dogs showed a large full-thickness cartilage ulcer on the distal and/or anterior surface of the medial femoral condyle of the unstable knee; in the sixth dog, a smaller ulcer was observed. However, the severity of pathology in each individual was not obviously related to difference among the dogs in postoperative joint kinematics.

CONCLUSIONS

These data, and results of prior studies in humans and dogs, suggest that knee hyperextension resulting from limb deafferentation, and knee instability resulting from anterior cruciate ligament transection, operate in concert to create a mechanical environment (i.e., increased tibiofemoral separation and changes in the loading of articular surfaces) that results in rapid joint breakdown.

Ability to reproduce head position after whiplash injury

STUDY DESIGN

A two-group design with repeated measures.

OBJECTIVES

To determine if there is loss of the ability to reproduce target position of the cervical spine individuals who have sustained a whiplash injury.

SUMMARY OF BACKGROUND DATA

The ability to sense position is a prerequisite for functional movement. Injury may have a deleterious effect on this ability, resulting in inaccurate positioning of the head and neck with respect to the body coordinates and to the environment.

METHODS

Eleven subjects with history of whiplash injury (age, 42 +/- 8.7 years) and 11 age-matched asymptomatic subjects (age, 43 +/- 3.1 years) participated in the study. Effects of whiplash injury on the ability to replicate a target position of the head were assessed. Maximum rotation of the neck and ability to reproduce the target angle were measured using a standard cervical range-of-motion device. Subjects' perception of "neutral" position was also assessed.

RESULTS

Analysis of variance indicated the whiplash subjects were less accurate in reproducing the target angle than were control subjects. These whiplash subjects tended to overshoot the target. In addition, the subjects in the whiplash group were often inaccurate in their assessment of neutral position.

CONCLUSIONS

Subjects who have experienced a whiplash injury demonstrate a deficit in their ability to reproduce a target position of the neck. These data are consistent with the hypothesis that these subjects possess an inaccurate perception of head position secondary to their injury. This study has implications for the rehabilitation of individuals with whiplash injury.

Neural and muscular electric activity in the cat's knee. Changes when the anterior cruciate ligament is transected

We studied the response of the normal and unstable knee to passive motion and anterior tibial displacement in the cat. 6 cats were anesthetized and the deep level of anesthesia was controlled by electroencephalograms. We recorded electric activity in the articular nerves (posterior PAN and medial MAN) and periarticular muscles (quadriceps and hamstring), while performing passive flexion, extension, internal and external rotation. We then produced anterior displacement of the tibia at 30 degrees and 90 degrees of flexion, as in the Lachman and the anterior drawer maneuvers. The anterior cruciate ligament was surgically sectioned and the same series of passive displacements was performed. We observed statistically significant increased activity in the MAN, the PAN and the quadriceps muscle during knee flexion, in the MAN during extension, and in the PAN and hamstring during external rotation with the knee 90 degrees flexed. Anterior cruciate transection caused anterior displacement of the tibia during stress. This produced a significant increase in the MAN activity and a significant decrease in the hamstring electric activity at 30 degrees and 90 degrees of flexion, as in Lachman and anterior drawer maneuvers. We conclude that electric activity in the articular nerves and periarticular muscles, in response to passive motion and anterior tibial displacement, is altered in the cat's knee after anterior cruciate transection. This suggests that various patterns of periarticular muscle reaction in the anterior cruciate-deficient knee may be related to the unconscious perception of abnormal motion.

Evidence of reinnervation of free patellar tendon autograft used for anterior cruciate ligament reconstruction

We studied six adult male dogs to determine whether free patellar tendon grafts show evidence of reinnervation when used for anterior cruciate ligament reconstruction. Histologic return of neural elements and return of a somatosensory-evoked potential defined evidence of reinnervation. Before removal, the native anterior cruciate ligament was electrically stimulated with a bipolar electrode and a somatosensory-evoked potential was recorded from a scalp electrode. The ligament was excised and reconstructed using an autogenous patellar tendon graft. Somatosensory-evoked potential was attempted immediately after reconstruction. Histology for nerve endings was performed on the native ligaments. Each animal underwent repeat arthrotomy 6 months later. The grafts were isolated and somatosensory-evoked potentials were attempted. An evoked potential was seen in all six dogs before reconstruction. No graft demonstrated a somatosensory-evoked potential acutely; however, 6 months postoperatively, the somatosensory-evoked potential returned in two cases. Histology of native ligaments showed that 25% of the 100 sections evaluated contained neural elements. Of the receptors present, 89% were mechanoreceptors and 11% were free nerve endings. Histologic examination of the graft tissue 6 months postoperatively revealed that all six grafts also contained neural elements. Mechanoreceptors and free nerve endings were present in approximately equal numbers in the grafts. The results of histology and somatosensory-evoked potential demonstrate that in at least some cases, free patellar tendon grafts show evidence of reinnervation when used for anterior cruciate ligament reconstruction.

Reflex muscle contraction in anterior shoulder instability

Reduced proprioception may contribute to recurrent anterior shoulder instability. Twelve patients with unilateral shoulder instability were investigated for evidence of deficient proprioception with an activated pneumatic cylinder and surface electromyography electrodes; the contralateral normal shoulder was used as a control. The latency between onset of movement and the detection of muscle contraction was used as an index of proprioception. No significant difference in muscle contraction latency was detected between the stable and unstable shoulders, suggesting that there was no significant defect in muscular reflex activity. This study does not support the use proprioception-enhancing physiotherapy in the treatment of posttraumatic anterior shoulder instability.

