The incidence and potential pathomechanics of patellofemoral pain in female athletes

Frontal and transverse plane hip kinematics and gluteus maximus recruitment correlate with frontal plane knee kinematics during single-leg squat tests in women

BACKGROUND

Hip muscle dysfunction may be associated with knee valgus that contributes to problems like patellofemoral pain syndrome. The purpose of this study was to (1) compare knee and hip kinematics and hip muscle strength and recruitment between "good" and "poor" performers on a single-leg squat test developed to assess hip muscle dysfunction and (2) examine relationships between hip muscle strength, recruitment and frontal plane knee kinematics to see which variables correlated with knee valgus during the test.

METHODS

Forty-one active women classified via visual rating as "good" or "poor" performers on the test participated. Participants completed 5-repetition single-leg squat tests. Isometric hip extension and abduction strength, gluteus maximus and gluteus medius recruitment, and 3-dimensional hip and knee kinematics during the test were compared between groups and examined for their association with frontal plane knee motion.

FINDINGS

"Poor" performers completed the test with more hip adduction (mean difference=7.6°) and flexion (mean difference=6.3°) than "good" performers. No differences in knee kinematics, hip strength or hip muscle recruitment occurred. However, the secondary findings indicated that increased medial hip rotation (partial r=0.94) and adduction (partial r=0.42) and decreased gluteus maximus recruitment (partial r=0.35) correlated with increased knee valgus.

INTERPRETATION

Whereas hip muscle function and knee kinematics did not differ between groups as we'd hypothesized, frontal plane knee motion correlated with transverse and frontal plane hip motions and with gluteus maximus recruitment. Gluteus maximus recruitment may modulate frontal plane knee kinematics during single-leg squats.

Sport specialization's association with an increased risk of developing anterior knee pain in adolescent female athletes

OBJECTIVES

To determine if sport specialization increases the risk of anterior knee pain in adolescent female athletes.

DESIGN

Retrospective cohort epidemiology study.

METHODS

Female basketball, soccer, and volleyball players (N = 546) were recruited from a single county public school district in Kentucky consisting of 5 middle schools and 4 high schools. A total of 357 multisport and 189 single-sport (66 basketball, 57 soccer, and 66 volleyball) athlete subjects were included due to their diagnosis of patellofemoral pain (PFP) on physical exam. Testing consisted of a standardized history and physician-administered physical examination to determine the presence of PFP. This study compared self-reported multisport athletes with sport-specialized athletes participating in only 1 sport. The sports-participation data were normalized by sport season, with each sport accounting for 1 season of exposure. Incidence rate ratios and 95% confidence intervals (CI) were calculated and used to determine significant differences between athletes who specialized in sport in early youth and multisport athletes.

RESULTS

Specialization in a single sport increased the relative risk of PFP incidence 1.5-fold (95% CI 1.0-2.2, P = .038) for cumulative PFP diagnoses. Specific diagnoses such as Sinding Larsen Johansson/ patellar tendinopathy (95% CI 1.5-10.1, P = .005) and Osgood Schlatter disease (95% CI 1.5-10.1, P = .005) demonstrated a 4-fold greater relative risk in single-sport compared with multisport athletes. Incidence of other specific PFP diagnoses such as fat pad, plica, trauma, pes anserine bursitis, and iliotibial-band tendonitis was not different between single-sport and multisport participants (P > .05).

CONCLUSION

Early sport specialization in female adolescents is associated with increased risk of anterior knee-pain disorders including PFP, Osgood Schlatter, Sinding Larsen-Johansson compared with multisport athletes.

Knee valgus angle during single leg squat and landing in patellofemoral pain patients and controls

BACKGROUND

Patellofemoral pain (PFP) is a commonly presenting disorder of the lower limb, frequently effecting young physically active individuals particularly females. The condition has been associated with poor control of limb alignment while undertaking unilateral limb loading tasks. This poor alignment of the limb is believed to alter loading stress within the patellofemoral joint. This study aims to investigate the degree of knee valgus, assessed as 2D frontal plane projection angle (FPPA) during single leg squatting (SLS) and hop landing (SLL) tasks in patients with PFP and compare their performance to controls and the uninjured limb.

METHOD

Twelve female subjects with unilateral PFP formed the patient group and thirty asymptomatic females formed the control group. They had their 2D frontal plane projection angle (FPPA) assessed during single leg squatting (SLS) and hop landing (SLL) tasks.

RESULTS

In the asymptomatic control group the mean FPPA for SLS was 8.4±5.1° and SLL had a mean FPPA of 13.5±5.7°. In the PFP group the mean FPPA for SLS was 16.8±5.4° and SLL had a mean FPPA of 21.7+/-3.6°, these differences were significant (p<0.01) for both tasks.

CONCLUSION

Patients with PFP have a greater degree of knee valgus on unilateral limb loading task than either their contralateral asymptomatic limb or an asymptomatic control group. If not corrected this may lead to further PFJ stress and ongoing morbidity.

Integrative neuromuscular training and sex-specific fitness performance in 7-year-old children: an exploratory investigation

CONTEXT

Integrative neuromuscular training (INT) has successfully enhanced physical fitness and reduced abnormal biomechanics, which appear to decrease injury rates in adolescent female athletes. If not addressed at the proper time, low levels of physical fitness and abnormal mechanics may predispose female athletes to an increased risk of musculoskeletal injuries.

