The incidence and potential pathomechanics of patellofemoral pain in female athletes

A Comparative Analysis of International Knee Documentation Committee Scores for Common Pediatric and Adolescent Knee Injuries

BACKGROUND

Several different etiologies cause knee pain in the pediatric and adolescent population, including anterior knee/patellofemoral pain, patellar instability, anterior cruciate ligament (ACL) tears, meniscal tears, osteochondritis dissecans (OCD) lesions, and discoid meniscus. The purpose of the current study was to determine the relative morbidity of different causes of knee pain in children and adolescents using the International Knee Documentation Committee (IKDC) score.

METHODS

We performed a retrospective review of prospectively collected data of a cohort of pediatric and adolescent patients with knee pain who presented to a single surgeon. Each patient completed an IKDC questionnaire at the time of diagnosis and patients were grouped by diagnosis for analysis. Statistical analysis was performed to compare the IKDC scores of the 7 diagnostic groups, and a P-value <0.05 was considered significant.

RESULTS

The IKDC mean score for all 242 patients was 50.3±18.3. The mean IKDC score for patients with isolated meniscal tears was 41.2±16.0, combined ACL and meniscal injuries was 50.2±13.9, and isolated ACL tears was 48.1±14.1. The mean IKDC score for patients with symptomatic discoid meniscus was 46.3±13.2, anterior knee pain/patellofemoral pain was 49.0±17.4, patellar instability was 49.2±22.1, and OCD lesions was 62.2±19.5.

CONCLUSIONS

The IKDC scores of most of the diagnostic groups were similar to the overall average score, with the notable exception of patients with OCD lesions exhibiting statistically significant less morbidity reflected by a higher IKDC score. Although symptoms in each individual clinical presentation may vary, knowledge of the relative morbidity of these diagnostic groups is valuable in counseling patients and their families regarding these common pediatric and adolescent sources of knee pain.

LEVEL OF EVIDENCE

Level IV.

The Effect of Patellofemoral Pain Syndrome on Gait Parameters: A Literature Review

Patellofemoral pain syndrome (PFPS) is one of the most frequent causes of anterior knee pain in adolescents and adults. This disorder can have a big effect on patients' ability and quality of life and gait. This review included all articles published during 1990 to 2016. An extensive literature search was performed in databases of Science Direct, Google Scholar, PubMed and ISI Web of Knowledge using OR, AND, NOT between the selected keywords. Finally, 16 articles were selected from final evaluation. In PFPS subjects, there was lower gait velocity, decreased cadence, and reduced knee extensor moment in the loading response and terminal stance, delayed peak rear foot eversion during gait and greater hip adduction compared to healthy subjects, while for hip rotation, there was controversy in studies. Changes in the walking patterns of PFPS subjects may be associated with the strategy used for the reduction of patellofemoral joint reaction force and pain.

Patellofemoral Pain

Patellofemoral pain is characterized by insidious onset anterior knee pain that is exaggerated under conditions of increased patellofemoral joint stress. A variety of risk factors may contribute to the development of patellofemoral pain. It is critical that the history and physical examination elucidate those risk factors specific to an individual in order to prescribe an appropriate and customized treatment plan. This article aims to review the epidemiology, risk factors, diagnosis, and management of patellofemoral pain.

The relationship between quadriceps strength and joint position sense, functional outcome and painful activities in patellofemoral pain syndrome

PURPOSE

The aim of this study was to investigate how strongly the concentric and eccentric quadriceps strengths were correlated with the joint position sense, functional outcomes and painful activities in patients with patellofemoral pain syndrome (PFPS).

METHODS

The study included forty-six women diagnosed with unilateral PFPS. Eccentric and concentric quadriceps strengths were recorded at 60 and 180°/s. Active knee joint position sense (JPS) was measured at 20° and 60° of flexion. Functional levels were determined by using Kujala patellofemoral scores. Pain levels during stair descending and ascending, squatting and prolonged sitting were measured using 0-10 cm visual analogue scale. The relationship of isokinetic quadriceps strength with JPS results, Kujala score and pain levels were evaluated using Spearman's correlation coefficient test.

RESULTS

Eccentric and concentric quadriceps strengths were significantly lower on involved side than uninvolved side. JPS results were poorer on the painful knee when compared to uninvolved side. While eccentric strength correlated with both JPS target angles, concentric strength was correlated only with 20°. Both eccentric and concentric strengths were significantly correlated with Kujala scores and pain levels.

CONCLUSION

Quadriceps eccentric strength was correlated more to joint position sense than concentric strength. Both eccentric and concentric quadriceps strength related to pain and functional level in PFPS patients.

Lower extremity rotational deformities and patellofemoral alignment parameters in patients with anterior knee pain

PURPOSE

Anterior knee pain is a common musculoskeletal condition amongst young adult population. Lower extremity structural factors, such as increased femoral anteversion and lateral tibial torsion, may contribute to patellofemoral malalignment and anterior knee pain. The aim of this study was to evaluate the lower extremity structural factors and related patellofemoral alignment parameters that play a role in the aetiology of anterior knee pain.

METHODS

This study involved three groups: patients with unilateral symptomatic knees (n = 35), asymptomatic contralateral knees in the same patients and a control group (n = 40). All subjects were physically examined, and Q-angles were measured. The lower extremities of all subjects were imaged by a very low-dose CT scan, and the symptomatic knees of patients were compared with their asymptomatic contralateral knees and with the healthy knees of controls regarding femoral anteversion, tibial torsion, sulcus angle, patellar tilt angle and lateral patellar displacement.

RESULTS

Regarding the Q-angle, femoral anteversion and lateral tibial torsion, no significant differences were found between the symptomatic and asymptomatic knees, whereas significant differences were found between the symptomatic knees and controls. The symptomatic group demonstrated significantly greater sulcus angle only in 30° of knee flexion than did the controls.

CONCLUSION

Patients with unilateral anterior knee pain may have similar morphology at their contralateral asymptomatic lower extremity, and different morphology compared with healthy controls. Lower extremity rotational deformities may increase the risk of anterior knee pain; however, these deformities alone are not sufficient to cause knee pain, and may be predisposing factor rather than a direct aetiology.

LEVEL OF EVIDENCE

Diagnostic study, Level III.

Relationships Between Age at Menarche, Walking Gait Base of Support, and Stance Phase Frontal Plane Knee Biomechanics in Adolescent Girls

BACKGROUND

Age at menarche impacts patterns of pubertal growth and skeletal development. These effects may carry over into variation in biomechanical profiles involved in sports-related traumatic and overuse knee injuries. The present study investigated whether age at menarche is a potential indicator of knee injury risk through its influence on knee biomechanics during normal walking.

OBJECTIVE

To test the hypothesis that earlier menarche is related to postpubertal biomechanical risk factors for knee injuries, including a wider, more immature gait base of support, and greater valgus knee angles and moments.

DESIGN

Cross-sectional observational study.

SETTING

University research facility.

PARTICIPANTS

Healthy, postmenarcheal, adolescent girls.

METHODS

Age at menarche was obtained by recall questionnaire. Pubertal growth and anthropometric data were collected by using standard methods. Biomechanical data were taken from tests of walking gait at self-selected speed. Reflective marker position data were collected with a 3-dimensional quantitative motion analysis system, and 3 force plates recorded kinetic data.

MAIN OUTCOME MEASURES

Age at menarche; growth and anthropometric measurements; base of support; static knee frontal plane angle; and dynamic knee frontal plane angles and moments during stance.