The role of proprioception in the management and rehabilitation of athletic injuries

Rehabilitation continues to evolve with the increased emphasis on patient management and proprioceptive training. Proprioception can be defined as a specialized variation of the sensory modality of touch that encompasses the sensation of joint movement (kinesthesia) and joint position (joint position sense). Numerous investigators have observed that afferent feedback to the brain and spinal pathways is mediated by skin, articular, and muscle mechanoreceptors. Examining the effects of ligamentous injury, surgical intervention, and proprioceptively mediated activities in the rehabilitation program provides an understanding of the complexity of this system responsible for motor control. It appears that this neuromuscular feedback mechanism becomes interrupted with injury and abnormalities, and approaches restoration after surgical intervention and rehabilitation. Rehabilitation programs should be designed to include a proprioceptive component that addresses the following three levels of motor control: spinal reflexes, cognitive programming, and brainstem activity. Such a program is highly recommended to promote dynamic joint and functional stability. Thus far, current knowledge regarding the basic science and clinical application of proprioception has led the profession of sports medicine one step closer to its ultimate goal of restoring function.

Proprioception in anterior cruciate ligament-deficient and reconstructed knees

Proprioceptive function of the knee was quantified and compared in three groups of patients: those with anterior cruciate ligament deficiency, with hamstring tendons-ligament augmentation device anterior cruciate ligament reconstructions, and with bone-patellar tendon-bone anterior cruciate ligament reconstructions. A total of 32 subjects, including 6 uninjured control subjects, were tested for threshold to perception of passive motion of the knee. All other sensory input was neutralized and testing occurred in the 30 degrees to 40 degrees range of knee flexion. The noninvolved contralateral knee served as a control for each subject. Each leg was moved at 0.5 deg/sec into flexion or extension in a random sequence. The variables of age, KT-1000 arthrometer scores, injury-to-surgery interval, injury-to-followup interval, and patient satisfaction were statistically analyzed for correlation with threshold to perception of passive motion of the knee. Control subjects showed no statistically significant differences in threshold between their two knees. The three test groups all showed significantly higher values in the involved knee compared with the noninvolved knee (P < 0.01). However, no statistically significant differences were found between the groups, including controls, with respect to mean threshold to perception of passive motion. According to these results, anterior cruciate ligament reconstruction did not improve proprioception in the patients in this study.

Proprioception after unicondylar knee arthroplasty versus total knee arthroplasty

Proprioception was measured in 2 groups of patients after successful knee arthroplasty. Twenty-eight patients had total knee arthroplasty and their results were compared with an age matched group of 10 subjects who had undergone unicondylar knee arthroplasty. The threshold to detection of passive motion was quantified as a measure of proprioception. The degree of preoperative arthritis was objectively classified according to Resnick. The anterior cruciate ligament and posterior cruciate ligament were present and preserved in all the patients who had undergone unicondylar knee arthroplasty. The anterior cruciate ligament was sacrificed and posterior cruciate ligament retained in 15 of the patients who had total knee arthroplasty and the anterior cruciate ligament and posterior cruciate ligament were sacrificed in 13 of the patients who had total knee arthroplasties. There was no difference in threshold to detection of passive motion among any of the 3 groups. Maintaining the anterior cruciate ligament and posterior cruciate ligament did not impart improved proprioception in unicondylar knee arthroplasty nor did maintaining the posterior cruciate ligament impart improved proprioception in total knee arthroplasty.

[Projections and fiber characteristics of sensory afferents of the anterior cruciate ligament in an animal experiment]

The sensory innervation of the rabbit anterior cruciate ligament was studied by retrograde tracing technique using wheat-germ-agglutinin-horseradish-peroxidase (WGA-HRP) and Fast Blue as neuronal tracers. Injection of the tracer into the ligament was followed by histo- and immunohistochemical investigation of labelled nerve cell bodies located in the dorsal root ganglia. In 4 animals we injected the tracer into the joint cavity to label general joint afferents. The segmental distribution of retrogradely labelled neurons following injection into the anterior cruciate ligament (L6, L7, S1) is significantly different from the distribution pattern after injection into the knee joint (L4-S2). Retrogradely labelled nerve cells innervating the anterior cruciate ligament were further investigated using immunohistochemical and morphometric analysis. The sensory innervation of the anterior cruciate ligament is therefore comprised of at least 2 different qualities of sensory afferent nerves: 1. Small neurones immunoreactive to the inflammatory peptide substance P most likely transmitting nociceptive information centrally (44%). 2. Large, presumably fast conducting A-fibre-afferents characterized by neurofilament proteins transmitting proprioceptive information from corpuscular mechanoreceptors (43%). The results of this study put further weight to the importance of the sensory role of the anterior cruciate ligament using neuroanatomical and immunohistochemical techniques.

