Prevalence of jumper's knee among elite athletes from different sports: a cross-sectional study

BACKGROUND: The prevalence of jumper's knee across different sports has not been examined, and it is not known if there is a gender difference. Data from surgical case series indicate that there may be a high prevalence in sports with high speed and power demands. HYPOTHESIS: The aim of this study was to estimate the prevalence of jumper's knee in different sports among female and male athletes and to correlate the prevalence to the loading characteristics of the extensor mechanism in these sports. STUDY DESIGN: Cross-sectional study; Level of evidence, 4. METHODS: The authors examined approximately 50 Norwegian male and female athletes at the national elite level from each of the following 9 sports: athletics (male athletes: high jump, 100- and 200-m sprint), basketball (male athletes), ice hockey (male athletes), volleyball (male athletes), orienteering (male athletes), road cycling (male athletes), soccer (male and female athletes), team handball (male and female athletes), and wrestling (male athletes). The examination included an interview on individual characteristics (weight, age, height, and training background), a clinical examination, and self-recorded Victorian Institute of Sport Assessment score from 0 (worst) to 100 (best). RESULTS: The overall prevalence of current jumper's knee was 14.2% (87 of 613 athletes), with a significant difference between sports with different performance characteristics (range, 0%-45%). In addition, 51 athletes (8%) reported previous symptoms. The prevalence of current symptoms was highest in volleyball (44.6%+/-6.6%) and basketball (31.9%+/-6.8%), whereas there were no cases in cycling or orienteering. The prevalence of current jumper's knee was lower among women (5.6%+/-2.2%) compared with men (13.5%+/-3.0%; chi2 test, P=.042). The duration of symptoms among athletes with current jumper's knee (n=87) was 32+/-25 (standard deviation) months, with a Victorian Institute of Sport Assessment score of 64+/-19. CONCLUSION: The prevalence of jumper's knee is high in sports characterized by high demands on speed and power for the leg extensors. The symptoms are often serious, resulting in long-standing impairment of athletic performance.     

Prevention and management of knee osteoarthritis and knee cartilage injury in sports

Articular cartilage defects in the knee of young or active individuals remain a problem in orthopaedic practice. These defects have limited ability to heal and may progress to osteoarthritis. The prevalence of knee osteoarthritis among athletes is higher than in the non-athletic population. The clinical symptoms of osteoarthritis are joint pain, limitation of range of motion and joint stiffness. The diagnosis of osteoarthritis is confirmed by the symptoms and the radiological findings (narrowing joint space, osteophyte formation and subchondral sclerosis). There is no strong correlation between symptoms and radiographic findings. The aetiology of knee osteoarthritis is multifactorial. Excessive musculoskeletal loading (at work or in sports), high body mass index, previous knee injury, female gender and muscle weakness are well-known risk factors. The high-level athlete with a major knee injury has a high incidence of knee osteoarthritis. Cartilage injuries are frequently observed in young and middle-aged active athletes. Often this injury precedes osteoarthritis. Reducing risk factors can decrease the prevalence of knee osteoarthritis. The prevention of knee injury, especially anterior cruciate ligament and meniscus injury in sports, is important to avoid progression of knee osteoarthritis.     

Criterion related validity of self-reported knee symptoms among athletes

The objective of this study was to investigate the validity of self-reported knee symptoms among athletes. During 12 months, 252 athletes answered a weekly questionnaire about concurrent sports activity, knee pain, knee instability, knee swelling and knee locking. Finally, the athletes answered a retrospective questionnaire summing up symptoms during the preceding 12 months. Accordingly, two 12 month period prevalences of the same period were calculated for each knee symptom. The proportion of agreement between the retrospective 12 month questionnaire and the concurrent weekly questionnaires was for knee pain, knee instability, knee swelling and knee locking, 86%, 89%, 89% and 90%, respectively. Using weekly reports as reference, the corresponding sensitivity of the 12 month period prevalence question was 0.86, 0.71, 0.66 and 0.56, respectively. The sensitivities were all significantly associated with the number of weeks since the last episode of the corresponding knee symptom. As concerns estimation of 12 month period prevalences, a retrospective summary questionnaire at the end of the period is a valid substitute for concurrent weekly questionnaire information on knee pain, knee instability and knee swelling, but only a moderate substitute for information on knee locking. A reduction in the length of the period the athlete should recall knee symptoms might improve the questionnaire validity.     