RESULTS

Earlier menarche was correlated significantly with abbreviated pubertal growth and postpubertal retention of immature traits, including a wider base of support. Earlier menarche and wider base of support were both correlated with more valgus static knee angles, more valgus knee abduction angles and moments at foot-strike, and a more valgus peak knee abduction angle during stance. Peak knee abduction moment during stance was not correlated with age at menarche or base of support.

CONCLUSIONS

Earlier menarche and its effects on growth are associated with retention of a relatively immature gait base of support and a tendency for static and dynamic valgus knee alignment. This biomechanical profile may put girls with earlier menarche at greater risk for sports-related knee injuries.

LEVEL OF EVIDENCE

Not applicable.

Is Knee Pain During Adolescence a Self-limiting Condition? Prognosis of Patellofemoral Pain and Other Types of Knee Pain

BACKGROUND

The prevalence of adolescent knee pain is 33%, and patellofemoral pain (PFP) is the most common diagnosis with a nontraumatic onset. The 2-year prognosis of adolescent PFP compared with other types of knee pain is unknown.

PURPOSE

To investigate the 2-year prognosis of knee pain among adolescents with and without a diagnosis of PFP.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

In 2011, a cohort of 2200 adolescents aged 15 to 19 years answered an online questionnaire on musculoskeletal pain. Of these, 504 reported knee pain, and 153 of these were clinically diagnosed with PFP. After 2 years, the 504 adolescents, as well as 252 randomly selected adolescents who did not report knee pain in 2011, were contacted again. Primary outcome at follow-up was the proportion of adolescents with knee pain during the last week prior to follow-up.

RESULTS

Overall, 55.9% (95% CI, 50.8%-60.9%) of those reporting knee pain at baseline also reported pain 2 years later. Adolescents diagnosed with PFP had a 1.26 (95% CI, 1.05-1.50) higher relative risk (RR) of knee pain at follow-up compared with other types of knee pain. Adolescents with PFP were significantly more likely to reduce or stop sports participation compared with adolescents with other types of knee pain. Of those without knee pain at baseline, 12.8% (95% CI, 8.4%-17.2%) reported knee pain at follow-up in 2013. Adolescents with knee pain at baseline had a 4.51 (95% CI, 3.15-6.45) higher RR of knee pain at follow-up compared with adolescents without knee pain at baseline.

CONCLUSION

Knee pain during adolescence, and PFP in particular, is in most cases present after 2 years and thus may not be self-limiting. A greater focus on early detection and prevention of knee pain during adolescence is needed.

Analysis of patient-reported anterior knee pain scale: implications for scale development in children and adolescents

PURPOSE

The purpose of this investigation was to estimate and document the reliability and validity of the Anterior Knee Pain Scale (AKPS) and to estimate its relative prediction accuracy of anterior knee pain in young females.

METHODS

Data from a prospective, epidemiologic study to diagnose patellofemoral knee pain among female athletes (n = 499) using the Anterior Knee Pain Scale (AKPS). Data were treated in 4 phases (descriptive phase, reliability phase, scale refinement phase) and a final validation stage that was focused on an effort to test and document the validation of the AKPS short form and perform head-to-head comparisons of the 6-item short form with the original, 13-item form.

RESULTS

The AKPS was reduced from 13 items (αCoeff = 0.77, σSEM = 0.004) to 6 items (αCoeff = 0.78, σSEM = 0.004). Point-biserial correlations with patellofemoral pain diagnosis were comparable: r [498] = 0.70 (R(2) = 0.49, short form) and r [498] = 0.71 (R(2) = 0.51, long form), as was sensitivity: 84% (short form) and 80% (long form), and specificity: 89% (short form) and 90% (long form; AUC = 0.94 both).

CONCLUSION

The current analyses indicate that a subset of measures from the AKPS is responsive to patellofemoral pain symptoms and may support screening for related diagnoses. A simpler and quicker scale optimized for diagnostic accuracy could reduce the demand on patients, clinicians and research teams focused on the identification and management of patellofemoral pain.

LEVEL OF EVIDENCE

III.

The immediate effect of lumbopelvic manipulation on EMG of vasti and gluteus medius in athletes with patellofemoral pain syndrome: A randomized controlled trial

OBJECTIVE

To evaluate the immediate effect of lubmopelvic manipulation on EMG activity of vastus medialis, vastus lateralis and gluteus medius as well as pain and functional performance of athletes with patellofemoral pain syndrome.

DESIGN

Randomized placebo-controlled trial.

METHODS

Twenty eight athletes with patellofemoral pain syndrome were randomly assigned to two groups. One group received a lubmopelvic manipulation at the side of the involved knee while the other group received a sham manipulation. EMG activity of the vasti and gluteus medius were recorded before and after manipulation while performing a rocking on heel task. The functional abilities were evaluated using two tests: step-down and single-leg hop. Additionally, the pain intensity during the functional tests was assessed using a visual analog scale.

RESULTS

The onset and amplitude of EMG activity from vastus medialis and gluteus medius were, respectively, earlier and higher in the manipulation group compared to the sham group. There were no significant differences, however, between two groups in EMG onset of vastus lateralis. While the scores of one-leg hop test were similar for both groups, significant improvement was observed in step-down test and pain intensity in the manipulation group compared to the sham group.

CONCLUSIONS

Lubmopelvic manipulation might improve patellofemoral pain and functional level in athletes with patellofemoral pain syndrome. These effects could be due to the changes observed in EMG activity of gluteus medius and vasti muscles. Therefore, the lubmopelvic manipulation might be considered in the rehabilitation protocol of the athletes with patellofemoral pain syndrome.

Motion Analysis and the Anterior Cruciate Ligament: Classification of Injury Risk

Anterior cruciate ligament (ACL) injuries are common, catastrophic events that incur large expense and lead to degradation of the knee. As such, various motion capture techniques have been applied to identify athletes who are at increased risk for suffering ACL injuries. The objective of this clinical commentary was to synthesize information related to how motion capture analyses contribute to the identification of risk factors that may predict relative injury risk within a population. Individuals employ both active and passive mechanisms to constrain knee joint articulation during motion. There is strong evidence to indicate that athletes who consistently classify as high-risk loaders during landing suffer from combined joint stability deficits in both the active and passive knee restraints. Implementation of prophylactic neuromuscular interventions and biofeedback can effectively compensate for some of the deficiencies that result from poor control of the active knee stabilizers and reduce the incidence of ACL injuries.

The relationship of foot and ankle mobility to the frontal plane projection angle in asymptomatic adults

Background

The frontal plane projection angle (FPPA) is frequently used as a measure of dynamic knee valgus during functional tasks, such as the single leg squat. Increased dynamic knee valgus is observed in people with knee pathologies including patellofemoral pain and anterior cruciate injury. As the foot is the primary interface with the support surface, foot and ankle mobility may affect the FPPA. This study investigated the relationship between foot and ankle mobility and the FPPA in asymptomatic adults.

Methods

Thirty healthy people (aged 18–50 years) performed 5 single leg squats. Peak FPPA and FPPA excursion were determined from digital video recordings. Foot mobility was quantified as the difference in dorsal midfoot height or midfoot width, between non-weightbearing and bilateral weightbearing positions. Ankle joint dorsiflexion range was measured as the maximum distance in centimetres between the longest toe and the wall during a knee-to-wall lunge. Linear regressions with generalised estimating equations were used to examine relationships between variables.