Eccentric knee flexor torque following anterior cruciate ligament surgery

The purposes of this study were to compare eccentric knee flexor torque and muscle activation in the limbs of normal (NOR) subjects and in subjects who had undergone unilateral ACI, autograft surgical reconstruction (INJ) and to assess the effect of movement speed on EMG/ torque ratios and eccentric-concentric actions. Fourteen subjects (7 NOR and 7 INJ) were tested for knee eccentric flexor torque and EMG activity at four isokinetic speeds (15 degrees, 30 degrees, 45 degrees and 60 degrees.s-1). Results revealed that post-surgical limbs (ACL) produced significantly less (P < 0.05) eccentric torque and flexor EMG activity at 60 degrees.s-1 than uninjured (UNI) contralateral limbs. Eccentric torque rose significantly as speed increased from 45 degrees to 60 degrees.s-1 for surgical group uninjured limbs and NOR group left and right limbs. Eccentric flexor torque increased with speed for both groups and approximated equality with concentric extensor torque at 60 degrees.s-1 for INJ group ACL and UNI limbs. Concentric flexor muscle EMG/torque ratios were 30-191% greater than eccentric muscle actions across groups and speeds. The results suggest that ACL dysfunction may result in reduced eccentric flexor torque at rapid movement speeds, that eccentric flexor torque increases with movement speed and may have the capacity to counter forceful extensor concentric torque, and that eccentric muscle actions produce less muscle activation per unit force than concentric actions which may reflect reduced energy cost.

Proprioception following total knee arthroplasty with and without the posterior cruciate ligament

Proprioception was measured in two groups of patients following successful total knee arthroplasty (TKA). In one group, the posterior cruciate ligament was retained and an unconstrained cruciate-retaining total knee component was used; in the other group, the posterior cruciate ligament was excised and a cruciate-substituting design was implanted. Threshold to detection of passive motion was quantified as a measure of proprioception. The degree of preoperative arthritis was objectively classified according to Resnick and Niwoyama. There was no difference in threshold to detection of passive motion in cruciate-retaining versus cruciate-substituting TKA. In patients with a moderate grade of arthritis before surgery, the postoperative scores were virtually identical. When the grade of preoperative arthritis was severe, patients with cruciate-substituting TKAs performed significantly better than those with cruciate-retaining TKAs.

Proprioceptive mechanisms in the cruciate ligaments: an electromyographic study on reflex activity in the thigh muscles

The hypothesis of a proprioceptive mechanism arising from mechanoreceptors in the cruciate ligaments and with efferences to the thigh muscles is investigated in an animal model. Electromyographic (EMG) studies of the quadriceps and hamstrings muscles were performed in six sheep anesthetized by intravenous injection of chloralose on applying static and dynamic shear forces to isolated fascicle bundles in the anterior (ACL) and posterior (PCL) cruciate ligaments at 200 to 500 N and 50 to 200 N/sec, respectively. With the help of an external fixator, the knee joint position was varied at 25 to 150 degrees. The relative preload of the anteromedial and posterolateral fascicles in the ACL and the anterior and posterior fascicles in the PCL induced by variation of the joint angle was measured with the help of strain gages. By static and dynamic loading of the anteromedial group of the ACL, EMG activity in the hamstrings increases significantly to 159 +/- 22 and 257 +/- 46 microV seconds, respectively (p < 0.001), with a simultaneous suppression of the quadriceps activity. Static and dynamic loading of the posterolateral ACL group results in a significant excitation of the quadriceps with mean potentials of 142 +/- 29 and 173 +/- 23 microV seconds, respectively (p < 0.001). Mechanical shear applied both to the anterior and posterior fascicles of the PCL induces a significant activation of the ipsilateral quadriceps muscles with a simultaneous inhibition of the hamstrings (p < 0.001). The quality of mechanical loading, i.e., static or dynamic shear, determines the degree of muscular recruitment significantly (p < 0.01). The joint angle contributes to a modulation in the quantitative EMG excitation. Linear regression analysis of the integrated EMG potential values and the amount of passive preload induced by the respective joint position results in a close correlation (r = + 0.78 to + 0.86). The results lead to the conclusion that a proprioceptive mechanism exists that arises from the cruciate ligaments and influences the tone in the thigh muscles. The degree of muscle excitation on mechanical ligament loading is modulated by the amount of preload in the ACL and PCL and the quality of load applied.

Role of proprioception in pathoetiology of shoulder instability

Proprioception is a specialized sensory modality that gives information about extremity position and direction of movement. This kind of afferent sensory feedback is probably important in mediating muscular control of the shoulder joint. As this articulation is minimally constrained, such a coordinated dynamic control of muscles about the joint is necessary for stability during arm motion. The authors evaluated proprioception in individuals with normal shoulders, unstable shoulders, and after surgical stabilization, by assessing threshold to detection of passive motion and the ability to passively reposition the arm in space. In normal shoulders there is no difference between the dominant and nondominant shoulder, though in unstable shoulders there is a significantly decreased proprioceptive ability. Surgical stabilization normalizes proprioception of the shoulder.

Isokinetic strength of the quadriceps and hamstrings and functional ability of anterior cruciate deficient knees in recreational athletes

OBJECTIVE

To test the hypothesis that increasing the hamstrings and quadriceps (H:Q) isokinetic strength ratio will, in the short term, improve the functional ability of an anterior cruciate ligament (ACL) deficient knee.

METHODS

The isokinetic muscular characteristics at a speed of 60 degrees s-1 and 180 degrees s-1 of 46 recreational athletes with an arthroscopically confirmed ACL tear were determined using the Cybex II+ isokinetic dynamometer. The variables tested included peak torque, endurance ratio, total work output, and explosive power. Functional ability was scored with the Cincinnati rating system, measuring the severity of pain and swelling, the degree of giving way, and the overall ability to walk, run, ascent and descent stairs, jump and twist.

RESULTS

Among all muscular characteristics, the H:Q ratio at 180 degrees s-1 at 30 degrees of knee flexion was shown to have the highest correlation to the functional score (r = 0.6249, P < 0.001). All variables involving hamstring strength were shown to be significantly correlated to the functional ability score (P < 0.01), while none of the variables involving quadriceps strength showed significant correlation with the functional ability of the injured knee.

