Lost in research translation: Female athletes are not male athletes, especially at the hip.

Altered shape of the proximal femur (cam morphology) or acetabulum (pincer morphology) is indicative of femoroacetabular impingement, which can result in hip pain and osteoarthritis of the hip. As mechanical load during growth affects the resulting bone shape, there is strong evidence in males that cam morphology develops during skeletal growth while physes are open, rather than as an adaptation after growth plates are closed (skeletal maturity). This adaptation is particularly evident in athletes who participate at elite levels prior to skeletal maturity. The research providing this evidence, however, has primarily focused on male athletes. Despite the lack of inclusion in the research, females consistently comprise two thirds of the clinical and surgical populations with structural hip pain or pathology. Knowledge gained from male-dominated cohorts may not appropriately transfer to female athletes, especially at the hip. This perspectives article briefly reviews differences between females and males in femoral and acetabular structure, hormones, timing of puberty/maturation, hypermobility, activity level and movement control-factors which affect hip structure development and loading. Without female-focused research, the application of research findings from male athletes to female athletes may lead to ineffective or even inappropriate recommendations and treatments. Thus, there is a critical need for investment in research to promote life-long hip health for females.

Protocol and validity testing of femoroacetabular posterior translation with dynamic hip ultrasonography.

OBJECTIVE: To describe femoroacetabular posterior translation (FAPT) using dynamic hip ultrasonography (DHUS), and to determine the inter- and intra-rater reliability of hip ultrasound measurements of FAPT. MATERIALS AND METHODS: The study design was a feasibility study of 13 healthy young adults (26 hips) using test-retest analysis. The data was collected prospectively over a 2-week time period. Three DHUS measurements (posterior neutral (PN), flexion, adduction, and internal rotation (PFADIR), and stand and load (PStand) were measured by four independent raters (2 senior who divided the cohort, 1 intermediate, 1 junior) at two time points for bilateral hips of each participant. Reliability was assessed by calculating the intraclass correlation coefficient (ICC) along with 95% confidence intervals (CIs) for each rater and across all raters. RESULTS: A total of 468 US scans were completed. The mean age of the cohort was 25.7 years (SD 5.1 years) and 54% were female. The inter-rater reliability was excellent for PFADIR (ICC 0.85 95% CI 0.76-0.91), good for PN (ICC 0.69 95% CI 0.5-0.81), and good for PStand (ICC 0.72 95% CI 0.55-0.83). The intra-rater reliability for all raters was good for PFADIR (ICC 0.60 95% CI 0.44-0.73), fair for PN (ICC 0.42 95% CI 0.21-0.59), and fair for PStand (ICC 0.42 95% CI 0.22-0.59). CONCLUSION: This is the first study to present a protocol using dynamic ultrasonography to measure FAPT. DHUS measure for FAPT was shown to be reliable across raters with varying levels of ultrasound experience.

Increased Duration and Intensity of Physical Activity Are Associated With Increased Pain in Individuals With Femoroacetabular Impingement Syndrome: An Ecological Momentary Assessment Study.

OBJECTIVE: To investigate the relation between accelerometer-measured physical activity and real-time pain in individuals with femoroacetabular impingement syndrome (FAIS). We tested the hypothesis that increased duration of high intensity activity would contribute to momentary increases in pain. DESIGN: Observational study. SETTING: Participants' natural, day-to-day environment. PARTICIPANTS: Population-based sample of 33 individuals with unilateral FAIS. Important eligibility criteria included no concomitant hip disorders or previous hip surgery. Key sociodemographic features include that all participants were required to have a smartphone. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Duration and intensity of physical activity as measured by a waist-worn accelerometer, and instantaneous pain reported in real-time smartphone-based ecological momentary assessment surveys. Physical activity variables included each person's average sedentary time, light physical activity (LPA), and moderate to vigorous physical activity (MVPA) in the 90 minutes proceeding all pain surveys as well as fluctuation in sedentary, LPA, and MVPA above or below average prior to each individual survey. RESULTS: Linear mixed models revealed that the significant predictors of pain included fluctuation in sedentary time (B=-0.031, P<.001), average LPA (B=0.26, P=.035), and the interaction between fluctuation in LPA and fluctuation in MVPA (B=0.001, P<.001). Fluctuation in sedentary time above a person's average was associated with lower pain, while average LPA and fluctuations above average in both LPA and MVPA were associated with higher pain. CONCLUSIONS: These results suggest that individuals with FAIS can engage in health-enhancing MVPA but should focus on avoiding concurrent increase above average in both high intensity and LPA in the same 90-minute period. Future work is warranted testing the efficacy of such an approach on pain. Additionally, given that high levels of LPA may arise from a host of socioeconomic factors, additional research is needed to disentangle the effect of LPA on pain in FAIS.