OBJECTIVES

To evaluate sex-specific effects of INT on selected measures of health- and skill-related fitness in children during physical education (PE).

DESIGN

Cohort study.

SETTING

Public primary school.

PATIENTS OR OTHER PARTICIPANTS

Forty children (16 boys, 24 girls; age = 7.6 ± 0.3 years, height = 124.5 ± 6.4 cm, mass = 29.5 ± 7.6 kg) from 2 second-grade PE classes.

INTERVENTION(S)

The classes were randomized into the PE-plus-INT group (10 boys, 11 girls) or the control group (6 boys, 13 girls) that participated in traditional PE. The INT was performed 2 times per week during the first approximately 15 minutes of each PE class and consisted of body weight exercises.

MAIN OUTCOME MEASURE(S)

Push-up, curl-up, standing long jump, single-legged hop, single-legged balance, sit-and-reach flexibility test, shuttle run, and 0.8-km run.

RESULTS

At baseline, the boys demonstrated higher levels of performance in most of the fitness measurements as evidenced by greater performance on the push-up, standing long jump, single-legged hop, shuttle run, and 0.8-km run (P < .05). In the evaluation of the training effects, we found intervention effects in the girls for enhanced INT-induced gains in performance relative to the control group on the curl-up, long jump, single-legged hop, and 0.8-km run (P < .05) after controlling for baseline. Boys did not demonstrate similar adaptations from the INT program (P ≥ .05).

CONCLUSIONS

These data indicate that INT is an effective and time-efficient addition to PE for enhancing motor skills and promoting physical activity in children. Seven-year-old girls appeared to be more sensitive to the effects of INT than 7-year-old boys. Future research is warranted to confirm these effects in larger cohorts of children.

Diagnostic Differences for Anterior Knee Pain between Sexes in Adolescent Basketball Players

BACKGROUND

The purpose of this study was to determine if there is a sex difference in the prevalence of specific patellofemoral disorders that cause anterior knee pain in adolescent basketball players undergoing pre-participation screening.

METHODS: SETTING

Biomechanical Laboratory.

METHODS: PARTICIPANTS

A total of 810 (688 female and 122 male) basketball players from a single county public school district.

METHODS: MAIN OUTCOME MEASURES

Prior to the start of three consecutive basketball seasons, participants were evaluated for anterior knee pain. Testing consisted of completion of the Anterior Knee Pain Scale. Those with positive findings completed an IKDC form, a standardized history and a physician-administered physical examination.

RESULTS

Anterior knee pain was noted in 410 of 1620 knees (25.3%). 26.6% of female knees and 18.0% of male knees were affected (p<0.05). Patellofemoral dysfunction (PFD) was the most common diagnosis with an overall prevalence of 6.4% (7.3% females; 1.2% males). Less common were Sinding-Larsen-Johanssen disease (SLJ), 4.8% (5.0% females; 3.7% males), Osgood-Schlatter Disease (OSD) 2.5% (2.3% females; 4.1% males); and plica syndrome 2.3% (2.1% females; 3.3% males). The remaining diagnoses (trauma, fat pad syndrome, IT band and pes anserine bursitis) had a combined prevalence of 1.7% (1.9% females; 1.6% males).

CONCLUSIONS

PFD was significantly more common in females (p<0.05). Anterior knee pain was more common in adolescent female basketball players than in adolescent male basketball players.

LEVEL OF EVIDENCE

Descriptive Laboratory Study. Level 1.

Patellofemoral pain syndrome

The patellofemoral pain syndrome (PFPS) is a possible cause for anterior knee pain, which predominantly affects young female patients without any structural changes such as increased Q-angle or significant chondral damage. This literature review has shown that PFPS development is probably multifactorial with various functional disorders of the lower extremity. Biomechanical studies described patellar maltracking and dynamic valgus in PFPS patients (functional malalignment). Causes for the dynamic valgus may be decreased strength of the hip abductors or abnormal rear-foot eversion with pes pronatus valgus. PFPS is further associated with vastus medialis/vastus lateralis dysbalance, hamstring tightness or iliotibial tract tightness. The literature provides evidence for a multimodal non-operative therapy concept with short-term use of NSAIDs, short-term use of a medially directed tape and exercise programmes with the inclusion of the lower extremity, and hip and trunk muscles. There is also evidence for the use of patellar braces and foot orthosis. A randomized controlled trial has shown that arthroscopy is not the treatment of choice for treatment of PFPS without any structural changes. Patients with anterior knee pain have to be examined carefully with regard to functional causes for a PFPS. The treatment of PFPS patients is non-operative and should address the functional causes.

LEVEL OF EVIDENCE

V.

Prevention of overuse sports injuries in the young athlete

The purpose of this article is to review the current theories regarding prevalence, mechanism, and prevention strategies for overuse injuries in a young athletic population. This information provides valuable insight into the state of the current evidence regarding overuse injuries in young athletes as well as the potential future directions in the development of overuse injury prevention interventions.

Proximal exercises are effective in treating patellofemoral pain syndrome: a systematic review

BACKGROUND

Patellofemoral pain syndrome is a common disorder of the knee with multifactorial aetiology. Multimodal treatment, including exercise therapy, has been shown to be effective in the treatment of patellofemoral pain, although some patients continue to experience pain and dysfunction despite treatment. To address this, recent research has started to investigate the lumbo-pelvic and hip girdle in patellofemoral pain.