CONCLUSIONS

The H:Q ratio is strongly correlated to the functional ability of ACL deficient knees in Chinese recreational athletes. It could be used as an additional measure to guide in the decision making process in the management of ACL deficient knees.

The future of anterior cruciate ligament restoration

Advancements in the understanding of anatomy, kinematics, and physiology should improve future treatment of anterior cruciate ligament injured knees. The ultimate goal of full restoration of an anterior cruciate ligament injured knee to preinjury status, may be possible in the distant future through genetic manipulation inducing regeneration of tissues. In the midterm future, resorbable stents with incorporated bioactive growth factors have the potential of inducing normal anterior cruciate ligament anatomy without the need for detrimental harvesting of the patient's tissues, or risk of microbial transmission with the use of an allograft. In the near future, the development of more benign autografts and allografts is possible along with methods of resorbable fixation of the graft to bone. Future development of 3-dimensional arthroscopic visualization and robotic surgical techniques have the potential for improvement in graft placement. Advancements in treatment of anterior cruciate ligament deficient knees also can be expected from nonsurgical areas, such as control of muscle atrophy, enhancing cerebellar-proprioceptive rehabilitation, and better bracing techniques. The basic principle of therapy should be to maximize the functional load acceptance and transference capacity of the knee with the least degree of risk to the patient.

[Electromyography studies of surgically managed knee ligament ruptures. A retrospective analysis of defined injury patterns]

In 52 patients (5 groups, average age 32.8 years) with operative treatment of knee ligament injuries cutaneous electromyograms (EMG) under dynamic and isometric conditions (100 N, 200 N, 300 N) were performed in an average of 61.2 weeks postoperatively. The subgroups consisted of 13 patients with operative reconstruction of the anterior cruciate ligament (ACL), 12 after reconstruction of the medial collateral ligament (MCL), 21 after combined ACL and MCL reconstruction and 6 patients with autologous or alloplastic ligament replacement, respectively. The control group consisted of seventeen young adults without a history of knee joint injuries. The intensified and filtered analogous signals of 8 investigated thigh muscles were digitalized and analysed with help of a specially developed computer program. In summary, group specific EMG-criteria reveal distinct ligamentomuscular inhibitory reflexes and, vice versa, EMG activities of thigh muscles may indicate tendencies for group specific criterion after operatively treated knee ligament injuries.

The Physiological Basis for Open and Closed Kinetic Chain Rehabilitation for the Upper Extremity

The confusion between the termsopen kinetic chainandclosed kinetic chainbecomes even greater with application to the upper extremity. Upper extremity function is very difficult to define, due to the numerous shoulder positions and the great velocities with which the shoulder can move. Classifying exercises for rehabilitation of the upper extremity is very difficult due to the complexity of the joint. Many definitions and classification systems have been proposed; however, none of these entirely encompass rehabilitation of the upper extremity. Using previous classifications we have developed a Functional Classification System that is designed to serve as a template for upper extremity rehabilitation. This system has been designed to restore functional shoulder stability, which is dependent upon proper scapulothoracic and glenohumeral stability, and humeral control; all of these are in part mediated by neuromuscular mechanisms. The objective of our new Functional Classification System is to restore functional stability of the shoulder by reestablishing neuromuscular control for overhead activities.

Knee joint proprioception: a comparison between female intercollegiate gymnasts and controls

The role of proprioception as a protective mechanism has gained interest in recent years. From the clinical standpoint, several studies have dealt with ways to enhance proprioception following surgery and during rehabilitation. If kinesthesia (ability to detect passive motion) can be enhanced as a consequence of long-term athletic training, such training must be included as a part of the rehabilitation process to protect the patient from reinjury. Consequently, the purpose of this study was to compare the kinesthetic knee pattern between trained gymnasts and healthy nongymnasts. The proprioception testing device (PTD) was used to evaluate knee kinesthesia. From 45 degrees of flexion, the knee was passively extended with the PTD. The device was stopped by the subject when this passive motion was detected. Fifteen healthy college-age female gymnasts (mean age 19.3 years) and 30 normal volunteers (mean age 20.7 years) comprised our study sample. A one-way analysis of variance (ANOVA) was used to compare the mean values of the dominant gymnastic knee to the dominant knee in the control group. Results revealed statistically significant mean differences between the trained gymnastic group and the untrained control group (F1.34(.95) = 7.17, P = 0.011). The results of this study suggest that extensive training has a positive influence on knee kinesthesia in addition to increasing muscle tone. According to the findings of this and other studies, highly trained athletes possess enhanced neurosensory pathways which are speculated to develop as a result of long-term athletic training. Although definite conclusions cannot be made from our investigation, prospective studies can determine the true role of athletic training in proprioceptive patterns.

Proprioception and joint stability

In the present paper the current clinical knowledge about proprioception is given for the shoulder, knee, ankle, elbow and the radiocarpal joint. Proprioceptive capabilities are decreased after joint injuries such as ACL or meniscus tears, shoulder dislocation, ankle sprain and in joints with degenerative joint disease. Some surgical procedures seem to restore the proprioceptive abilities; others do not. Elastic knee bandages or ankle braces increase different proprioceptive factors like ankle reproduction capability or sports-specific abilities. The present information on proprioception will influence our clinical practice in the future. We should choose surgical procedures that not only reconstruct the anatomy, but also the neurophysiologic feed-back mechanism.

