Cara L. Lewis

• PT, PhD
• Professor (Associate) at Boston University

Background There is little known about translation of the hip and the relationship with hip rotation and morphology in asymptomatic patients. Hypotheses (1) Femoral head would exhibit significant translations in asymptomatic hips, (2) femoral head translations would correlate to femoral rotations, and (3) range of femoral head translations would c...

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 whi...

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. 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-we...

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 artic...

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 co...

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-r...

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 anter...

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:...

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 an...

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 mac...

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: Observati...

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 St...

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 e...

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 (C...

Objective To 1) develop and evaluate a machine learning model incorporating gait and physical activity to predict medial tibiofemoral cartilage worsening over two years in individuals without or with early knee osteoarthritis and 2) identify influential predictors in the model and quantify their effect on cartilage worsening. Design An ensemble ma...

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 inve...

Obesity increases the risk of knee osteoarthritis. Knee joint contact characteristics have been thought to provide insights into the pathogenesis of knee OA; however, the cartilage contact characteristics in individuals with obesity have not been fully described. We conducted cartilage‐to‐cartilage contact analyses through high‐precision fluoroscop...

Foot arch structure contributes to lower-limb joint mechanics and gait in adults with obesity. However, it is not well-known if excessive weight and arch height together affect gait mechanics compared to the effects of excessive weight and arch height alone. The purpose of this study was to determine the influences of arch height and obesity on gai...

Fast walking may require a non-uniform change of dynamic stiffness among lower limb joints to deal with this daily task’s demands. The change of dynamic joint stiffness may be distinct between females and males. This study aimed to test for differences in dynamic stiffness among lower limb joints in response to increased walking speed in males and...

Background: Individuals with hip osteoarthritis (OA) commonly walk with less hip extension compared to individuals without hip OA. This alteration is often attributed to walking speed, structural limitation, and/or hip pain. It is unclear if individuals who are at increased risk for future OA (i.e., individuals with pre-arthritic hip disease [PAHD]...

Pelvic drop is caused by decreased hip abductor muscle activity and is associated with lower-extremity injury. Hip abductor strengthening exercises are well established; however, no standard method exists to increase hip abductor activity during functional activities. The purpose of this research was to study the effects of walking with a unilatera...

Context: The single leg squat (SLS) is appropriate for targeting activation, strengthening, and/or neuromuscular retraining of the gluteus maximus, gluteus medius, and quadriceps. However, the effect of different non-stance leg positions on muscle activity has not been fully evaluated. Objective: To compare the muscle activity of selected stance...

Objective To compare ground reaction force patterns (GRF) during walking among legs defined by presence or absence of knee pain and/or radiographic knee osteoarthritis (ROA). Method Principal component analysis extracted major modes of variation (PCs) in GRF data from the Multicenter Osteoarthritis Study during self-paced walking. Legs were catego...

Discerning whether individuals with obesity transfer walking adaptation from treadmill to over-ground walking is critical to advancing our understanding of walking adaptation and its usefulness in rehabilitating obese populations. We examined whether the aftereffects following split-belt treadmill adaptation transferred to over-ground walking in ad...

Physeal changes corresponding to cam morphology are currently measured using 2D methods. These methods are limited by definitions of thefemoral neckaxis and head center that are dependent on the radiographic plane of view. To address theselimitations, we developed 3D methods for analyzing continuous growth plate shape using MRI scans. These newmeth...

Post‐operative gait mechanics in persons with femoroacetabular impingement syndrome (FAIS) remain understudied as a treatment outcome despite observed, yet inconclusive, pre‐operative gait abnormalities. Females with FAIS demonstrate worse pre‐operative patient‐reported hip function and altered hip mechanics when compared to males; it is unknown wh...

Background The alignment of the foot-ankle complex may influence the kinematics and kinetics of the entire lower limb during walking. Objectives This study investigated the effect of different magnitudes of varus alignment of the foot-ankle complex (small versus large) on the kinematics and kinetics of foot, ankle, knee, and hip in the frontal and...