PURPOSE

The aim of this systematic review was to investigate the effectiveness of proximal exercises, compared with knee exercises, for patients with patellofemoral pain, in improving pain and function.

METHODS

A computer-based search (population: patients with patellofemoral pain, intervention: proximal [hip or lumbo-pelvic] exercises, comparator: knee exercises, outcome: self-reported pain and/or functional questionnaire) was undertaken. Medline, Embase, CINAHL, SportsDiscus, Cochrane Library and PEDro were searched for studies published between January 2011 and January 2013. The included studies were appraised independently using the McMaster Critical Review Form for Quantitative Studies. Data was extracted for the exercise prescription and applicable outcome measures, and a descriptive analysis undertaken.

RESULTS

Eight studies (three randomized controlled trials, one clinical controlled trial, three cohort studies and one case series) of moderate to high methodological quality met the inclusion criteria. Proximal exercise programs showed a consistent reduction of pain and function in the treatment of patellofemoral pain. Knee exercise programs had variable outcomes.

CONCLUSION

Proximal interventions provide relief of pain and improved function in the short and long term and therefore physical therapists should consider using proximal interventions for treatment of patellofemoral pain.

LEVEL OF EVIDENCE

3a.

Anterior knee pain after total knee arthroplasty: a narrative review

Anterior knee pain is one of the most common causes of persistent problems after implantation of a total knee replacement. It can occur in patients with or without patellar resurfacing. As a result of the surgical procedure itself many changes can occur which may affect the delicate interplay of the joint partners in the patello-femoral joint. Functional causes of anterior knee pain can be distinguished from mechanical causes. The functional causes concern disorders of inter- and intramuscular coordination, which can be attributed to preoperative osteoarthritis. Research about anterior knee pain has shown that not only the thigh muscles but also the hip and trunk stabilising muscles may be responsible for the development of a dynamic valgus malalignment. Dynamic valgus may be a causative factor for patellar maltracking. The mechanical causes of patello-femoral problems after knee replacement can be distinguished according to whether they increase instability in the joint, increase joint pressure or whether they affect the muscular lever arms. These causes include offset errors, oversizing, rotational errors of femoral or tibial component, instability, maltracking and chondrolysis, patella baja and aseptic loosening. In these cases, reoperation or revision is often necessary.

Treatment options for patellofemoral instability in sports traumatology

Patellofemoral instability not only involves lateral patellar dislocation, patellar mal-tracking or subluxation but can also cause a limiting disability for sports activities. Its underlying causes are known as morphological anomalies of the patellofemoral joint or the mechanical axis, femorotibial malrotation, variants of the knee extensor apparatus, and ligamentous insufficiencies often accompanied by poor proprioception. Athletes with such predisposing factors are either suffering from unspecific anterior knee pain or from slightly traumatic or recurrent lateral patellar dislocation Treatment options of patellar instability are vast, and need to be tailored individually depending on the athlete’s history, age, complaints and physical demands. Different conservative and surgical treatment options are reviewed and discussed, especially limited expectations after surgery.

Sex-specific differences in the severity of symptoms and recovery rate following sports-related concussion in young athletes

INTRODUCTION

While research on adult recovery from concussion indicates sex-specific symptoms and recovery rates, there is little existing data on younger patient populations.

OBJECTIVE

To determine sex-specific differences in the severity of presenting symptoms and recovery rate between groups of young athletes who presented ≤ 7 or > 7 days after sports-related concussion.

METHODS

This study was a retrospective review of athletes aged 9 to 17 years who were referred for evaluation of a sports-related concussion over a 24-month period. The study groups were divided by sex and post-injury presentation to the clinic at ≤ 7 days and > 7 days from the date of injury. Athletes with learning disabilities were excluded from the study and data analysis. Age, height, and weight were recorded for each subject. Each subject also reported their initial degree of confusion, amnesia, or loss of consciousness, and whether a helmet was worn when the injury was sustained. A 22-item post-concussion symptom score (SS) scale was completed by both groups on initial assessment (SS1) and follow-up visit (SS2). The recovery rate (SSR) was calculated as (SS2-SS1)/days between SS2 and SS1. Sex and group comparisons for SS1 and SSR were performed using 2 × 2 analysis of variance. A similar analysis was also performed for effects of sex on SS1 and SSR in patients who were not wearing a helmet.

RESULTS

Thirty-seven athletes aged 15.0 ± 1.9 years were evaluated. Males, regardless of day of presentation, had a lower SS1 evaluation than females (15.8 vs 30.9; P < 0.05). Males without helmets did not differ from females without helmets, but this was not significantly different (14.1 vs 29.6; P = 0.1). There was not a significant difference in SS1 evaluation between the groups who presented at ≤ 7 or > 7 days. The overall mean SSR was -1.2/day, with no significant difference seen between groups or sex. There were no significant differences in degree of loss of consciousness, amnesia, confusion, or age between the sexes or groups.

CONCLUSION

Whether presenting at ≤ 7 or > 7 days following a sports-related concussion, female athletes reported a higher SS1 evaluation. With SSR being similar between sexes, the current data suggest that young, female athletes may take longer to become symptom free following sports-related concussion. This information may be an important factor in returning a young athlete to sport after sports-related concussion.

Expected prevalence from the differential diagnosis of anterior knee pain in adolescent female athletes during preparticipation screening

CONTEXT

Anterior knee pain is a common disorder in female athletes with an undefined cause. The relative prevalence of specific patellofemoral disorders associated with anterior knee pain in adolescent females remains undetermined.