Prospects for gene therapy in sports medicine

For the orthopedic sports medicine physician soft tissue injuries often present the greatest clinical problems. Not only do many of the most frequently injured tissues, such as the cruciate ligaments and articular cartilage, have very limited capabilities for spontaneous repair, but they also respond poorly to surgical or nonsurgical intervention. In this article we try to define the role of growth factors in these conditions and to outline concepts for future treatment based upon modulation of the native repair response. We suggest that gene transfer could improve the management of such injuries, particularly when used as vehicles for the targeted delivery of growth factors. The concept of gene therapy in orthopedic sports medicine can be extended to include disorders that present as laxity or mechanical weakness of ligaments. We speculate that subtle genetic differences between individuals may account for those who appear to be injury prone. In these cases it is likely that genes encoding the structural macromolecules of the matrix are defective. Local gene supplementation in such cases could be useful in the future.

Occurrence and distribution of free nerve endings in the distal iliotibial tract system of the knee

Free nerve endings (FNE) are nociceptive sensory elements transmitting information on pain and inflammation from the connective tissues to the brain. They form an important part of the proprioceptive sensory system of the knee. We present a qualitative and quantitative analysis of FNEs in the distal iliotibial tract (ITT), documenting their occurrence in this structure as well as their specific distribution pattern. FNEs were found in all elements of the distal ITT, with their maximum density in the fixation sites of the distal ITT to the femur and the tibia. This finding correlates well with anatomical and biomechanical studies and stresses the importance of the deep ITT fibre system for lateral knee stability. The relative number of FNEs in the distal ITT ranges from 5 to 10 per 50 mm2 and is comparable to the frequency found in the synovial sheath of the cruciate ligaments. These findings have clinical implications for surgical procedures on the lateral side of the knee. The distinct anatomy of the distal ITT should be respected in all procedures, since extensive operations in this area may cause pain and loss of range-of-motion due to alterations of proprioceptive function.

Proprioception in the nearly extended knee. Measurements of position and movement in healthy individuals and in symptomatic anterior cruciate ligament injured patients

Proprioception of the knee was measured in 19 healthy individuals to evaluate whether there were any differences between extension and flexion movements from two different starting positions. The threshold before detecting a passive movement, visual estimation on a protractor of a passive change in position (30 degrees angular change) and active reproduction of the same angular change were registered. The reference population was tested twice to study normal variation and reproducibility, followed by the evaluation of 20 patients with chronic, symptomatic and unilateral anterior cruciate ligament (ACL)-deficient knees. In the normal population no differences were found between the right and the left leg, men and women, or measurements made at the first and at the second test occasion. The thresholds from a starting position of 20 degrees were lower for extension than for flexion. When comparing the thresholds for extension between the 20 degrees and the 40 degrees starting position, lower values were found in the more extended position. The thresholds for flexion were lower from the 40 degrees starting position than from the 20 degrees starting position. The active reproduction of an angular change of 30 degrees was more accurate during flexion (30 degrees-60 degrees) than during extension (60 degrees-30 degrees). There were no differences in the reproduction tests or in thresholds from the 40 degrees starting position between the patients and the normal group, but the patients had higher thresholds from the 20 degrees starting position, in movements towards both extension 1.0 degree (range 0.5 degree-12.0 degrees) and flexion 1.5 degrees (range 0.5 degree-10.0 degrees) than the normal group 0.75 degree (range 0.5 degree-2.25 degrees) (P = 0.01) and 1.0 degree (range 0.5 degree-3.0 degrees) (P = 0.06), respectively. Thus, information of passive movements in the nearly extended knee position was more sensitive towards extension than towards flexion in threshold tests and the sensitivity improved closer to full extension, which implies a logical joint protective purpose. In this nearly extended knee position, which is the basis for most weight-bearing activities, patients with symptomatic ACL-deficient knees had an impaired awareness in detecting a passive movement. There were no differences in the more flexed position or in the reproduction tests between the patients and the normal group, and reproduction tests in the present form seem less appropriate to use in the evaluation of ACL injuries.

Proprioceptive function of the shoulder girdle in healthy volunteers

In 27 healthy volunteers (9 females, 18 males) we evaluated the proprioceptive function of the glenohumeral joint. The volunteers were asked to place the arm in different positions with and without visual control. The test was performed for the dominant and for the nondominant extremity. The following joint positions were measured: 50 degrees, 100 degrees, 150 degrees abduction; 50 degrees, 100 degrees, 150 degrees flexion; +45 degrees, 0 degrees, -45 degrees rotation in 90 degrees abduction. Joint position was documented with a motion-analyzing system with passive reflecting markers. The results showed significant differences between the measurements with and without visual control. Proprioception was worse below the shoulder level (50 degrees abduction, flexion). Two volunteers with generally good coordinative capabilities showed better results than the rest of the group. We observed no differences between dominant and nondominant extremities nor between males and females. Our results demonstrated low variance of the proprioceptive function of the glenohumeral joint in healthy volunteers. Our findings serve as a base for further evaluations in different patients' populations.

Knee joint proprioception in normal volunteers and patients with anterior cruciate ligament tears, taking special account of the effect of a knee bandage

Proprioception of the knee joint was tested in 30 healthy volunteers with clinically inconspicuous knee joints. To examine proprioception, an angle reproduction test was performed. We could not document any differences between the left and the right knee joint or between men and women. At the mid-range, proprioception was worse compared with the end range of motion. In addition, 25 patients with an isolated rupture of the anterior cruciate ligament were evaluated, 14 before and 11 after operative anterior cruciate ligament (ACL) reconstruction. Preoperatively, there was a significant deterioration of proprioception compared with the control group. We were able to show a positive influence of a knee bandage on the proprioception of the injured knee. Patients after ACL reconstruction showed no significantly better proprioception compared with the preoperative group.

