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During the 2013‐14 school year, over 763,000 female athletes participated in interscholastic running sports in the United States. Recent studies have indicated associations between the female athlete triad (Triad) and stress fracture or other musculoskeletal injuries in elite or collegiate female running populations. Little is known about these relationships in an adolescent interscholastic running population. The purpose of this study was to determine the associations between Triad and risk of lower extremity musculoskeletal injury among adolescent runners.
Eighty‐nine female athletes competing in interscholastic cross‐country and track in southern California were followed, prospectively. The runners were monitored throughout their respective sport season for lower extremity musculoskeletal injuries. Data collected included daily injury reports, Eating Disorder Examination Questionnaire (EDE‐Q) that assessed disordered eating attitudes/behaviors, a questionnaire on menstrual history and demographic characteristics, a dual‐energy x‐ray absorptiometry scan that measured whole‐body bone mineral density (BMD) and body composition (lean tissue and fat mass), and anthropometric measurements.
Thirty‐eight runners (42.7%) incurred at least one lower extremity musculoskeletal injury. In the BMD Z‐score ≤ ‐1 standard deviation (SD) adjusted model, low BMD relative to age (BMD Z‐score of ≤ ‐1SD) was significantly associated (Odds Ratio [OR]=4.6, 95% confidence interval [CI]: 1.5‐13.3) with an increased occurrence of musculoskeletal injury during the interscholastic sport season. In the BMD Z‐score ≤ ‐2 SDs adjusted model, a history of oligo/amenorrhea was significantly associated (OR=4.1, 95% CI: 1.2‐13.5) with increased musculoskeletal injury occurrence.
Oligo/amenorrhea and low BMD were associated with musculoskeletal injuries among the female interscholastic cross‐country and track runners.
Clinical Relevance:
Regular, close monitoring of adolescent female runners during seasonal and off‐season training may be warranted, so that potential problems can be recognized and addressed promptly in order to minimize the risk of running injury.
Level Of Evidence:
PMCID: PMC4275199  PMID: 25540710
Adolescent runners; bone mineral density; disordered eating; females; menstrual dysfunction; musculoskeletal injuries
2.  Subsequent Injury Patterns in Girls' High School Sports 
Journal of Athletic Training  2007;42(4):486-494.
Context: Girls' participation in high school sports has increased 79.5% since 1975–1976. The incidence of injury among boys in high school sports has been well documented, but information regarding the incidence, severity, and type of injury among girls in high school sports is limited.
Objective: To examine the effects of subsequent injuries among high school girls in 5 sports.
Design: Observational cohort.
Setting: Existing data from the 1995–1997 National Athletic Trainers' Association High School Injury Surveillance database.
Patients or Other Participants: Girl athletes (n = 25 187 player-seasons) participating in 5 varsity high school sports: basketball, field hockey, soccer, softball, and volleyball.
Main Outcome Measure(s): Injury status, body location, injury type, time lost from injury, and number of players at risk for injury as recorded by athletic trainers and submitted to the Sports Injury Monitoring System.
Results: Overall, 23.3% of the athletes had 2 or more injuries within a sport; basketball and soccer athletes were most vulnerable. Overall, the probability of an athlete sustaining 3 or more injuries was 38.6%, and the risk was highest for field hockey players (61.9%). The risk of subsequent injury at a new body location was almost 2 times higher than reinjury at the same body location (risk ratio = 1.7, 95% confidence interval = 1.6, 1.8) and was similar for all sports except volleyball. Only in softball was the proportion of reinjuries causing 8 or more days lost from participation greater than the proportion of new injuries causing similar time loss. Softball and volleyball had the highest proportion of reinjuries at the shoulder, especially rotator cuff strains. The proportion of knee reinjuries was significantly higher than new injuries for all sports except soccer. The proportion of anterior cruciate ligament injuries was significantly higher for volleyball players only. Overall, the proportion of reinjuries was significantly higher for stress fractures and musculoskeletal condition injuries.
