Group- and sex-related differences in psychological and pain processing factors in people with and without patellofemoral pain: correlation with clinical outcomes.

BACKGROUND: People with patellofemoral pain (PFP) exhibit impaired psychological and pain processing factors (i.e., kinesiophobia, pain catastrophizing and pressure pain thresholds [PPTs]). However, it remains unclear whether these factors have different presentations in women and men with PFP, as well as whether their correlation with clinical outcomes differ according to sex. The aims of this study were to: (1) compare psychological and pain processing factors between women and men with and without patellofemoral pain (PFP); (2) investigate their correlation with clinical outcomes in people with PFP. METHODS: This cross-sectional study included 65 women and 38 men with PFP, 30 women and 30 men without PFP. The psychological and pain processing factors were assessed with the Tampa Scale of Kinesiophobia, Pain Catastrophizing Scale, and PPTs of shoulder and patella measured with an algometer. Clinical outcomes assessed were self-reported pain (Visual Analogue Scale), function (Anterior Knee Pain Scale), physical activity level (Baecke's Questionnaire), and physical performance (Single Leg Hop Test). Generalized linear models (GzLM) and effect sizes [Cohen's d] were calculated for group comparisons and Spearman's correlation coefficients were calculated to investigate correlations between outcomes. RESULTS: Women and men with PFP had higher kinesiophobia (d = .82, p = .001; d = .80, p = .003), pain catastrophizing (d = .84, p < .001; d = 1.27, p < .001), and lower patella PPTs (d = -.85, p = .001; d = -.60, p = .033) than women and men without PFP, respectively. Women with PFP had lower shoulder and patella PPTs than men with PFP (d = -1.24, p < .001; d = -.95, p < .001), but there were no sex differences in those with PFP for psychological factors (p > .05). For women with PFP, kinesiophobia and pain catastrophizing had moderate positive correlations with self-reported pain (rho = .44 and .53, p < .001) and moderate negative correlations with function (rho = -.55 and -.58, p < .001), respectively. For men with PFP, only pain catastrophizing had moderate positive correlations with self-reported pain (rho = .42, p = .009) and moderate negative correlations with function (rho = -.43, p = .007). CONCLUSIONS: Psychological and pain processing factors differ between people with and without PFP and between sexes, respectively. Also, correlations between psychological and pain processing factors with clinical outcomes differ among women and men with PFP. These findings should be considered when assessing and managing people with PFP.

Gender-Specific Risk Factor Profiles for Patellofemoral Pain.

OBJECTIVE: To determine the association between selected biomechanical variables and risk of patellofemoral pain (PFP) in males and females. DESIGN: Prospective cohort. SETTING: US Service Academies. PARTICIPANTS: Four thousand five hundred forty-three cadets (1727 females and 2816 males). ASSESSMENT OF RISK FACTORS: Three-dimensional biomechanics during a jump-landing task, lower-extremity strength, Q-angle, and navicular drop. MAIN OUTCOME MEASURES: Cadets were monitored for diagnosis of PFP during their enrollment in a service academy. Three-dimensional hip and knee kinematic data were determined at initial contact (IC) and at 50% of the stance phase of the jump-landing task. Logistic regression analyses were performed for each risk factor variable in males and females (P < 0.05). RESULTS: Less than 10 degrees of hip abduction at IC [odds ratio (OR) = 1.86, P = 0.03] and greater than 10 degrees of knee internal rotation at 50% of the stance phase (OR = 1.71, P = 0.02) increased the risk of PFP in females. Greater than 20 degrees of knee flexion at IC (OR = 0.47, P < 0.01) and between 0 and 5 degrees of hip external rotation at 50% of the stance phase (OR = 0.52, P = 0.04) decreased the risk of PFP in males. No other variables were associated with risk of developing PFP (P > 0.05). CONCLUSIONS: The results suggest males and females have differing kinematic risk factor profiles for the development of PFP. CLINICAL RELEVANCE: To most effectively reduce the risk of developing PFP, the risk factor variables specific to males (decreased knee flexion and increased hip external rotation) and females (decreased hip abduction and increased knee internal rotation) should be addressed in injury prevention programs.

Longitudinal Changes in Hip Strength and Range of Motion in Female Youth Soccer Players: Implications for ACL Injury, A Pilot Study.