Electromyography and biomechanics of a dynamic knee brace for anterior cruciate ligament deficiency

Twelve anterior cruciate ligament (ACL)-deficient subjects performed concentric isokinetic knee extensions at maximum effort both with and without the Bledsoe Pro Shifter knee brace. Electromyogram signals from the quadriceps, hamstrings, knee angle, and the extension force were recorded and evaluated to determine the effects of such dynamic bracing on muscle activity and joint stability. High activity, or asymptomatic, subjects (n = 5) experienced no change in muscle activity, but displayed a decrease in extension force throughout the active range of the brace. Low activity, or symptomatic, subjects (n = 7) exhibited increased quadriceps activity and decreased hamstrings activity, and displayed a minor increase in force in the mid-range (80 degrees to 40 degrees flexion). These results indicate that dynamic bracing prevents quadriceps inhibition in symptomatic subjects by exerting a posteriorly directed force to the superior tibia; thus, the brace compensates externally for the absence of the ACL.

Effects of an accelerated rehabilitation program after anterior cruciate ligament reconstruction with combined semitendinosus-gracilis autograft and a ligament augmentation device

Forty patients with anterior cruciate reconstructions using semitendinosus and gracilis autografts and a ligament augmentation device were reviewed at a minimum of 20 months postoperatively to determine if an accelerated rehabilitation program was detrimental to intermediate follow-up results. The rehabilitation program included immediate full weightbearing, using crutches as aids for 2 weeks only, and a Generation II rehabilitation brace set at full range of motion for 2 weeks followed at 2 weeks by bicycle riding and strengthening exercises. Return to sports was allowed at 4 months for nonpivoting sports and at 6 months for level 1 sports involving pivoting. Thirty-seven patients were available for followup. At followup, three grafts were determined to be nonfunctional (KT-1000 arthrometer testing indicating > 4 mm of side-to-side difference). The other 34 patients had good or excellent results, with all returning to their preinjury levels of sport with a brace. Early accelerated rehabilitation after anterior cruciate ligament reconstruction with semitendinosus and gracilis tendon autograft and a ligament augmentation device does not seem to affect the results adversely. Results in this series were as good as or better than other series using the same reconstructive technique.

Comparison of Open versus Closed Kinetic Chain Test Positions for Measuring Joint Position Sense

The purpose of this study was to determine if a difference exists in the reproducibility of knee joint flexion angles in an open versus a closed kinetic chain. Thirty generally healthy subjects (12 males, 18 females; mean age 23.8 years) participated. Subjects actively reproduced small, medium, and large knee flexion angles (with target angles of 15°, 45°, and 75°, respectively) in an open and a closed kinetic chain while being videotaped. Goniometric measurements were taken from the videotape of initial and reproduced joint angles. Data were analyzed using ANOVA with repeated measures on kinetic chain test position and joint angle. Subjects more accurately reproduced knee flexion angles in a closed kinetic chain position. The main effect for angle and the interaction of angle and test position were nonsignificant. The results indicate that knee joint position is more accurately reproduced in closed kinetic chain. Closed kinetic chain testing is also a more functional assessment of joint position sense, and thus closed kinetic chain assessment of lower extremity joint position sense is recommended.

The contributions of proprioceptive deficits, muscle function, and anatomic laxity to functional instability of the ankle

Functional instability is a common complication following an acute ankle sprain. Three potential contributing factors underlying the ankle which chronically gives way are proprioceptive deficits, muscle weakness, and ligamentous laxity. This study's purpose was to document the presence or absence of these concerns in a sample of subjects with unilateral functional ankle instability. Both ankles of 42 subjects were randomly assessed for passive movement sense into inversion and generation of peak torque by the evertors isokinetically. Thirty-four subjects were available for documentation of talar tilt of both ankles through inversion stress radiographs. Analysis found significantly greater mean values for passive movement sense and talar tilt for the involved ankles compared with the uninvolved, while no significant strength differences in peak torque of the evertors were present. Fifty-eight percent of the sample demonstrated clinical impairments in at least one of these three categories. In conclusion, deficits in passive movement sense and anatomic stability are greater concerns than strength deficits when managing the ankle with functional instability.

The effect of elastic bandages on human knee proprioception in the uninjured population

Elastic bandages are often used to treat musculoskeletal disorders, even though there is little scientific evidence currently to support this generalized practice. We tested the hypothesis that elastic bandages improve proprioception of the bandaged joint during their use, and that this benefit was more than temporary. The uninjured human knee was used as a model. Fifty-four volunteers (54 knees), aged 22 to 40 years, were asked to identify a prior set joint angle as their knee was passively extended. Each knee was tested without the elastic bandage, immediately after bandage application, after 1 hour of bandage wear, and finally after removal of the bandage. Results showed that elastic bandages significantly improved knee joint proprioception in the uninjured knee during the entire interval of their use (mean decrease in inaccuracy of 1.0 degree, equivalent to 25% improvement, P < 0.05), and that this benefit was lost when the bandage was removed. The magnitude of the improvement, or the potential beneficial effect of the bandage, was inversely related to the participant's inherent knee proprioceptive ability, which was demonstrated in the test group before the initial application of the bandage.