Arthritis Foundation/HSS Workshop on Hip Osteoarthritis, Part 3: Rehabilitation and Exercise.

Far more publications are available for osteoarthritis of the knee than of the hip. Recognizing this research gap, the Arthritis Foundation (AF), in partnership with the Hospital for Special Surgery (HSS), convened an in-person meeting of thought leaders to review the state of the science of and clinical approaches to hip osteoarthritis. This article summarizes the recommendations gleaned from 5 presentations given on hip-related rehabilitation at the 2023 Hip Osteoarthritis Clinical Studies Conference, which took place on February 17 and 18, 2023, in New York City.

Neonatal Hip Loading in Developmental Dysplasia: Finite Element Simulation of Proximal Femur Growth and Treatment.

Background: Abnormal prenatal hip joint loading can lead to compromised hip joint function. Early intervention is crucial for favorable outcomes. Purpose: This study investigates the impact of treatment timing (initiation and duration) on cartilage growth and ossification in the proximal femur of infants with developmental dysplasia of the hip, a condition affecting newborns. Methods: We used a mechanobiological model to simulate proximal femur growth during treatment durations of 3 months, 6 months, and a late-start treatment. Results: The findings indicate that the timing of treatment initiation is crucial, while a longer treatment duration does not contribute to improved morphological development of the hip joint. Conclusions: Mechanobiological models of growth can be used to develop treatments and therapies that correct loading conditions. Growing bone is particularly sensitive to loading conditions, and altered loading during growth can affect bone shape and functionality.

Rehabilitation Phases, Precautions, and Mobility Goals Following Total Hip Arthroplasty.

The prevalence of total hip arthroplasty (THA) for advanced hip osteoarthritis (OA) is both increasing and shifting toward a younger average age. However, THA alone does not typically normalize function in these patients. Postoperative rehabilitation is often recommended to optimize joint motion, strength, and function. To date, there are no peer-reviewed clinical practice guidelines for postoperative rehabilitation following THA. Thus, optimal postoperative rehabilitation requires consideration of the existing literature and clinical expertise. This review article summarizes current recommendations for postoperative management of THA, including phases of rehabilitation, postoperative hip precautions, the effect of rehabilitation setting and mode of delivery on postoperative outcomes, and gait mechanics.

Frontal plane pelvic kinematics during high velocity running: Association with hamstring injury history.

INTRODUCTION: Hamstring injuries are the most prevalent non-contact soft tissue injury in sports, with a larger portion of injuries being recurrent. The sagittal plane running kinematics correlated to hamstring injury history has been well documented. However, analysis of frontal plane kinematics allows for observation of stability and symmetry. This study aimed to examine the frontal plane running kinematics of elite collegiate level sprinters, with and without previous hamstring injury, compared to healthy counterparts. METHODS: Thirty-nine participants performed three 50-m sprints, with three inertial measurement unit sensors placed on the pelvis: one on each iliac crest and one on the sacrum. Participants were classified based on sex, competitive status, and injury history. To investigate differences based on group classification, the data were used to analyze mediolateral motion (relative magnitude of mediolateral acceleration) and asymmetry (difference in acceleration between right and left iliac crests) during each stance phase throughout the run. RESULTS: Injured sprinters displayed significantly greater mediolateral motion and asymmetry during stances than healthy counterparts. CONCLUSIONS: This study demonstrates that frontal plane running stance dynamics are different in athletes with previous hamstring injury than healthy athletes. These athletes may benefit from rehabilitation strategies targeting postural control and stability during dynamic tasks.

Can pelvic tilt cause cam morphology? A computational model of proximal femur development mechanobiology.

Cam deformity of the proximal femur is a risk factor for early osteoarthritis. While cam morphology is related to mechanical force at a formative time in skeletal growth, the specific problematic forces contributing to the development of cam morphology remain unknown. Individuals with femoroacetabular impingement syndrome exhibit an increased anterior pelvic tilt during walking, which alters their hip joint forces. This study aims to investigate the influence of altered joint force caused by anterior pelvic tilt on proximal femur epiphyseal growth and the potential association between increased anterior pelvic tilt and the development of cam morphology. A computational model is utilized to simulate the endochondral ossification in the proximal femur and predict cam formation. Cartilage growth and ossification patterns for a gait cycle with and without anterior pelvic tilt were modeled. The simulated growth results indicated an increased alpha angle (53° for typically developing to 68° for anterior pelvic tilt) and aspherical femoral head in the model with anterior pelvic tilt. We conclude that anterior pelvic tilt may be sufficient to cause the formation of the cam morphology. Identifying the critical mechanical conditions that increase the risk of cam deformity could help prevent this condition by adjusting the physical activities before skeletal maturity.

