Calcitonin gene related peptide and neuropeptide Y in skeletal muscle after eccentric exercise: a microdialysis study.

OBJECTIVES: To detect neuropeptides in human skeletal muscle at rest and after eccentric exercise. METHOD: Eight healthy subjects participated in the study. Microdialysis of the distal part of the vastus lateralis of the quadriceps muscle and pain evaluation were performed immediately after eccentric exercise, after two days, and at rest. Calcitonin gene related peptide (CGRP) and neuropeptide Y (NPY), representatives of the sensory and autonomic nervous system, were analysed by radioimmunoassay. RESULTS: Overall, the measured concentrations were low, some even below the limit of detection. At rest, CGRP was detected in two of seven samples, but after eccentric exercise it was detected in 27 of 30 samples. At rest, all NPY concentrations were below the limit of detection, but after exercise it was found in six of 30 samples. CONCLUSION: The significant increase in detectability of CGRP after eccentric exercise may be related to the increased experience of pain. Therefore the occurrence of CGRP after heavy eccentric exercise may be associated with the regulation of delayed onset muscle soreness and possibly also the stimulation of tissue regeneration.

Ankle ligament injury risk factors: a prospective study of college athletes.

Over two million individuals suffer ankle ligament trauma each year in the United States, more than half of these injuries are severe ligament sprains; however, very little is known about the factors that predispose individuals to these injuries. The purpose of this study was to determine the risk factors associated with ankle injury. We performed a prospective study of 118 Division I collegiate athletes who participated in soccer, lacrosse, or field hockey. Prior to the start of the athletic season, potential ankle injury risk factors were measured, subjects were monitored during the athletic season, and injuries documented. The number of ankle injuries per 1,000 person-days of exposure to sports was 1.6 for the men and 2.2 for the women. There were 13 injuries among the 68 women (19%) and seven injuries among the 50 men (13%), but these proportions were not significantly different. Women who played soccer had a higher incidence of ankle injury than those who played field hockey or lacrosse. Among men, there was no relationship between type of sport and incidence of injury. Factors associated with ankle ligament injury differ for men relative to women. Women with increased tibial varum and calcaneal eversion range of motion are at greater risk of suffering ankle ligament trauma, while men with increased talar tilt are at greater risk. Generalized joint laxity, strength, postural stability, and muscle reaction time were unrelated to injury.

The elongation behavior of the anterior cruciate ligament graft in vivo. A long-term follow-up study.

The relationship between the elongation values of an autogenous bone-patellar tendon-bone graft immediately after fixation and the anterior-posterior laxity of the knee 5 years later was studied in vivo. Immediately after fixation, the change in the graft midsubstance length during passive knee flexion-extension was measured using a Hall-effect transducer, and anterior-posterior knee laxity was measured with the KT-1000 arthrometer. Subjects were divided into group 1 (N = 6), with graft elongation values bounded by the 95% confidence intervals of the normal anterior cruciate ligament elongation values, and group 2 (N = 7), subjects with values outside these intervals. Immediately after reconstruction, the side-to-side difference in anterior-posterior laxity between the reconstructed and uninjured knees was not different between group 1 (-2.6 +/- 0.7 mm, mean +/- SEM) and group 2 (-1.7 +/- 1.0 mm) (P = 0.49). At 5-year follow-up, the difference was 1.2 +/- 0.7 mm for group 1, while for group 2 it was significantly greater at 4.7 +/- 0.6 mm (P = 0.004). At surgery, graft elongation values produced by flexion of the knee that are outside the limits of the anterior cruciate ligament result in significant increases in anterior knee laxity at long-term follow-up, while grafts with elongation values similar to the normal anterior cruciate ligament do not. Not only is restoration of anterior-posterior laxity values to within normal limits important, but the biomechanical behavior of the graft produced by flexion-extension of the knee should be appreciated.

The effect of weightbearing and external loading on anterior cruciate ligament strain.