Conclusions: Patterns of subsequent injury risk appear to vary among these 5 sports. Almost one quarter of the athletes incurred 2 or more injuries over a 3-year period, so the effects of subsequent injuries deserve more consideration.
PMCID: PMC2140074  PMID: 18176621
epidemiology; surveillance; sports injuries; reinjuries; female athletes
3.  Incidence of Injury Among Male Brazilian Jiujitsu Fighters at the World Jiu-Jitsu No-Gi Championship 2009 
Journal of Athletic Training  2014;49(1):89-94.
Brazilian jiujitsu is a modern combat martial art that uses joint locks to submit an opponent and achieve victory. This form of martial art is a relatively young but rapidly growing combat sport worldwide.
To determine the cumulative injury incidence and risk of injury by belt rank and body region at an international-level Brazilian jiujitsu tournament.
Descriptive epidemiology study.
World Jiu-Jitsu No-Gi Championship 2009 in Long Beach, California.
Patients or Other Participants:
We monitored 951 athletes (age range, 18–50 years) enrolled to compete in the World Jiu-Jitsu No-Gi Championship 2009.
Fighters were categorized by belt level for group comparisons (belt experience). Incidence rates per 1000 athlete-exposures (AEs) and incidence rate ratios were compared by belt rank.
Main Outcome Measure(s):
Incidence rates and incidence rate ratios.
During the tournament, 1606 AEs and 62 total injuries were reported. Of these injuries, 40 affected the joints, for an overall incidence rate of 24.9 per 1000 AEs. The joint incidence rate by belt rank was 21.5 per 1000 AEs for blue, 21.3 per 1000 AEs for purple, 25.2 per 1000 AEs for brown, and 35.1 per 1000 AEs for black. We found no differences for incidence rate ratios of joint injury among individual belt groups (P > .05). More experienced (brown belt and black belt) competitors had a higher injury risk than the less experienced (blue belt and purple belt) competitors; however, the difference was not significant (incidence rate ratio = 1.65, 95% confidence interval = 0.9, 2.9; P = .06). The incidence of joint injury was highest at the knee (7.5 per 1000 AEs) and elbow (7.5 per 1000 AEs).
The data from this international Brazilian jiujitsu tournament indicated that the risk of joint injury was similar among belt ranks or experience during this Brazilian jiujitsu competition. The knee and elbow were the joints most susceptible to injury. Future investigation of injury mechanism is warranted to develop strategies to reduce potential risk factors attributed to injury.
PMCID: PMC3917302  PMID: 24377959
mixed martial arts; combat sports; collegiate wrestling
4.  Relationships Among Injury and Disordered Eating, Menstrual Dysfunction, and Low Bone Mineral Density in High School Athletes: A Prospective Study 
Journal of Athletic Training  2010;45(3):243-252.
Prior authors have reported associations among increased risk of injury and factors of the female athlete triad, as defined before the 2007 American College of Sports Medicine position stand, in collegiate and adult club sport populations. Little is known about this relationship in an adolescent competitive sports population.
To examine the relationship among disordered eating, menstrual dysfunction, and low bone mineral density (BMD) and musculoskeletal injury among girls in high school sports.
Prospective cohort study.
The sample consisted of 163 female athletes competing in 8 interscholastic sports in southern California during the 2003–2004 school year. Each participant was followed throughout her respective sport season for occurrence of musculoskeletal injuries.
Main Outcome Measure(s):
Data collected included daily injury reports, the Eating Disorder Examination Questionnaire that assessed disordered eating attitudes and behaviors, a dual-energy x-ray absorptiometry scan that measured BMD and lean tissue mass, anthropometric measurements, and a questionnaire on menstrual history and demographic characteristics.
Sixty-one athletes (37.4%) incurred 90 musculoskeletal injuries. In our BMD z score model of ≤−1 SD, a history of oligomenorrhea/amenorrhea during the past year and low BMD (z score ≤−1 SD) were associated with the occurrence of musculoskeletal injury during the interscholastic sport season. In our BMD z score model of ≤−2 SDs, disordered eating (Eating Disorder Examination Questionnaire score ≥4.0), a history of oligomenorrhea/amenorrhea during the past year, and a low BMD (z score ≤−2 SDs) were associated with musculoskeletal injury occurrence.