Females with hip-related pain demonstrate reduced kinetics at the hip and ankle during terminal stance of gait.

BACKGROUND: Individuals with hip-related pain (HRP) commonly report pain with walking and demonstrate altered movement patterns compared to healthy controls (HCs). Individuals with HRP may attempt to reduce pain during walking by decreasing kinetics and joint forces at the hip through increased use of the ankle during pushoff. RESEARCH QUESTION: Do individuals with HRP have increased kinetics at the ankle and decreased kinetics at the hip during pushoff in gait compared to HCs, and do kinetic patterns differ between males and females with HRP? METHODS: This retrospective observational study included 42 individuals with HRP and 20 HCs. Participants completed overground gait trials at their self-selected speed while kinematics and kinetics were recorded through a motion capture system and force plates. Peak internal hip and ankle moments and hip flexion and ankle plantarflexion angular impulse during terminal stance were used in general estimating equations for comparison of group by limb interactions for males and females separately, as well as a comparison of males and females within the HRP group. RESULTS: Females with HRP demonstrated reduced hip flexion impulse on their involved limb (.070 Nm*s/kg*m) compared to female HCs (.083Nm*s/kg*m; p = .032), as well as reduced peak ankle plantarflexion moment (-.94Nm/kg*m) compared to their contralateral limb (-.99Nm/kg*m) and the involved limb of HRP males (-1.00Nm/kg*m) (p ≤ .007). There were no between-limb or between-group differences in hip or ankle peak moments or impulses in males. SIGNIFICANCE: Females with HRP show decreased kinetics at both the hip and ankle; these patterns were not identified in males. Future investigations should examine whether increasing ankle kinetics during pushoff reduces pain at the hip, as this may be a valuable clinical treatment strategy.

Hip Abductor Weakness and Its Association With New or Worsened Knee Pain: Data From the Multicenter Osteoarthritis Study.

OBJECTIVE: Hip abductors, important for controlling pelvic and femoral orientation during gait, may affect knee pain. Our objective was to evaluate the relation of hip abductor strength to worsened or new-onset frequent knee pain. Given previously noted associations of knee extensor strength with osteoarthritis in women, we performed sex-specific analyses. METHODS: We used data from the Multicenter Osteoarthritis study. Hip abductor and knee extensor strength was measured. Knee pain was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire and a question about frequent knee pain at baseline (144-month visit), and 8, 16, and 24 months thereafter. Knee pain outcomes were worsened knee pain (2-point increase in WOMAC pain) and incident frequent knee pain (answering yes to the frequent knee pain question among those without frequent knee pain at baseline). Leg-specific analyses tested hip abductor strength as a risk factor for worsened and new frequent knee pain, adjusting for potential covariates. Additionally, we stratified by knee extensor strength (high versus low). RESULTS: Among women, compared to the highest quartile of hip abductor strength, the lowest quartile had 1.7 (95% confidence interval [95% CI] 1.1-2.6) times the odds of worsened knee pain; significant associations were limited to women with high knee extensor strength (odds ratio 2.0 [95% CI 1.1-3.5]). We found no relation of abductor strength to worsening knee pain in men or with incident frequent knee pain in men or women. CONCLUSION: Hip abductor weakness was associated with worsening knee pain in women with strong knee extensors, but not with incident frequent knee pain in men or women. Knee extensor strength may be necessary, but not sufficient, to prevent pain worsening.

The Women's Soccer Health Study: From Head to Toe.