OBJECTIVE

To determine the prevalence of specific patellofemoral disorders obtained using the differential diagnosis of anterior knee pain in adolescent female athletes during preparticipation screening.

DESIGN

Descriptive epidemiology study.

SETTING

Preparticipation screening evaluations at a county public school district in Kentucky.

PATIENTS OR OTHER PARTICIPANTS

A total of 419 unique middle and high school-aged female athletes.

MAIN OUTCOME MEASURE(S)

Participants were evaluated by physicians for anterior knee pain over 3 consecutive basketball seasons. Given the longitudinal nature of this study, some participants were tested longitudinally over multiple years.

RESULTS

Over the course of 3 basketball seasons, 688 patient evaluations were performed. Of these, 183 (26.6%) were positive for anterior knee pain. A statistically significant difference was noted in the prevalence of anterior knee pain by school level, with 34.4% (n = 67) in high school-aged athletes versus 23.5% (n = 116) in middle school-aged athletes (P < .05). In the 1376 knees evaluated, patellofemoral dysfunction was the most common diagnosis, with an overall prevalence of 7.3% (n = 100). The only diagnosis shown to be statistically different between age levels was Sinding-LarsenJohansson disease or patellar tendinopathy, with 38 cases (9.7%) in high school-aged and 31 (3.1%) in middle school-aged athletes (P < .05).

CONCLUSIONS

Anterior knee pain was present in 26.6% of the adolescent female athletes screened over 3 years. Symptoms of anterior knee pain likely persist after middle school-aged onset and reach peak prevalence during the high school years.

Are mechanics different between male and female runners with patellofemoral pain?

INTRODUCTION

Patellofemoral pain (PFP) has often been attributed to abnormal hip and knee mechanics in females. To date, there have been few investigations of the hip and knee mechanics of males with PFP. The purpose of this study was to compare the lower extremity mechanics and alignment of male runners with PFP with healthy male runners and female runners with PFP. We hypothesized that males with PFP would move with greater varus knee mechanics compared with male controls and compared with females with PFP. Furthermore, it was hypothesized that males with PFP would demonstrate greater varus alignment.

METHODS

A gait and single-leg squat analysis was conducted on each group (18 runners per group). Measurement of each runner's tibial mechanical axis was also recorded. Motion data were processed using Visual 3D (C-Motion, Bethesda, MD). ANOVAs were used to analyze the data.

RESULTS

Males with PFP ran and squatted in greater peak knee adduction and demonstrated greater peak knee external adduction moment compared with healthy male controls. In addition, males with PFP ran and squatted with less peak hip adduction and greater peak knee adduction compared with females with PFP. The static measure of mechanical axis of the tibial was not different between groups. However, a post hoc analysis revealed that males with PFP ran with greater peak tibial segmental adduction.

CONCLUSION

Males with PFP demonstrated different mechanics during running and during a single-leg squat compared with females with PFP and with healthy males. Based upon the results of this study, therapies for PFP may need to be sex specific.

A longitudinal evaluation of maturational effects on lower extremity strength in female adolescent athletes

PURPOSE

Recent studies demonstrate that adolescent growth without corresponding strength adaptations may lead to the development of risk factors for patellofemoral pain and anterior cruciate ligament injuries. Our purpose was to investigate the longitudinal trajectories of lower extremity strength across maturational stages for a cohort of female student athletes.

METHODS

A nested cohort design was used to identify 39 subjects who had complete knee flexion, knee extension, and hip abduction strength data for 3 test sessions spaced approximately 1 year apart and during which they transitioned from prepubertal to a pubertal status.

RESULTS

Knee extension strength increased while hip abduction and hamstrings-to-quadriceps ratio strength decreased from prepubertal to pubertal stages (P < .05). No effects of time with respect to knee flexion strength or nondominant/dominant limb differences were found (P > .05).

CONCLUSION

These data provide support that preadolescence is an optimal time to institute strength training programs aimed toward injury prevention.

Knee loading patterns in a simulated netball landing task

The knee is a common site of injury in netball players. In this study, 10 high-performance netball players underwent a biomechanical assessment of their single leg landing technique whilst receiving a pass. Three-dimensional video and ground reaction force data were recorded using a motion analysis system. Net internal knee joint moments were calculated using a rigid body analysis and inverse dynamics. The kinematics of the support leg and front-on video footage was used to investigate whether players adhered to guidelines on safe and effective landing strategies. Results indicated that for most players the internal valgus moment was the largest frontal plane knee moment during the landing phase. This may reflect a relatively greater need to resist varus knee excursion or may be related to the kinematics of the hip. For 6 of the 10 players the rapid change to an internal knee valgus moment coincided with hip adduction. Since an increase in the magnitude of the internal valgus moment may increase the compressive forces in the medial compartment of the knee, further work should be undertaken to determine if a neuromuscular training intervention to improve the strength of the hip musculature may be beneficial for these players. A large relative excursion of the knee compared to the hip may indicate that these players had a greater reliance on the more distal segments of the lower extremity for the attenuation of the ground reaction forces. This information may be used to better understand potential knee injury mechanisms in netball players.