These findings indicate that disordered eating, oligomenorrhea/amenorrhea, and low BMD were associated with musculoskeletal injuries in these female high school athletes. Programs designed to identify and prevent disordered eating and menstrual dysfunction and to increase bone mass in athletes may help to reduce musculoskeletal injuries.
PMCID: PMC2865962  PMID: 20446837
adolescents; female athletes; menstrual status; musculoskeletal injuries; sports
5.  Incidence of Contralateral and Ipsilateral Anterior Cruciate Ligament (ACL) Injury After Primary ACL Reconstruction and Return to Sport 
Incidence rate (IR) of an ipsilateral or contralateral injury after anterior cruciate ligament reconstruction (ACLR) is unknown. The hypotheses were that the IR of anterior cruciate ligament (ACL) injury after ACLR would be greater than the IR in an uninjured cohort of athletes and would be greater in female athletes after ACLR than male athletes.
Prospective case–control study.
Regional sports community.
Sixty-three subjects who had ACLR and were ready to return to sport (RTS) and 39 control subjects.
Independent Variables
Second ACL injury and sex.
Main Outcome Measures
Second ACL injury and athletic exposure (AE) was tracked for 12 months after RTS. Sixteen subjects after ACLR and 1 control subject suffered a second ACL injury. Between- and within-group comparisons of second ACL injury rates (per 1000 AEs) were conducted.
The IR of ACL injury after ACLR (1.82/1000 AE) was 15 times greater [risk ratio (RR) = 15.24; P = 0.0002) than that of control subjects (0.12/1000AE). Female ACLR athletes demonstrated 16 times greater rate of injury (RR = 16.02; P = 0.0002) than female control subjects. Female athletes were 4 (RR = 3.65; P = 0.05) times more likely to suffer a second ACL injury and 6 times (RR = 6.21; P = 0.04) more likely to suffer a contralateral injury than male athletes.
An increased rate of second ACL injury after ACLR exists in athletes when compared with a healthy population. Female athletes suffer contralateral ACL injuries at a higher rate than male athletes and seem to suffer contralateral ACL injuries more frequently than graft re-tears. The identification of a high-risk group within a population of ACLR athletes is a critical step to improve outcome after ACLR and RTS.
PMCID: PMC4168893  PMID: 22343967
incidence rate; anterior cruciate ligament reconstruction; second injury; subsequent injury
Division III (D III) collegiate coaches are challenged to assess athletic readiness and condition their athletes during the preseason. However, there are few reports on off‐season training habits and normative data of functional assessment tests among D III athletes. The purpose of this study was to examine off‐season training habits of D III athletes and their relationships to the standing long jump (SLJ) and single‐leg hop (SLH) tests.
One‐hundred and ninety‐three athletes (110 females, age 19.1 ± 1.1 y; 83 males, age 19.5 ± 1.3 y) were tested prior to the start of their sports seasons. Athletes reported their off‐season training habits (weightlifting, cardiovascular exercise, plyometric exercise, and scrimmage) during the six weeks prior to the preseason. Athletes also performed three maximal effort SLJs and three SLHs.
Male athletes reported training more hours per exercise category than their female counterparts. Mean SLJ distances (normalized to height) were 0.79 ± 0.10 for females and 0.94 ± 0.12 for males. Mean SLH distances for female athletes' right and left limbs were 0.66 (± 0.10) and 0.65 (± 0.10), respectively. Mean SLH distances for male athletes' right and left limbs were 0.75 (± 0.13) and 0.75 (± 0.12), respectively. Several significant differences between off‐season training habits and functional test measures were found for both sexes: males [SLJ and weightlifting (p = 0.04); SLH and weightlifting (p = 0.04), plyometrics (p = 0.05)]; females [SLJ and plyometrics (p = 0.04); SLH and scrimmage (p = 0.02)].
This study provides normative data for off‐season training habits and preseason functional test measures in a D III athlete population. Greater SLJ and SLH measures were associated with increased time during off‐season training.