OBJECTIVES: Women are under-represented in the sports literature despite increasing rates of sports participation. Our objective was to investigate the risks and benefits of an elite women's soccer career in five health domains: general, musculoskeletal, reproductive endocrinology, post-concussion, and mental. METHODS: An online survey was distributed to retired US college, semi-professional, professional, and national team soccer players using personal networks, email, and social media. Short validated questionnaires were used to evaluate the health domains, including the Patient-Reported Outcomes Measurement Information System (PROMIS), Single Assessment Numerical Evaluation (SANE), Post-Concussion Symptom Scale (PCSS), and Patient Health Questionnaire (PHQ). RESULTS: A total of 560 eligible players responded to the survey over a 1-year period. The highest competitive levels were 73% college, 16% semi-professional, 8% professional, and 4% national team. The mean number of years since retirement was 12 (SD = 9), and 17.0% retired for involuntary reasons. The mean SANE scores (0-100 scale as percentage of normal) were knee = 75% (SD = 23), hip = 83% (SD = 23), and shoulder = 87% (SD = 21). The majority (63%) reported that their current activity level included participation in impact sports. A substantial proportion of players reported menstrual irregularities during their careers: 40% had fewer periods with increasing exercise and 22% had no periods for ≥ 3 months. The players (n = 44) who felt that post-concussion symptoms were due to soccer reported more time-loss concussions (F[2] = 6.80, p = 0.002) and symptom severity (F[2] = 30.26, p < 0.0001). Players who recently retired (0-5 years) reported the highest anxiety/depression scores and lowest satisfaction rates compared with those who retired 19+ years ago. CONCLUSION: Health concerns include musculoskeletal injuries, post-concussion symptoms, and lower mental health in the early years following retirement. This comprehensive survey provides initial results that will lay the foundation for further analyses and prioritize research studies that can help all female athletes.

Gait, physical activity and tibiofemoral cartilage damage: a longitudinal machine learning analysis in the Multicenter Osteoarthritis Study.

OBJECTIVE: To (1) develop and evaluate a machine learning model incorporating gait and physical activity to predict medial tibiofemoral cartilage worsening over 2 years in individuals without advanced knee osteoarthritis and (2) identify influential predictors in the model and quantify their effect on cartilage worsening. DESIGN: An ensemble machine learning model was developed to predict worsened cartilage MRI Osteoarthritis Knee Score at follow-up from gait, physical activity, clinical and demographic data from the Multicenter Osteoarthritis Study. Model performance was evaluated in repeated cross-validations. The top 10 predictors of the outcome across 100 held-out test sets were identified by a variable importance measure. Their effect on the outcome was quantified by g-computation. RESULTS: Of 947 legs in the analysis, 14% experienced medial cartilage worsening at follow-up. The median (2.5-97.5th percentile) area under the receiver operating characteristic curve across the 100 held-out test sets was 0.73 (0.65-0.79). Baseline cartilage damage, higher Kellgren-Lawrence grade, greater pain during walking, higher lateral ground reaction force impulse, greater time spent lying and lower vertical ground reaction force unloading rate were associated with greater risk of cartilage worsening. Similar results were found for the subset of knees with baseline cartilage damage. CONCLUSIONS: A machine learning approach incorporating gait, physical activity and clinical/demographic features showed good performance for predicting cartilage worsening over 2 years. While identifying potential intervention targets from the model is challenging, lateral ground reaction force impulse, time spent lying and vertical ground reaction force unloading rate should be investigated further as potential early intervention targets to reduce medial tibiofemoral cartilage worsening.

The effect of trunk and shank position on the hip-to-knee moment ratio in a bilateral squat.

OBJECTIVES: The effect of knee position on joint moments during squats has been studied; however, the effect of trunk angle has been less well investigated. This study evaluated the effect of both trunk and knee sagittal plane position on the distribution of moments between the hip and knee extensors during the bilateral squat. DESIGN: Observational study. SETTING: Biomechanics laboratory. PARTICIPANTS: One hundred individuals performed bilateral squats. MAIN OUTCOME MEASURES: Motion and force data were collected using motion capture and force plates. Trunk and shank angles and hip and knee moments were calculated. A linear regression was used to associate the ratio between the hip and knee moments (hip-to-knee moment ratio) with the sagittal plane trunk and shank angles, while accounting for six squat depths (between 60° and 110° of knee flexion) and side. RESULTS: Trunk angle and shank angle each contributed to the hip-to-knee moment ratio (P < .001) with trunk accounting for a higher proportion of variance than the other variables. The hip-to-knee moment ratio increased with increasing trunk angle and with decreasing shank angle. CONCLUSIONS: This large cohort study supports the use of trunk position to instruct squat technique with the goal of modifying hip and knee moments.

Patients with cam-type femoroacetabular impingement demonstrate increased change in bone-to-bone distance during walking: A dual fluoroscopy study.