CONTEXT: Risk of anterior cruciate ligament (ACL) injuries in young female athletes increases with age, appearing to peak during maturation. Changes in hip muscle strength and range of motion (ROM) during this time may contribute to altered dynamic movement patterns that are known to increase risk of ACL injuries. Understanding the longitudinal changes in hip strength and ROM is needed to develop appropriate interventions to reduce the risk of ACL injuries. OBJECTIVE: To examine the longitudinal changes in hip strength and ROM in female youth soccer players. DESIGN: Longitudinal descriptive study. SETTING: Field setting. PARTICIPANTS: 14 female youth soccer athletes (14.1 ± 1.1 y, 165.8 ± 5.3 cm, 57.5 ± 9.9 kg) volunteered as part of a multiyear risk factor screening project. MAIN OUTCOME MEASURES: Clinical measures of hip strength and ROM were collected annually over 3 consecutive years. Passive hip internal rotation (IR), external rotation (ER), abduction (ABD), and adduction (ADD) ROM were measured with a digital inclinometer. Isometric hip ABD and extension (EXT) strength were evaluated using a hand-held dynamometer. Separate repeated-measures ANOVAs compared hip strength and ROM values across 3 consecutive years (P < .05). RESULTS: As youth female soccer players increased in age, there were no changes in normalized hip ABD (P = .830) or EXT strength (P = .062) across 3 consecutive years. Longitudinal changes in hip ROM were observed with increases in hip IR (P = .001) and ABD (P < .001), while hip ADD (P = .009) and ER (P < .001) decreased. CONCLUSIONS: Anatomical changes at the hip occur as youth female soccer players increase in age. While there are no changes in hip strength, there is an increase in hip IR and ABD ROM with a concomitant decrease in hip ER and ADD ROM. The resulting asymmetries in hip ROM may decrease the activation and force producing capabilities of the hip muscles during dynamic activities, contributing to altered lower extremity mechanics known to increase the risk of ACL injuries.

Maturation and Sex Differences in Neuromuscular Characteristics of Youth Athletes.

Understanding how neuromuscular factors that are associated with lower extremity injury risk, such as landing kinematics, muscle strength, and flexibility, change as children mature may enhance age-specific recommendations for injury prevention programs. The purpose of this study was to compare these factors in prepubertal, pubertal, and postpubertal male and female athletes. Subjects were classified on maturation stage (prepubertal: 16 males, 15 females, age: 9 ± 1 years; pubertal: 13 males, 12 females, age: 12 ± 3 years; postpubertal: 30 males, 27 females, age: 16 ± 2 years). Researchers measured lower extremity isometric muscle strength and flexibility and evaluated kinematics and vertical ground reaction forces (VGRFs) during a jump-landing task. Three-dimensional kinematics at initial contact (IC), joint displacements, and peak VGRF were calculated. Separate multivariate analyses of variance were performed to evaluate sex and maturation differences (α ≤ 0.05). Postpubertal females landed with less knee flexion at IC (p = 0.006) and demonstrated lower knee extension strength (p = 0.01) than prepubertal and pubertal females. Postpubertal males landed with less hip adduction displacement (postpubertal males = 12.53 ± 6.15°, prepubertal males = 18.84 ± 7.47°; p = 0.04) and less peak VGRF (postpubertal males = 1.53 ± 0.27% body weight [BW], prepubertal males = 1.99 ± 0.32% BW; p = 0.03) compared with prepubertal males. These findings suggest encouraging sagittal plane absorption and decreasing frontal plane motion at the hip, whereas maintaining quadriceps strength may be important for reducing injury risk in postpubertal athletes.

Ankle Dorsiflexion Displacement During Landing is Associated With Initial Contact Kinematics but not Joint Displacement.

The ankle, knee, and hip joints work together in the sagittal plane to absorb landing forces. Reduced sagittal plane motion at the ankle may alter landing strategies at the knee and hip, potentially increasing injury risk; however, no studies have examined the kinematic relationships between the joints during jump landings. Healthy adults (N = 30; 15 male, 15 female) performed jump landings onto a force plate while three-dimensional kinematic data were collected. Joint displacement values were calculated during the loading phase as the difference between peak and initial contact angles. No relationship existed between ankle dorsiflexion displacement during landing and three-dimensional knee and hip displacements. However, less ankle dorsiflexion displacement was associated with landing at initial ground contact with larger hip flexion, hip internal rotation, knee flexion, knee varus, and smaller plantar flexion angles. Findings of the current study suggest that restrictions in ankle motion during landing may contribute to contacting the ground in a more flexed position but continuing through little additional motion to absorb the landing. Transverse plane hip and frontal plane knee positioning may also occur, which are known to increase the risk of lower extremity injury.