Clinical Relevance:
The findings between functional tests and off‐season training activities may be useful for sports medicine professionals and strength coaches when designing their preseason training programs.
Level of Evidence:
PMCID: PMC4127507  PMID: 25133073
college; field test; functional test; single‐leg hop; standing long jump
7.  Altered Postural Sway Persists after Anterior Cruciate Ligament Reconstruction and Return to Sport 
Gait & posture  2012;38(1):136-140.
Postural sway is defined as the movement of a body’s center of mass within the base of support to maintain postural equilibrium. Deficits in postural sway are present after ACL injury; however, current evidence linking it to future injury risk is unclear. The purpose of this study was to determine if postural sway deficits persist after ACL reconstruction (ACLR). The hypothesis tested was that after ACLR, patients who return to sport (RTS) would demonstrate differences in postural sway compared to control (CTRL) subjects. Fifty-six subjects with unilateral ACLR released to RTS, and 42 uninjured CTRL subjects participated. Dynamic postural sway was assessed and 3-way (2×2×2) ANOVA was used to analyze the variables. A side X group X sex (p=0.044) interaction in postural sway was observed. A side X group analysis also revealed an interaction (p=0.04) however, no effect of sex was observed (p=0.23). Analysis within the ACLR cohort showed less (p=0.001) postural sway on the involved side (1.82 ± 0.84°) versus the uninvolved side (2.07 ± 0.96°). No side-to-side differences (p=0.73) were observed in the CTRL group. The involved limb of subjects after ACLR demonstrated the least postural sway. In conclusion, these findings indicate that dynamic postural sway may be significantly altered in a population of athletes after ACLR and RTS compared to CTRL subjects. Further investigation is needed to determine if deficits in postural sway can be used as an effective criterion to assist in the decision to safely RTS after ACLR.
PMCID: PMC3619022  PMID: 23219783
Anterior Cruciate ligament reconstruction; Postural Sway; postural stability; return to sport
Functional tests have been used primarily to assess an athlete's fitness or readiness to return to sport. The purpose of this prospective cohort study was to determine the ability of the standing long jump (SLJ) test, the single‐leg hop (SLH) for distance test, and the lower extremity functional test (LEFT) as preseason screening tools to identify collegiate athletes who may be at increased risk for a time‐loss sports‐related low back or lower extremity injury.
A total of 193 Division III athletes from 15 university teams (110 females, age 19.1 ± 1.1 y; 83 males, age 19.5 ± 1.3 y) were tested prior to their sports seasons. Athletes performed the functional tests in the following sequence: SLJ, SLH, LEFT. The athletes were then prospectively followed during their sports season for occurrence of low back or LE injury.
Female athletes who completed the LEFT in $118 s were 6 times more likely (OR=6.4, 95% CI: 1.3, 31.7) to sustain a thigh or knee injury. Male athletes who completed the LEFT in #100 s were more likely to experience a time‐loss injury to the low back or LE (OR=3.2, 95% CI: 1.1, 9.5) or a foot or ankle injury (OR=6.7, 95% CI: 1.5, 29.7) than male athletes who completed the LEFT in 101 s or more. Female athletes with a greater than 10% side‐to‐side asymmetry between SLH distances had a 4‐fold increase in foot or ankle injury (cut point: >10%; OR=4.4, 95% CI: 1.2, 15.4). Male athletes with SLH distances (either leg) at least 75% of their height had at least a 3‐fold increase (OR=3.6, 95% CI: 1.2, 11.2 for the right LE; OR=3.6, 95% CI: 1.2, 11.2 for left LE) in low back or LE injury.
The LEFT and the SLH tests appear useful in identifying Division III athletes at risk for a low back or lower extremity sports injury. Thus, these tests warrant further consideration as preparticipatory screening examination tools for sport injury in this population.
Clinical Relevance:
The single‐leg hop for distance and the lower extremity functional test, when administered to Division III athletes during the preseason, may help identify those at risk for a time‐loss low back or lower extremity injury.