Comparing sports injuries in men and women.

OBJECTIVE: To compare the pattern of injury between men and women in seven collegiate sports to determine if gender-specific factors exist which could be modified to reduce the risk of injury to female athletes. DESIGN: Retrospective cohort study of injury reports compiled by certified athletic trainers between Fall 1980 and Spring 1995. SETTING: An NCAA division III College. PARTICIPANTS: Eighteen to 22 year-old male and female college athletes competing in seven like sports (basketball, cross-country running, soccer, swimming, tennis, track and water polo) at the intercollegiate level, playing similar number of contests and using the same facilities. MAIN OUTCOME MEASURES: Analyses of injury patterns, classified by sport and anatomic location, for men and women in seven like sports. RESULTS: A total of 3,767 participants were included in the study, with 1874 sports-related injuries reported among the men and women's teams. Of these injuries, 856 (45.7%) were sustained by female and 1018 (54.3%) by male athletes. Overall, no statistically significant gender difference was found for injuries per 100 participant-years (52.5 for female athlete versus 47.7 for males). A statistically significant gender difference in injury incidence (p < 0.001) was seen for two sports: swimming and water polo. Female swimmers reported more back/neck, shoulder, hip, knee and foot injuries: and female water polo players reported more shoulder injuries. When evaluating all sports concurrently, female athletes reported a higher rate of hip, lower-leg and shoulder injuries, while male athletes reported a higher rate of thigh injuries. CONCLUSION: Except for some minor gender differences in total injuries for two sports and several differences in total injuries by anatomic location, our data suggest very little difference in the pattern of injury between men and women competing in comparable sports. The increased rate of shoulder injury among female swimmers probably resulted from the more rigorous training philosophy of their coach. Thus, no gender-specific recommendations can be suggested for decreasing the incidence of injury to female athletes competing in these sports.     

The prevalence of chronic ankle instability and its relationship to foot arch characteristics in female collegiate athletes

ObjectiveTo determine the prevalence of chronic ankle instability (CAI) and to investigate its relationship to the foot arch in collegiate female athletes by each sports event.DesignCross-sectional study.SettingUniversity setting.Participants138 collegiate female athletes.Main outcome measuresAll subjects were asked about previous ankle sprains, and the arch height index (AHI) was calculated. Athletes with a previous sprain history were evaluated based on the criteria by the International Ankle Consortium (IAC), the severity of ankle instability (CAIT), and foot and ankle function (FAAM). The prevalence of CAI and the relationship between the AHI and ankle instability were analyzed by each sports event.ResultsOf 106 athletes with a previous ankle sprain, 10 (9.4%) met the IAC criteria below the cut-off value of the CAIT, and only 1 athlete (0.9%) was below the FAAM cut-off value. The AHI was not significantly different in athletes with CAI. The AHI was significantly lower in swimmers than in track and field (sprint) athletes.ConclusionMost female athletes with CAI were aware of the severity of ankle instability, but they did not feel dysfunction of the ankle during sports. Additionally, the AHI may depend on the characteristics of sports events.     