Lower Extremity Muscle Volume in Unilateral and Bilateral Patellofemoral Pain: A Cross-Sectional Exploratory Study Including Superficial and Deep Muscles Authors.

CONTEXT: Existing patellofemoral pain (PFP) literature has primarily focused on quadriceps muscle volume, with limited attention given to the lower limbs deep and superficial muscle volumes in individuals with unilateral and bilateral PFP. This research aims to fill this gap. OBJECTIVE: To explore superficial and deep lower extremity muscle volume in women with unilateral and bilateral PFP compared to a normative database of pain-free women. DESIGN: Cross-sectional study. SETTING: University imaging research center. PATIENTS OR OTHER PARTICIPANTS: Twenty women with PFP (10 unilateral and 10 bilateral) and 8 pain-free women. MAIN OUTCOME MEASURE(S): We quantified lower extremity muscle volume via 3.0 Tesla magnetic resonance imaging. Two separate one-way analyses of variance were performed: (1) unilateral PFP (painful vs. non-painful limb) vs. pain-free control and (2) bilateral PFP (more painful vs. less painful limb) vs. pain-free control. RESULTS: There were no differences in age and body mass index across groups (P >.05). Compared to pain-free women, both women with unilateral and bilateral PFP had bilaterally smaller volumes of the anterior (iliacus: P ≤ .0004, d = 2.12-2.65), medial (adductor brevis, adductor longus, gracilis, and pectineus: P ≤ .02, d = 1.25-2.24), posterior (obturator externus, obturator internus, and quadratus femoris: P < .05, d = 1.17-4.82), and lateral (gluteus minimus: P ≤ .03, d = 1.16-2.09) hip muscles, and knee extensors (rectus femoris: P ≤.003, d = 1.67-2.16) and flexors (biceps femoris: long and short head: P ≤ .01, d = 1.56-1.93). CONCLUSIONS: Both women with unilateral and bilateral PFP 25 displayed decreased volume of multiple superficial and deep muscles of the bilateral hips and knees compared with pain-free women. Interventions should bilaterally target lower limb muscles when treating PFP, and hypertrophy exercises for specific muscles should be explored to enhance interventional choices.

Pain severity during functional activities in individuals with patellofemoral pain: A systematic review with meta-analysis.

OBJECTIVES: Patellofemoral pain (PFP) is a common lower extremity condition that results in pain during functional tasks. Currently, it is unknown the extent to which differences in pain levels exist in individuals with PFP compared to asymptomatic controls during functional task and if pain differ across various functional tasks. The purpose of this systematic review and meta-analysis is to evaluate pain levels between individuals with PFP and asymptomatic controls and compare pain severity across various functional tasks. DESIGN: Systematic review. METHODS: OVID, SPORTSDiscus, CINAHL, Web of Science and Embase were searched for studies that included PFP and asymptomatic controls with pain assessed during a functional task. Pooled pain scores mean with 95% confidence intervals were calculated between groups across 11 functional tasks. Standardized mean differences (SMD) were calculated based on Hedge's g effect sizes. Tasks whose SMD 95% confidence intervals were non-overlapping were considered significantly different. RESULTS: 28 articles were included for data analysis. Pain was greater across 10 tasks (SMD = 1.52-6.08) in individuals with PFP compared to the asymptomatic controls with an average SMD of 2.45. Running and star excursion balance testing resulted in greater pain than walking. Limited evidence showed greater pain in sitting than seven other tasks. CONCLUSIONS: Moderate evidence exists for greater pain levels in individuals with PFP compared to asymptomatic controls in functional tasks. Pain was greater during running and star excursion balance compared to walking. Clinicians should assess knee pain before and after functional tasks to improve our understanding of patient specific pain experiences.

Distance running stride-to-stride variability for sagittal plane joint angles.

