Simple Mobility Tests Predict Use of Assistive Devices in Older Adults.

BACKGROUND: Assistive devices (ADs) for ambulation are commonly provided to improve safety and independence in older adults. Despite the common use of these devices, there are no standard prescribing guidelines, and non-health care providers, including caregivers and family members, often make decisions about the need for ADs. Identifying factors or a single screening test associated with AD use would benefit clinicians and non-health care caregivers in making decisions to adopt an AD for patients, clients, and family members. PURPOSE/OBJECTIVES: The purpose of this cross-sectional study was to identify the test that best predicts ADs for ambulation and non-AD use among community-dwelling individuals. METHODS: Eighty-five older adults (81.6 ± 8.2 years old) who underwent outpatient physical therapy participated in this study. They participated in a series of tests, including the Timed Up and Go, handgrip and quadriceps strength, the 30-second chair-rise test, the 5-m fast gait speed, the Functional Independence Measure, the locomotive syndrome tests (stand-up test, 2-step test [2ST], and the Locomo-5 Checklist), and numeric pain scales. Mann-Whitney U tests were used to identify differences between those who did and did not use an AD for ambulation. Logistic regression analyses were used to examine which test best predicted AD use. RESULTS: 80% of participants (n = 68) used an AD for ambulation. There were significant differences in all test variables between users and nonusers (P = .033 to P < .001), except for quadriceps strength, age, and pain (all P > .05). Only the 2ST was a significant predictor of AD use, with a cutoff distance of the toe-to-toe stride shorter than 93% of body height (sensitivity: 72%, and specificity: 82%, P = .048). DISCUSSION: Simple functional measures differed between those who did and did not use ADs for ambulation; however, only the 2ST predicted AD status. Individuals who cannot step 93% of their body height may be appropriate for an AD. CONCLUSIONS: If comprehensive clinical evaluations are not available to make decisions about AD use, the 2ST can be used to make clinical recommendations for an AD for ambulation.

Concurrent Validity Between Potential Screening Tests for Early Mobility Decline in Independent Community Dwellers.

BACKGROUND AND PURPOSE: Standardized screening tests that detect early mobility decline, regardless of etiology, are needed for healthy aging. The locomotive syndrome (LS) tests are designed to identify stages of mobility decline and inform appropriate levels of intervention. The long-term goal of this research is to develop standardized mobility screening tests that can be used across health care settings and throughout a patient's lifespan to guide appropriate medical care. As the first step in this process, this study examines the concurrent validity between the reference and the LS tests. METHODS: This cross-sectional study examined correlations between the LS functional tests and a set of reference tests and the ability to differentiate the 3 stages of mobility decline. The reference tests included the stair-climbing test, the 30-second chair rise test, the 6-minute walk test, the Global Physical Health (GPH) portion of the PROMIS, and the Lower Extremity Functional Scale (LEFS). The LS tests included the Stand-Up Test, the 2-Step Test, and the 25-question Geriatric Locomotive Function Scale (25-GLFS). A total of 115 community dwellers of 61.2 years old on average (±10.0 years), with n = 71 (61%) older than 60 years, voluntary participated in this prospective study. Nonparametric analyses of variance and correlations were used to examine the concurrent validity. RESULTS AND DISCUSSION: Performance-based tests were significantly correlated (| r | = 0.38-0.61, P < .001) with LS tests. The LEFS was correlated with all LS tests, but the GPH was only correlated with the 25-GLFS. Also, significant differences were found in reference test scores between the 3 LS stages ( P < .05). CONCLUSIONS: The LS tests and reference tests demonstrated significant correlations, and participants performed significantly worse on reference tests as LS severity increased. Given these results, it is possible that the LS standardized tests may play an important role in mobility screening. Future research should investigate feasibility, sensitivity, and specificity of these tests.

Knee biomechanics and contralateral knee osteoarthritis progression after total knee arthroplasty.