A force balance between the ligaments, articular contact, muscles and body weight maintains knee joint stability. Thus, it is important to study anterior cruciate ligament (ACL) biomechanics, in vivo, under weightbearing conditions. Our objective was to compare the ACL strain response under weightbearing and non-weightbearing conditions and in combination with three externally applied loadings: (1) anterior-posterior shear forces, (2) internal-external torques, and (3) varus-valgus moments. A strain transducer was implanted on the ACL of 11 subjects. All joint loadings were performed with the knee at 20 degrees of flexion. A significant increase in ACL strain was observed as the knee made the transition from non-weightbearing to weightbearing. During anterior shear loading, the strain values produced during weightbearing were greater than those of the non-weightbearing knee (shear loads <40N). At higher shear loads, the strain values became equal. During axial torsion, an internal torque of 10Nm strained the ACL when the knee was non-weightbearing while an equivalent external torque did not. Weightbearing significantly increased ACL strain values in comparison to non-weightbearing with the application of external torques and low internal torques (<3Nm). The strains became equal for higher internal torques. For V-V loading, the ACL was not strained in the non-weightbearing knee. However, weightbearing increased the ACL strain values over the range of moments tested. These data have important clinical ramifications in the development of rehabilitation protocols following ACL reconstruction since weightbearing has been previously thought to provide a protective mechanism to the healing graft.

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

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

The influence of functional knee bracing on the anterior cruciate ligament strain biomechanics in weightbearing and nonweightbearing knees.

Functional knee braces are commonly prescribed after anterior cruciate ligament injury or reconstruction; however, their ability to protect the ligament, or graft, remains unclear. Our objective was to evaluate the anterior cruciate ligament strain response in braced and unbraced knees during weightbearing and nonweightbearing in combination with three externally applied loads: 1) anterior-posterior shear forces, 2) internal-external torques, and 3) varus-valgus moments. The Legend brace was tested. All external loads were applied to the tibia with the knee flexed to 20 degrees. Reproducible data were obtained from 11 subjects. For anterior shear loads up to 130 N, the brace significantly reduced strain values compared with the unbraced knee during nonweightbearing and weightbearing conditions. For internal torques of the tibia (up to 9 N x m), strain in the braced knee was significantly less than in the unbraced knee when the knee was nonweightbearing only. The brace did not reduce strain values when the knee was subjected to external torques (9 N x m) or varus-valgus moments (10 N x m) in weightbearing and nonweightbearing knees. These data indicate that a functional knee brace can protect the anterior cruciate ligament during anterior-posterior shear loading in the nonweightbearing and weightbearing knee and during internal torques in the nonweightbearing knee.

The benefit of a single-leg strength training program for the muscles around the untrained ankle.

Severe ankle injuries can require extended periods of immobilization that adversely affect the strength of the ankle muscles. We have investigated a single-leg strength training program of the muscles surrounding the ankle to determine if it produces a crossover benefit for the contralateral ankle muscles. Twenty subjects without any history of ankle injuries were randomly divided into a control and a training group. Both groups underwent isokinetic testing of the ankle muscles at the beginning and end of an 8-week period. The control group maintained normal activities between the tests. Half of the training group trained the dominant leg only and the other half trained the nondominant leg only for the 8-week period, three times per week. The subjects who trained the dominant leg improved peak torque values by 8.5% in the trained leg and 1.5% in the untrained leg. Similarly, the subjects who trained the nondominant leg improved peak torque values by 9.3% in the trained leg and 3.5% in the untrained leg. In contrast, the control group showed no significant change in peak torque, power, or endurance between the initial and final tests. With improvements in peak torque as high as 40% in the trained leg and a crossover benefit of 19% in the untrained leg in eccentric inversion, this strength training technique deserves further investigation in an injured population where the benefits may be more substantial.

Groin injuries in sport: treatment strategies.