Recent research indicates that distance running stride-to-stride variability (SSV) is related to performance and injury. Previous studies have primarily focused on stride characteristics (stride length and time). We assessed SSV for sagittal plane joint angles with the primary purpose of testing for significant differences among the lower body joints. The secondary purpose was to determine if strong correlations exist among joint SSV measures. Thirty recreational adult runners participated in the study (8 females, 22 males, 39 ± 10 years; 53.1 ± 25.7 km/week). A 6-camera motion capture system (200 Hz) collected kinematic data during treadmill running at a preferred pace. A 2 by 3 repeated measures factorial ANOVA (phase-stance, swing; joint-hip, knee, ankle) was run (p = 0.05). There was a significant interaction effect (p < 0.001) and post hoc analysis revealed knee swing to be the most variable condition by far. For all three joints, there were strong correlations between stance and swing SSV (r = 0.80 to r = 0.88) and correlations among the joints were moderate to strong (r = 0.55 to 0.86). This study helps to better understand the joints/phases that contribute most to variability in the overall stride. Also, the strong correlations suggest that runners appear to have an overall SSV pattern that is similar across joints/phases.

In Vivo Compositional Changes in the Articular Cartilage of the Patellofemoral Joint Following Anterior Cruciate Ligament Reconstruction.

OBJECTIVE: To compare T1ρ relaxation times of the medial and lateral regions of the patella and femoral trochlea at 6 and 12 months following anterior cruciate ligament reconstruction (ACLR) on the ACLR and contralateral extremity. Greater T1ρ relaxation times are associated with a lower proteoglycan density of articular cartilage. METHODS: This study involved 20 individuals (11 males, 9 females; mean ± SD age 22 ± 3.9 years, weight 76.11 ± 13.48 kg, and height 178.32 ± 12.32 cm) who underwent a previous unilateral ACLR using a patellar tendon autograft. Magnetic resonance images from both extremities were acquired at 6 and 12 months post-ACLR. Voxel by voxel T1ρ relaxation times were calculated using a 5-image sequence. The medial and lateral regions of the femoral trochlea and patellar articular cartilage were manually segmented on both extremities. Separate extremity (ACLR and contralateral extremity) by time (6 months and 12 months) analysis of variance tests were performed for each region (P < 0.05). RESULTS: For the medial patella and lateral trochlea, T1ρ relaxation times increased in both extremities between 6 and 12 months post-ACLR (medial patella P = 0.012; lateral trochlea P = 0.043). For the lateral patella, T1ρ relaxation times were significantly greater on the contralateral extremity compared to the ACLR extremity (P = 0.001). The T1ρ relaxation times of the medial trochlea on the ACLR extremity were significantly greater at 6 (P = 0.005) and 12 months (P < 0.001) compared to the contralateral extremity. T1ρ relaxation times of the medial trochlea significantly increased from 6 to 12 months on the ACLR extremity (P = 0.003). CONCLUSION: Changes in T1ρ relaxation times occur within the first 12 months following ACLR in specific regions of the patellofemoral joint on the ACLR and contralateral extremity.

Anterior Knee Pain Risk in Male and Female Military Tactical Athletes.

CONTEXT: Anterior knee pain (AKP) is ubiquitous in early career military members and exacerbated during functional tasks required during military duties. Therefore, it is important to understand the risk of this condition among male and female tactical athletes in diverse military occupations. OBJECTIVE: To assess sex and occupation with respect to the AKP risk in military members. DESIGN: Descriptive epidemiology study. SETTING: United States Armed Forces. PATIENTS OR OTHER PARTICIPANTS: All military members diagnosed with anteropatellar or retropatellar pain, patellar instability, or knee tendinopathy on their initial encounter from 2006 to 2015. MAIN OUTCOME MEASURE(S): The Defense Medical Epidemiology Database was queried for the number of individuals with AKP. Relative risk (RR) and χ2 statistics were calculated in the assessment of sex and occupational category. Regressions were calculated to determine associations between service branch, sex, and AKP across time. RESULTS: From 2006 to 2015, a total of 151 263 enlisted and 14 335 officer service members were diagnosed with AKP. Enlisted females had an incidence rate of 16.7 per 1000 person-years compared with enlisted males' incidence rate of 12.7 per 1000 person-years (RR = 1.32; 95% CI = 1.30, 1.34; P < .001) across all AKP diagnoses. Female officers had an incidence rate of 10.7 per 1000 person-years; male officers had an incidence rate of 5.3 per 1000 person-years (RR = 2.01; 95% CI = 1.94, 2.09). Differences in risk were also noted across military occupations for both enlisted and officer service members (P values < .05). CONCLUSIONS: Sex and military occupation were salient factors for the AKP risk. Evaluating training requirements and developing intervention programs across military occupations could serve as a focus for future research aiming to decrease the incidence of chronic knee pain.