BACKGROUND: Despite the success rate of Total Knee Arthroplasty (TKA), many patients undergo contralateral TKA. It is possible that altered gait mechanics after unilateral TKA play a role in the progression of contralateral OA progression. RESEARCH QUESTION: The purpose of this study was to identify biomechanical predictors of radiographic OA progression in the contralateral (non-surgical) knee after unilateral (primary/initial) TKA. In addition, this study quantified for patients who had contralateral OA progression. METHODS: Biomechanical outcomes were collected 6-24 months after unilateral primary TKA and were used to predict changes in contralateral OA severity at follow-up. Participants were divided into "Progressor" and "Non-Progressor" groups based on changes in Kellgren-Lawrence (KL) OA grade and Joint Space Width (JSW) between baseline and follow-up testing sessions. Biomechanical factors during walking were peak knee adduction moment, knee flexion/extension excursions, knee angle at initial foot contact, and peak knee flexion/extension. Multiple independent t-tests were used to examine the magnitude of differences in biomechanical variables between the groups. Logistic regression was used to examine the association between the biomechanical predictors and change in KL scores and JSW. RESULTS: The mean time between surgery and follow-up x-rays was 8.8 (2.4) years. Of 40 participants, 62.5-78% had contralateral radiographic knee OA progression by follow-up. There were no significant differences in the biomechanical variables between groups. For the regression analysis, none of the biomechanical variables were found to be predictors for contralateral OA progression. SIGNIFICANCE: Although abnormal biomechanics are known risk factors for primary knee OA, it is possible that the mechanisms that result in OA progression of the contralateral limb are different than primary knee OA progression. Future work should evaluate other objective measures of OA progression and determine if cumulative measures of joint loading are related to OA worsening.

Falling risk in patients with end-stage knee osteoarthritis.

Although 25% of patients with end-stage knee osteoarthritis (OA) have reported a fall, there is limited information about risk factors for falling in patients awaiting total knee arthroplasty (TKA). The purpose of this study was to identify clinical and functional measures related to fall risk. A total of 259 participants awaiting TKA for OA participated in this secondary cross-sectional study. Participants were divided into fallers and non-fallers based on falling history in the prior 6 months. Clinical measures (hip and knee pain, neck and low back pain (LBP), knee range of motion, and quadriceps strength) and functional measures (six-minute walk test (6MWT), timed up and go test, and Knee Injury and Osteoarthritis Outcome Score (KOOS)) were assessed in patients 2-4 weeks prior to TKA. Independent t tests were used to examine differences between groups. Odds ratio was calculated to identify clinical risk factors for falling. Of all participants, 47 (18%) reported a fall in the previous 6 months. Fallers had 30% greater LBP (3.0 ± 2.5 vs. 2.1 ± 2.6; p = 0.025). Fallers walked 12% shorter distance in the 6MWT than non-fallers (378 ± 100 vs. 422 ± 105 m; p = 0.010). For every 1-point increase in LBP on a 0-10 scale, there was a 14% greater risk of falling (p = 0.028). For every 10-m increase in 6MWT, there was a 3.8% reduction in fall risk (p = 0.011). Greater LBP and worse walking endurance are associated with falls in individuals with end-stage OA. Future studies should determine if interventions that reduce LBP and improve walking performance also reduce the chance of falling.

Gait mechanics are influenced by quadriceps strength, age, and sex after total knee arthroplasty.

Although most patients are satisfied with outcomes after total knee arthroplasty (TKA), many retain preoperative altered gait mechanics. Identifying patient characteristics associated with gait mechanics will improve rehabilitation strategies and enhance our understanding of movement disorders. Therefore, the purpose of this study was to identify which patient characteristics are related to gait mechanics in the surgical limb during walking post-TKA. Patient characteristics included age, body mass, sex, quadriceps strength, self-reported function, and knee pain. General linear regression was used to compare patient characteristics associated with gait mechanics, after controlling for gait speed, functional capacity and time from surgery. We tested 191 patients cross-sectionally at 6-24 months after primary, unilateral TKA. Quadriceps weakness in the surgical limb was associated with less peak vertical ground reaction force (PvGRF) (ß = .245, p = .044), knee extension moment (ß = .283, p = .049), and knee extension excursion (ß = .298, p = .038). Older age (ß = .168, p = .050) was associated with less PvGRF. Quadriceps strength in the nonsurgical limb (ß = -.357, p = .021) was associated with greater knee extension excursion in the surgical limb. Females with TKA (ß = -.276, p = .007) had less knee flexion excursion compared to males. Faster gait speed was also associated with greater PvGRF (ß = .585, p < .001), knee extensor moment (ß = .481, p < .001), and knee flexion excursion (ß = .318, p < .001). Statement of Clinical Significance: This study showed quadriceps weakness, slower gait speed, older age and being female were related to altered gait mechanics post-TKA. These findings will help clinicians better educate patients and develop targeted interventions for improving care in patients post-TKA.