Results

Higher midfoot width mobility was associated with greater peak FPPA (β 0.90, p < 0.001, odds ratio [OR] 2.5), and FPPA excursion (β 0.67, p < 0.001, OR 1.9). Lower midfoot height mobility was associated with greater peak FPPA (β 0.37, p = 0.030, OR 1.4) and FPPA excursion (β 0.30, p = 0.020, OR 1.3). Lower ankle joint dorsiflexion was also associated with greater peak FPPA (β 0.61, p = 0.008, OR 1.8) and greater FPPA excursion (β 0.56, p < 0.001, OR 1.7).

Conclusions

Foot and ankle mobility was significantly related to the FPPA during the single leg squat in healthy individuals. Specifically, higher midfoot width mobility, or lower ankle joint dorsiflexion range and midfoot height mobility, were associated with a greater FPPA. These foot mobility factors should be considered in the clinical management of knee-related disorders that are associated with a high FPPA.

Three-dimensional hip and knee kinematics during walking, running, and single-limb drop landing in females with and without genu valgum

BACKGROUND

Dynamic knee valgus in females has been associated with various knee pathologies. Abnormal 3D hip and knee kinematics contribute prominently to this presentation, and these may become more aberrant with more demanding tasks. Underlying genu valgus may also accentuate such kinematics, but this effect has never been tested. Therefore, the purpose of this study was to compare 3D hip and knee kinematics during walking, running, and single-limb drop landing in females with and without genu valgus malalignment. We expected abnormal kinematics to become more evident in the valgus subjects as task demands increased.

METHODS

Eighteen healthy females with genu valgum and 18 female controls with normal alignment underwent 3D motion analysis while performing walking, running, and single-limb drop-landing trials. Sagittal, frontal, and transverse plane hip and knee kinematics were compared between groups across tasks using analyses of variance and between-group effect sizes.

FINDINGS

Group differences did not generally increase with higher forces. The valgus females demonstrated decreased hip flexion (ES=0.72-0.88) and increased knee abduction (ES=0.87-1.47) across the tasks. During running and single-limb drop landing, they showed increased knee external rotation (ES=0.69-0.73). Finally, during walking, the valgus females showed increased hip adduction (ES=0.69).

INTERPRETATION

These results suggest that females with genu valgus alignment utilize aberrant hip and knee mechanics previously associated with dynamic valgus in the literature, but that these pathomechanics do not generally worsen with rising task demands. Healthy females that present with genu valgus may be natively at elevated risk for knee pathology.

Knee orthoses for treating patellofemoral pain syndrome

BACKGROUND

Patellofemoral pain syndrome (PFPS) is a painful musculoskeletal condition, which is characterised by knee pain located in the anterior aspect (front) and retropatellar region (behind) of the knee joint. Various non-operative interventions are suggested for the treatment of this condition. Knee orthoses (knee braces, sleeves, straps or bandages) are worn over the knee and are thought to help reduce knee pain. They can be used in isolation or in addition to other treatments such as exercise or non-steroidal anti-inflammatory medications.

OBJECTIVES

To assess the effects (benefits and harms) of knee orthoses (knee braces, sleeves, straps or bandages) for treating PFPS.

SEARCH METHODS

We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (11 May 2015), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2015 Issue 5), MEDLINE (1946 to 8 May 2015), EMBASE (1980 to 2015 Week 18), SPORTDiscus (1985 to 11 May 2015), AMED (1985 to 8 May 2015), CINAHL (1937 to 11 May 2015), PEDro (1929 to June 2015), trial registries and conference proceedings.

SELECTION CRITERIA

Randomised and quasi-randomised controlled clinical trials evaluating knee orthoses for treating people with PFPS. Our primary outcomes were pain and function.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for eligibility, assessed study risk of bias and extracted data. We calculated mean differences (MD) or, where pooling data from different scales, standardised mean differences (SMD) with 95% confidence intervals (CI) for continuous outcomes and risk ratios (RR) with 95% CIs for binary outcomes. We pooled data using the fixed-effect model.

MAIN RESULTS

We included five trials (one of which was quasi-randomised) that reported results for 368 people who had PFPS. Participants were recruited from health clinics in three trials and were military recruits undergoing training in the other two trials. Although no trials recruited participants who were categorised as elite or professional athletes, military training does comprise intensive exercise regimens. All five trials were at high risk of bias, including performance bias reflecting the logistical problems in these trials of blinding of participants and care providers. As assessed using the GRADE approach, the available evidence for all reported outcomes is 'very low' quality. This means that we are very uncertain about the results.The trials covered three different types of comparison: knee orthosis and exercises versus exercises alone; one type of orthosis versus another; and knee orthosis versus exercises. No trials assessed the mode of knee orthosis use, such as whether the orthosis was worn all day or only during physical activity. Two trials had two groups; two trials had three groups; and one trial had four groups.All five trials compared a knee orthosis (knee sleeve, knee brace, or patellar strap) versus a 'no treatment' control group, with all participants receiving exercises, either through a military training programme or a home-based exercise programme. There is very low quality evidence of no clinically important differences between the two groups in short-term (2 to 12 weeks follow-up) knee pain based on the visual analogue scale (0 to 10 points; higher scores mean worse pain): MD -0.46 favouring knee orthoses, 95% CI -1.16 to 0.24; P = 0.19; 234 participants, 3 trials). A similar lack of clinically important difference was found for knee function (183 participants, 2 trials). None of the trials reported on quality of life measures, resource use or participant satisfaction. Although two trials reported on the impact on sporting or occupational participation, one trial (35 participants) did not provide data split by treatment group on the resumption of sport activity and the other reported only on abandonment of military training due to knee pain (both cases were allocated a knee orthosis). One trial (59 participants, 84 affected knees) recording only adverse events in the two knee orthoses (both were knee sleeves) groups, reported 16 knees (36% of 44 knees) had discomfort or skin abrasion.Three trials provided very low quality evidence on single comparisons of different types of knee orthoses: a knee brace versus a knee sleeve (63 participants), a patella strap with a knee sleeve (31 participants), and a knee sleeve with a patellar ring versus a knee sleeve only (44 knees). None of three trials found an important difference between the two types of knee orthosis in pain. One trial found no clinically important difference in function between a knee brace and a knee sleeve. None of the three trials reported on quality of life, resource use or participant satisfaction. One trial comparing a patella strap with a knee sleeve reported that both participants quitting military training due to knee pain were allocated a knee sleeve. One poorly reported trial found three times as many knees with adverse effects (discomfort or skin abrasion) in those given knee sleeves with a patella ring than those given knee sleeves only.One trial compared a knee orthosis (knee brace) with exercise (66 participants). It found very low quality evidence of no clinically important difference between the two intervention groups in pain or knee function. The trial did not report on quality of life, impact on sporting or occupational participation, resource use, participant satisfaction or complications.

AUTHORS' CONCLUSIONS

Overall, this review has found a lack of evidence to inform on the use of knee orthoses for treating PFPS. There is, however, very low quality evidence from clinically heterogeneous trials using different types of knee orthoses (knee brace, sleeve and strap) that using a knee orthosis did not reduce knee pain or improve knee function in the short term (under three months) in adults who were also undergoing an exercise programme for treating PFPS. This points to the need for good-quality clinically-relevant research to inform on the use of commonly-available knee orthoses for treating PFPS.

