Injury risk factors in junior tennis players: a prospective 2-year study.

The aim was to investigate injury risk factors in junior tennis players. Fifty-five players, 35 boys and 20 girls, answered a questionnaire about training habits, time of exposure, previous injuries and equipment factors. A battery of clinical tests and functional performance tests were also carried out. All tennis-related injuries that occurred during a 2-year period were identified and recorded. An injury was defined as an injury if it was impossible to participate in regular tennis training or playing matches during at least one occasion, a time loss injury. Potential injury risk factors were tested in a forward stepwise logistic regression model for injury. Thirty-nine players sustained totally 100 new and recurrent injuries. Injuries to the lower extremity were the most common ones (51%) followed by the upper extremity (24%) and the trunk (24%). Injured players performed more singles per week (P<0.0001) and played more tennis hours per year (P=0.016) than the uninjured players. Playing tennis more than 6 h/week was found to be a risk factor for back pain. A previous injury regardless of location was identified as an injury risk factor, and a previous injury to the back was a risk factor for back pain.

Prolonged immobilization compromises up-regulation of repair genes after tendon rupture in a rat model.

It was hypothesized that mobilization vs immobilization after injury would promote tissue healing by regulating gene expression for molecules associated with repair. Cast immobilization vs free mobilization was studied after rat Achilles tendon rupture. Reverse transcriptase-polymerase chain reaction was performed at 8 and 17 days post-rupture to assess different growth factors [brain-derived neurotrophic factor (BDNF), basic fibroblast growth factor (bFGF), nerve growth factor (NGF) and insulin-like growth factor-1 (IGF-1)] and inflammatory mediators [cyclooxygenase 1 and 2 (COX 1 and COX 2), inducible nitric oxide synthase and hypoxia-inducible factor-1alpha (HIF-1alpha)] in the healing region. At 8 days post-injury, tendon mRNA levels were comparable in both groups. However, by day 17, the mRNA levels for BDNF, bFGF, COX 1 and HIF-1alpha in the mobilized group had increased significantly. Corresponding mRNA levels in the immobilized group decreased during the same period. There were no significant differences in the expression of NGF, IGF-1 or COX 2 between the different groups, indicating that injury-associated expression of these molecules is not overtly influenced by loading. This study supports the notion that prolonged immobilization post-rupture hampers the healing process by compromising the up-regulation of repair gene expression in the healing tendon. It might be speculated that a shorter period of immobilization, i.e. 1 week, would not impair the healing process significantly. The findings support the current development of earlier and more active rehabilitation programs after tendon injuries.

Consensus statement on epidemiological studies of medical conditions in tennis, April 2009.

BACKGROUND: The reported incidence, severity and nature of injuries sustained in tennis vary considerably between studies. While some of these variations can be explained by differences in sample populations and conditions, the main reasons are related to differences in definitions and methodologies employed in the studies. OBJECTIVE: This statement aims to review existing consensus statements for injury surveillance in other sports in order to establish definitions, methods and reporting procedures that are applicable to the specific requirements of tennis. DESIGN: The International Tennis Federation facilitated a meeting of 11 experts from seven countries representing a range of tennis stakeholders. Using a mixed methods consensus approach, key issues related to definitions, methodology and implementation were discussed and voted on by the group during a structured 1-day meeting. Following this meeting, two members of the group collaborated to produce a draft statement, based on the group discussions and voting outcomes. Three revisions were prepared and circulated for comment before the final consensus statement was produced. RESULTS: A definition of medical conditions (injuries and illnesses) that should be recorded in tennis epidemiological studies and criteria for recording the severity and nature of these conditions are proposed. Suggestions are made for recording players' baseline information together with recommendations on how medical conditions sustained during match play and training should be reported. CONCLUSIONS: The definitions and methodology proposed for recording injuries and illnesses sustained during tennis activities will lead to more consistent and comparable data being collected. The surveillance procedures presented here may also be applicable to other racket sports.