Self-Reported and Performance-Based Outcome Measures Estimation Using Wearables After Unilateral Total Knee Arthroplasty.

Total knee arthroplasty is a common surgical treatment to improve ambulatory function for individuals with end-stage osteoarthritis of the knee. Functional and self-reported measures are widely used to assess functional ability and impairment before and after total knee arthroplasty. However, clinical assessments have limitations and often provide subjective and limited information. Seamless gait characteristic monitoring in the real-world condition is a viable alternative to address these limitations, but the effectiveness of using wearable sensors for knee treatment is unclear. The purpose of this study was to determine if inertial gait variables from wearable sensors effectively estimate the questionnaire, performance (6-min walk test, timed up and go, and 30-s chair stand test), and isometric measure outcomes in individuals after unilateral total knee arthroplasty. Eighteen subjects at least 6 months post-surgery participated in the experiment. In one session, three tasks, including self-reported surveys, functional testing, and isometric tests were conducted. In another session, the participants' gait patterns were measured during a 1-min walking test at their self-selected gait speed with two accelerometers worn above the lateral malleoli. Session order was inconsistent between subjects. Significant inertial gait variables were selected using stepwise regressions, and the contributions of different categories of inertial gait variables were examined using hierarchical regressions. Our results indicate inertial gait variables were significantly correlated with performance test and questionnaire outcomes but did not correlate well with isometric strength measures. The findings demonstrate that wearable sensor-based gait analysis may be able to help predict clinical measures in individuals after unilateral knee treatment.

Movement pattern biofeedback training after total knee arthroplasty: Randomized clinical trial protocol.

INTRODUCTION: Total knee arthroplasty (TKA) reduces joint symptoms, but habitual movement compensations persist years after surgery. Preliminary research on movement training interventions have signaled initial efficacy for remediating movement compensations and restoring knee joint loading symmetry during dynamic functional tasks after TKA. The purpose of this clinical trial is to determine if physical rehabilitation that includes movement training restores healthy movement patterns after TKA and reduces the risk of osteoarthritis (OA) progression in the contralateral knee. METHODS/DESIGN: 150 participants will be enrolled into this randomized controlled trial. Participants will be randomly allocated to one of two dose-equivalent treatment groups: standard rehabilitation plus movement training (MOVE) or standard rehabilitation without movement training (CONTROL). Movement training will promote between-limb symmetry and surgical knee loading during activity-based exercises. Movement training strategies will include real-time biofeedback using in-shoe pressure sensors and verbal, visual, and tactile cues from the physical therapist. The primary outcome will be change in peak knee extension moment in the surgical knee during walking, from before surgery to six months after surgery. Secondary outcomes will include lower extremity movement symmetry during functional tasks, physical function, quadriceps strength, range of motion, satisfaction, adherence, contralateral knee OA progression, and incidence of contralateral TKA. DISCUSSION: This study will provide insights into the efficacy of movement training after unilateral TKA, along with mechanisms for optimizing long-term physical function and minimizing negative sequelae of compensatory movement patterns.

The effect of extension assist orthosis with pneumatic bladders on pain and function for patients with early knee osteoarthritis.

BACKGROUND: There are few non-invasive treatment options to slow the progression of osteoarthritis (OA). Recently, a novel knee unloader brace with knee extension assist has become commercially available. Therefore, the purpose of this study was to evaluate the preliminary effectiveness of using a novel unloader brace with extension assist to improve pain and functional outcomes for patients with knee OA. METHODS: Thirty subjects (17 control group, 13 brace group) completed baseline and 6-week follow up testing with no brace. Patients were randomized into a Brace or No Brace group after baseline testing. Functional tests [timed up and go (TUG), stair climbing test (SCT) and six-minute walk (6MW)], self-reported measures [Knee Outcome Survey (KOS), pain, Patient Specific Functional Scale (PSFS)] and isometric knee extension strength were assessed. Repeated measure ANOVAs were used to identify differences in group and time. Pearson correlation coefficients were calculated for both average number of steps in the brace and exercises compliance compared to change in clinical scores for each group. RESULTS: There was a significant interaction effect for "worst pain" (P=0.002), the brace group improved from a 7.3/10 to 4.7/10 at follow-up (P=0.006) while the control group had no change. There was an effect of time for the SCT (P=0.02), "best knee pain" (P=0.050), and knee extension range of motion (ROM) (P=0.041). There were no significant correlations between exercise compliance and change in outcomes, but when the groups were collapsed there was a significant correlation between compliance and change in knee extension ROM (r=0.526; P=0.025). CONCLUSIONS: The extension assist pneumatic unloader brace group demonstrated a significant and important reduction in the "worst knee pain". This may indicate that wearing the brace was able to reduce painful flares. Both groups improved over time for the SCT, "best knee pain", and knee extension ROM, which can be attributed to the stretching protocol. This unloader brace is a promising non-invasive treatment option for patients with knee OA when combined with a stretching program.