Cam-type femoroacetabular impingement (FAI) syndrome is a painful, structural hip disorder. Herein, we investigated hip joint mechanics through in vivo, dynamic measurement of the bone-to-bone distance between the femoral head and acetabulum in patients with cam FAI syndrome and morphologically screened controls. We hypothesized that individuals with cam FAI syndrome would have larger changes in bone-to-bone distance compared to the control group, which we would interpret as altered joint mechanics as signified by greater movement of the femoral head as it articulates within the acetabulum. Seven patients with cam FAI syndrome and 11 asymptomatic individuals with typical morphology underwent dual fluoroscopy imaging during level and inclined walking (upward slope). The change in bone-to-bone distance between femoral and acetabular bone surfaces was evaluated for five anatomical regions of the acetabulum at each timepoint of gait. Linear regression analysis of the bone-to-bone distance considered two within-subject factors (activity and region) and one between-subjects factor (group). Across activities, the change in minimum bone-to-bone distance was 1.38-2.54 mm for the cam FAI group and 1.16-1.84 mm for controls. In all regions except the anterior-superior region, the change in bone-to-bone distance was larger in the cam group than the control group (p ≤ 0.024). An effect of activity was detected only in the posterior-superior region where larger changes were noted during level walking than incline walking. Statement of clinical significance: Patients with cam FAI syndrome exhibit altered hip joint mechanics during the low-demand activity of walking; these alterations could affect load transmission, and contribute to pain, tissue damage, and osteoarthritis.

Relation of Temporal Asymmetry During Walking to Two-Year Knee Pain Outcomes in Those With Mild-to-Moderate Unilateral Knee Pain: An Exploratory Analysis From the Multicenter Osteoarthritis Study.

OBJECTIVE: We aimed to explore the cross-sectional relation of unilateral knee pain severity and temporal asymmetry during walking and to determine relations of temporal asymmetry during walking to 2-year changes in ipsilateral and contralateral knee pain in those with mild-to-moderate unilateral knee pain. METHODS: The Multicenter Osteoarthritis Study is a prospective cohort study of adults with or at risk for knee osteoarthritis. The current study included participants with unilateral knee pain. Gait was assessed during self-selected and fast walking at baseline. Knee pain was assessed at baseline and 2 years. We calculated limb symmetry indices (LSIs; nonpainful limb/painful limb × 100) for stance, single-limb support time, and double-limb support time, then examined their relations to unilateral knee pain severity, incident contralateral knee pain, and persistent ipsilateral knee pain. RESULTS: Unilateral knee pain severity was not associated with temporal asymmetry during self-selected or fast walking. At 2 years, 17.1% of participants had incident contralateral knee pain and 51.4% had persistent ipsilateral knee pain. For self-selected walking, greater LSIs (i.e., longer time on the nonpainful limb) for stance and single-limb support time were associated with decreased odds of incident contralateral knee pain. Measures of temporal asymmetry were not associated with persistent ipsilateral knee pain, except for single-limb support time during fast walking. CONCLUSION: For those with unilateral knee pain, temporal asymmetry during walking is not associated with pain severity. However, select measures of stance and single-limb support time during self-selected and fast walking relate to longitudinal knee pain outcomes.

Females with hip-related pain display altered lower limb mechanics compared to their healthy counterparts in a drop jump task.

BACKGROUND: Hip-related pain describes femoroacetabular impingement syndrome, acetabular dysplasia, and other hip pain conditions without clear morphological features. Movement strategies in this population, notably sex-related patterns, are poorly understood and may provide insights into why females report more pain and worse function. This study examined the sex-related differences during a drop vertical jump task between those with hip-related pain and healthy controls. METHODS: Patients with hip-related pain and healthy controls completed five repetitions of a drop jump while their kinematics and kinetics were recorded using a motion capture system and force plates. Hip, knee, and ankle joint angles and external joint moments during landing were used in general estimating equations for comparison of group by sex by limb interactions. Time series data were further investigated using statistical parametric mapping. FINDINGS: Females with hip-related pain had 9.1° less hip flexion (P = .041) and 9.2° less knee flexion (P = .024) than healthy females, and 8.3° less knee flexion than male counterparts with hip-related pain (P = .039). Males demonstrated 1.4° less hip flexion on the affected side compared to their uninvolved side (P = .004). Statistical parametric mapping results showed significant differences in knee flexion angle for females with hip-related pain compared to healthy females (P = .042). There were no significant differences in hip, knee, or ankle moments. INTERPRETATION: Females with hip-related pain showed kinematic patterns distinct from healthy controls. Sex may be an important variable of interest in characterizing movement impairments in this population and movement impairments may be an appropriate target for intervention for these patients.