Valgus knee motion during landing in high school female and male basketball players

PURPOSE: The purpose of this study was to utilize three-dimensional kinematic (motion) analysis to determine whether gender differences existed in knee valgus kinematics in high school basketball athletes when performing a landing maneuver. The hypothesis of this study was that female athletes would demonstrate greater valgus knee motion (ligament dominance) and greater side-to-side (leg dominance) differences in valgus knee angle at landing. These differences in valgus knee motion may be indicative of decreased dynamic knee joint control in female athletes. METHODS: Eighty-one high school basketball players, 47 female and 34 male, volunteered to participate in this study. Valgus knee motion and varus-valgus angles during a drop vertical jump (DVJ) were calculated for each subject. The DVJ maneuver consisted of dropping off of a box, landing and immediately performing a maximum vertical jump. The first landing phase was used for the analysis. RESULTS: Female athletes landed with greater total valgus knee motion and a greater maximum valgus knee angle than male athletes. Female athletes had significant differences between their dominant and nondominant side in maximum valgus knee angle. CONCLUSION: The absence of dynamic knee joint stability may be responsible for increased rates of knee injury in females but is not normally measured in athletes before participation. No method for accurate and practical screening and identification of athletes at increased risk of ACL injury is currently available to target those individuals that would benefit from neuromuscular training before sports participation. Prevention of female ACL injury from five times to equal the rate of males would allow tens of thousands of young females to avoid the potentially devastating effects of ACL injury on their athletic careers.     

Neuromuscular and hormonal factors associated with knee injuries in female athletes. Strategies for intervention

Female athletes who participate in jumping and cutting sports are 4 to 6 times more likely to sustain a serious knee injury than male athletes participating in the same sports. More than 30,000 serious knee injuries are projected to occur in female intercollegiate and high school athletics in the US each year. The majority of these injuries occur by non-contact mechanisms, most often during landing from a jump or making a lateral pivot while running. Knee instability, due possibly to decreased neuromuscular strength and coordination or increased ligamentous laxity, may underlie the increased incidence of knee injury in females. Neuromuscular training can significantly increase dynamic knee stability in female athletes. Female sex hormones (i.e. estrogen, progesterone and relaxin) fluctuate radically during the menstrual cycle and are reported to increase ligamentous laxity and decrease neuromuscular performance and, thus, are a possible cause of decreases in both passive and active knee stability in female athletes. Oral contraceptives stabilise hormone levels during the menstrual cycle and may function to either passively or actively stabilise the knee joint. The long term objective of clinicians and researchers should be to determine the factors that make women more susceptible than men to knee ligament injury and to develop treatment modalities to aid in the prevention of these injuries. The immediate objectives of this review are to examine how female and male athletes differ in neuromuscular and ligamentous control of the lower extremity. The review will examine the effects of neuromuscular training on knee stability. The effects of female hormone levels and oral contraceptives on neuromuscular control of the female athletes' knee will also be discussed.     

Recurrent shoulder instability among athletes: changes in quality of life,sports activity,and muscle function following open repair

Background: Recurrent anterior shoulder instability is a disabling condition in young athletes with possibly underestimated impact on quality of life and sports activity. Commonly used clinical scoring systems do not reflect the impairment of quality of life and sports activity. It was our aim to assess the return to preinjury levels of quality of life and sports activity as well as the changes in muscle function among competitive and recreational athletes. Hypothesis: Patients suffering from post-traumatic recurrent shoulder instability have to adopt their participation in sports and therefore discover a reduction in quality of life. Open stabilization procedures are able to improve shoulder function and to reduce recurrence rates. However, return to preinjury shoulder function is not guaranteed. Study design: Retrospective longitudinal cohort study on 19 consecutive athletes with recurrent, post-traumatic shoulder instability. All patients were treated with an open, capsulo-labral repair. The minimum follow-up was 24 months. Methods: Life quality (SF12) and sports activity data (Athletic Shoulder Outcome Scoring System) were retrospectively collected for the time before injury (time 1) and for the time with recurrent instability (time 2). Two years after surgical stabilization (time 3), we followed our patients with different clinical outcome scores, rotator surface EMG measurement, isokinetic muscle strength testing, and a radiological evaluation. This design of a three-step follow-up allowed for calculating the impact on quality of life and sports activity following the injury. Results: Two years after surgery, the clinical scoring systems revealed good-to-excellent results in all patients. Quality of life physical component summary remained diminished by 9.2% despite the surgical procedure and was therefore significantly lower as compared to preinjury levels (p < 0.05). Sports activity was also significantly lower at the time of follow-up (p < 0.05). In this specific procedure, external rotation was not impaired postoperatively. EMG testing showed an overall reduction of muscle activity, however not significant. Isokinetic muscle strength was significantly diminished for external rotation and shoulder abduction. Conclusions: Open reconstruction procedures for recurrent shoulder instability can restore shoulder function and stability to near-normal values. Despite good-to-excellent clinical results, there is a significant impairment of quality of life and sports activity 2 years after surgery. Muscle activity and muscle strength are diminished. Recurrent shoulder instability remains a disabling condition to the young athlete. Future strategies have to emphasize restoration of quality of life, sports activity, and muscle function.     