Postural control measured as the center of pressure excursion in young female gymnasts with low back pain or lower extremity injury.

Gymnasts are known to practice and compete although suffering from injuries and pain. Pain may change strategies for postural control. The primary aim of the present study was to investigate how center of pressure (COP) measurements are influenced by low back pain and lower extremity injury in top-level female gymnasts. A secondary aim was to study the reliability of these measurements using a test-retest design, and how this depends on the duration of the test. Fifty-seven top-level gymnasts were included in four groups: non-injured (NI, n=18), low back pain (LBP, n=11), lower extremity injury (LEI, n=17) and a multiple injury group (MI, n=11). COP excursion during quiet stance was measured on a force platform, during 120s: (1) hard surface/eyes open, (2) hard surface/eyes closed, (3) foam surface/eyes open and (4) foam surface/eyes closed. The COP excursion increased, for all groups, during the foam surface/eyes closed measurement compared to the other three tests. Furthermore, the LBP group showed a 49% (p=0.01) larger COP area compared to the LEI group in the foam surface/eyes closed condition. Measurements on foam surface were in general more reliable than tests on hard surface and tests with eyes closed were more reliable than tests with eyes open. Tests during 120s were in most cases more reliable than tests during 60s. In conclusion the COP excursion is influenced by injury location. Quiet stance measurements on foam surface with eyes closed seems to be reliable and sensitive in young female gymnasts.

Injury surveillance in multi-sport events: the International Olympic Committee approach.

BACKGROUND: The protection of athletes' health by preventing injuries is an important task for international sports federations. Standardised injury surveillance provides not only important epidemiological information, but also directions for injury prevention, and the opportunity for monitoring long-term changes in the frequency and circumstances of injury. Numerous studies have evaluated sports injuries during the season, but few have focused on injuries during major sport events such as World Championships, World Cups or the Olympic Games. OBJECTIVES: To provide an injury surveillance system for multi-sports tournaments, using the 2008 Olympic Games in Beijing as an example. METHODS: A group of experienced researchers reviewed existing injury report systems and developed a scientific sound and concise injury surveillance system for large multi-sport events. RESULTS: The injury report system for multi-sport events is based on an established system for team sports tournaments and has proved feasible for individual sports during the International Association of Athletics Federations World Championships in Athletics 2007. The most important principles and advantages of the system are comprehensive definition of injury, injury report by the physician responsible for the athlete, a single-page report of all injuries, and daily report irrespective of whether or not an injury occurred. Implementation of the injury surveillance system, all definitions, the report form, and the analysis of data are described in detail to enable other researchers to implement the injury surveillance system in any sports tournament. CONCLUSION: The injury surveillance system has been accepted by experienced team physicians and shown to be feasible for single-sport and multi-sport events. It can be modified depending on the specific objectives of a certain sport or research question; however, a standardised use of injury definition, report forms and methodology will ensure the comparability of results.

Non-contact ACL injuries in female athletes: an International Olympic Committee current concepts statement.

The incidence of anterior cruciate ligament (ACL) injury remains high in young athletes. Because female athletes have a much higher incidence of ACL injuries in sports such as basketball and team handball than male athletes, the IOC Medical Commission invited a multidisciplinary group of ACL expert clinicians and scientists to (1) review current evidence including data from the new Scandinavian ACL registries; (2) critically evaluate high-quality studies of injury mechanics; (3) consider the key elements of successful prevention programmes; (4) summarise clinical management including surgery and conservative management; and (5) identify areas for further research. Risk factors for female athletes suffering ACL injury include: (1) being in the preovulatory phase of the menstrual cycle compared with the postovulatory phase; (2) having decreased intercondylar notch width on plain radiography; and (3) developing increased knee abduction moment (a valgus intersegmental torque) during impact on landing. Well-designed injury prevention programmes reduce the risk of ACL for athletes, particularly women. These programmes attempt to alter dynamic loading of the tibiofemoral joint through neuromuscular and proprioceptive training. They emphasise proper landing and cutting techniques. This includes landing softly on the forefoot and rolling back to the rearfoot, engaging knee and hip flexion and, where possible, landing on two feet. Players are trained to avoid excessive dynamic valgus of the knee and to focus on the "knee over toe position" when cutting.