The Feasibility of Using Augmented Auditory Feedback From a Pressure Detecting Insole to Reduce the Knee Adduction Moment: A Proof of Concept Study

The objective of this work was to conduct a proof of concept study utilizing auditory feedback from a pressure-detecting shoe insole to shift plantar pressure medially in order to reduce the knee adduction moment (KAM). When compared with normal walking, 32 healthy subjects significantly reduced their peak KAM using feedback (p < 0.001). When compared with medial thrust gait, an established gait modification, walking with pressure-based feedback was equally effective at reducing the peak KAM, yet it successfully mitigated other potentially detrimental gait measures such as the peak knee flexion moment (KFM), knee internal rotation moment (KIrM), and a reduction in speed.

CLINICAL PROGNOSTIC FACTORS FOR PATIENTS WITH ANTERIOR KNEE PAIN IN PHYSICAL THERAPY; A SYSTEMATIC REVIEW

BACKGROUND

Although many authors have studied the prognostic factors that may contribute to anterior knee pain, synthesis of the existing evidence has not been performed.

PURPOSE

The purpose of this systematic review is to summarize and examine existing prognostic models in patients with anterior knee pain that first present to physical therapists (primary care setting).

DESIGN

Systematic review.

METHOD

For this review Pubmed, Embase and Cinahl databases were searched and published papers that reported prognostic models for patients with anterior knee pain that first present to physical therapists (primary care setting) were selected. The authors extracted and summarized the univariate and multivariate predictors and evaluated which predictors consistently appeared to be relevant to pain, function, or recovery.

RESULTS

Nine studies were included. The quality scores of these studies ranged from 9 to 17 positive items out of 21 items included in the assessment for quality. None of the prognostic models were validated internally or externally. Four studies were considered to be of sufficient quality. The authors of these four studies found 14 different predictors significantly related to pain intensity of which seven with limited evidence. Fifteen different predictors were found that were related to function of which seven with limited evidence. Furthermore, strong evidence was found that baseline pain intensity, pain coping and kinesiophobia are of no predictive value for pain, and activity related pain, pain coping and kinesiophobia are of no predictive value for function at follow up.

CONCLUSIONS

Because of the low quality of a number of studies and the heterogeneity of the examined variables and outcome measures of most of the studies, only limited evidence for seven predictors related to pain and seven predictors related to function in patients with anterior knee pain in a primary care setting was found.

LEVEL OF EVIDENCE

1b.

Hip Strength Is Greater in Athletes Who Subsequently Develop Patellofemoral Pain

BACKGROUND

Hip and knee strength abnormalities have been implicated in patellofemoral pain (PFP) in multiple studies. However, the relationship is unclear, as many of these studies have been retrospective.

PURPOSE

To compare prospective hip and knee isokinetic strength in young female athletes who subsequently went on to develop PFP relative to their uninjured, healthy peers.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

Adolescent female athletes (N = 329) were tested for isokinetic strength of the knee (flexion and extension) and hip (abduction) and screened for the prevalence of PFP before their basketball seasons. After exclusion based on current PFP symptoms, 255 participants were prospectively enrolled in the study. A 1-way analysis of variance was used to determine between-group differences in incident PFP and the referent (no incident PFP) participants.

RESULTS

The cumulative incidence rate for the development of PFP was 0.97 per 1000 athlete-exposures. Female athletes who developed PFP demonstrated increased normalized hip abduction strength (normalized torque, 0.013 ± 0.003) relative to the referent control group (normalized torque, 0.011 ± 0.003) (P < .05). Unlike hip strength, normalized knee extension and knee flexion strength were not different between the 2 groups (P > .05).

CONCLUSION

The findings in this study indicate that young female athletes with greater hip abduction strength may be at an increased risk for the development of PFP. Previous studies that have looked at biomechanics indicated that those with PFP have greater hip adduction dynamic mechanics.

CLINICAL RELEVANCE

Combining the study data with previous literature, we theorize that greater hip abduction strength may be a resultant symptom of increased eccentric loading of the hip abductors associated with increased dynamic valgus biomechanics, demonstrated to underlie increased PFP incidence. Further research is needed to verify the proposed mechanistic link to the incidence of PFP.

Sports Specialization, Part II: Alternative Solutions to Early Sport Specialization in Youth Athletes

Context:

Many coaches, parents, and children believe that the best way to develop elite athletes is for them to participate in only 1 sport from an early age and to play it year-round. However, emerging evidence to the contrary indicates that efforts to specialize in 1 sport may reduce opportunities for all children to participate in a diverse year-round sports season and can lead to lost development of lifetime sports skills. Early sports specialization may also reduce motor skill development and ongoing participation in games and sports as a lifestyle choice. The purpose of this review is to employ the current literature to provide evidence-based alternative strategies that may help to optimize opportunities for all aspiring young athletes to maximize their health, fitness, and sports performance.

Evidence Acquisition:

Nonsystematic review with critical appraisal of existing literature.

Study Design:

Clinical review.

Level of Evidence:

Level 4.

Conclusion:

Based on the current evidence, parents and educators should help provide opportunities for free unstructured play to improve motor skill development and youth should be encouraged to participate in a variety of sports during their growing years to influence the development of diverse motor skills. For those children who do choose to specialize in a single sport, periods of intense training and specialized sport activities should be closely monitored for indicators of burnout, overuse injury, or potential decrements in performance due to overtraining. Last, the evidence indicates that all youth should be involved in periodized strength and conditioning (eg, integrative neuromuscular training) to help them prepare for the demands of competitive sport participation, and youth who specialize in a single sport should plan periods of isolated and focused integrative neuromuscular training to enhance diverse motor skill development and reduce injury risk factors.

Strength of Recommendation Taxonomy (SORT):

B.

Long-term athletic development, part 2: barriers to success and potential solutions

The first installment of this two-part commentary reviewed existing models of long-term athletic development. However, irrespective of the model that is adopted by practitioners, existing structures within competitive youth sports in addition to the prevalence of physical inactivity in a growing number of modern-day youth may serve as potential barriers to the success of any developmental pathway. The second part of this commentary will initially highlight common issues that are likely to impede the success of long-term athletic development programs and then propose solutions that will address the negative impact of such issues.

Can two-dimensional video analysis during single-leg drop vertical jumps help identify non-contact knee injury risk? A one-year prospective study

BACKGROUND

Previous studies showed that the amount of hip flexion and the combination of knee valgus and lateral trunk motion, measured with two-dimensional video analysis, were related to three-dimensional measured knee joint moments during single-leg drop vertical jumps, but it remains unclear whether these measurements can be used to identify non-contact knee injury risk.

METHODS

Fifty injury-free female athletes participated in the study. Two-dimensional video analysis was used to measure hip flexion, knee valgus and lateral trunk motion angles during single-leg drop vertical jumps. Time loss non-contact knee injuries were registered during a one-year follow-up. Independent t-tests and receiver operating characteristic analysis were used to analyze the predictive ability of the two-dimensional angles.

FINDINGS

Seven participants sustained a time loss non-contact knee injury. Hip flexion was not significantly different between groups (P>.05). The combination of knee valgus and lateral trunk motion was significantly smaller in the injured (P=.036) and non-injured legs (P=.009) of the future injured group compared with the respective matched leg of the non-injured group. The receiver operating characteristic analysis showed a significant discriminative accuracy between groups for the combination of knee valgus and lateral trunk motion of the uninjured leg of the future injured group with the matched leg of the non-injured group (area under curve=0.803; P=.012).

INTERPRETATION

The measurement of a combination of increased knee valgus and ipsilateral trunk motion during the single-leg drop vertical jump with two-dimensional video analysis can be used to help identify female athletes with increased non-contact knee injury risk.