Relationships between lower extremity alignment and the quadriceps angle.

OBJECTIVE: To determine the extent to which select lower extremity alignment characteristics of the pelvis, hip, knee, and foot are related to the Q angle. DESIGN: Descriptive cohort study design. SETTING: Applied Neuromechanics Research Laboratory. PARTICIPANTS: Two hundred eighteen participants (102 males, 116 females). ASSESSMENT OF RISK FACTORS: Eight clinical measures of static alignment of the left lower extremity were measured by a single examiner to determine the impact of lower extremity alignment on the magnitude of Q angle. MAIN OUTCOME MEASURES: Q angle, pelvic angle, hip anteversion, tibiofemoral angle, genu recurvatum, tibial torsion, navicular drop, and femur and tibia length. RESULTS: Once all alignment variables were accounted for, greater tibiofemoral angle and femoral anteversion were significant predictors of greater Q angle in both males and females. Pelvic angle, genu recurvatum, tibial torsion, navicular drop, and femur to tibia length ratio were not significant independent predictors of Q angle in males or females. CONCLUSIONS: Greater femoral anteversion and tibiofemoral angle result in greater Q angle, with changes in tibiofemoral angle having a substantially greater impact on the magnitude of the Q angle compared with femoral anteversion. As such, the Q angle seems to largely represent a frontal plane alignment measure. As many knee injuries seem to result from a combination of both frontal and transverse plane motions and forces, this may in part explain why Q angle has been found to be a poor independent predictor of lower extremity injury risk.

The relationship between anterior tibial shear force during a jump landing task and quadriceps and hamstring strength.

BACKGROUND: Eccentric quadriceps contraction during landing and the resulting anterior tibial shear force are anterior cruciate ligament injury risk factors, while hamstring contraction limits anterior cruciate ligament loading. Anterior tibial shear force is derived from quadriceps and hamstring co-contraction, and a greater quadriceps/hamstring strength ratio has been associated with heightened lower extremity injury risk. The purpose of this investigation was to evaluate relationships between anterior tibial shear force during landing and quadriceps and hamstring strength. METHODS: Anterior tibial shear force was calculated during a jump landing task in 26 healthy females. Isokinetic eccentric quadriceps strength and concentric hamstrings strength were assessed at 60 degrees /s, 180 degrees /s, and 300 degrees /s. Correlational analyses were conducted to evaluate relationships between lower extremity strength and anterior tibial shear force. FINDINGS: Quadriceps (r=0.126 to 0.302, P>0.05) and hamstrings strength (r=-0.019 to 0.058, P>0.05) and the quadriceps/hamstring ratio (r=0.036 to 0.127, P>0.05) were not significant predictors of anterior tibial shear force. INTERPRETATION: Quadriceps and hamstring strength are not indicative of sagittal-plane knee loading during landing. Contractile force resulting from maximal strength testing may not represent that produced during landing, as it is unlikely that landing requires maximal effort. Additionally, peak anterior tibial shear force, quadriceps torque, and hamstrings torque are generated at different points in the knee flexion/extension range of motion. Therefore, peak anterior tibial shear force is a function of the available strength at a given point in the range of motion rather than of peak strength. These findings illustrate the limitations of peak strength values in predicting dynamic loading during landing.

Y-balance test performance and BMI are associated with ankle sprain injury in collegiate male athletes.

OBJECTIVES: To determine if static balance, dynamic balance, ankle range of motion, body mass index (BMI), or history of an ankle sprain were associated with ankle sprain injuries within male and female collegiate athletes. DESIGN: Prospective cohort. METHODS: Three hundred and eighty-four male (age=19.79±1.80 years, height=178.02±10.39cm, mass=85.71±17.59kg) and one hundred and sixty seven female (age=19.80±1.52 years, height=165.61±7.08cm, mass=66.16±10.53kg) collegiate athletes involved in a variety of sports at a NCAA Division II or NAIA institution participated. Baseline measures of the Y-Balance (YBT), modified Balance Error Scoring System (mBESS), weight-bearing lunge test (WBLT), BMI, and history of ankle sprain were recorded. Participants were followed prospectively for two years and incidence of ankle sprain injury was documented. The average of the WBLT, mBESS, and YBT measures were used for analysis. Male and female participants were analyzed separately. Mann-Whitney U tests were utilized to identify variables which may be significantly associated with ankle sprain injury for logistic regression analysis. RESULTS: A total of 59 (38 males and 21 females) individuals sustained an ankle sprain during the follow up period. The binary logistic regression revealed BMI (Nagelkerke R2=0.069; X2=12.89; p<0.001; OR=3.85; 95% CI, 1.90-7.79; p<0.001) and anterior reach of the YBT (Nagelkerke R2=0.074; X2=13.70, p<0.001; OR=3.64; 95% CI=1.83-7.23; p=0.01) were significantly associated with ankle sprain injury in male athletes. No variables were associated with ankle sprain injury within female athletes. CONCLUSIONS: Male collegiate athletes with greater BMI and lesser YBT anterior reach were at a greater risk of sustaining an ankle sprain injury.