The contralateral knee may not be a valid control for biomechanical outcomes after unilateral total knee arthroplasty.

BACKGROUND: Although unilateral symptoms and unilateral total knee arthroplasty (TKA) are common, many patients have bilateral radiographic osteoarthritis (OA). Because the contralateral (non-operated) limb is often used as a comparison for clinical and biomechanical outcomes, it is important to know if the presence of OA influences movement patterns in either limb. RESEARCH QUESTION: The purpose of this study was to compare bilateral sagittal plane biomechanics between subjects with and without contralateral knee OA after unilateral TKA. METHODS: Fifty-three subjects who underwent unilateral TKA underwent three-dimensional gait analysis 6-24 months after surgery participated in this cross-sectional study. Kellgren-Lawrence (KL) OA severity in the contralateral limb was measured, and subjects were classified into either a non-OA (KL 0 or 1) or OA (KL 2-4) group. Mixed-model ANOVA tests with factors of group and limb were used to compare biomechanical measures. In the presence of a significant interaction effect, post-hoc comparisons were performed. RESULTS: The OA group had more knee flexion at initial contact, less knee flexion and extension excursions, and less knee extension in the contralateral limb compared to the non-OA group. The non-OA group had significant differences between limbs, with more knee flexion at initial contact, less knee joint excursion, and less peak knee extension on the operated limb compared to the contralateral limb, whereas there were no limb differences for the OA group. Kinetic variables were not different in the ANOVA models. SIGNIFICANCE AND INTERPRETATION: Subjects with contralateral knee OA have more symmetrical gait, although they adopt a more abnormal and stiff-legged gait pattern bilaterally. Researchers and clinicians should consider radiographic disease severity, not just symptoms, in the contralateral limb when identifying appropriate subject samples for unilateral biomechanical studies. Symmetrical movement patterns between limbs after surgery should not be the sole factor upon which movement recovery is based.

Stiff knee gait may increase risk of second total knee arthroplasty.

Osteoarthritis (OA) progression in the contralateral limb after unilateral total knee arthroplasty (TKA) may be related to altered and asymmetrical movement patterns that overload the contralateral joints. The purpose of this study was to determine if biomechanical factors after unilateral TKA were associated with future contralateral TKA. One hundred and fifty-eight individuals who underwent unilateral TKA completed three dimensional motion analysis 6-24 months after unilateral TKA (baseline). Subjects were re-contacted for follow-up (mean 5.89 years after baseline testing) to determine if they had undergone a contralateral TKA. Biomechanical variables from gait at baseline were compared between those who did and did not undergo contralateral TKA at follow-up using one-way ANOVAs. Odds ratios were calculated for variables found to be significant in the ANOVA models. Individuals who underwent contralateral TKA had less knee flexion excursion (10.5° vs. 12.1°; p = 0.032) and less knee extension excursion (8.2° vs. 9.6°; p = 0.035) at baseline on the operated side during walking. Individuals who underwent contralateral TKA also had less knee flexion excursion on the contralateral limb at baseline (11.9° vs. 14.0°; p = 0.017). For every additional degree of knee flexion excursion on the contralateral knee at baseline, there was a 9.1% reduction in risk of future contralateral TKA. Individuals who walked with stiffer gait patterns were more likely to undergo future contralateral TKA. Clinical Significance: Altered movement patterns after surgery may increase the risk for contralateral TKA. Knee excursion is an important metric to include in outcome studies and may serve as a target of rehabilitation after TKA. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:397-402, 2019.

Biomechanical Gait Variable Estimation Using Wearable Sensors after Unilateral Total Knee Arthroplasty.