Improving Single-Legged-Squat Performance: Comparing 2 Training Methods With Potential Implications for Injury Prevention

CONTEXT

Poor dynamic limb alignment during loading tasks has links to the development of knee injuries, including patellofemoral pain and anterior cruciate ligament injury. Therefore, modalities to improve limb alignment during loading tasks are thought to reduce loading through these structures and potentially prevent injury.

OBJECTIVE

To compare hip-strengthening and skill-acquisition training to examine if they can improve lower limb biomechanics, potentially preventing injury, and to examine whether changes demonstrated can be maintained after 6 weeks of no practice.

DESIGN

Controlled laboratory study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 19 recreationally active individuals volunteered, and 17 (9 women: age = 27.9 ± 3.1 years, height = 165.4 ± 8.4 cm, mass = 60.5 ± 9.2 kg; 8 men: age = 30.4 ± 6.4 years, height = 181.4 ± 7.1 cm, mass = 69.8 ± 15.2 kg) completed the study. Nine participants were allocated to a hip-strengthening program; 8, to a skill-acquisition program.

INTERVENTION(S)

Participants performed a 6-week training program of either hip strengthening (n = 9) or skill acquisition (n = 8) 3 times per week.

MAIN OUTCOME MEASURE(S)

Measurements of clam-exercise strength, hip-abduction strength, frontal-plane projection angle, hip-adduction angle, and a qualitative score were taken at baseline, 6 weeks, and 12 weeks.

RESULTS

We observed improvements in frontal-plane projection angle (strength: t8 = 5.344, P = .001; skill: t7 = 4.393, P = .003), hip-adduction angle (strength: t8 = 3.597, P = .007; skill: t7 = 4.722, P = .002), and qualitative score (strength: t8 = 3.900, P = .005; skill: t7 = 8.283, P < .001) postintervention, which were retained at the 12-week retest in both groups.

CONCLUSIONS

A 6-week intervention of either hip-strengthening or skill-acquisition training improved lower limb biomechanics. The changes in biomechanics after skill training were retained at 12 weeks, suggesting a change in motor patterning that could be favorable to longer-term injury prevention.

Clinical assessment of countermovement jump landing kinematics in early adolescence: Sex differences and normative values

BACKGROUND

Adolescent females have been reported to have a higher risk of non-contact knee joint injuries compared to their male counterparts, with deficiencies in neuromuscular control being purported to be the primary differentiating factor. As such, assessment of movement quality during functional screening tests in this population is warranted. Widespread implementation of such screening requires clinically accessible screening measures and normative data. Therefore, the aim of the present study was to provide normative data for clinical analysis of landing kinematics in early adolescent male and female athletes, with a corollary of determining whether a difference between the sexes is evident with such screening.

METHODS

Ninety seven male and 84 female athletes (mean age=13±1.41years) in the first year of high school participated. Each participant performed 3 countermovement jump trials. Frontal and sagittal plane knee joint angles were recorded by video cameras for both dominant and non-dominant limbs. A multivariate analysis of variance (MANOVA) was used to determine the effect of sex on the dependent variables.

FINDINGS

Males displayed significantly greater knee flexion prior to initial contact (P<0.001) and knee varus displacement (P<0.001). No differences were observed between males and females for max knee flexion (P>0.05).

INTERPRETATION

Early adolescent female athletes demonstrate less desirable landing biomechanics than their male peers. The first year in high school, when early adolescent females are first exposed to high school sports, may be an ideal time to assess movement quality during functional tasks and intervene with injury prevention programs if necessary.

Evaluating eccentric hip torque and trunk endurance as mediators of changes in lower limb and trunk kinematics in response to functional stabilization training in women with patellofemoral pain

BACKGROUND

Altered movement patterns of the trunk and lower limbs have been associated with patellofemoral pain (PFP). It has been assumed that increasing the strength of the hip and trunk muscles would improve lower limb and trunk kinematics in these patients. However, evidence in support of that assumption is limited.

PURPOSE

To determine whether increases in the strength of hip muscles and endurance of trunk muscles in response to functional stabilization training will mediate changes in frontal plane lower limb kinematics in patients with PFP.

STUDY DESIGN

Controlled laboratory study.

METHODS

Thirty-one female athletes were randomized to either a functional stabilization training group that emphasized strengthening of the trunk and hip muscles or a standard training group that emphasized stretching and quadriceps strengthening. Patients attended a baseline assessment session, followed by 8 weeks of intervention, and were then reassessed at the end of the intervention period. The potential mediators that were evaluated included eccentric torque of hip muscles and endurance of the trunk muscles. The outcome variables were the lower limb and trunk kinematics in the frontal plane assessed during a single-legged squat task.

RESULTS

The eccentric strength of the gluteus muscles showed a mediation effect ranging from 18% to 32% on changes to frontal plane kinematics (decreased ipsilateral trunk inclination, pelvis contralateral depression, and hip adduction excursions) observed in the functional stabilization training group after intervention.

CONCLUSION

Although the mediation effects were small, the results suggest that improvements in the strength of the gluteus muscles can influence the frontal plane movement patterns of the lower limb and trunk in women with PFP.

CLINICAL RELEVANCE

Patients with PFP might benefit from strengthening of the hip muscles to improve frontal plane lower limb and trunk kinematics during functional tasks.

DEMOGRAPHIC AND EPIDEMIOLOGICAL TRENDS IN PATELLOFEMORAL PAIN

BACKGROUND

Understanding the demographics of patellofemoral pain is important to determine the best practices in diagnosis and treatment of this difficult pathology. The occurrence of patellofemoral pain has been reported from isolated sports medicine clinics and from within the military, but its incidence has never been examined in the general population within the United States.

PURPOSE

The purpose of this study was to examine the reported occurrence of patellofemoral pain for those individuals seeking medical care and to compare that to all other pathologies that result in anterior knee pain, such as tendinopathies, patella subluxation, osteoarthritis, or meniscal and bursal conditions. Occurrence rates were examined across sex, age and region within a large healthcare provider database that contains over 30 million individuals.

METHODS

Data were queried with the PearlDiver Patient Record Database, a national database containing orthopedic patient records. Two common International Classification of Disease, Ninth Revision (ICD-9) codes for patellofemoral pain (717.7 - Patella Chondromalacia and 719.46 - Pain in joint, lower leg) were utilized and were searched from the years 2007-2011. The top twenty additional ICD-9 codes that were concurrently coded with 717.7 and 719.46 were removed from the data. Chi-squared and Mantel-Haenszel tests were utilized to identify statistically significant differences in the diagnosis of patellofemoral pain between sex, age, and year.

RESULTS

During this five-year period, there were 2,188,753 individuals diagnosed with patellofemoral pain. The diagnosis was more common in females compared to males with 1,211,665 and 977,088 cases respectfully (p<0.001). Statistically significant differences between ages was found, with 50-59 year olds having the most cases with 578,854, p<0.001. And, during the five-year examination period, there was a steady increase between 2007-2011, p<0.01.

CONCLUSION

Patellofemoral pain was diagnosed between 1.5% and 7.3% of all patients seeking medical care within the United States. Females experienced patellofemoral pain more often than males and there was a steady increase of cases in the United States during the 2007-2011 examination period. The diagnosis of patellofemoral pain increased with age and the 50-59 year old age group had the most cases.

LEVEL OF EVIDENCE

2b.

Can two-dimensional measured peak sagittal plane excursions during drop vertical jumps help identify three-dimensional measured joint moments?