National Athletic Trainers' Association Position Statement: Management of Individuals With Patellofemoral Pain.

OBJECTIVE:: To present recommendations for athletic trainers and other health care providers regarding the identification of risk factors for and management of individuals with patellofemoral pain (PFP). BACKGROUND:: Patellofemoral pain is one of the most common knee diagnoses; however, this condition continues to be one of the most challenging to manage. Recent evidence has suggested that certain risk factors may contribute to the development of PFP. Early identification of risk factors may allow clinicians to develop and implement programs aimed at reducing the incidence of this condition. To date, clinicians have used various treatment strategies that have not necessarily benefitted all patients. Suboptimal outcomes may reflect the need to integrate clinical practice with scientific evidence to facilitate clinical decision making. RECOMMENDATIONS:: The recommendations are based on the best available evidence. They are intended to give athletic trainers and other health care professionals a framework for identifying risk factors for and managing patients with PFP.

Various methods for assessing static lower extremity alignment: implications for prospective risk-factor screenings.

CONTEXT: Accurate, efficient, and reliable measurement methods are essential to prospectively identify risk factors for knee injuries in large cohorts. OBJECTIVE: To determine tester reliability using digital photographs for the measurement of static lower extremity alignment (LEA) and whether values quantified with an electromagnetic motion-tracking system are in agreement with those quantified with clinical methods and digital photographs. DESIGN: Descriptive laboratory study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Thirty-three individuals participated and included 17 (10 women, 7 men; age = 21.7 ± 2.7 years, height = 163.4 ± 6.4 cm, mass = 59.7 ± 7.8 kg, body mass index = 23.7 ± 2.6 kg/m2) in study 1, in which we examined the reliability between clinical measures and digital photographs in 1 trained and 1 novice investigator, and 16 (11 women, 5 men; age = 22.3 ± 1.6 years, height = 170.3 ± 6.9 cm, mass = 72.9 ± 16.4 kg, body mass index = 25.2 ± 5.4 kg/m2) in study 2, in which we examined the agreement among clinical measures, digital photographs, and an electromagnetic tracking system. INTERVENTION(S): We evaluated measures of pelvic angle, quadriceps angle, tibiofemoral angle, genu recurvatum, femur length, and tibia length. Clinical measures were assessed using clinically accepted methods. Frontal- and sagittal-plane digital images were captured and imported into a computer software program. Anatomic landmarks were digitized using an electromagnetic tracking system to calculate static LEA. MAIN OUTCOME MEASURE(S): Intraclass correlation coefficients and standard errors of measurement were calculated to examine tester reliability. We calculated 95% limits of agreement and used Bland-Altman plots to examine agreement among clinical measures, digital photographs, and an electromagnetic tracking system. RESULTS: Using digital photographs, fair to excellent intratester (intraclass correlation coefficient range = 0.70-0.99) and intertester (intraclass correlation coefficient range = 0.75-0.97) reliability were observed for static knee alignment and limb-length measures. An acceptable level of agreement was observed between clinical measures and digital pictures for limb-length measures. When comparing clinical measures and digital photographs with the electromagnetic tracking system, an acceptable level of agreement was observed in measures of static knee angles and limb-length measures. CONCLUSIONS: The use of digital photographs and an electromagnetic tracking system appears to be an efficient and reliable method to assess static knee alignment and limb-length measurements.

Lower extremity muscle activation and knee flexion during a jump-landing task.