Perturbation-enhanced neuromuscular training alters muscle activity in female athletes

Female athletes involved in jumping and cutting sports injure their anterior cruciate ligaments (ACL) 4-6 times more frequently than their male counterparts in comparable sports. Neuromuscular factors, including quadriceps dominance, has been incriminated as contributing to the higher rates of injury in women. Currently, the most effective form of intervention developed to reduce female ACL injury rates has been neuromuscular training. The purpose of this study was to (1) identify gender based muscle activity patterns during disturbed walking that may contribute to ACL injury, and (2) determine if a novel training program could positively influence patterns among healthy female athletes utilizing a disturbed gait paradigm. Twenty healthy athletes (female=10, male=10) were tested. All subjects participated in five trials during which a platform translated horizontally in a lateral direction at heel contact before and after completing ten sessions of a perturbation training program. Electromyographic (EMG) data from the vastus lateralis, medial and lateral hamstrings, and medial gastrocnemius were collected. Trials were analyzed for the muscle onset, termination of activity, peak amplitude, time to peak amplitude, and integrated EMG activity. Muscle cocontraction, the simultaneous activation of antagonistic muscles (lateral hamstrings-vastus lateralis, and medial gastrocnemius-vastus lateralis), was calculated as indicators of active knee stiffness in preparation for heel strike, during weight acceptance and midstance. Prior to training, women had significantly higher peak quadriceps activity and higher integrated quadriceps activity during midstance than men. Both medial and lateral hamstring integrals during midstance increased from pre to posttraining. Onset times to peak activities for hamstrings and quadriceps were similar before training except for medial hamstring time to peak which occurred after heel strike in most women. Time to peak medial hamstring activity moved from after to just before heel strike after training. Women had higher medial gastrocnemius-vastus lateralis cocontraction indices in the preparatory and weight acceptance phases of gait than men after training. Prior to training, the athletic women in our sample demonstrated characteristic quadriceps dominance and decreased active knee stiffness when compared to male athletes. Modulation of activity and timing of ACL agonist musculature (hamstrings and gastrocnemius) from before to after training resulted in normal quadriceps-hamstring balance and increased active stiffness. These alterations in ACL agonist muscle activation patterns may reduce the risk of biomechanical strain injury among a high risk population.     

Sports ability after Bankart procedure in professional athletes

Recurrent anterior shoulder instability and the restoration of sports ability after surgery are common problems, especially among professional athletes. The purpose of this study was to evaluate the rate, level and time of returning to sports activity after Bankart procedure in anterior shoulder instability in high level atheletes. From 1992–1994 61 patients suffering from recurrent anterior shoulder instability were operated on open Bankart procedure. 44 out of 61 were professional athletes. There were 7 handball, 7 basketball, 6 football, 2 waterpolo and 1 base-ball player and 4 wrestlers, 2 weightlifters, 2 boxers, 3 bicyclists, 2 motorists, 2 swimmers, 2 sailors, 2 kayakers and 2 skiers. The mean duration of instability was 19.1 months (3–72) before operation. 29 patients had posttraumatic recurrent anterior dislocation and 15 patients had posttraumatic anterior subluxations. The average number of redislocations was 4.4, ranging from 2 to 11. At the follow-up examination the patients were tested clinically for instability using the special score created by Walch and Duplay and the Constant functional score. We measured the strength of the rotator cuff by Kintrex isokinetic device from the 10th postoperative week. 35 out of 44 professional athletes could be fellowed-up. The average follow-up period was 14.2 months, from 6 to 31. 88% of the patients were able to return to sports participation, 66% on the previous levels and 22% on a lower level. 12% of the patients finished their professional sports career. The mean rehabilitation period was 5.8 months, the average period of full restoration of sports ability was 9.3 months. Similar results were documented with the Constant score and the Walch-Duplay test (88% excellent or good, 12% fair). The main reason for the inability to continue sports activity was some pain during extreme abduction and extrnal rotation of the arm and recurrent sensations of subluxation (3 cases). Based on the results of the follow-up examinations an early diagnosis is paramount followed by timely surgical intervention to restore anatomical integrity in proven cases of shoulder instability in professional athletes. The open Bankart procedure is preferred giving excellent functional results and providing good chances for the atheletes to return to their previous sports level.     