Total knee arthroplasty is a common surgical treatment for end-stage osteoarthritis of the knee. The majority of existing studies that have explored the relationship between recovery and gait biomechanics have been conducted in laboratory settings. However, seamless gait parameter monitoring in real-world conditions may provide a better understanding of recovery post-surgery. The purpose of this study was to estimate kinematic and kinetic gait variables using two ankle-worn wearable sensors in individuals after unilateral total knee arthroplasty. Eighteen subjects at least six months post-unilateral total knee arthroplasty participated in this study. Four biomechanical gait variables were measured using an instrumented split-belt treadmill and motion capture systems. Concurrently, eleven inertial gait variables were extracted from two ankle-worn accelerometers. Subsets of the inertial gait variables for each biomechanical gait variable estimation were statistically selected. Then, hierarchical regressions were created to determine the directional contributions of the inertial gait variables for biomechanical gait variable estimations. Selected inertial gait variables significantly predicted trial-averaged biomechanical gait variables. Moreover, strong directionally-aligned relationships were observed. Wearable-based gait monitoring of multiple and sequential kinetic gait variables in daily life could provide a more accurate understanding of the relationships between movement patterns and recovery from total knee arthroplasty.

A SIX-WEEK SUPERVISED EXERCISE AND EDUCATIONAL INTERVENTION AFTER TOTAL HIP ARTHROPLASTY: A CASE SERIES.

BACKGROUND AND PURPOSE: Most rehabilitation interventions after total hip arthroplasty (THA) are not designed to return patients to high-levels of physical activity and, thus, low levels of physical activity and residual weakness are common. The purpose of this case series was to describe the feasibility and preliminary efficacy of an exercise and education intervention for patients after THA who have already completed formal outpatient physical therapy. STUDY DESIGN: Case series. CASE DESCRIPTION: Two participants underwent unilateral THA seven (case A) or eight (case B) months prior to the intervention. Individuals participated in 18 treatment sessions that included progressive aerobic and strengthening exercises and meetings with a health coach. Change in function, strength, and self-reported physical activity were measured. Outcomes 12 months after surgery were compared to a historical cohort of patients after THA. OUTCOME: There were no adverse events during the intervention. At the end of the intervention, hip and knee strength on the surgical side increased approximately 30% compared to baseline in both cases. Activity level, and recreational performance, including walking up stairs and hiking uphill (case A), and running and golfing (case B), improved by the end of the intervention. Most changes were maintained at follow-up, although hip strength for case B decreased 27% after discharge from the intervention. Outcomes for both cases exceeded historical averages for patients 12 months after THA, with the exception of strength in case B. DISCUSSION: The exercise intervention was well tolerated and without negative effects in two participants. Both participants increased their ability to complete demanding recreational and sports-related activities, physical activity, and demonstrated improved hip abductor and knee extensor strength. Further research is needed to evaluate the implementation and effectiveness of similar interventions after THA. LEVEL OF EVIDENCE: Level 4.

Arthrofibrosis Associated With Total Knee Arthroplasty.

BACKGROUND: Arthrofibrosis is a debilitating postoperative complication of total knee arthroplasty (TKA). It is one of the leading causes of hospital readmission and a predominant reason for TKA failure. The prevalence of arthrofibrosis will increase as the annual incidence of TKA in the United States rises into the millions. METHODS: In a narrative review of the literature, the etiology, economic burden, treatment strategies, and future research directions of arthrofibrosis after TKA are examined. RESULTS: Characterized by excessive proliferation of scar tissue during an impaired wound healing response, arthrofibrotic stiffness causes functional deficits in activities of daily living. Postoperative, supervised physiotherapy remains the first line of defense against the development of arthrofibrosis. Also, adjuncts to traditional physiotherapy such as splinting and augmented soft tissue mobilization can be beneficial. The effectiveness of rehabilitation on functional outcomes depends on the appropriate timing, intensity, and progression of the program, accounting for the patient's ability and level of pain. Invasive treatments such as manipulation under anesthesia, debridement, and revision arthroplasty improve range of motion, but can be traumatic and costly. Future studies investigating novel treatments, early diagnosis, and potential preoperative screening for risk of arthrofibrosis will help target those patients who will need additional attention and tailored rehabilitation to improve TKA outcomes. CONCLUSION: Arthrofibrosis is a multi-faceted complication of TKA, and is difficult to treat without an early, tailored, comprehensive rehabilitation program. Understanding the risk factors for its development and the benefits and shortcomings of various interventions are essential to best restore mobility and function.