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.

Laxity and flexibility of the ankle following reconstruction with the Chrisman-Snook procedure.

The effect of reconstruction of the anterior talofibular ligament with the Chrisman-Snook procedure on neutral zone laxity (anterior-posterior displacement at low loads) and flexibility (a measure of the nonlinear load-displacement response) of the ankle was investigated in vitro during the anterior drawer test. Neutral zone laxity was defined as the magnitude of anterior-posterior displacement of the ankle joint at +/- 2.5 N of applied load. The flexibility parameter was defined as the slope of a line between the natural logarithm of the anterior load applied to the ankle and the resulting displacement. After reconstruction with the Chrisman-Snook procedure, the values for neutral zone laxity of the ankle were significantly less than normal at 0 degree of plantar flexion, whereas the flexibility values were significantly greater than normal. This study revealed that, after the Chrisman-Snook procedure, values for ankle flexibility are not restored to normal even if those for neutral zone laxity are reduced to less than normal. The findings suggest that this nonanatomical reconstruction procedure does not reproduce normal kinematics of the ankle joint. This may help explain some of the adverse clinical reports associated with the Chrisman-Snook reconstruction procedure.

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.

Biomechanical analysis of the ankle anterior drawer test for anterior talofibular ligament injuries.

The effect of sectioning the anterior talofibular ligament on the load-displacement behavior of the ankle was evaluated in vitro during the anterior drawer test using the flexibility approach. Controlled forces were applied across the ankle joint in the anterior-posterior direction, and the resulting displacements were measured at four flexion angles (10 degrees of dorsiflexion, neutral, and 10 degrees and 20 degrees of plantar flexion). The anterior talofibular ligament then was sectioned, and the anterior-posterior loadings were repeated at the four flexion angles. Two parameters were developed to describe the nonlinear load-displacement response of the ankle joint: neutral zone laxity (joint displacement between +/- 2.5 N) and flexibility (a measure of the nonlinear load-displacement response of the ankle between 10 and 50 N of anterior drawer loading). After sectioning the anterior talofibular ligament, significant increases in neutral zone laxity were observed at all angles of ankle flexion. The largest increases in neutral zone laxity were found with the ankle in 10 degrees of plantar flexion (76.3% increase) and 20 degrees of plantar flexion (89.7% increase). After sectioning the ligament, a significant increase (19.3%) in flexibility of the ankle was observed at 10 degrees of dorsiflexion, but no change in flexibility was observed with the ankle in the neutral and plantar flexed positions. These findings indicate that anterior drawer testing of the anterior talofibular ligament-deficient ankle between 10 degrees and 20 degrees of plantar flexion results in the largest increase in neutral zone laxity compared with the normal ankle with intact ligaments.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Determination of a zero strain reference for the anteromedial band of the anterior cruciate ligament.

The objective of this study was to verify a method previously used to determine a reference length for calculations of anterior cruciate ligament strain. In nine knee specimens, an arthroscopic force probe and a Hall effect transducer were placed in the anteromedial band of the ligament. Anteroposterior-directed shear loads then were applied to the knee joint with the knee flexed to 30 degrees. From the sigmoidal curve for shear load versus displacement of the anterior cruciate ligament midsubstance, the length of the transducer at the inflection point was determined graphically by two independent examiners. Previous studies suggested that the inflection point corresponds to the slack-taut transition of the anteromedial band. The force probe was used to determine the actual length of the transducer when the anteromedial band became load bearing. No significant differences were found between the reference lengths determined by the inflection point method and the force probe. The force probe demonstrated that the anterior cruciate ligament became load bearing when an anterior shear load of 8.8 N was applied to the tibia with the knee at 30 degrees of flexion. Furthermore, multiple cycles of anteroposterior shear loading did not influence these values. The force probe verified that the inflection method provides a reasonable estimate of the absolute strain reference (within 0.7% strain).