Groin pain in athletes is a common problem that can result in significant amounts of missed playing time. Many of the problems are related to the musculoskeletal system, but care must be taken not to overlook other more serious and potentially life threatening medical cases of pelvis and groin pain. Stress fractures of the bones of the pelvis occur, particularly after a sudden increase in the intensity of training. Most of these stress fractures will heal with rest, but femoral neck stress fractures can potentially lead to more serious problems, and require closer evaluation and sometimes surgical treatment. Avulsion fractures of the apophyses occur through the relatively weaker growth plate in adolescents. Most of these will heal with a graduated physical therapy programme and do not need surgery. Osteitis pubis is characterised by sclerosis and bony changes about the pubic symphysis. This is a self-limiting disease that can take several months to resolve. Corticosteroid injection can sometimes hasten the rehabilitation process. Sports hernias can cause prolonged groin pain, and provide a difficult diagnostic dilemma. In athletes with prolonged groin pain, with increased pain during valsalva manoeuvres and tenderness along the posterior inguinal wall and external canal, an insidious sports hernia should be considered. In cases of true sports hernia, treatment is by surgical reinforcement of the inguinal wall. Nerve compression can occur to the nerves supplying the groin. In cases that do not respond to desensitisation measures, neurolysis can relieve the pain. Adductor strains are common problems in kicking sports such as soccer. The majority of these are incomplete muscle tendon tears that occur just adjacent to, the musculotendinous junction. Most of these will respond to a graduated stretching and strengthening programme, but these can sometimes take a long time to completely heal. Patience is the key to obtain complete healing, because a return to sports too early can lead to chronic pain, which becomes increasingly difficult to treat. Management of groin injuries can be challenging, and diagnosis can be difficult because of the degree of overlap of symptoms between the different problems. By careful history and clinical examination, with judicious use of special tests and good team work, a correct diagnosis can be obtained.

[Anterior cruciate ligament injuries--still an enormous challenge. Life style-related surgery likely to be used more widely]. / Främre korsbandsskador i knäleden--fortfarande en stor utmaning. "Livsstilskirurgi" som kan förväntas få ökad omfattning.

Anterior cruciate ligament (ACL) injuries still constitute the greatest single problem in orthopaedic sports medicine. The natural history is not well known. Conservative treatment is appropriate in cases where there are no instability problems, and where activity modifications are acceptable to the patient. However, there is an increased risk of meniscus and cartilage injuries, and thus of arthrosis. The indication for surgery depends on the level of activity, and on whether instability symptoms are present. Arthroscopic surgery of the ACL seems to yield good short-term results in 80-90 per cent of cases. Out-patient ACL surgery is becoming increasingly common. Rehabilitation is often vigorous, with early mobilisation and weight-bearing. Functional range-of-motion and closed kinetic chain exercises predominate. Successful surgical outcome often allows former levels of activity to be resumed. There is still uncertainty as to whether surgery reduces the risk of arthrosis. The nature of the original trauma, and continued top level sports activity may be factors of importance. Further research is needed to elucidate the natural history, and determine the long-term effects of modern ACL surgery.

Joint position sense is not changed after acute disruption of the anterior cruciate ligament.

We evaluated the impact of acute, isolated ACL disruption on knee joint proprioception by means of passive-active and active-active joint position sense (JPS) measurement techniques. 18 subjects with acute, isolated and unilateral ACL disruption were tested for JPS in a standing position. The test protocol included 6 trials for each leg. In each trial, the lower leg was passively positioned to an index angle approximating either 30 degrees or 70 degrees, followed by 5 active repetitions of the index angle where the subjects attempted to reproduce the index angle to the best of their ability. The errors from the exact index angle reproduction were calculated as both real (showing both magnitude and direction) and absolute values (only magnitude). All subjects had a tendency to reproduce the index angle with both the injured and normal knees in a more flexed position (overestimation). Only the absolute error produced by the active-active test at flexion angles greater than 45 degrees produced a significant difference with a larger error for the normal knee. In all other comparisons between the injured and the normal knee no differences were found. We conclude that the afferent signals which are compromised by an acute tear of the ACL are insignificant compared to afferent signals from the other joint and muscle receptors.

Repair of distal biceps tendon rupture with suture anchors.