Single-limb drop landing biomechanics in active individuals with and without a history of anterior cruciate ligament reconstruction: A total support analysis.

BACKGROUND: The purpose of this study was to characterize the magnitude and distribution of the total support moment during single-limb drop landings in individuals after anterior cruciate ligament reconstruction compared to a control group. METHODS: Twenty participants after reconstruction and twenty control participants matched on sex, limb dominance and activity level were recruited. Motion analysis was performed during a single-limb drop landing task. Total support moment was determined by summing the internal extensor moments at the ankle, knee, and hip. Each relative joint contribution to the total support moment was calculated by dividing each individual contribution by the total support moment. Data were captured during a landing interval that started at initial contact and ended at the lowest vertical position of the pelvis. Data were then time-normalized and indexed at 25, 50, 75, and 100% of the landing interval. FINDINGS: No between-group differences for total support moment magnitude were observed. At both 75% and 100% of the landing, the relative contribution of the knee joint was lower in those with a history of surgery (p<0.001). At the same instances, the relative contribution to the total support moment by the hip joint was greater in those with a history of surgery (p=0.004). INTERPRETATION: In active participants after anterior cruciate ligament reconstruction, relative contributions to anti-gravity support of the center of mass shifted from the knee to the hip joint during single-limb landing, which became evident towards the end of the landing interval.

Association of Psychosocial Factors With Physical Activity and Function After Total Knee Replacement: An Exploratory Study.

OBJECTIVES: To examine the association between self-efficacy, social support, and fear of movement with physical activity and function at baseline and after 12 weeks of physical therapy. DESIGN: Nonrandomized cohort study, repeated-measures design. SETTING: Outpatient rehabilitation clinic within the general community. PARTICIPANTS: Adults (N=49) undergoing outpatient physical therapy for total knee replacement (TKR). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Self-efficacy for exercise (SEE), fear of movement, leisure-time physical activity (LTPA), 6-minute walk test (6MWT), and Knee Outcome Survey-Activities of Daily Living Scale (KOS-ADLS) were assessed at baseline and 12 weeks. RESULTS: Mean functional change scores significantly increased at 12 weeks for the 6MWT (95% confidence interval [CI], 42.3-106.2), KOS-ADLS (95% CI, 12.7-23.3), and LTPA (95% CI, 6.5-26.1). Self-efficacy and fear of movement were not significantly associated with function at baseline or 12 weeks. Participants with lower SEE had 6 fewer metabolic equivalents per week of improvement in LTPA than those with high self-efficacy (95% CI, -27.9 to 14.8), and those with high fear of movement had 26.1m less improvement in the 6MWT than those with low fear of movement (95% CI, -42.2 to 94.5). Most participants reported having no family or peer support for exercise. CONCLUSIONS: Physical therapy for TKR improves physical function and self-reported physical activity. High fear of movement and low SEE may be associated with less improvement in physical activity and function over time.

Quadriceps strength asymmetry predicts loading asymmetry during sit-to-stand task in patients with unilateral total knee arthroplasty.

PURPOSE: This study aimed to examine interlimb differences in muscle strength and sit-to-stand (STS) kinetics in persons who underwent unilateral total knee arthroplasty (TKA) and to determine whether knee pain, quadriceps or hip abductor weakness contributes to altered STS performance. It was hypothesized that the operated limb would have weaker muscles, lower mechanical loading and that operated knee pain and muscle strength symmetry would predict loading symmetry between limbs during STS. METHODS: One hundred and forty-two patients, 6 or 12 months post-unilateral TKA, underwent 3D motion analysis (VICON) of the STS task and isometric strength testing of the quadriceps and hip abductors. Knee pain was also quantified using a question from the Knee Outcome Survey-Activities of Daily Living Scale. RESULTS: The operated limb had weaker quadriceps (P < 0.001), lower hip (P = 0.004) and knee extension moments (P < 0.001), and lower vertical ground reaction forces (P < 0.001). Operated knee pain and quadriceps strength symmetry were related to symmetry in knee extension moment (P < 0.04), and vertical ground reaction forces (P < 0.02) 6 months after surgery, while quadriceps strength symmetry was related to symmetry in vertical ground reaction forces (P = 0.03), 1 year after surgery. CONCLUSION: Patients with unilateral TKA unload the operated limb and shift the mechanical load to the joints of the contralateral limb even 1 year after surgery. Knee pain and quadriceps strength asymmetry may play a role in the asymmetrical loading during STS post-TKA. Clinicians should consider addressing these modifiable impairments to resolve the loading asymmetry. LEVEL OF EVIDENCE: III.