Proprioception of the shoulder joint in healthy, unstable, and surgically repaired shoulders

Shoulder proprioception was measured in 90 subjects who were assigned to three experimental groups: group 1 (n = 40), healthy college-age subjects; group 2 (n = 30), patients with anterior instability; and group 3 (n = 20), patients who have had surgical reconstruction. Kinesthesia and joint position sense were measured with a specially designed proprioception testing device. The results revealed no significant differences in proprioception between dominant and nondominont shoulders in group 1 for any test condition. Significant differences (p < 0.05) were revealed between the unstable and uninvolved shoulder for both kinesthesia and joint position sense in group 2. No significant mean differences were revealed between the surgical and contralaterol shoulder in group 3 under any test condition. This series of studies provides evidence that proprioceptive deficits caused by partial deafferentiation result when copsuloligomentous structures are damaged. Reconstructive surgery appears to restore some of these proprioception characteristics.

The relationship between subjective knee scores, isokinetic testing, and functional testing in the ACL-reconstructed knee

It is important to examine the functional relationships between commonly performed clinical tests and to resolve inconsistencies in previous investigative results. The purpose of this study was to determine if a correlation exists between three commonly performed clinical tests: isokinetic isolated knee concentric muscular testing, the single-leg hop test, and the subjective knee score in anterior cruciate ligament reconstructed knees. To determine if a relationship exists would be beneficial to clinicians in determining patient progression, treatment modification, and return-to-sport objective parameters. Several investigators have analyzed two of these parameters, but no one has investigated three parameters to date. Additionally, this study explored the concept of limb acceleration and deceleration during high-speed isokinetics and its relationship to function. Fifty patients were randomly selected (29 males) with a mean age of 23.7 years (range 15-52). The subjects completed a subjective knee score questionnaire that rated symptoms (pain, swelling, giving way) and specific sport function and completed an overall knee score assessment. The patients were then evaluated performing three one-legged functional tests: 1) hop for distance, 2) timed hop, and 3) cross-over triple hop. Isokinetic testing was performed on a Biodex dynamometer at 180, 300, and 450 degrees/sec for knee extension/flexion. The patients' mean value of the self-assessed knee rating was 86 points. Sixty-four percent of the patients exhibited normal limb symmetry (within 85%) on all three single-leg hop tests. Sixteen percent exhibited quadriceps strength at least 90% of the contralateral limb isokinetically. A positive correlation was noted between isokinetic knee extension peak torque (180, 300 degrees/sec) and subjective knee scores, and the three hop tests (p < 0.001). A statistical trend was noted between knee extension acceleration and deceleration range at 180 and 300 degrees/sec for the timed hop test and triple cross-over hop (r = 0.48, r = 0.49, r = 0.51, r = 0.49). No positive correlations were found for isokinetic test results for the knee flexors.

Injury and proprioception in the lower back

No known research has attempted to quantify proprioception of the lower back or to examine the relationship between injury and proprioception in this region. The primary purpose of this study was to explore relationships between low back injury and proprioception of the lower back. Subjects were 88 working male firefighters from public emergency medical service departments. Three types of lower back proprioception (passive motion threshold, directional motion perception, and repositioning accuracy) were tested. Each type of proprioception was examined in the three primary planes of motion using a device designed by the author. Some anthropometric and personal variables were statistically controlled. All variables underwent multiple correlation analysis. The primary findings were: 1) longevity factors [age (r = .30, p < .01) and years of experience (r = .35, p < .001)] were best correlated with proprioceptive deficits in the sagittal plane; 2) injuries were correlated (p < .05) with proprioceptive deficits in the coronal (r = .22) and sagittal planes (r = .17) and with deficits in multiple planes (r = .19); 3) proprioceptive asymmetries were associated with injuries; and 4) the factor most highly correlated with the history of low back injuries was the presence of a spinal disorder (r = .40, p < .001). Impaired proprioception resulting from injury may degrade lumbar motor function, increasing workers' risk of reinjury. Restoring proprioception of the lumbar spine after injury should be a goal of treatment.

Reflex inhibition of the quadriceps femoris muscle after injury or reconstruction of the anterior cruciate ligament

A burst-superimposition technique was used to assess the strength of the quadriceps femoris muscle in three groups of patients. Group 1 comprised twenty patients who had had a torn anterior cruciate ligament of the knee and had a reconstruction of the ligament one to six months after the injury. Group 2 comprised twelve patients who had had a torn anterior cruciate ligament for an average of three months (a subacute tear). Group 3 comprised eight patients who had had a torn anterior cruciate ligament for an average of two years (a chronic tear). The patients in Groups 2 and 3 had not had an operation for the torn ligament. The patients in Groups 1 and 3 had no evidence of failure of activation of the involved quadriceps, but nine of the twelve patients in Group 2 had reflex inhibition of contraction of the muscle.

Reflex hamstring contraction latency in anterior cruciate ligament deficiency

Decreased dynamic stability of the knee joint associated with functional disability is a feature of anterior cruciate ligament deficiency (ACLD). The purposes of this study were to examine the between-limbs difference in reflex contraction latency of the hamstring muscles in patients with unilateral ACLD and to investigate its relationship with instability and function. Fifty patients with arthroscopically diagnosed unilateral ACLD were measured bilaterally for reflex hamstring contraction latency (RHCL), and 20 normal volunteers were similarly tested. The subjects were measured in a position of single-limb full weight-bearing with the knee flexed 30 degrees. An anteriorly directed shear force was applied to the tibia, and surface electromyographs (EMGs) recorded the activity of the hamstrings in response to the applied force. The latency of contraction was defined as the time from initial tibial movement, identified by accelerometry, to the onset of increased hamstring EMG activity. Both legs were tested and a between-limbs difference was computed. A significant difference in RHCL was found between the limb with ACLD and the control limb. The mean RHCL of the limb with ACLD was nearly double that of the unaffected limb, for a significant mean between-limbs difference (p < 0.05). The mean between-limbs difference for the control subjects was not statistically significant. The conclusion is that patients with ACLD have an increased RHCL of the injured leg. As the RHCL is dependent on proprioceptive activity around the joint, it can be used as a measure of proprioceptive ability. The loss of the neurophysiological protective reflex involving the anterior cruciate ligament and hamstrings in patients with ACLD is likely to be a contributory factor in the decreased joint stability experienced by these patients.