CONTEXT: Decreased sagittal-plane motion at the knee during dynamic tasks has been reported to increase impact forces during landing, potentially leading to knee injuries such as anterior cruciate ligament rupture. OBJECTIVE: To describe the relationship between lower extremity muscle activity and knee-flexion angle during a jump-landing task. DESIGN: Cross-sectional study. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: Thirty recreationally active volunteers (15 men, 15 women: age = 21.63 ± 2.01 years, height = 173.95 ± 11.88 cm, mass = 72.57 ± 14.25 kg). INTERVENTION(S): Knee-flexion angle and lower extremity muscle activity were collected during 10 trials of a jump-landing task. MAIN OUTCOME MEASURE(S): Simple correlation analyses were performed to determine the relationship between each knee-flexion variable (initial contact, peak, and displacement) and electromyographic amplitude of the gluteus maximus (GMAX), quadriceps (VMO and VL), hamstrings, gastrocnemius, and quadriceps : hamstring (Q : H) ratio. Separate forward stepwise multiple regressions were conducted to determine which combination of muscle activity variables predicted each knee-flexion variable. RESULTS: During preactivation, VMO and GMAX activity and the Q : H ratio were negatively correlated with knee-flexion angle at initial contact (VMO: r = 0.382, P = .045; GMAX: r = 0.385, P = .043; Q : H ratio: r = 0.442, P = .018). The VMO, VL, and GMAX deceleration values were negatively correlated with peak knee-flexion angle (VMO: r = 0.687, P = .001; VL: r = 0.467, P = .011; GMAX: r = 0.386, P = .043). The VMO and VL deceleration values were negatively correlated with knee-flexion displacement (VMO: r = 0.631, P = .001; VL: r = 0.453, P = .014). The Q : H ratio and GM activity predicted 34.7% of the variance in knee-flexion angle at initial contact (P = .006). The VMO activity predicted 47.1% of the variance in peak knee-flexion angle (P = .001). The VMO and VL activity predicted 49.5% of the variance in knee-flexion displacement (P = .001). CONCLUSIONS: Greater quadriceps and GMAX activation and less hamstrings and gastrocnemius activation were correlated with smaller knee-flexion angles. This landing strategy may predispose an individual to increased impact forces due to the negative influence on knee-flexion position.

An update for the conservative management of patellofemoral pain syndrome: a systematic review of the literature from 2000 to 2010.

PURPOSE/BACKGROUND: Patellofemoral pain syndrome (PFPS) is one of the most common and clinically challenging knee pathologies. Historically, clinicians have used a myriad of interventions, many of which have benefited some but not all patients. Suboptimal outcomes may reflect the need for an evidence-based approach for the treatment of PFPS. The authors believe that integrating clinical expertise with the most current scientific data will enhance clinical practice. The purpose of this systematic review is to provide an update on the evidence for the conservative treatment of PFPS. METHODS: The PubMed, CINAHL, and SPORTDiscus databases were searched for studies published between January 1, 2000 and December 31, 2010. Studies used were any that utilized interventions lasting a minimum of 4 weeks for subjects with PFPS. Data were examined for subject sample, intervention duration, intervention type, and pain outcomes. RESULTS: General quadriceps strengthening continues to reduce pain in patients with PFPS. Data are inconclusive regarding the use of patellar taping, patellar bracing, knee bracing, and foot orthosis. Although emerging data suggest the importance of hip strengthening exercise, ongoing investigations are needed to better understand its effect on PFPS. CONCLUSIONS: Current evidence supports the continued use of quadriceps exercise for the conservative management of PFPS. However, inconsistent or limited data regarding the other interventions precluded the authors' ability to make conclusive recommendations about their use. Future investigations should focus on identifying cohorts of patients with PFPS who may benefit from the other treatment approaches included in this systematic review.

Reliability of the landing error scoring system-real time, a clinical assessment tool of jump-landing biomechanics.

CONTEXT: There is a need for reliable clinical assessment tools that can be used to identify individuals who may be at risk for injury. The Landing Error Scoring System (LESS) is a reliable and valid clinical assessment tool that was developed to identify individuals at risk for lower extremity injuries. One limitation of this tool is that it cannot be assessed in real time and requires the use of video cameras. OBJECTIVE: To determine the interrater reliability of a real-time version of the LESS, the LESS-RT. DESIGN: Reliability study. SETTING: Controlled research laboratory. PARTICIPANTS: 43 healthy volunteers (24 women, 19 men) between the ages of 18 and 23. INTERVENTION: The LESS-RT evaluates 10 jump-landing characteristics that may predispose an individual to lower extremity injuries. Two sets of raters used the LESS-RT to evaluate participants as they performed 4 trials of a jump-landing task. MAIN OUTCOME MEASURES: Intraclass correlation coefficient (ICC2,1) values for the final composite score of the LESS-RT were calculated to assess interrater reliability of the LESS-RT. RESULTS: Interrater reliability (ICC2,1) for the LESS-RT ranged from .72 to .81 with standard error of measurements ranging from .69 to .79. CONCLUSIONS: The LESS-RT is a quick, easy, and reliable clinical assessment tool that may be used by clinicians to identify individuals who may be at risk for lower extremity injuries.