Level of Evidence:
PMCID: PMC3679628  PMID: 23772338
epidemiology; functional test; single‐leg hop; lower extremity functional test
9.  Menstrual Irregularity and Musculoskeletal Injury in Female High School Athletes 
Journal of Athletic Training  2012;47(1):74-82.
The female athlete triad describes the interrelatedness of energy availability, menstrual function, and bone density. Although associations between triad components and musculoskeletal injury (INJ) have been reported in collegiate athletes, limited information exists about menstrual irregularity (MI) and INJ in the high school population.
To determine the prevalence of and relationship between MI and INJ in high school athletes.
Cross-sectional study.
High schools.
Patients or Other Participants:
The sample consisted of 249 female athletes from 3 high schools who competed in 33 interscholastic, school-sponsored sport teams, dance teams, and cheerleading or pom-pon squad during the 2006–2007 school year. Each athlete remained on the roster throughout the season.
Main Outcome Measure(s):
Participants completed a survey regarding injury type, number of days of sport participation missed, and menstrual history in the past year.
The prevalences of MI and INJ were 19.7% and 63.1%, respectively. Athletes who reported MI sustained a higher percentage of severe injuries (missing ≥22 days of practice or competition) than did athletes who reported normal menses. Although the trend was not significant, athletes with MI were almost 3 times more likely to sustain an injury resulting in 7 or more days of time lost from sport (odds ratio = 2.7, 95% confidence interval = 0.8, 8.8) than those who sustained an injury resulting in 7 or fewer days of time lost.
The incidences of MI and INJ in this high school population during the study period were high. Athletes who reported MI sustained a higher percentage of severe injuries than did athletes who reported normal menses. Education programs to increase knowledge and improve management of MI and its potential effects on injury in female high school athletes are warranted.
PMCID: PMC3418118  PMID: 22488233
female athlete triad; sports injuries; musculoskeletal disorders
10.  Incidence of Injuries in High School Softball and Baseball Players 
Journal of Athletic Training  2011;46(6):648-654.
Participation in high school sports has grown 16.1% over the last decade, but few studies have compared the overall injury risks in girls' softball and boys' baseball.
To examine the incidence of injury in high school softball and baseball players.
Cohort study.
Greenville, South Carolina, high schools.
Patients or Other Participants:
Softball and baseball players (n = 247) from 11 high schools.
Main Outcome Measure(s):
Injury rates, locations, types; initial or subsequent injury; practice or game setting; positions played; seasonal trends.
The overall incidence injury rate was 4.5/1000 athlete-exposures (AEs), with more injuries overall in softball players (5.6/1000 AEs) than in baseball players (4.0/1000 AEs). Baseball players had a higher initial injury rate (75.9/1000 AEs) than softball players (66.4/1000 AEs): rate ratio (RR) = 0.88, 95% confidence interval (CI) = 0.4, 1.7. The initial injury rate was higher than the subsequent injury rate for the overall sample (P < .0001) and for softball (P < .0001) and baseball (P < .001) players. For both sports, the injury rate during games (4.6/1000 AEs) was similar to that during practices (4.1/1000 AEs), RR = 1.22, 95% CI = 0.7, 2.2. Softball players were more likely to be injured in a game than were baseball players (RR = 1.92, 95% CI = 0.8, 4.3). Most injuries (77%) were mild (3.5/1000 AEs). The upper extremity accounted for the highest proportion of injuries (63.3%). The incidence of injury for pitchers was 37.3% and for position players was 15.3%. The rate of injury was highest during the first month of the season (7.96/1000 AEs).
The incidence of injury was low for both softball and baseball. Most injuries were minor and affected the upper extremity. The injury rates were highest in the first month of the season, so prevention strategies should be focused on minimizing injuries and monitoring players early in the season.
PMCID: PMC3418943  PMID: 22488191
injury rates; injury epidemiology; athletic injuries
Injury rates for softball players are similar to baseball players yet information regarding risk factors, pitching, and physical characteristics for high school windmill softball pitchers is limited. This information is needed to guide prevention, training, and rehabilitation efforts. The purpose of this study was to report descriptive data regarding the physical characteristics and pitching volume experienced by high school softball pitchers during one academic season. A secondary aim was to track and describe upper extremity injuries suffered by high school softball pitchers throughout the course of the 2009 season.