Clinical test for diagnosis of patellofemoral pain syndrome: Systematic review with meta-analysis

The high incidence and diversity of factors attributed to the etiology of patellofemoral pain syndrome (PFPS) makes the diagnosis of this problem somewhat complex and susceptible to misinterpretation. Currently, there is not a defined set of procedures considered as ideal to diagnose PFPS. To investigate the diagnostic accuracy of clinical and functional tests used to diagnose PFPS through a systematic review. We searched relevant studies in the databases Medline, CINAHL, SPORTDiscus and Embase. The QUADAS score was used to assess the methodological quality of the eligible studies. We analyzed data that indicated the diagnostic properties of tests, such as sensibility, specificity, positive (LR+) and negative (LR-) likelihood ratio, and predictive values. The search identified 16,169 potential studies and five studies met the eligibility criteria. The 5 studies analyzed 25 tests intending to accurately diagnose PFPS. Two tests were analyzed in two studies and were possible to perform a meta-analysis. Within the five studies included, one study had high methodological quality, two studies had good methodological quality and two studies had low methodological quality. Two tests, the patellar tilt (LR+ = 5.4 and LR- = 0.6) and squatting (LR+ = 1.8 and LR- = 0.2), had values that show a trend for the diagnosis of PFPS (LR+ >5.0 and LR- <0.2), however their values do not represent clear evidence regarding diagnostic properties as suggested in the literature (LR+ >10 and LR- <0.1). Future diagnostic studies should focus on the sample homogeneity and standardization of tests analyzed so future systematic reviews can determine with more certainty the accuracy of the tests for diagnosis of PFPS.

The effects of movement pattern modification on lower extremity kinematics and pain in women with patellofemoral pain

STUDY DESIGN

Controlled laboratory study.

OBJECTIVES

To compare hip and knee kinematics and pain during a single-limb squat between 3 movement conditions (usual, exaggerated dynamic knee valgus, corrected dynamic knee valgus) in women with patellofemoral pain.

BACKGROUND

Altered kinematics (increased hip adduction, hip medial rotation, knee abduction, and knee lateral rotation, collectively termed dynamic knee valgus) have been proposed to contribute to patellofemoral pain; however, cross-sectional study designs prevent interpreting a causal link between kinematics and pain.

METHODS

The study sample included 20 women with patellofemoral pain, who demonstrated observable dynamic knee valgus. Participants performed single-limb squats under usual, exaggerated, and corrected movement conditions. Pain during each condition was assessed using a 0-to-100-mm visual analog scale. Hip and knee frontal and transverse plane angles at peak knee flexion and pain levels were compared using repeated-measures 1-way analyses of variance. Pearson correlation coefficients were used to determine within-condition associations between kinematic variables and pain.

RESULTS

In the exaggerated compared to the usual condition, increases were detected in hip medial rotation (mean ± SD difference, 5.8° ± 3.2°; P<.001), knee lateral rotation (5.5° ± 4.9°, P<.001), and pain (8.5 ± 10.8 mm, P = .007). In the corrected compared to the usual condition, decreases were detected in hip adduction (mean ± SD difference, 3.5° ± 3.7°; P = .001) and knee lateral rotation (1.6° ± 2.8°, P = .06); however, average pain was not decreased (1.2 ± 14.8 mm, P = 1.0). Pain was correlated with knee lateral rotation in the usual (r = -0.47, P = .04) and exaggerated (r = -0.49, P = .03) conditions. In the corrected condition, pain was correlated with hip medial rotation (r = 0.44, P = .05) and knee adduction (r = 0.52, P = .02).

CONCLUSION

Avoiding dynamic knee valgus may be an important component of rehabilitation programs in women with patellofemoral pain, as this movement pattern is associated with increased pain.

Male and female gluteal muscle activity and lower extremity kinematics during running

BACKGROUND

Patellofemoral pain is one of the most common lower extremity overuse injuries in runners and is significantly more common in females. This study evaluated differences in the timing and magnitude of gluteal muscle activity as well as hip and knee joint frontal and transverse plane kinematics between male and female runners in the context of this gender bias.

METHODS

Twenty healthy male and 20 healthy female runners were participants. Three-dimensional lower extremity kinematics, and gluteus medius and gluteus maximus muscle activation were recorded using motion analysis and electromyography as subjects ran at 3.7 m/s (+/-5%). Comparisons of hip and knee joint kinematic and gluteus muscle activation data were made using independent t-tests (α=0.05).

FINDINGS

Females ran with 40% greater peak gluteus maximus activation level (P=0.028, effect size=0.79) and 53% greater average activation level (P=0.013, effect size=0.93) than males. Female runners also displayed greater hip adduction (P=.001, effect size=1.20) and knee abduction (P=0.011, effect size=0.87) angles at initial contact, greater hip adduction at peak vertical ground reaction force (P<0.001, effect size=1.31), and less knee internal rotation excursion than males (P=0.035, effect size=0.71).

INTERPRETATION

Greater gluteus maximus activation levels during running may predispose females to earlier gluteus maximus fatigue, promoting altered lower extremity running kinematics thought to be associated with the etiology of patellofemoral pain. Gender differences in transverse and frontal plane hip and knee kinematics observed in this study may also contribute to the gender bias for patellofemoral pain among females.

Prospective Predictors of Patellofemoral Pain Syndrome: A Systematic Review With Meta-analysis

Context:

Patellofemoral pain syndrome (PFPS) is one of the most common overuse injuries.

Objective:

To assess the collective evidence of predisposing factors to PFPS.

Data Sources:

MEDLINE (1960–June 2010), EMBASE (1980–June 2010), and CINAHL (1982–June 2010).