BACKGROUND

Less optimal sagittal plane movement patterns are believed to increase knee injury risk in female athletes. To facilitate clinical screening with a user-friendly method, the purpose of the present study was to examine the temporal relationships between two-dimensional measured sagittal plane kinematics and three-dimensional joint moments during the double-leg drop vertical jump (DVJ) and single-leg DVJ (SLDVJ).

METHODS

Fifty injury-free female athletes were tested. Maximal excursions of hip flexion, knee flexion and ankle dorsiflexion were measured through two-dimensional video analysis. Three-dimensional motion and ground reaction forces were recorded to calculate external hip flexion, knee flexion and knee abduction moments during the entire stance phase of DVJ and SLDVJ. One-dimensional statistical parametric mapping was used to examine relationships between peak two-dimensional kinematic variables and three-dimensional moment profiles.

RESULTS

Hip flexion was significantly related to the hip and knee flexion moment for both tests and knee abduction moment for DVJ during the time frames corresponding with highest three-dimensional moments, while knee flexion was significantly related to the hip flexion moment during these time frames. No significant relationships were found for ankle dorsiflexion with any of the joint moments.

CONCLUSIONS

Two-dimensional measured sagittal plane hip flexion angles at the deepest landing position were associated with peak joint moments of the hip and knee during DVJ and SLDVJ, while the amount of knee flexion was only associated with the hip flexion moment. Assessment of knee injury risk with two-dimensional video analysis could benefit from measuring maximal hip flexion, more so than knee flexion.

Low prevalence of isolated medial meniscal tears in young females with stable knees

The information regarding isolated tears of the meniscus in stable knees (ie, without cruciate ligament tears), specifically in a younger population, is scarce. Although surgical treatment is preferred for young patients with meniscal tears, the diagnosis at this age may be misled by other sources of knee pain. The purpose of this study was to report on the prevalence and sex variance of isolated meniscal tears in a younger population based on arthroscopic findings. From a database of 2425 arthroscopic knee surgeries performed over a period of 6 years, 591 patients (480 males and 111 females) younger than 40 years were included. Patients were divided into 5 age groups and subdivided according to their surgical findings. Measures included the prevalence of meniscal tears according to sex and age groups and also odds ratio calculations for the presence of meniscal tears. Of 591 arthroscopic surgeries in young patients with stable knees, only 6 females (vs 87 males) younger than 30 years had isolated medial meniscus tears. The number of stable knees without meniscal tear at arthroscopy in all age groups was relatively high. The odds ratio for having a medial meniscal tear was significantly higher in males. The results suggest a protective mechanism for isolated medial meniscal tears in younger females as opposed to other injuries of the knee. Isolated medial meniscus tears in stable knees are uncommon in females younger than 30 years; thus, young females with suspected tears should be reevaluated and treated conservatively before considering surgical solutions.

Hip rotation angle is associated with frontal plane knee joint mechanics during running

Inability to control lower extremity segments in the frontal and transverse planes resulting in large knee abduction angle and increased internal knee abduction impulse has been associated with patellofemoral pain (PFP). However, the influence of hip rotation angles on frontal plane knee joint kinematics and kinetics remains unclear. The purpose of this study was to explore how hip rotation angles are related to frontal plane knee joint kinematics and kinetics during running. Seventy runners participated in this study. Three-dimensional marker positions and ground reaction forces were recorded with an 8-camera motion analysis system and a force plate while subjects ran along a 25-m runway at a speed of 4m/s. Knee abduction, hip rotation and toe-out angles, frontal plane lever arm at the knee, internal knee abduction moment and impulse, ground reaction forces and the medio-lateral distance from the ankle joint center to the center of pressure (AJC-CoP) were quantified. The findings of this study indicate that greater hip external rotation angles were associated with greater toe-out angles, longer AJC-CoP distances, smaller internal knee abduction impulses with shorter frontal plane lever arms and greater knee abduction angles. Thus, there appears to exist a conflict between kinematic and kinetic risk factors of PFP, and hip external rotation angle may be a key factor to control frontal plane knee joint kinematics and kinetics. These results may help provide an appropriate manipulation and/or intervention on running style to reduce the risk of PFP.

Effects of compliance on trunk and hip integrative neuromuscular training on hip abductor strength in female athletes

Recent studies demonstrate the link between reduced hip abductor strength and increased risk for knee injury such as patellofemoral pain syndrome in women athletes. Meta-analytic reports indicate that the efficacy of integrative neuromuscular training (INT) is associated with compliance to the prescribed programming. Thus, the purpose was to investigate the compliance effects of a trunk and hip-focused INT exercises on hip abductor strength in young women athletes. In a controlled laboratory study design, 21 high school women volleyball players (mean age = 15.6 ± 1.4 years, weight = 64.0 ± 7.4 kg, height = 171.5 ± 7.0 cm) completed isokinetic hip abductor strength testing in pre- and postintervention, which consisted of 5 phases of supervised progressive trunk and hip-focused INT exercises twice a week for 10 weeks. The compliance effects were analyzed based on the changed hip abductor strength values between pre- and postintervention and 3 different compliance groups using 1-way analysis of variance and Pearson's correlation coefficients. The participants in the high-compliance group demonstrated significant hip abductor peak torque increases compared with noncompliance group (p = 0.02), but not between moderate-compliance and noncompliance groups (p = 0.27). The moderate correlation coefficient value (r = 0.56) was recorded between the isokinetic hip abductor peak torque changes and the 3 compliance groups. Because of the observed significant effects and moderate linear association, the effectiveness of a trunk and hip-focused INT protocol to improve hip abduction strength seems dependent on compliance. Compliance of trunk and hip-focused INT is an important aspect of increasing hip abductor strength increase in young women athletes.

High knee abduction moments are common risk factors for patellofemoral pain (PFP) and anterior cruciate ligament (ACL) injury in girls: is PFP itself a predictor for subsequent ACL injury?

BACKGROUND

Identifying risk factors for knee pain and anterior cruciate ligament (ACL) injury can be an important step in the injury prevention cycle.

OBJECTIVE

We evaluated two unique prospective cohorts with similar populations and methodologies to compare the incidence rates and risk factors associated with patellofemoral pain (PFP) and ACL injury.

METHODS

The 'PFP cohort' consisted of 240 middle and high school female athletes. They were evaluated by a physician and underwent anthropometric assessment, strength testing and three-dimensional landing biomechanical analyses prior to their basketball season. 145 of these athletes met inclusion for surveillance of incident (new) PFP by certified athletic trainers during their competitive season. The 'ACL cohort' included 205 high school female volleyball, soccer and basketball athletes who underwent the same anthropometric, strength and biomechanical assessment prior to their competitive season and were subsequently followed up for incidence of ACL injury. A one-way analysis of variance was used to evaluate potential group (incident PFP vs ACL injured) differences in anthropometrics, strength and landing biomechanics. Knee abduction moment (KAM) cut-scores that provided the maximal sensitivity and specificity for prediction of PFP or ACL injury risk were also compared between the cohorts.

RESULTS

KAM during landing above 15.4 Nm was associated with a 6.8% risk to develop PFP compared to a 2.9% risk if below the PFP risk threshold in our sample. Likewise, a KAM above 25.3 Nm was associated with a 6.8% risk for subsequent ACL injury compared to a 0.4% risk if below the established ACL risk threshold. The ACL-injured athletes initiated landing with a greater knee abduction angle and a reduced hamstrings-to-quadriceps strength ratio relative to the incident PFP group. Also, when comparing across cohorts, the athletes who suffered ACL injury also had lower hamstring/quadriceps ratio than the players in the PFP sample (p<0.05).