Hip-related pain is a well-recognised complaint among active young and middle-aged active adults. People experiencing hip-related disorders commonly report pain and reduced functional capacity, including difficulties in executing activities of daily living. Patient-reported outcome measures (PROMs) are essential to accurately examine and compare th...

There is no agreement on how to classify, define or diagnose hip-related pain—a common cause of hip and groin pain in young and middle-aged active adults. This complicates the work of clinicians and researchers. The International Hip-related Pain Research Network consensus group met in November 2018 in Zurich aiming to make recommendations on how t...

Hip-related pain can significantly impact quality of life, function, work capacity, physical activity and family life. Standardised measurement methods of physical capacity of relevance to young and middle-aged active adults with hip-related pain are currently not established. The aim of this consensus paper was to provide recommendations for clini...

The 1st International Hip-related Pain Research Network meeting discussed four prioritised themes concerning hip-related pain in young to middle-aged adults: (1) diagnosis and classification of hip-related pain; (2) patient-reported outcome measures for hip-related pain; (3) measurement of physical capacity for hip-related pain; (4) physiotherapist...

Background: Kinematic differences between females and males for the single leg squat (SLS) have been identified. However, kinetic differences between sexes and how variations of the non-stance leg position during the SLS may affect kinematics and kinetics differently in females and males have not been examined. Objectives: Examine sex-specific k...

The purpose of this study was to determine if females and males use different hip and knee mechanics when walking with standardized military-relevant symmetric loads. Fifteen females and fifteen males walked on a treadmill for 2-min at a constant speed under three symmetric load conditions (unloaded: 1.71 kg, medium: 15 kg, heavy: 26 kg). Kinematic...

[This corrects the article DOI: 10.1371/journal.pone.0174663.].

Gait data file, control group. Six degree-of-freedom kinematics during stance phase of treadmill gait in healthy individuals with knee pain. (CSV)

Background Individuals with developmental dysplasia of the hip (DDH) often report hip pain and exhibit gait adaptations. Previous studies in this patient population have focused on average kinematic and acceleration measures during gait, but have not examined variability. Research question Do individuals with hip pain and DDH have altered kinemati...

Context: Weakness or decreased activation of the hip abductors and external rotators has been associated with lower extremity injury, especially in females. Resisted side stepping is commonly used to address hip weakness. Whereas multiple variations of this exercise are used clinically, few data exist regarding which variations to select. Objecti...

Background: Obesity is a mechanical risk factor for osteoarthritis. In individuals with obesity, knee joint pain is prevalent. Weight loss reduces joint loads, and therefore potentially delays disease progression; however, how the knee joint responds to weight loss in individuals with obesity and knee pain is not clear. Research question: To ass...

Background Femoroacetabular impingement (FAI) syndrome may affect gait kinematics differently between males and females. Objectives To investigate whether individuals with FAI syndrome have different hip and pelvic motion during gait, at their preferred speed and a prescribed speed, compared to individuals of the same sex without pain. Methods Tw...

Study Design Controlled laboratory study, case-control design. Background Despite recognition that femoroacetabular impingement syndrome (FAIS) is a movement-related disorder, few studies have examined dynamic unilateral tasks in individuals with FAIS. Objectives To determine whether movements of the pelvis and lower extremities in individuals wi...

Knee joint pain is a common symptom in obese individuals and walking is often prescribed as part of management programs. Past studies in obese individuals have focused on standing alignment and kinematics in the sagittal and coronal planes. Investigation of 6 degree-of-freedom (6DOF) knee joint kinematics during standing and gait is important to th...

Gait data file. Six degree-of-freedom kinematics during stance phase of treadmill gait in obese individuals with knee pain. (CSV)

The shift to habitual bipedalism 4–6 million years ago in the hominin lineage created a morphologically and functionally different human pelvis compared to our closest living relatives, the chimpanzees. Evolutionary changes to the shape of the pelvis were necessary for the transition to habitual bipedalism in humans. These changes in the bony anato...