Study Selection:

Studies were included if patients were asymptomatic at baseline testing (free of PFPS) and were prospectively followed for the development of the disorder. Only studies that assessed at least 1 variable that can be measured at a typical clinic were included. After duplicates were removed, 973 studies were assessed from their titles or abstracts, 20 from the full text, and from these, 7 met the inclusion criteria.

Data Extraction:

Data were extracted for age, weight, height, sample size, patient type (military vs civilian), follow-up periods, diagnostic methods, and diagnostic criteria. Means and standard deviations were extracted for all outcome variables.

Results:

Meta-analyses were performed for height, weight, leanness, Q angle, number of sit-ups, knee extension strength, and peak knee valgus angle during landing. Lower knee extension strength was the only variable that was predictive of PFPS (P < 0.01). Other variables that were identified as predictive of PFPS by single studies were vertical jump, push-ups, knee flexion and hip abduction strength, thumb-to-forearm flexibility, quadriceps and gastrocnemius flexibility, genu varum, navicular drop, knee valgus moment at initial contact during landing, social support, and palliative reaction.

Conclusions:

It appears that anthropometric variables are not associated with PFPS, while knee extension strength deficits appear to be predictors of PFPS.

Trunk, pelvis, hip, and knee kinematics, hip strength, and gluteal muscle activation during a single-leg squat in males and females with and without patellofemoral pain syndrome

STUDY DESIGN

Controlled laboratory study using a cross-sectional design.

OBJECTIVES

To determine whether there are any differences between the sexes in trunk, pelvis, hip, and knee kinematics, hip strength, and gluteal muscle activation during the performance of a single-leg squat in individuals with patellofemoral pain syndrome (PFPS) and control participants.

BACKGROUND

Though there is a greater incidence of PFPS in females, PFPS is also quite common in males. Trunk kinematics may affect hip and knee function; however, there is a lack of studies of the influence of the trunk in individuals with PFPS.

METHODS

Eighty subjects were distributed into 4 groups: females with PFPS, female controls, males with PFPS, and male controls. Trunk, pelvis, hip, and knee kinematics and gluteal muscle activation were evaluated during a single-leg squat. Hip abduction and external rotation eccentric strength was measured on an isokinetic dynamometer. Group differences were assessed using a 2-way multivariate analysis of variance (sex by PFPS status).

RESULTS

Compared to controls, subjects with PFPS had greater ipsilateral trunk lean (mean ± SD, 9.3° ± 5.3° versus 6.7° ± 3.0°; P = .012), contralateral pelvic drop (10.3° ± 4.7° versus 7.4° ± 3.8°; P = .003), hip adduction (14.8° ± 7.8° versus 10.8° ± 5.6°; P<.0001), and knee abduction (9.2° ± 5.0° versus 5.8° ± 3.4°; P<.0001) when performing a single-leg squat. Subjects with PFPS also had 18% less hip abduction and 17% less hip external rotation strength. Compared to female controls, females with PFPS had more hip internal rotation (P<.05) and less muscle activation of the gluteus medius (P = .017) during the single-leg squat.

CONCLUSION

Despite many similarities in findings for males and females with PFPS, there may be specific sex differences that warrant consideration in future studies and when clinically evaluating and treating females with PFPS.

Patellofemoral pain: proximal, distal, and local factors, 2nd International Research Retreat

Patellofemoral pain (PFP) is one of the most common lower extremity conditions seen in orthopaedic practice. The mission of the second International Patellofemoral Pain Research Retreat was to bring together scientists and clinicians from around the world who are conducting research aimed at understanding the factors that contribute to the development and, consequently, the treatment of PFP. The format of the 2.5-day retreat included 2 keynote presentations, interspersed with 6 podium and 4 poster sessions. An important element of the retreat was the development of consensus statements that summarized the state of the research in each of the 4 presentation categories. In this supplement, you will find the consensus documents from the meeting, as well as the keynote addresses, schedule, and platform and poster presentation abstracts.

Comparison of landing knee valgus angle between female basketball and football athletes: possible implications for anterior cruciate ligament and patellofemoral joint injury rates

OBJECTIVE

To evaluate landing strategies of female football and basketball athletes with relation to possible injury mechanisms and disparity in injury.

DESIGN

Descriptive laboratory study.

PARTICIPANTS

52 female football players and 41 female basketball players.

MAIN OUTCOME MEASURES

Frontal plane projection angle (FPPA) was measured during the single leg land (SLL) and drop jump (DJ) screening tasks.

RESULTS

2 × 2 × 2 mixed factorial ANOVA showed significant main effects were observed for sport, whilst significant interaction effects were seen between sport and task. Females in both sports exhibited significantly greater FPPA values during the SLL task than the DJ task (p < 0.001). Basketball players demonstrated significantly greater FPPA values during SLL than football players (p < 0.001), whilst no differences were found between sports in the DJ task (p = 0.328).

CONCLUSION

Female basketball players display greater FPPA values during unilateral landing tasks than female football players which may reflect the greater ACL injury occurrence in this population. Injury prevention programs in these athletes should incorporate unilateral deceleration and landing tasks and should consider the specific injury mechanisms in each sport.

Is body composition associated with an increased risk of developing anterior knee pain in adolescent female athletes?

OBJECTIVE

To determine the relationship between relative body composition and body mass to height, anterior knee pain, or patellofemoral pain (PFP) in adolescent female athletes.