Change in knee contact force with simulated change in body weight.

The relationship between obesity, weight gain and progression of knee osteoarthritis is well supported, suggesting that excessive joint loading may be a mechanism responsible for cartilage deterioration. Examining the influence of weight gain on joint compressive forces is difficult, as both muscles and ground reaction forces can have a significant impact on the forces experienced during gait. While previous studies have examined the relationship between body weight and knee forces, these studies have used models that were not validated using experimental data. Therefore, the objective of this study was to evaluate the relationship between changes in body weight and changes in knee joint contact forces for an individual's gait pattern using musculoskeletal modeling that is validated against known internal compressive forces. Optimal weighting constants were determined for three subjects to generate valid predictions of knee contact forces (KCFs) using in vivo data collection with instrumented total knee arthroplasty. A total of five simulations per walking trial were generated for each subject, from 80% to 120% body weight in 10% increments, resulting in 50 total simulations. The change in peak KCF with respect to body weight was found to be constant and subject-specific, predominantly determined by the peak force during the baseline condition at 100% body weight. This relationship may be further altered by any change in kinematics or body mass distribution that may occur as a result of a change in body weight or exercise program.

Sit-To-Stand Biomechanics Before and After Total Hip Arthroplasty.

The purpose of this study was to evaluate changes in movement patterns during a sit-to-stand (STS) task before and after total hip arthroplasty (THA), and to compare biomechanical outcomes after THA to a control group. Forty-five subjects who underwent THA and twenty-three healthy control subjects participated in three-dimensional motion analysis. Pre-operatively, subjects exhibited inter-limb movement asymmetries with lower vertical ground reaction force (VGRF) and smaller moments on the operated limb. Although there were significant improvements in movement symmetry 3 months after THA, patients continued to demonstrate lower VGRF and smaller moments on the operated limb compared to non-operated and to control limbs. Future studies should identify the contributions of physical impairments and the influence of surgical approach on STS biomechanics.

Hip abductor strength reliability and association with physical function after unilateral total knee arthroplasty: a cross-sectional study.

BACKGROUND: Because people with total knee arthroplasty (TKA) have persistent functional limitations and disability, identifying modifiable risk factors for persistent disability is warranted. Before surgery, people have pervasive lower extremity muscle weakness. The fact that hip abductor muscle strength is often not targeted in postoperative rehabilitation may contribute to functional limitations. OBJECTIVE: Study objectives were: (1) to examine the reliability of handheld dynamometry (HHD) for measuring hip abductor strength and (2) to determine whether hip abductor strength contributes to physical function beyond the contribution of quadriceps muscle strength. DESIGN: This was a cross-sectional study. METHODS: Two-hundred ten participants underwent quadriceps and hip abductor muscle strength testing and measurement of physical function (performance-based and self-reported outcomes). Correlation and regression equations were built to determine the relationships of strength, pain, and functional ability. A subset of 16 participants underwent hip abductor strength testing at 2 sessions to determine the reliability of the measure. RESULTS: Measuring hip abductor strength with HHD yielded excellent relative reliability, with an intraclass correlation coefficient (ICC [2,3]) of .95 and a 95% confidence interval of .86 to .98, but moderate absolute reliability, with a minimal detectable change (with 95% confidence) of 47.6 N and a 95% confidence interval of 35.5 to 76.5. Hip abductor strength made a significant additional contribution to performance-based measures of physical function after anthropometric covariates and quadriceps muscle strength were accounted for. Hip abductor strength did not show bivariate correlations with patient-reported measures of physical function and did not contribute to patient-reported physical function after covariates and quadriceps muscle strength were accounted for. LIMITATIONS: A cause-and-effect relationship between hip abductor strength and physical function could not be established. CONCLUSIONS: In people with unilateral TKA, HHD testing of hip abductor strength is reliable. Hip abductor strength contributes to performance-based but not patient-reported measures of physical function in people with unilateral TKA.