Background The identification of risk factors for lower extremity musculoskeletal (MSK) injury in sport is required to inform primary and secondary injury prevention strategies. Objective To determine whether measures of poor movement quality are associated with lower extremity MSK injury in sport. Design Systematic Review. Methods Five electron...

Background Identification of risk factors for lower extremity (LE) injury in sport and military/first-responder occupations is required to inform injury prevention strategies. Objective To determine if poor movement quality is associated with LE injury in sport and military/first-responder occupations. Materials and methods 5 electronic databases...

Objective: Many persons with knee pain have joint pain outside the knee but despite the impact and high frequency of this pain, its distribution and causes have not been studied. Those studying gait abnormalities have suggested that knee pain causes pain in adjacent joints but pain adaptation strategies are highly individualized. Methods: We stu...

Gait can be powered from the hip and/or from the trailing ankle [1] and a trade-off exists between the two [2]. The verbal cue to “push more with your foot when you walk” increased ankle pushoff, reduced internal net hip muscle moments [3] and decreased the anterior hip joint force [4] in shod walking. Large forces at the hip have been associated w...

Single leg squats (SLSs) have been advocated as both a means to screen for, and intervene in, hip pathology [1]. Previous investigations of SLS kinetics have, however, primarily focused on the knee [e.g., 2]. The role each joint plays in controlling movement during SLS has not been previously explored. Further, the effects of progression through th...

Background Gradual increases in mass such as during pregnancy are associated with changes in gait at natural velocities. The purpose of this study was to examine how added mass at natural and imposed slow walking velocities would affect gait parameters. Methods Eighteen adult females walked at two velocities (natural and 25 % slower than their nat...

Unlabelled: To compare sports-related hip injuries on the basis of sex and age in a cohort of young athletes. A 5% random probability sample of all new patients' charts over a 10-year time period was selected for investigation. The most common hip injury diagnoses, sport at time of injury, mechanism (acute/traumatic vs. overuse), and types (bony v...

Background: The single leg squat (SLS) is a functional task used by practitioners to evaluate and treat multiple pathologies of the lower extremity. Variations of the SLS may have different neuromuscular and biomechanical demands. The effect of altering the non-stance leg position during the SLS on trunk, pelvic, and lower extremity mechanics has...

Purpose: To determine if contact forces and electromyography (EMG) muscle amplitudes were altered during the lunge for patients with symptomatic labral tears compared with asymptomatic control subjects. Methods: Surface electromyography electrodes were placed over the gluteus medius, gluteus maximus, adductor longus, and rectus femoris muscles o...

During pregnancy, the female body experiences structural changes, such as weight gain. As pregnancy advances, most of the additional mass is concentrated anteriorly on the lower trunk. The purpose of this study is to analyze kinematic and kinetic changes when load is added anteriorly to the trunk, simulating a physical change experienced during pre...

Snapping hip, or coxa saltans is a palpable or auditory snapping with movement of the hip joint. Extra-articular snapping is divided into external and internal types, and is caused laterally by the iliotibial band and anteriorly by the iliopsoas tendon. Snapping of the iliopsoas usually requires contraction of the hip flexors and may be difficult t...

Objective: Investigate the relation of step length to the sex-specific prevalence and worsening of MRI-detected structural damage in the patellofemoral joint (PFJ) among a cohort of older women and men with or at risk for knee osteoarthritis (OA). Methods: The Multicenter Osteoarthritis (MOST) Study is a cohort study of persons aged 50-79 years...

Study design: Controlled laboratory study, repeated-measures design. Objectives: To compare hip abductor muscle activity and hip and knee joint kinematics in the moving limb to the stance limb during resisted side stepping, and to determine whether muscle activity was affected by the posture (upright standing versus squat) used to perform the ex...

The single leg squat and single leg step down are two commonly used functional tasks to assess movement patterns. It is unknown how kinematics compare between these tasks. The purpose of this study was to identify kinematic differences in the lower extremity, pelvis and trunk between the single leg squat and the step down. Fourteen healthy individu...