BACKGROUND

Patellofemoral pain is common in female athletes and has an undefined etiology. The purpose of this study was to examine whether there was an association among higher body mass index (BMI), BMI z-scores, and relative body fat percentage in the development of PFP in an adolescent female athlete population. We hypothesized that female athletes who developed PFP over the course of a competitive basketball season had higher relative body mass or body fat percentage compared with those who did not develop PFP.

METHODS

Fifteen middle school basketball teams that consisted of 248 basketball players (mean age, 12.76 ± 1.13 years; height, 158.43 ± 7.78 cm; body mass, 52.35 ± 12.31 kg; BMI, 20.73 ± 3.88 kg/m(2)) agreed to participate in this study over the course of 2 basketball seasons, resulting in 262 athlete-seasons. Testing included the completion of the Anterior Knee Pain Scale (AKPS), International Knee Documentation Committee (IKDC) form, standardized history, physician-administered physical examination, maturational estimates, and anthropometrics.

RESULTS

Of the 262 athlete-seasons monitored, 39 athletes developed PFP over the course of the study. The incidence rate of new PFP was 1.57 per 1000 athlete-exposures. The cumulative incidence of PFP was 14.9%. There was no difference in BMI between those who developed PFP (mean body mass, 20.2 kg/m(2); 95% CI,18.9-21.4) and those who did not develop PFP (mean body mass, 20.8 kg/m(2); 95% CI, 20.3-21.3;P > 0.05). Body mass index z-scores were not different between those who developed PFP (mean, 0.3; 95% CI, 0.7-0.6) and those who did not develop PFP (mean, 0.4; 95% CI, 0.3-0.6;P > 0.05). A similar trend was noted in relative body fat percentage, with mean scores of similar ranges in those who developed PFP (mean body fat percentage, 22.2%; 95% CI, 19.4-24.9) to the referent group who did not (mean body fat percentage, 22.9%; 95% CI, 21.8-24.1;P > 0.05).

CONCLUSIONS

Our results do not indicate a relationship between relative body composition or relative body mass to height to the propensity to develop PFP in middle school-aged female basketball players. Although previous data indicate a relationship between higher relative body mass and overall knee injury, these data did not support this association with PFP specifically. These data suggest the underlying etiology of PFP may be neuromuscular in nature. Further research is needed to understand the predictors, etiology, and ultimate prevention of this condition.

The effect of a hip-strengthening program on mechanics during running and during a single-leg squat

STUDY DESIGN

Block randomized controlled trial.

OBJECTIVES

To investigate whether a strengthening and movement education program, targeting the hip abductors and hip external rotators, alters hip mechanics during running and during a single-leg squat.

BACKGROUND

Abnormal movement patterns during running and single-leg squatting have been associated with a number of running-related injuries in females. Therapeutic interventions for these aberrant movement patterns typically include hip strengthening. While these strengthening programs have been shown to improve symptoms, it is unknown if the underlying mechanics during functional movements is altered.

METHODS

Twenty healthy females with excessive hip adduction during running, as determined by instrumented gait analysis, were recruited. The runners were matched by age and running distance, and randomized to either a training group or a control group. The training group completed a hip strengthening and movement education program 3 times per week for 6 weeks in addition to single-leg squat training with neuromuscular reeducation consisting of mirror and verbal feedback on proper mechanics. The control group did not receive an intervention but maintained the current running distance. Using a handheld dynamometer and standard motion capture procedures, hip strength and running and single-leg squat mechanics were compared before and after the strengthening and movement education program.

RESULTS

While hip abductor and external rotation strength increased significantly (P<.005) in the training group, there were no significant changes in hip or knee mechanics during running. However, during the single-leg squat, hip adduction, hip internal rotation, and contralateral pelvic drop all decreased significantly (P = .006, P = .006, and P = .02, respectively). The control group exhibited no changes in hip strength, nor in the single-leg squat or running mechanics at the conclusion of the 6-week study.

CONCLUSION

A training program that included hip strengthening and movement training specific to single-leg squatting did not alter running mechanics but did improve single-leg squat mechanics. These results suggest that hip strengthening and movement training, when not specific to running, do not alter abnormal running mechanics.

LEVEL OF EVIDENCE

Therapy, level 2b.

Gluteal muscle activation during running in females with and without patellofemoral pain syndrome

BACKGROUND

Hip and knee joint motion in the transverse and frontal plane during running may increase patellofemoral joint stress and contribute to the etiology of patellofemoral joint pain. We evaluated the association between these kinematics and the magnitude and timing of gluteus medius and maximus activity during running in females with patellofemoral pain. We also compared the magnitude and timing of gluteal muscle activity during running between females with and without patellofemoral pain.

METHODS

Twenty females with patellofemoral pain and twenty females without knee pain participated in this study. Three-dimensional running kinematics, gluteus medius and gluteus maximus onset time, activation duration, mean activation level, and peak activation level were recorded simultaneously. Gluteal muscle timing and activation level were compared between groups using independent t-tests. The association of gluteal muscle activation parameters running kinematics in females with patellofemoral pain was quantified using Pearson correlation coefficients.

FINDINGS

Females with patellofemoral pain demonstrated delayed (P=0.028, effect size=0.76) and shorter (P=0.01, effect size=0.88) gluteus medius activation than females without knee pain during running. The magnitude and timing of gluteus maximus activation was not different between groups. Greater hip adduction and internal rotation excursion was correlated with later gluteus medius and gluteus maximus onset, respectively.