Twelve uninjured female softball pitchers (13‐18y) from 5 Greenville, South Carolina high schools participated. Prior to the 2009 season, the pitchers' shoulder internal, external, total arc of rotation and horizontal adduction PROM was measured. During the 10‐week season, aggregate pitch counts (pitch volume) and occurrence of upper extremity injury were tracked for each pitcher.
Mean preseason internal, external, and total arc of rotation PROM was observed to be similar between the pitchers' dominant and non‐dominant shoulders. The PROM measures of horizontal abduction (HA) appear to demonstrate a side‐to‐side difference with less HA on the dominant arm of the pitchers who were examined. Subjects threw in an average of 10.1 games (±4.9) during the season. Six pitchers threw in 60% or more of the team's games and 3 of 12 pitchers pitched less than 25% of games. Pitchers averaged 61.8 pitches per game (±31.5) and 745.8 (±506.4) per season. Pitch count data did not appear to be different between injured and non‐injured pitchers.
Knowledge of pitch volume can be used to prepare windmill softball pitchers for the seasonal stresses, guide establishment of goals when recovering from injury, or assist in training for an upcoming season. Further research is needed to examine larger samples of pitchers over multiple seasons and years.
Level of Evidence:
PMCID: PMC3474308  PMID: 23091788
Pitch count; shoulder; softball
The purpose of this study was to examine the relationships between isotonic ankle plantar flexor endurance (PFE), foot pronation as measured by navicular drop, and exercise-related leg pain (ERLP).
Exercise-related leg pain is a common occurrence in competitive and recreational runners. The identification of factors contributing to the development of ERLP may help guide methods for the prevention and management of overuse injuries.
Seventy-seven (44 males, 33 females) competitive runners from five collegiate cross-country (XC) teams consented to participate in the study. Isotonic ankle PFE and foot pronation were measured using the standing heel-rise and navicular drop (ND) tests, respectively. Demographic information, anthropometric measurements, and ERLP history were also recorded. Subjects were then prospectively tracked for occurrence of ERLP during the 2009 intercollegiate cross-country season. Multivariate logistic regression analysis was used to examine the relationships between isotonic ankle joint PFE and ND and the occurrence of ERLP.
While no significant differences were identified for isotonic ankle PFE between groups of collegiate XC runners with and without ERLP, runners with a ND >10 mm were almost 7 times (OR=6.6, 95% CI=1.2–38.0) more likely to incur medial ERLP than runners with ND <10 mm. Runners with a history of ERLP in the month previous to the start of the XC season were 12 times (OR=12.3, 95% CI=3.1–48.9) more likely to develop an in-season occurrence of ERLP.
While PFE did not appear to be a risk factor in the development of ERLP in this group of collegiate XC runners, those with a ND greater than 10 mm may be at greater odds of incurring medial ERLP.
Level of Evidence:
PMCID: PMC3362985  PMID: 22666641
exercise related leg pain; medial tibial stress syndrome; running; shin splints
Researchers have previously reported on the importance of dynamic balance in assessing an individual's risk for injury during sport. However, to date there is no research on whether multiple sport participation affects dynamic balance ability. Therefore, the purpose of this study was to determine if there was a difference in dynamic balance scores in high school athletes that competed in one sport only as compared athletes who competed in multiple sports, as tested by the Lower Quarter Y Balance Test (YBT-LQ).
Ninety-two high school athletes who participated in one sport were matched, by age, gender and sport played, to athletes who participated in the same sport as well as additional sports. All individuals were assessed using the YBT-LQ to examine differences in composite reach score and reach direction asymmetry between single sport and multiple sport athletes. The greatest reach distance of three trials in each reach direction for right and left lower-extremities was normalized by limb length and used for analysis. A two-way ANOVA (gender x number of sports played) was used to statistically analyze the variables in the study.