Development of biologically inspired exoskeletons to assist soldiers in carrying load is a rapidly expanding field. Understanding how the body modulates stiffness in response to changing loads may inform the development of these exoskeletons and is the purpose of the present study. Seventeen subjects walked on a treadmill at a constant preferred wa...

This is a case report of a female who underwent a Girdlestone arthroplasty at age 10 and a total hip arthroplasty at age 21. Despite early post-operative rehabilitation, the patient experienced increasing pain, progressive gait deviations and functional limitations during the year following surgery. This course of care was initiated one year after...

Developmental dysplasia of the hip is often diagnosed in infancy, but less severe cases of acetabular dysplasia are being detected in young active adults. The purpose of this case report is to present a non-surgical intervention for a 31-year-old female with mild acetabular dysplasia and an anterior acetabular labral tear. The patient presented wit...

Walking and foot arch structure have risk-increasing effects that contribute to decreased physical activity in adults with overweight and obese body mass index (BMI) scores. However, it is unknown whether both excessive weight and arch height influence walking compared to the effects of excessive weight or arch height alone. The purpose of this stu...

Anterior acetabular labral tears and anterior hip pain may result from high anteriorly directed forces from the femur on the acetabulum. While providing more pushoff is known to decrease sagittal plane hip moments, it is unknown if this gait modification also decreases hip joint forces. The purpose of this study was to determine if increasing pusho...

Anterior hip pain is common in young, active adults. Clinically, we have noted that patients with anterior hip pain often walk in a swayback posture, and that their pain is reduced when the posture is corrected. The purpose of this study was to investigate a potential mechanism for the reduction in pain by testing the effect of posture on movement...

Problematic femoroacetabular impingement frequently is seen following Legg-Calvé-Perthes disease (LCPD) in young children and following slipped capital femoral epiphysis (SCFE) in older children and adolescents. Although symptoms may be mild in adolescents and young adults, chondral damage following LCPD and SCFE deformity is cumulative and irrever...

The biomechanical mechanisms that link foot structure to injuries of the musculoskeletal system during gait are not well understood. This study had two parts. The purpose of part one was to determine the relation between clinical rearfoot and forefoot angles and foot angles as they make contact with the ground. The purpose of part two was to determ...

Anterior hip or groin pain is a common complaint for which people are referred for physical therapy. We have observed that people with anterior hip pain often walk in greater hip extension than people without anterior hip pain, and that the pain is reduced when they walk in less hip extension. Therefore, we investigated anterior hip joint forces wh...

To improve design of robotic lower limb exoskeletons for gait rehabilitation, it is critical to identify neural mechanisms that govern locomotor adaptation to robotic assistance. Previously, we demonstrated soleus muscle recruitment decreased by approximately 35% when walking with a pneumatically-powered ankle exoskeleton providing plantar flexor t...

Snapping hip, or coxa saltans, is a vague term used to describe palpable or auditory snapping with hip movements. As increasing attention is paid to intra-articular hip pathologies such as acetabular labral tears, it is important to be able to identify and understand the extra-articular causes of snapping hip. The search terms snapping hip and coxa...

During human walking, plantar flexor activation in late stance helps to generate a stable and economical gait pattern. Because plantar flexor activation is highly mediated by proprioceptive feedback, the nervous system must modulate reflex pathways to meet the mechanical requirements of gait. The purpose of this study was to quantify ankle joint me...

To guide development of robotic lower limb exoskeletons, it is necessary to understand how humans adapt to powered assistance. The purposes of this study were to quantify joint moments while healthy subjects adapted to a robotic ankle exoskeleton and to determine if the period of motor adaptation is dependent on the magnitude of robotic assistance....

Groin pain is a common cause of athletic disability and often involves the adductor longus. A common complaint of patients with groin problems is pain while preparing to kick the ball. The purpose of this study was to examine muscle length and activation of the adductor longus while kicking a soccer ball. Three-dimensional joint positions and muscl...