We retrospectively evaluated six cases of distal biceps tendon rupture that were treated by a two-incision operative repair using suture anchor attachment to the radial tuberosity for clinical outcome and strength testing. All patients had repair performed by the same surgeon. The average age of the patients, all male, was 43 years (range, 32-57 years). Average time from injury to operative repair was 22 days (range, 9-54 days). Follow-up time averaged 24 months after definitive treatment (range, 11-46 months). At follow-up no patient had limitation of activity and all patients were able to return to their previous employment, although three noted some minor antecubital fossa discomfort. No patient developed a synostosis. Cybex (Medway, Mass.) isokinetic testing revealed elbow flexion strength return for peak torque, total work, and average power, of 107%, 103%, and 110% of the uninjured arm, respectively. Elbow flexion endurance was 2% less in the injured arm. Forearm supination strength measured by peak torque, total work, and average power, was 97%, 85%, and 88% of the uninjured arm, respectively. Forearm supination endurance was 10% less in the injured arm. Our results using suture anchor repair are similar to those previously reported in the literature from bone tunnel repair. Based on our data, we believe that a two-incision repair with suture anchor attachment is a safe and effective method for treatment of distal biceps tendon ruptures.

The strain behavior of the anterior cruciate ligament during stair climbing: an in vivo study.

Stair climbing is a closed kinetic chain exercise that is thought to be useful for knee rehabilitation following anterior cruciate ligament (ACL) reconstruction while protecting the graft from excessive strain. The objectives of this study were to measure the strain produced in the anteromedial band (AMB) of the normal ACL during stair climbing in vivo. We have previously shown that the normal AMB strain pattern during knee passive flexion-extension motion is similar to that of an ACL graft immediately after graft fixation. We successfully tested five subjects with normal ACLs, who were candidates for arthroscopic meniscectomy under local anesthesia. AMB strain was measured in vivo using the Differential Variable Reluctance Transducer (MicroStrain, Burlington, VT). The stair climbing activities were performed on a StairMaster 4000PT (Randall Sports Medicine, Kirkland, WA). Two different climbing cadences were evaluated; 80 and 112 steps per minute. Consistent with our previous studies of ACL biomechanics, strain values increased as the knee was moved from a flexed to an extended position. The mean peak AMB strain values for the 80 and 112 steps per minute conditions were 2.69% (+/-2.89&) and 2.76% (+/-2.68%), respectively. These values were not significantly different. Compared with other rehabilitation activities previously tested in the same manner, the AMB strain values produced during stair climbing were highly variable across subjects. High strain values were observed in some patients but not in others.

The effect of anterior cruciate ligament trauma and bracing on knee proprioception.

We studied the effect that chronic anterior cruciate ligament disruption, functional bracing, and a neoprene sleeve have on knee proprioception by measuring the threshold to detection of passive knee motion in all three conditions. The threshold to detection of passive knee motion was worse in knees with chronic anterior cruciate ligament insufficiency when compared with uninjured knees. This difference was small, on average an additional 0.28 degree of flexion-extension rotation was required for the anterior cruciate ligament-deficient knee before the subject detected motion, and of questionable significance from a clinical and functional perspective. Wearing a functional brace or neoprene sleeve on the anterior cruciate ligament-deficient knee did not significantly change the threshold to detection of passive motion in comparison with the same knee without a brace, although improvements were observed. There was no relationship between the most common clinical means of characterizing altered biomechanics of the anterior cruciate ligament-deficient knee (that is, the magnitude of anterior-posterior knee laxity and the grade of pivot shift) and the threshold to detection of passive knee motion.

Treatment of acute lateral ankle ligament rupture in the athlete. Conservative versus surgical treatment.