No significant interactions or main effects related to number of sports played were observed for any YBT-LQ score (p>0.05). Male athletes exhibited significantly greater normalized reach values for the posteromedial, posterolateral, and composite reach while also exhibiting a larger anterior reach difference when compared to the females. Athletes who participated in multiple sports had similar performances on the YBT-LQ when compared to athletes who participated in a single sport.
The findings of this study suggest that the number of sports played by a high school athlete does not need to be controlled for when evaluating dynamic balance with the YBT-LQ.
PMCID: PMC3325637  PMID: 22530189
Lower Quarter Y Balance Test; Pre-Participation testing; Multiple-sport athlete
14.  The Incidence and Potential Pathomechanics of Patellofemoral Pain in Female Athletes 
The aims of this study were to determine the prevalence and incidence of patellofemoral pain (PFP) in young female athletes and prospectively evaluate measures of frontal plane knee loading during landing to determine their relationship to development of PFP. We hypothesized that increased dynamic knee abduction measured during preseason biomechanical testing would be increased in those who developed PFP relative to teammates who did not develop PFP.
Middle and high school female athletes (n=240) were evaluated by a physician for PFP and for landing biomechanics prior to their basketball season. The athletes were monitored for athletic exposures and PFP injury during their competitive seasons.
At the beginning of the season, the point prevalence of PFP was 16.3 per 100 athletes. The cumulative incidence risk and rate for the development of new unilateral PFP was 9.66 per 100 athletes and 1.09 per 1000 athletic exposures, respectively. All new PFP developed in middle school athletes who demonstrated mean International Knee Documentation Committee score of 85.6 ± 7.7 at diagnosis. The new PFP group demonstrated increased knee abduction moments at initial contact (95% CI: 0.32 to 4.62 Nm) on the most-symptomatic limb and maximum (95% CI: 1.3 to 10.1 Nm; p=0.02) on the least-symptomatic (or no symptoms) limb relative to the matched control limbs. Knee abduction moments remained increased in the new PFP group when normalized to body mass (p<0.05).
The increased knee abduction landing mechanics in the new PFP group indicate that frontal plane loads contribute to increased incidence of PFP.
PMCID: PMC2900391  PMID: 20466469
Patellofemoral Pain Syndrome; Anterior Knee Pain; Biomechanics; Neuromuscular Control; Knee Valgus
15.  Alternative Methods for Measuring Scapular Muscles Protraction and Retraction Maximal Isometric Forces 
The importance of the scapular stabilizing muscles has led to an increased interest in quantitative measurements of their strength. Few studies have measured isometric or concentric isokinetic forces. Additionally, limited reports exist on the reliability of objective measures for testing scapular protraction and retraction muscle strength or scapular testing that does not involve the glenohumeral joint.
To determine the reliability of four new methods of measuring the maximal isometric strength of key scapular stabilizing muscles for the actions of protraction and retraction, both with and without the involvement of the glenohumeral (GH) joint.
The Isobex® stationary tension dynamometer was used to measure the maximal isometric force (kg) on thirty healthy females (ages 22–26 years). Three measures were taken for each method that was sequentially randomized for three separate testing sessions on three nonconsecutive days.
Intraclass correlations (ICC2,3) for intrasession reliability and (ICC3,3) for intersession reliability ranged from 0.95 to 0.98, and 0.94 to 0.96 respectively. The standard errors of measurement (95% confidence interval [CI]) were narrow. Scatter grams for both protraction and retraction testing methods demonstrated a significant relationship, 0.92 for protraction (95% CI 0.83 to 0.96) and 0.93 for retraction (95% CI 0.87 to 0.97). Bland-Altman plots indicated good agreement between the two methods for measuring protraction strength but a weaker agreement for the two methods measuring retraction strength.
The four new methods assessed in this study indicate reliable options for measuring scapular protraction or retraction isometric strength with or without involving the GH joint for young healthy females.
PMCID: PMC2953350  PMID: 21509104
scapular stabilizing muscles; isometric strength; static tension dynamometer

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