Neuromuscular performance in normal and anterior cruciate ligament-deficient lower extremities

The neuromuscular function of the lower extremity in 40 normal and 100 anterior cruciate ligament-deficient volunteers was evaluated by physical examination, KT-1000 arthrometer measurements, isokinetic strength and endurance testing, subjective functional assessment, and an anterior tibial translation stress test. A specially designed apparatus delivered an anteriorly directed step force to the posterior aspect of the leg while anterior tibial translation was monitored and electromyographic signals were recorded at the medial and lateral quadriceps, medial and lateral hamstrings, and gastrocnemius muscles. Testing was done at 30 degrees of knee flexion with the foot fixed to a scale to monitor weightbearing, while the tibia remained unconstrained. Results indicate that muscle timing and recruitment order in response to anterior tibial translation are affected by anterior cruciate ligament injury. These alterations in muscle performance change with time from injury, correlate with an individual's physical activity level, affect subjective functional parameters, and are directly related to the degree of dynamic anterior tibial laxity seen with stress testing.

Effect of reconstruction of the anterior cruciate ligament on proprioception of the knee and the heel strike transient

Abnormal proprioception of the knee joint has been documented after rupture of the anterior cruciate ligament (ACL) and may result in the loss of muscular reflexes. Excessive loading from the lack of muscular control may predispose the joint to osteoarthrosis. To investigate this problem, 10 patients were studied at an average of 31.6 months after ACL reconstruction. Three tests of joint proprioception and measurements of the vertical component of heel strike force during normal gait were used. A normal control group also was studied. For two of the proprioception tests (reproduction of passive motion and relative reproduction), there were no statistical differences among the uninjured (control) limbs, the normal contralateral limb of patients with a reconstructed ACL, and the extremity with a reconstructed ACL. In the third test (threshold of detection of motion), which previously has been shown to be adversely affected by ACL injury, the measurements for both extremities of patients with a reconstructed ACL were more accurate than those for the control group. The reconstructed extremity performed less accurately than the contralateral extremity (p < 0.05). The heel strike transient (vertical component of ground reaction force at heel strike) for uninjured and ACL-reconstructed limbs was not significantly different. In fact, the extremity with the reconstructed ACL had a lower transient than the uninjured extremity. Heel strike transients in patients with a reconstructed ACL were higher than those in the controls, but the differences were significant only when corrected for velocity of gait.(ABSTRACT TRUNCATED AT 250 WORDS)

Intraarticular anterior cruciate ligament reconstruction in the symptomatic arthritic knee

We reviewed a consecutive series of young symptomatic patients with chronic anterior cruciate ligament-deficient knees to determine if an autogenous patellar tendon graft reconstruction decreased their symptoms and increased the stability of the knee. All patients had radiographic evidence of posttraumatic arthritis. Thirty-three patients met our criteria for inclusion in the study. Time from injury to reconstruction of the anterior cruciate ligament averaged 105 months. All patients underwent an accelerated rehabilitation program designed to help them regain full range of motion as soon as possible. Preoperative and postoperative range of motion, strength, stability, and subjective evaluations were compared. Followup averaged 44.8 months. Follow-up range of motion was not significantly different from preoperative measurements (P = 0.51). Postoperative stability, as measured by KT-1000 arthrometer maximum manual test, averaged 2.7 mm versus 8.4 mm preoperatively (P < 0.001). Isokinetic testing revealed no difference in the quadriceps strength after reconstruction (P = 0.99). Patients' subjective scores on a modified Noyes questionnaire improved for pain, stability, and activity level, with a total improvement from 55 to 81 points. Although the procedure and rehabilitation were successful in providing stability and decreasing pain, patients were still encouraged to limit high-impact athletic and occupational activity.

Comparison of symptomatic versus nonsymptomatic patients with chronic anterior cruciate ligament insufficiency. Radiographic sagittal displacement during weightbearing

The sagittal anterior displacement of the tibia, induced by weightbearing, in chronic anterior cruciate ligament-insufficient knees was measured radiographically in 2 groups of patients. All patients in both groups had an increased laxity when assessed with the Lachman and flexion-rotation-drawer test. Sixteen patients were functionally improved and were relatively asymptomatic after a neuromuscular rehabilitation program, while the second group consisted of another 16 patients with persistent functional instability, despite the same rehabilitation program, who eventually had ligament reconstruction. The mean radiographic anterior displacement during weightbearing in the nonsymptomatic group was 4.3 mm, and 8 patients had a displacement < or = 2 mm. In the symptomatic group, the corresponding value was 8.1 mm (P < 0.05), and 3 patients had a displacement < or = 2 mm. No correlations to meniscal injuries, age, or time from injury were found between the patients having a displacement >2 mm and those with < or = 2 mm. The findings should be explained by differences in neuromuscular control of the increased laxity in the injured knee.