CONCLUSIONS

In adolescent girls aged 13.3 years, >15 Nm of knee abduction load during landing is associated with greater likelihood of developing PFP. Also, in girls aged 16.1 years who land with >25 Nm of knee abduction load during landing are at increased risk for both PFP and ACL injury.

Forefoot varus predicts subtalar hyperpronation in young people

BACKGROUND

Subtalar joint hyperpronation is a foot misalignment that has been associated with several musculoskeletal injuries. Forefoot varus is thought to result in subtalar hyperpronation during weightbearing circumstances. However, few studies have aimed to verify whether there is a significant relationship between forefoot alignment and subtalar hyperpronation. Moreover, no study has attempted to verify whether forefoot varus can predict subtalar hyperpronation in young individuals. Therefore, the purpose of this study was to verify whether forefoot varus can predict subtalar hyperpronation, measured using the rearfoot eversion angle test, the navicular drop test, and the Foot Posture Index (FPI), in young people.

METHODS

Fifty-four healthy adolescents volunteered for this study (28 boys and 26 girls). A single examiner evaluated the forefoot angle, rearfoot angle, navicular drop, and FPI of each participant. Statistical analysis included the Pearson correlation test and a linear regression analysis to establish the relationship between the variables.

RESULTS

These results showed a high positive correlation between forefoot varus and rearfoot angle (r = 0.86; P < .001), navicular drop (r = 0.76; P < .001), and FPI (r = 0.82; P < .001). Moreover, the forefoot varus variable was able to predict 74% of the variability in the rearfoot angle, 58% in the navicular drop, and 67% in the FPI (P < .001).

CONCLUSIONS

These findings support previous assumptions that individuals with forefoot varus present subtalar hyperpronation. Clinicians should not overlook forefoot alignment when prescribing foot orthoses for treating patients with foot misalignments.

Increased medial foot loading during drop jump in subjects with patellofemoral pain

PURPOSE

To compare medial-to-lateral plantar forces during drop jump and single leg squat in individuals with and without patellofemoral pain.

METHODS

This cross-sectional study compared 23 young adults with patellofemoral pain to 20 age- and sex-matched controls without knee pain. The plantar pressure distribution was collected during drop jump and single leg squat using pressure-sensitive Pedar insoles, inserted into a standard flat shoe. The primary outcome was the medial-to-lateral force, quantified as the peak force under the medial forefoot as the percentage of force under the total forefoot during drop jump. Secondary outcomes included peak medial-to-lateral force during single leg squat and mean forces during drop jump and single leg squat.

RESULTS

The primary outcome showed that individuals with patellofemoral pain had a 22% higher medial-to-lateral peak force during drop jump, (p=0.03). Secondary outcomes showed 32% higher medial-to-lateral peak force during single leg squat (p=0.01) and 19-23% higher medial-to-lateral mean force during drop jump and single leg squat (p=0.02-0.04).

CONCLUSION

These findings indicate that individuals with patellofemoral pain display a more medially oriented loading pattern of the forefoot compared to individuals without knee pain. This loading pattern may be associated with the distribution of forces acting on the patellofemoral joint and suggest treatment of PFP should consider interventions that target normalisation of foot loading.

LEVEL OF EVIDENCE

III.

The effect of videotape augmented feedback on drop jump landing strategy: Implications for anterior cruciate ligament and patellofemoral joint injury prevention

BACKGROUND

Modification of high-risk movement strategies such as dynamic knee valgus is key to the reduction of anterior cruciate ligament (ACL) and patellofemoral joint (PFJ) injuries. Augmented feedback, which includes video and verbal feedback, could offer a quick, simple and effective alternative to training programs for altering high-risk movement patterns. It is not clear whether feedback can reduce dynamic knee valgus measured using frontal plane projection angle (FPPA).

METHODS

Vertical ground reaction force (vGRF), two-dimensional FPPA of the knee, contact time and jump height of 20 recreationally active university students were measured during a drop jump task pre- and post- an augmented feedback intervention. A control group of eight recreationally active university students were also studied at baseline and repeat test.

RESULTS

There was a significant reduction in vGRF (p=0.033), FPPA (p<0.001) and jump height (p<0.001) and an increase in contact time (p<0.001) post feedback in the intervention group. No changes were evident in the control group.

CONCLUSION

Augmented feedback leads to significant decreases in vGRF, FPPA and contact time which may help to reduce ACL and PFJ injury risk. However, these changes may result in decreased performance.

CLINICAL RELEVANCE

Augmented feedback reduces dynamic knee valgus, as measured via FPPA, and forces experienced during the drop jump task and therefore could be used as a tool for helping decrease ACL and PFJ injury risk prior to, or as part of, the implementation of injury prevention training programs.

Return to play following ACL reconstruction: a systematic review about strength deficits

PURPOSE

There is a lack of consensus regarding appropriate criteria attesting patients' unrestricted sports activities after ACL reconstruction. Purpose of this study was to perform a systematic review about strength deficits to find out if a strength test might be a return to play criterion.

DATA SOURCE

Pubmed central, Google Scholar.

STUDY ELIGIBILITY CRITERIA

English language articles.

INTERVENTIONS

Strength tests after ACL reconstruction with autologous tendon grafts.

METHODS

A systematic search for articles about muscle strength after ACL reconstruction was performed.

RESULTS

Forty-five articles could be identified. All articles identified reported strength deficits after ACL reconstruction in comparison to control subjects. Some of these deficits persisted up to 5 years after surgery. Knee flexor strength is more impaired after ACL reconstruction with hamstring grafts and quadriceps strength after BPTB ACL reconstruction.

CONCLUSION

Strength deficits of hip, knee and ankle muscles are reported after ACL reconstruction. Muscular strength test may be an important tool to determine if an athlete can return to competitive sports after ACL reconstruction.

Effects of open and closed kinetic chains of sling exercise therapy on the muscle activity of the vastus medialis oblique and vastus lateralis

[Purpose] The muscle strength of the quadriceps muscle is critical in patellofemoral pain syndrome. The quadriceps muscle supplies the power for dynamic patellar movement, and the vastus medialis oblique (VMO) and vastus lateralis (VL) enable the patella to stabilize during tracking. We followed the theories about open and closed kinetic chain exercises to design two exercises, sling open chain knee extension (SOCKE) exercise and sling closed chain knee extension (SCCKE) exercise. The purpose of our study was to research the changes in quadriceps muscle activity during both exercises. [Methods] Electromyographic analysis was used to explore the different effects of the two exercises. The MVC% was calculated for the VMO and VL during exercise for analysis. [Results] We found that the mean MVC% values of the VMO and VL during the SOCKE exercise were higher than those during the SCCKE exercise. The ratio of the VMO to VL was 1.0 ± 0.19 during the SOCKE exercise and 1.11 ± 0.15 during the SCCKE exercise. [Conclusions] The SOCKE exercise is targeted at quadriceps muscle training and has a recruitment effect on the VMO. The beneficial effect of the SOCKE exercise is better than that of the SCCKE exercise.

Comparison of isokinetic hip abduction and adduction peak torques and ratio between sexes

OBJECTIVE

To evaluate hip abductor and adductor peak torque outputs and compare their ratios between sexes.

DESIGN

A cross-sectional laboratory-controlled study.