The effects of core proprioception on knee injury: a prospective biomechanical-epidemiological study

BACKGROUND: In sports involving pivoting and landing, female athletes suffer knee injury at a greater rate than male athletes. HYPOTHESES: Proprioceptive deficits in control of the body's core may affect dynamic stability of the knee. Female, but not male, athletes who suffered a knee injury during a 3-year follow-up period would demonstrate decreased core proprioception at baseline testing as compared with uninjured athletes. STUDY DESIGN: Cohort study (prognosis); Level of evidence, 2. METHODS: Study subjects were 277 collegiate athletes (140 female, 137 male) who were prospectively tested for core proprioception by active and passive proprioceptive repositioning. Athletes were monitored for injury for 3 years. An ANOVA and multivariate logistic regression were used to test whether core proprioception was related to knee injuries in athletes. RESULTS: Twenty-five athletes sustained knee injuries (11 women, 14 men). Deficits in active proprioceptive repositioning were observed in women with knee injuries (2.2 degrees ) and ligament/meniscal injuries (2.4 degrees ) compared with uninjured women (1.5 degrees , P or= .05). Uninjured women demonstrated significantly less average error in active proprioceptive repositioning than uninjured men (1.5 degrees vs 1.7 degrees , P 相似文献   

Inferior capsular shift procedure in athletes with multidirectional instability based on isolated capsular and ligamentous redundancy

Twenty-five athletes (26 shoulders) who underwent an inferior capsular shift procedure for multidirectional glenohumeral instability based on isolated capsular and ligamentous redundancy were evaluated at a median of 54 months (range, 25 to 113) after the operation. Twenty-one athletes (84%) returned to their preinjury activity level at a median of 5 months after surgery. Of 21 athletes involved in sports using overhead motions, 16 (76%) returned to their previous sport after the operation, and 12 (57%) were still active in this sport at the preinjury level at follow-up. According to the Rowe score, 23 shoulders (88%) were excellent or good. The University of California at Los Angeles score for 24 shoulders (92%) was excellent or good. The operations on two shoulders (8%) failed. One patient had a spontaneous redislocation, and one had recurrent subluxations. Nine contralateral shoulders had a history of significant instability; four of these had undergone Bankart repair. We concluded that athletes who have multidirectional instability based on isolated capsular and ligamentous redundancy can be successfully treated by an inferior capsular shift preserving the subscapularis tendon insertion. We found a high rate of return to demanding upper extremity sports in our patients, range of motion was restored in the majority of shoulders, and the failure rate after a median of 54 months was acceptable.     