Overuse injuries in sports. A review.

Because knowledge of overuse syndromes is limited, the diagnosis and treatment of these conditions are a challenge to sports medicine physicians. Trial and error methods of treatment and too little attention to basic research have resulted in less than optimum solutions. We do know that these maladies most frequently result from overload or repetitive microtrauma stemming from extrinsic factors such as training errors, poor performance, poor techniques and inappropriate surfaces or intrinsic factors including malalignment and muscle imbalance. Overuse injuries involving the muscles include compartment syndromes and muscle soreness; while those involving the tendons result from a variety of degenerative and inflammatory processes. Overstress of bone results in stress fractures, apophysitis and periostitis. Bursitis and joint overstress problems are also discussed briefly. General guidelines for establishing the appropriate diagnosis are: the initial stages of therapy require rest, often a modification or scaled down exposure to the athlete's usual performance rather than complete abstinence; in acutely symptomatic cases pain medications and various measures to control inflammation may be necessary; an exercise programme should start early with range of motion exercises and isometric muscle contractions; when pain allows, dynamic muscle and flexibility exercises can resume together with a conditioning programme; if possible, eccentric exercises should be performed. The treatment may also include other conservative treatment modalities and surgery in special cases. Overuse injuries constitute a great diagnostic and therapeutic problem because the symptoms are often diffuse and uncharacteristic. An appropriate diagnosis followed by adequate treatment can improve or eliminate most of these conditions, but perhaps even more importantly a proper understanding of overuse syndromes should allow physicians to assist athletes, trainers, and coaches in preventing them.

Cross-country skiing injuries and biomechanics.

Cross-country skiing exercises most of the joints, muscles and tendons in the body giving the skier an all around workout. This, in combination with a low incidence of injury, makes cross-country skiing an ideal recreational and competitive sport. The new skating techniques developed during the last decade have resulted in greater velocity. The maximum speed during the diagonal stride technique is 6 m/sec compared to 8 to 9 m/sec when skating and double poling. Top-level skiers today use strong and ultra light skis of fiberglass and graphite. The ski weight is less than 500g. Today's skating technique does not require any waxing and only the cambered portion of the ski is waxed when performing the diagonal stride. The preparation of the ski course has improved with the development of special track machines. This allows top-level skiers to reach 60 to 80 km/h on downhill slopes, which has resulted in an increased risk of injury. Because cross-country skiing takes place wherever snow is available, it is difficult to establish accurate injury rates in comparison to alpine skiing which is performed on very specialised terrain at ski areas. Studies estimate the cross-country ski injury rate in Sweden to be around 0.2 to 0.5 per thousand skier days. A prospective study of cross-country ski injuries conducted in Vermont revealed an injury rate of 0.72 per thousand skier days. 75% of the injuries sustained by members of the Swedish national cross-country ski team during 1983 and 1984 were overuse injuries while 25% resulted from trauma. The most common overuse injuries included medial-tibial stress syndrome, Achilles tendon problems and lower back pain. Most common among traumatic injuries were ankle ligament sprains and fractures, muscle ruptures, and knee ligament sprains. Shoulder dislocation, acromioclavicular separation and rotator cuff tears are not infrequent in cross-country skiing. Injuries to the ulnar collateral ligament of the metacarpal phalangeal joint of the thumb (Stener's lesion) is the most common ski injury involving the upper extremity. Cross-country skiers 16 to 21 years of age complained more frequently of mild lower back pain than similarly aged non-skiers. This may result from repetitive hyperextension motions during the kick phase and the recurring spinal flexion and extension during the double poling phase. Repeated slipping on hard and icy tracks infrequently produce partial tears or microtrauma in the muscle tendinous units of the groin.(ABSTRACT TRUNCATED AT 400 WORDS)

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.

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.

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.