INTERPRETATION

Neuromuscular control differences of the gluteal muscles appear to exist among females with patellofemoral pain during running. Interventions to facilitate earlier activation of these muscles may be warranted among females with patellofemoral pain who demonstrate altered running kinematics.

Relationship among eccentric hip and knee torques, symptom severity and functional capacity in females with patellofemoral pain syndrome

OBJECTIVE

To determine the relationships between eccentric hip and knee torques, symptom severity and functional capacity in females with patellofemoral pain syndrome (PFPS).

DESIGN

Within-subject correlational study.

SETTING

University biomechanics laboratory.

PARTICIPANTS

10 females diagnosed with PFPS.

MAIN OUTCOME MEASURES

Eccentric strength of the hip abductors and lateral rotators, and knee extensors were assessed using an isokinetic dynamometer. A 10-cm visual analog scale was used to determine usual knee pain in the last week. The Anterior Knee Pain Scale (AKPS) was used to determine the functional capacity of the patients.

RESULTS

The study found that the greater the eccentric knee extensor and hip lateral rotator torques, the higher the functional capacity of the patients (p = 0.02, r = 0.72; p = 0.02, r = 0.72). It was also shown that the greater hip lateral rotator torque, the less the usual pain reported in the last week (p = 0.004, r = -0.84). Despite the lack of statistical significance (p = 0.11), it was also found a modest negative relationship between the eccentric knee extensor torque and the usual pain reported in the last week (r = -0.56) that was considered clinically meaningful (d = 1.4).

CONCLUSIONS

This study showed that eccentric knee extensor and hip lateral rotator torques were associated with functional capacity and pain level in females with PFPS. Further investigations should be carried out to verify the effects of an intervention program focused on the eccentric action of these muscles with respect to the symptoms in patients with PFPS.

When to initiate integrative neuromuscular training to reduce sports-related injuries and enhance health in youth?

Regular participation in organized youth sports does not ensure adequate exposure to skill- and health-related fitness activities, and sport training without preparatory conditioning does not appear to reduce risk of injury in young athletes. Current trends indicate that widespread participation in organized youth sports is occurring at a younger age, especially in girls. Current public health recommendations developed to promote muscle strengthening and bone building activities for youth aged 6 yr and older, along with increased involvement in competitive sport activities at younger ages, has increased interest and concern from parents, clinicians, coaches, and teachers regarding the optimal age to encourage and integrate more specialized physical training into youth development programs. This review synthesizes the latest literature and expert opinion regarding when to initiate neuromuscular conditioning in youth and presents a how-to integrative training conceptual model that could maximize the potential health-related benefits for children by reducing sports-related injury risk and encouraging lifelong, regular physical activity.

Relationships between the Foot Posture Index and foot kinematics during gait in individuals with and without patellofemoral pain syndrome

Background

Foot posture assessment is commonly undertaken in clinical practice for the evaluation of individuals with patellofemoral pain syndrome (PFPS), particularly when considering prescription of foot orthoses. However, the validity of static assessment to provide insight into dynamic function in individuals with PFPS is unclear. This study was designed to evaluate the extent to which a static foot posture measurement tool (the Foot Posture Index - FPI) can provide insight into kinematic variables associated with foot pronation during level walking in individuals with PFPS and asymptomatic controls.

Methods

Twenty-six individuals (5 males, 21 females) with PFPS aged 25.1 ± 4.6 years and 20 control participants (4 males, 16 females) aged 23.4 ± 2.3 years were recruited into the study. Each participant underwent clinical evaluation of the FPI and kinematic analysis of the rearfoot and forefoot during walking using a three-dimensional motion analysis system. The association of the FPI score with rearfoot eversion, forefoot dorsiflexion, and forefoot abduction kinematic variables (magnitude, timing of peak and range of motion) were evaluated using partial correlation coefficient statistics with gait velocity entered as a covariate.

Results

A more pronated foot type as measured by the FPI was associated with greater peak forefoot abduction (r = 0.502, p = 0.013) and earlier peak rearfoot eversion relative to the laboratory (r = -0.440, p = 0.031) in the PFPS group, and greater rearfoot eversion range of motion relative to the laboratory (r = 0.614, p = 0.009) in the control group.

Conclusion

In both individuals with and without PFPS, there was fair to moderate association between the FPI and some parameters of dynamic foot function. Inconsistent findings between the PFPS and control groups indicate that pathology may play a role in the relationship between static foot posture and dynamic function. The fair association between pronated foot posture as indicated by the FPI and earlier peak rearfoot eversion relative to the laboratory observed exclusively in those with PFPS is consistent with the biomechanical model of PFPS development. However, prospective studies are required to determine whether this relationship is causal.

Common lower extremity injuries in the skeletally immature athlete

Lower extremity musculoskeletal pain is a common complaint in the adolescent athlete. During rapid growth, several common biomechanical changes occur that may predispose to overuse injury. Unlike fractures, most of these office-based sports medicine complaints are initially evaluated by the primary care provider. This review discusses several of the most common complaints and briefly discusses some clinically significant conditions that masquerade as common injuries. The article discusses only the injuries unique to the growing athlete. The article's goal is to help develop a framework for the pediatric clinician to evaluate common complaints and formulate a plan that includes simple stretches and physical therapy recommendations.