Preseason strength and flexibility imbalances associated with athletic injuries in female collegiate athletes

One hundred thirty-eight female collegiate athletes, participating in eight weightbearing varsity sports, were administered preseason strength and flexibility tests and followed for injuries during their sports seasons. Strength was measured as the maximal isokinetic torque of the right and left knee flexors and knee extensors at 30 and 180 deg/sec. Flexibility was measured as the active range of motion of several lower body joints. An athletic trainer evaluated and recorded injuries occurring to the athletes in practice or competition. Forty percent of the women suffered one or more injuries. Athletes experienced more lower extremity injuries if they had: 1) a right knee flexor 15% stronger than the left knee flexor at 180 deg/sec; 2) a right hip extensor 15% more flexible than the left hip extensor; 3) a knee flexor/knee extensor ratio of less than 0.75 at 180 deg/sec. There was a trend for higher injury rates to be associated with knee flexor or hip extensor imbalances of 15% or more on either side of the body. These data demonstrate that specific strength and flexibility imbalances are associated with lower extremity injuries in female collegiate athletes.     

Prévalence des troubles du comportement alimentaire chez le sportif

AimThe aim of the study was to determine the prevalence and relationships between disordered eating and psychological characteristics in 127 male and female elite athletes competing in 5 different sports and 31 non-competitive students matched for BMI and used as controls. All these parameters were assessed by a health/medical, dieting and menstrual history questionnaire, the Eating Attitudes Test (EAT-26), the Multidimensional perfectionism scale, the Body esteem scale, and the Self-Esteem scale.Results and discussion19% of female athletes had scores above the cut-off point on the Eating Attitudes Test questionnaire. 30.7% of female cyclists (30.7%), 25% of judoists and 22.3% of gymnasts (22.3%) would be "at risk" of EDs (EAT-26 > 20) and 0% in the male and female sedentary groups, basket- ball group and male athlete groups. The total frequency of menstrual dysfunction among females athletes was 33.1%. Females with eating disorders presented higher menstrual disturbances (71.4%) than the non-EDs (27.7%).ConclusionThe prevalence of disordered eating was higher in athletes than in sedentary groups, higher in female than in male athletes and more common among those competing in leanness-dependent and weight-dependent sports than in other sports. The prevalence of clinical eating disorders would increase when Self-oriented Perfectionism would be high and Body Satisfaction low.     

Knee injuries in volleyball

The knee is the most frequent site of injury in volleyball players. More than 40% of high level players suffer overuse injuries during this activity; this particularly painful syndrome is caused by the amount of jumping typical in volleyball play, and in its training which aims at strengthening the quadriceps muscle. In volleyball players the extensor apparatus is subject to continuously high stress and the bone tendon junction, being the weakest point, is susceptible to lesion. The prevention and treatment of 'jumper's knee' requires a high degree of cooperation among trainers, doctors and athletes. Although volleyball is a sport without contact between players, traumatic acute injuries are more frequent and more serious than would be expected. It is therefore important to emphasise that volleyball must be considered among the high risk sports that expose the knee not only to twisting, but also to contact with other players. Generally, the lesions are caused by frequent jumps with loss of balance and a consequent 'one-footed' landing. There is no specific method of preventing knee instability. Accurate diagnoses, rest and rapid surgical treatment after the first injury are recommended in order to avoid chronic knee instability with subsequent meniscal lesions and post-traumatic osteoarthritis.     

Nearly 40% of adolescent athletes report anterior knee pain regardless of maturation status,age, sex or sport played

ObjectiveTo report point prevalence of anterior knee pain (AKP) in adolescent athletes by (1) maturation status, (2) chronological age, (3) sex, and (4) primary sport.DesignCross-sectional.MethodsMale and female participants aged 11–15 years were recruited from specialised sports programs for basketball, volleyball, Australian Rules Football and tennis. Standing height, sitting height, and body mass were measured and used to calculate maturity status. Past injury history, self-reported physical activity, and Victorian Institute of Sport Assessment Questionnaire Patellar Tendon (VISA-P) questionnaires were completed. Anterior knee pain was defined as any pain experienced on the anterior surface of the knee and recorded using a visual analogue scale (VAS). A single leg decline squat (SLDS) was performed for provocation of AKP.ResultsTwo hundred and seventeen male and female adolescent athletes participated in this study. Twenty participants were excluded from data analysis. Point prevalence of AKP was 39% (N = 76). Average self-reported physical activity/week was 7.9 ± 4.1 h of their specialised sport and 2.0 ± 2.0 h of other physical activity/week. Maturation status, chronological age, sex nor primary sporting program was statistically significant in explaining the presence or absence of AKP.ConclusionDue to the right-skewed maturation sample, the authors cannot state conclusively that maturation status was not associated with AKP. Nearly 40% of this cohort reported AKP during a pain provocation test. The presence of AKP was not explained by maturation status, age, sex or primary sport program. Given the chronic nature of AKP and future morbidity reported, this high prevalence provides rationale for intervention or prevention studies targeting younger athletes.     