Acute lateral ankle ligament sprains are common in young athletes (15 to 35 years of age). Diagnostic and treatment protocols vary. Therapies range from cast immobilisation or acute surgical repair to functional rehabilitation. The lateral ligament complex includes 3 capsular ligaments: the anterior tibiofibular (ATFL), calcaneofibular (CFL) and posterior talofibular (PTFL) ligaments. Injuries typically occur during plantar flexion and inversion; the ATFL is most commonly torn. The CFL and the PTFL can also be injured and, after severe inversion, subtalar joint ligaments are also affected. Commonly, an athlete with a lateral ankle ligament sprain reports having 'rolled over' the outside of their ankle. The entire ankle and foot must be examined to ensure there are no other injuries. Clinical stability tests for ligamentous disruption include the anterior drawer test of ATFL function and inversion tilt test of both ATFL and CFL function. Radiographs may rule out treatable fractures in severe injuries or when pain or tenderness are not associated with lateral ligaments. Stress radiographs do not affect treatment. Ankle sprains are classified from grades I to III (mild, moderate or severe). Grade I and II injuries recover quickly with nonoperative management. A non-operative 'functional treatment' programme includes immediate use of RICE (rest, ice, compression, elevation), a short period of immobilisation and protection with a tape or bandage, and early range of motion, weight-bearing and neuromuscular training exercises. Proprioceptive training on a tilt board after 3 to 4 weeks helps improve balance and neuromuscular control of the ankle. Treatment for grade III injuries is more controversial. A comprehensive literature evaluation and meta-analysis showed that early functional treatment provided the fastest recovery of ankle mobility and earliest return to work and physical activity without affecting late mechanical stability. Functional treatment was complication-free, whereas surgery had serious, though infrequent, complications. Functional treatment produced no more sequelae than casting with or without surgical repair. Secondary surgical repair, even years after an injury, has results comparable to those of primary repair, so even competitive athletes can receive initial conservative treatment. Sequelae of lateral ligament injuries are common. After conservative or surgical treatment, 10 to 30% of patients have chronic symptoms, including persistent synovitis or tendinitis, ankle stiffness, swelling, pain, muscle weakness and 'giving-way'. Well-designed physical therapy programmes usually reduce instability. For individuals with chronic instability refractory to conservative measures, surgery may be needed. Subtalar instability should be carefully evaluated when considering surgery.

Anatomy of the proximal musculotendinous junction of the adductor longus muscle.

Injuries to the adductor longus commonly occur in the proximal part of the muscle tendon unit, close to the insertion site on the pubic bone. Ultrasonography, magnetic resonance imaging (MRI) and surgery have been helpful in localising the lesions, but the exact anatomy of the musculotendinous junction (MTJ) and insertion of the muscle remain unclear. We studied the anatomical features of the MTJ and measured the dimensions of the tendinous insertion into the pubic bone on 37 cadavers: 18 men and 19 women. The medial boundaries were the longest part of the tendon bilaterally in women, while the lateral aspect of the left muscle was greater in men. Tendinous fibres were predominantly found on the anterior surface, while the posterior surface consisted mainly of muscle tissue. The MTJ was clearly demarcated. There were several types of anomalies present which partially explains the difficulty in localising the site of injury and highlights the importance of individualized treatment.

The strain behavior of the anterior cruciate ligament during bicycling. An in vivo study.

Stationary bicycling is commonly prescribed after anterior cruciate ligament injury or reconstruction; however, the strains on the ligament or ligament graft during stationary bicycling remain unknown. In this study we measured ligament strain on eight patients who were candidates for arthroscopic meniscectomy under local anesthesia. Six different riding conditions were evaluated: three power levels (75, 125, and 175 W), each of which was performed at two cadences (60 and 90 rpm). The peak ligament strain values ranged from 1.2% for the 175-W, 90-rpm, condition to 2.1% for the 125-W, 60-rpm, condition. No significant differences were found in peak strain values due to changes in power level or cadence. Thus, the strain values were pooled across the six riding conditions tested. The mean peak strain value was 1.7%, a value that is relatively low compared with other rehabilitation activities previously tested. These data suggest that knee rehabilitation programs can be designed to include this selection of power and cadence levels without significantly changing ligament strain values. Thus, stationary bicycling is a rehabilitation exercise that permits the patient to increase muscle activity by increasing the power level or decreasing the cadence without subjecting the ligament or ligament graft to higher strain values.

How can injuries be prevented in the World Cup soccer athlete?

In order to prevent soccer injuries, different risk factors have to be identified as intrinsic (e.g., joint stability or muscle imbalance) and extrinsic (e.g., equipment, turf, and rules risk factors). Some preventive measures are discussed in this article, such as shin guards, prophylactic braces and taping (or both), and proprioceptive training.

The strain behavior of the anterior cruciate ligament during squatting and active flexion-extension. A comparison of an open and a closed kinetic chain exercise.