Concentric and eccentric torque of the hip musculature in individuals with and without patellofemoral pain.

CONTEXT: Individuals suffering from patellofemoral pain have previously been reported to have decreased isometric strength of the hip musculature; however, no researchers have investigated concentric and eccentric torque of the hip musculature in individuals with patellofemoral pain. OBJECTIVE: To compare concentric and eccentric torque of the hip musculature in individuals with and without patellofemoral pain. DESIGN: Case control. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty participants with patellofemoral pain (age = 26.8 +/- 4.5 years, height = 171.8 +/- 8.4 cm, mass = 72.4 +/- 16.8 kg) and 20 control participants (age = 25.6 +/- 2.8 years, height = 169.5 +/- 8.9 cm, mass = 70.0 +/- 16.9 kg) were tested. Volunteers with patellofemoral pain met the following criteria: knee pain greater than or equal to 3 cm on a 10-cm visual analog scale, insidious onset of symptoms not related to trauma, pain with palpation of the patellar facets, and knee pain during 2 of the following activities: stair climbing, jumping or running, squatting, kneeling, or prolonged sitting. Control participants were excluded if they had a prior history of patellofemoral pain, knee surgery in the past 2 years, or current lower extremity injury that limited participation in physical activity. INTERVENTION(S): Concentric and eccentric torque of the hip musculature was measured on an isokinetic dynamometer. All volunteers performed 5 repetitions of each strength test. Separate multivariate analyses of variance were performed to compare concentric and eccentric torque of the hip extensors, abductors, and external rotators between groups. MAIN OUTCOME MEASURE(S): Average and peak concentric and eccentric torque of the hip extensors, abductors, and external rotators. Torque measures were normalized to the participant's body weight multiplied by height. RESULTS: The patellofemoral pain group was weaker than the control group for peak eccentric hip abduction torque (F(1,38) = 6.630, P = .014), and average concentric (F(1,38) = 4.156, P = .048) and eccentric (F(1,38) = 4.963, P = .032) hip external rotation torque. CONCLUSIONS: The patellofemoral pain group displayed weakness in eccentric hip abduction and hip external rotation, which may allow for increased hip adduction and internal rotation during functional movements.

A prospective investigation of biomechanical risk factors for patellofemoral pain syndrome: the Joint Undertaking to Monitor and Prevent ACL Injury (JUMP-ACL) cohort.

BACKGROUND: Patellofemoral pain syndrome is one of the most common chronic knee injuries; however, little research has been done to determine the risk factors for this injury. HYPOTHESIS: Altered lower extremity kinematics and kinetics, decreased strength, and altered postural measurements will be risk factors. STUDY DESIGN: Cohort study (prognosis); Level of evidence, 2. METHODS: A total of 1597 participants were enrolled in this investigation and prospectively followed from the date of their enrollment (July 2005, July 2006, or July 2007) through January 2008, a maximum of 2.5 years of follow-up. Each participant underwent baseline data collection during their pre-freshman summer at the United States Naval Academy. Baseline data collection included 3-dimensional motion analysis during a jump-landing task, 6 lower extremity isometric strength tests, and postural alignment measurements (navicular drop and Q angle). RESULTS: Risk factors for the development of patellofemoral pain syndrome included decreased knee flexion angle, decreased vertical ground-reaction force, and increased hip internal rotation angle during the jump-landing task. Additionally, decreased quadriceps and hamstring strength, increased hip external rotator strength, and increased navicular drop were risk factors for the development of patellofemoral pain syndrome. CONCLUSION: Multiple modifiable risk factors for patellofemoral pain syndrome pain have been identified in this investigation. To decrease the incidence of this chronic injury, the risk factors for patellofemoral pain syndrome need to be targeted in injury prevention programs. CLINICAL RELEVANCE: Prevention programs should focus on increasing strength of the lower extremity musculature along with instructing proper mechanics during dynamic movements to decrease the incidence of patellofemoral pain syndrome.