Injuries to the posterior cruciate ligament of the knee.

The posterior cruciate ligament (PCL) is the strongest ligament about the knee and is approximately twice as strong as the anterior cruciate ligament. Its main function is to prevent the posterior dislocation of the tibia in relation to the femur, providing 95% of the strength to resist the tibial posterior displacement. Along with the anterior cruciate ligament (ACL) the PCL controls the passive 'screw home' mechanism of the knee in terminal knee extension. It also provides mechanical support for the collateral ligaments during valgus or varus stress of the knee. PCL ruptures are uncommon apparently due to its strong fibre structure. The most frequent injury mechanism in isolated PCL tears is a direct blow on the anterior tibia with the knee flexed thus driving the tibia posteriorly. Automobile accidents (in which the knee hits the dashboard) and soccer injuries (in which an athlete receives a blow to the anterior surface of the tibia during knee flexion) characteristically produce this type of injury. In other PCL injury mechanisms (hyperextension, hyperflexion or rotational injuries with associated valgum/varum stress), other knee structures are also often damaged. The most characteristic diagnostic finding in a knee with a PCL rupture is the 'posterior sag sign' meaning the apparent disappearance of the tibial tubercle in lateral inspection when the knee is flexed 90 degrees. This is due to gravity-assisted posterior displacement of the tibia in relation to the femur. A positive posterior drawer test performed at 90 degrees of flexion and a knee hyperextension sign are sensitive but nonspecific tests. False negative findings are frequent, especially in acute cases. If necessary, the clinical diagnosis of the PCL tear can be verified by magnetic resonance imaging, examination under anaesthesia, arthroscopy, or a combination of these modalities. If a PCL avulsion fragment has been dislocated, surgical treatment is recommended. In isolated, complete midsubstance tears of the PCL the majority of the recent studies recommend conservative treatment, since abnormal residual posterior laxity1 in most of these knees is consistent with functional stability and minimal symptoms. This has been the case even in athletes. In isolated PCL tears, the outcome seems to depend more on the muscular (quadriceps) status of the knee than on the amount of residual posterior laxity. Therefore, the conservative treatment protocol emphasises intensive quadriceps exercises, and only a short (under 2 weeks) immobilisation period followed by early controlled activities and early weightbearing.(ABSTRACT TRUNCATED AT 400 WORDS)

Quadriceps function and training after knee ligament surgery.

A follow-up study of 30 patients operated on for knee ligament injuries was performed with measurements of maximal isometric and isokinetic (angular velocity 30, 42, 120 degrees/s) torque for knee extension and muscle biopsy from vastus laternalis. The maximal torque values of the operated side were reduced in spite of resumed physical activities and athletic training. Isokinetic training, weight training (10 RM), and self-training were compared. All training groups increased their muscle strength with the largest increase for the isokinetically trained group. Before training, the mean fiber areas were somewhat low, especially for type II fibers and there was a tendency for an increase after training. There was no significant change in ATP, CP, and contractile enzyme activities with training. With the isokinetic training principle, maximal torque can in contrast to weight training be achieved through the whole range of motion, which may explain its larger training effect.

A comparison of ankle taping methods.

Four different types of ankle tapings were applied to a model of the human ankle joint. The model was constructed so that it contained a hinge to represent the ankle joint and had an external shape identical to a real ankle and foot. A mechanical testing machine was used to apply moments to the model at a controlled loading rate. From these tests, the deflection and torque to failure and the tangent stiffness were determined. Loadings of an ankle joint in vivo revealed that the angular deflection to initiate pain was approximately 8 degrees. Only the figure eight and full tapings could withstand 8 degrees of angular displacement on the ankle model prior to failure. Analysis of athletic trauma revealed that torques of 420 Nm could be applied to the ankle joint. Only the figure eight taping with three or more wraps has adequate strength to withstand this moment, and thus this taping is recommended. In practice, tapings failed by shearing away from the surface of the foot of shrinking rather than by rupture of the tape.