The effects of weightbearing (closed kinetic chain) and nonweightbearing (open kinetic chain) exercises on the biomechanical behavior of an injured anterior cruciate ligament or a healing anterior cruciate ligament graft are unknown. To understand the effects of these exercises on the healing graft, we measured the strain behavior of the normal anterior cruciate ligament in human subjects while they performed squatting, a closed kinetic chain exercise, and active flexion-extension of the leg, an open kinetic chain exercise. The maximum anterior cruciate ligament strain values obtained during squatting did not differ from those obtained during active flexion-extension. Also, anterior cruciate ligament strain values obtained during squatting were unaffected by the application of elastic resistance intended to increase muscle activity. These findings indicate that squatting, which produces a substantial compressive joint force, does not necessarily protect the anterior cruciate ligament more than active flexion-extension of the leg, which is characterized primarily by contraction of the dominant quadriceps muscle. These findings also demonstrate that increasing resistance during the squat exercise does not produce a significant increase in anterior cruciate ligament strain values, unlike increased resistance during active flexion-extension exercise.

Subtalar ankle instability. A review.

The aetiology of chronic functional lateral ankle instability is fairly well understood. Pathophysiological factors such as mechanical instability, proprioceptive deficit and peroneal muscle weakness have been demonstrated. Subtalar instability has been in focus during the last years as one of the possible factors behind chronic functional instability of the foot. The exact aetiology and the true incidence of subtalar ligament injuries remain unknown. Most subtalar ligamentous injuries probably occur in combination with injuries of the talo-tibial articulation. Subtalar instability can have the characteristics of chronic lateral instability or recurrent ankle sprains. Patients with chronic subtalar instability typically complain of 'giving way' symptoms and a history of recurrent sprains. Clinical examination including increased inwards rotation and forward displacement of the calcaneus may not be sufficient for the differentiation between ankle and subtalar instability. Radiographic imaging using stress radiographs may be necessary to assess subtalar instability. Subtalar instability can be defined as chronic functional instability with increased values of talar tilt and talo-calcaneal displacement as measured with standardised stress radiographs. Few authors have addressed the treatment of subtalar instability and the condition has not been clearly defined. Subtalar instability can be treated either with a tendon transfer or tenodesis procedure, such as the Chrisman-Snook or triligamentous tenodeses, or with an anatomic ligament reconstruction using the calcaneo-fibular, lateral talo-calcaneal and cervical ligaments combined with a reinforcement of the inferior extensor retinaculum. There have been no studies comparing anatomical and non-anatomical reconstructions and the long term results after ligamentous stabilisation are unknown. The focus of this article is on subtalar instability causing chronic functional ankle instability.

The effect of functional knee bracing on the anterior cruciate ligament in the weightbearing and nonweightbearing knee.

We investigated the effect of functional bracing on anterior cruciate ligament strain in humans by arthroscopic implantation of a differential variable reluctance transducer on the ligament and measurement of its strain behavior. Strains were measured while "injury mechanism" loads were applied to the weightbearing and nonweightbearing knees for both braced and unbraced conditions. For the unbraced knee, there was a significant increase in ligament strain values when subjects went from a seated position (minimal shear and compressive loads across the knee) to a standing posture (substantial shear and compressive loads across the knee). Similar strain values were found between these same seated and standing postures when a 140-N anterior-directed load was applied to the tibia. This indicates that the ligament is strained during weightbearing and demonstrates that the compressive load across the knee produced during weightbearing does not significantly reduce ligament strain values in comparison with the unweighted joint with relaxed muscles for the 140-N load limit of our anterior shear test. Bracing produced a protective effect on the ligament by significantly reducing the strain values for anterior-directed loading of the tibia up to 140 N with the knee in both weightbearing and nonweightbearing conditions. Likewise, bracing produced a protective effect on the ligament by significantly reducing strain values in response to internal-external torque of the tibia up to 6 N-m with the knee nonweightbearing. The brace strap that contacts the tibia just distal to the insertion of the patellar tendon was instrumented with a load sensor, allowing us to measure the posterior-directed loads applied by the brace to the tibia. Adjustment of strap tension between low and high settings did not modulate the protective effect of the brace on the ligament.