Knee injuries account for the sports-related increased risk of knee osteoarthritis

Increased risk of osteoarthritis has been found among athletes active in different kinds of sports. Knee injury is an established risk factor for knee osteoarthritis. In this population-based case-control study we investigated the risk of knee osteoarthritis with respect to sports activity and previous knee injuries. A total of 825 cases with x-ray-verified femorotibial osteoarthritis were identified at six hospitals in southern Sweden. The cases were matched (age, sex and residential area) with 825 controls from the general population. Mailed questionnaire data on sports activity for more than 1 year after the age of 16, knee injuries and confounding variables (weight, height, heredity, smoking and occupation) were collected and analyzed using logistic regression models. The response frequency was 89%. Among men knee osteoarthritis was related to soccer (odds ratio (OR) 1.6, 95% confidence interval (CI) 1.1-2.2), ice hockey (OR 1.9, 95% CI 1.2-3.0) and tennis (OR 2.0, 95% CI 1.1-3.8) but not to track and field sports, cross-country skiing, and orienteering. After adjustment for confounding variables soccer and ice hockey remained significantly related to knee osteoarthritis, but after adjustment for knee injuries no significant relation remained. The sports-related increased risk for knee osteoarthritis was explained by knee injuries.     

Active knee joint flexibility and sports activity

The aim of the study was to estimate active knee flexion and active knee extension in athletes and to investigate the potential association of each to different types of sports activity. Active knee extension and active knee flexion was measured in 339 athletes. Active knee extension was significantly higher in women than in men and significantly positively associated with weekly hours of swimming and weekly hours of competitive gymnastics. Active knee flexion was significantly positively associated with participation in basketball, and significantly negatively associated with age and weekly hours of soccer, European team handball and swimming. The results point to sport-specific adaptation of active knee flexion and active knee extension.     

Dynamic stability after ACL injury: who can hop?

Single-leg hops are used clinically to assess knee function in patients following anterior cruciate ligament (ACL) rupture and reconstruction. Researchers study ACL-deficient individuals in order to identify movement strategies in the absence of a major knee stabilizer, thereby providing information to clinicians regarding treatment options. Single-leg hops represent an activity which places higher demands on the knee than walking or jogging. Hops are thought by some to represent demands that are more comparable to those found during high level sports. Therefore hopping might provide more information about knee stability during dynamic activities than less strenuous activities. This paper reflects one component of a larger study involving comparisons of joint motions and muscle activity patterns in uninjured individuals (n=10) and two groups of athletes who had complete ACL ruptures; one group had substantial knee instability (noncopers, n=10), and the other had no signs of knee instability (copers, n=11). In this paper we report the findings from the single-leg hop activity. The results indicate that coper subjects move in a manner nearly identical to uninjured persons. Kinetic data suggest that copers stabilize their knees with greater contributions from the ankle extensor muscles. Muscle activity data demonstrate that there is no reduction in quadriceps femoris activity in the coper subjects. In the group of ten subjects with knee instability (noncopers) who participated in the overall study involving walking, jogging, hopping, and a step activity only four were willing to hop. Work in our laboratory has established that when high level athletes rupture their ACL, the majority of them cannot return to high level sports. The small number of noncopers in this study who were willing to hop supports our previous findings. Those noncopers who did hop displayed reduced knee range of motion and external knee flexion moments, a movement strategy remarkably similar to that found during other activities. Neither the copers nor the noncopers showed evidence that quadriceps activation was diminished.