SETTING

Participants visited a laboratory and performed an isokinetic hip abductor and adductor test. All participants performed 2 sets of 5 repetitions of concentric hip abduction and adduction in a standing position at 60 degrees per second. Gravity was determined as a function of joint angle relative to the horizontal plane and was corrected by normalizing the weight of the limb on an individual basis.

PARTICIPANTS

A total of 36 collegiate athletes.

INDEPENDENT VARIABLES

Sex (20 females and 16 males).

MAIN OUTCOME MEASURES

Bilateral peak hip abductor and adductor torques were measured. The 3 highest peak torque values were averaged for each subject.

RESULTS

Independent t tests were used to compare sex differences in hip abductor and adductor peak torques and the abductor:adductor peak torque ratios. Males demonstrated significantly greater hip abductor peak torque compared with females (males 1.29 ± 0.24 Nm/kg, females 1.13 ± 0.20 Nm/kg; P = 0.03). Neither hip adductor peak torque nor their ratios differed between sexes.

CONCLUSIONS

Sex differences in hip abductor strength were observed. The role of weaker hip abductors in females deserves further attention and may be a factor for higher risk of knee pathologies.

Consistency of clinical biomechanical measures between three different institutions: implications for multi-center biomechanical and epidemiological research

PURPOSE/BACKGROUND

Multi-center collaborations provide a powerful alternative to overcome the inherent limitations to single-center investigations. Specifically, multi-center projects can support large-scale prospective, longitudinal studies that investigate relatively uncommon outcomes, such as anterior cruciate ligament injury. This project was conceived to assess within- and between-center reliability of an affordable, clinical nomogram utilizing two-dimensional video methods to screen for risk of knee injury. The authors hypothesized that the two-dimensional screening methods would provide good-to-excellent reliability within and between institutions for assessment of frontal and sagittal plane biomechanics.

METHODS

Nineteen female, high school athletes participated. Two-dimensional video kinematics of the lower extremity during a drop vertical jump task were collected on all 19 study participants at each of the three facilities. Within-center and between-center reliability were assessed with intra- and inter-class correlation coefficients.

RESULTS

Within-center reliability of the clinical nomogram variables was consistently excellent, but between-center reliability was fair-to-good. Within-center intra-class correlation coefficient for all nomogram variables combined was 0.98, while combined between-center inter-class correlation coefficient was 0.63.

CONCLUSIONS

Injury risk screening protocols were reliable within and repeatable between centers. These results demonstrate the feasibility of multi-site biomechanical studies and establish a framework for further dissemination of injury risk screening algorithms. Specifically, multi-center studies may allow for further validation and optimization of two-dimensional video screening tools.

LEVEL OF EVIDENCE

2b.

Epidemiology of basketball, soccer, and volleyball injuries in middle-school female athletes

BACKGROUND

An estimated 30 to 40 million school children participate in sports in the United States; 34% of middle-school participants become injured and seek medical treatment at an annual cost close to $2 billion. The purpose of the current study was to evaluate the injury incidence and rates in female athletes in the middle-school setting during the course of 3 seasons.

METHODS

Female basketball, soccer, and volleyball players were recruited from a single county public school district in Kentucky consisting of 5 middle schools. A total of 268 female athletes (162 basketball, 26 soccer, and 80 volleyball) participated. Athletes were monitored for sports-related injury and number of athlete exposures (AEs) by an athletic trainer. Injury rates were calculated for specific types of injuries within each sport. Injury rates for games and practices were also calculated and compared for each sport.

RESULTS

A total of 134 injuries were recorded during the 3 sport seasons. The knee was the most commonly injured body part (99 injuries [73.9%]), of which patellofemoral dysfunction (31.3%), Osgood-Schlatter disease (10.4%), and Sinding-Larsen-Johansson/patella tendinosis (9%) had the greatest incidence. The ankle was the second most commonly injured body part, accounting for 16.4% of all injuries. The overall rates of injury by sport were as follows: soccer, 6.66 per 1000 AEs; volleyball, 3.68 per 1000 AEs; and basketball, 2.86 per 1000 AEs.

CONCLUSIONS

Female middle-school athletes displayed comparable injury patterns to those seen in their high-school counterparts. Future work is warranted to determine the potential for improved outcomes in female middle-school athletes with access to athletic training services.

CLINICAL RELEVANCE

As the participation levels and number of injuries continue to rise, middle-school athletes demonstrate an increasing need for medical services provided by a certified athletic trainer.

A predictive model to estimate knee-abduction moment: implications for development of a clinically applicable patellofemoral pain screening tool in female athletes

CONTEXT

Prospective measures of high external knee-abduction moment (KAM) during landing identify female athletes at increased risk of patellofemoral pain (PFP). A clinically applicable screening protocol is needed.

OBJECTIVE

To identify biomechanical laboratory measures that would accurately quantify KAM loads during landing that predict increased risk of PFP in female athletes and clinical correlates to laboratory-based measures of increased KAM status for use in a clinical PFP injury-risk prediction algorithm. We hypothesized that we could identify clinical correlates that combine to accurately determine increased KAM associated with an increased risk of developing PFP.

DESIGN

Descriptive laboratory study.

SETTING

Biomechanical laboratory.

PATIENTS OR OTHER PARTICIPANTS

Adolescent female basketball and soccer players (n = 698) from a single-county public school district.

MAIN OUTCOME MEASURE(S)

We conducted tests of anthropometrics, maturation, laxity, flexibility, strength, and landing biomechanics before each competitive season. Pearson correlation and linear and logistic regression modeling were used to examine high KAM (>15.4 Nm) compared with normal KAM as a surrogate for PFP injury risk.

RESULTS

The multivariable logistic regression model that used the variables peak knee-abduction angle, center-of-mass height, and hip rotational moment excursion predicted KAM associated with PFP risk (>15.4 NM of KAM) with 92% sensitivity and 74% specificity and a C statistic of 0.93. The multivariate linear regression model that included the same predictors accounted for 70% of the variance in KAM. We identified clinical correlates to laboratory measures that combined to predict high KAM with 92% sensitivity and 47% specificity. The clinical prediction algorithm, including knee-valgus motion (odds ratio [OR] = 1.46, 95% confidence interval [CI] = 1.31, 1.63), center-of-mass height (OR = 1.21, 95% CI = 1.15, 1.26), and hamstrings strength/body fat percentage (OR = 1.80, 95% CI = 1.02, 3.16) predicted high KAM with a C statistic of 0.80.

CONCLUSIONS

Clinical correlates to laboratory-measured biomechanics associated with an increased risk of PFP yielded a highly sensitive model to predict increased KAM status. This screening algorithm consisting of a standard camcorder, physician scale for mass, and handheld dynamometer may be used to identify athletes at increased risk of PFP.

Training the developing brain, part I: cognitive developmental considerations for training youth

Based on the fundamental principles of pediatric exercise science and developmental physiology, childhood provides a critical window to develop the physical readiness of youth through age-related training programs that are designed purposely to teach and reinforce fundamental movement skills to enhance preparedness for physical activity and sport. Successful implementation of developmental programs requires age-related instruction by qualified professionals who understand the physical and psychosocial uniqueness of children and adolescents. An understanding of the interaction of physical and cognitive development is needed to design and implement training strategies that optimize training outcomes. Regular training with structured and integrative modalities throughout the developmental years as part of physical education, recreation, and sports practice can improve athletic performance while reducing common sports-related injuries and can facilitate the adoption of healthy lifestyles throughout adulthood. In this commentary, we outline cognitive developmental considerations in youth that may influence the design and implementation of training programs aimed at optimizing motor skill development in youth.