Changes in dynamic balance control in adults with obesity across walking speeds.

Adults with obesity have gait instability, leading to increased fall risks and decreased physical activity. Whole-body angular momentum (WBAM) is regulated over a gait cycle, essential to avoid a fall. However, how obese adults regulate WBAM during walking is unknown. The current study investigated changes in WBAM about the body's center of mass (COM) during walking in obese and non-obese adults across different walking speeds. Twenty-eight young adults with obesity and normal weight walked barefoot at a fixed walking speed (FWS, 1.25 m/s) and at five different speeds based on their preferred walking speed (PWS): 50, 75, 100, 125, and 150 % of PWS. Adults with obesity walked slower with shorter step length, wider step width, and longer double support time (p < 0.01). The ranges of frontal- and transverse-plane WBAM were greater in obese adults (p < 0.01). We also found that the range of frontal-plane WBAM did not significantly change with walking speed (p > 0.05), while the range of transverse-plane WBAM increased with walking speed (p < 0.01). The ranges of frontal- and transverse-plane WBAM increased with the mediolateral ground reaction force and mediolateral moment arm (p < 0.01), which may be most affected by lateral foot placement relative to the body's COM. Our findings suggest that controlling mediolateral stability during walking is more challenging in obese adults, independent of their slow walking speed. Understanding whole-body rotational dynamics observed in obese walking provides an insight into the biomechanical link between obesity and gait instability, which may help find a way to reduce fall risks and increase physical activity.

The effect of obesity on whole-body angular momentum during steady-state walking.

BACKGROUND: Individuals with obesity demonstrate deficits in postural stability, leading to increased fall risks. Controlling whole-body angular momentum is essential for maintaining postural stability during walking and preventing falls. However, it is unknown how obesity impacts whole-body angular momentum during walking. RESEARCH PURPOSE: To investigate the change in angular momentum about the body's COM during walking in individuals with different degrees of obesity. METHODS: Thirty-eight young adults with different body mass index (BMI) scores walked barefoot at their preferred speed on a treadmill for 2 min. The whole-body angular momentum has been quantified from ground reaction force and moment data to capture the rotational behavior of walking in individuals with obesity without relying solely on placing markers on anatomical landmarks. RESULTS: We found that adults with higher BMI scores walked slower with shorter step length, wider step width, and longer double support time (ps<.01). Ranges of the frontal- and transverse-plane angular momentum were greater in adults with higher BMI scores (ps<.01), while no difference was observed between BMI groups in the total sum of changes in whole-body angular momentum in any plane (ps>.05). SIGNIFICANCE: Obesity not only decreased walking speed but also limited the ability to control mediolateral stability during walking. Investigating how obesity affects whole-body angular momentum may help better understand why adults with obesity have atypical gait with poor balance, address fall risk factors, and facilitate participation in physical activities.

Effect of simulated changes in pelvic tilt on hip joint forces.

Musculoskeletal modeling is commonly used to simulate and compare various movements between individuals. For conditions such as femoroacetabular impingement syndrome (FAIS), individuals tend to walk with more anterior pelvic tilt than those without FAIS. However, it is unknown whether accounting for pelvic tilt in musculoskeletal modeling would lead to a change in muscle forces and in turn, joint forces. Gait data of six individuals were collected and processed using Vicon and Visual3D. Each participant's pelvic tilt was adjusted by ± 10° at all time points during gait. Three analyses were performed per individual: no adjustment in tilt, one posterior (positive) tilt, and one anterior (negative) tilt. The resulting data were imported into OpenSim to determine muscle forces and the resulting femur-on-acetabulum (hip joint) forces in the pelvic and femoral reference frames. Data for each participant were normalized for gait cycle and body weight in MATLAB, and statistical parametric mapping was used to determine if the differences in joint and muscle forces were significant across different pelvic orientations. Shifting from posterior to anterior pelvic tilt reduced resultant forces. In the pelvic reference frame, anteriorly-directed joint forces decreased, while medially-directed forces increased. In the femoral reference frame, anteriorly- and medially-directed joint forces increased, while superiorly-directed forces decreased. Anterior gluteus medius and iliacus muscle forces decreased, while quadratus femoris, piriformis, and gemellus muscle forces increased. Given these results, future studies using musculoskeletal modeling should account for pelvic tilt in musculoskeletal models to obtain more realistic comparisons between healthy and pathological conditions.