Does hip implant positioning affect the peak external adduction moments of the healthy knees of subjects with total hip replacements?

After unilateral total hip replacement (THR) for hip osteoarthritis (OA), knee OA incidence or progression is common. The contralateral knee is at particular risk, and some have speculated that abnormal THR‐hip biomechanics contributes to this asymmetry. We investigated the relationships between operated‐hip joint geometry or gait variables and the peak external knee adduction moments—an indicator of knee OA risk—in 21 subjects with unilateral THRs. We found that the peak adduction moment was 14% higher on the contralateral versus the ipsilateral knee (p = 0.131). The best predictors of ipsilateral knee adduction moments were superior‐inferior joint center position and operated‐hip peak adduction moment (adj R² = 0.291, p = 0.017). The sole predictor of the contralateral knee adduction moment was the medial‐lateral hip center position (adj R² = 0.266, p = 0.010). A postoperative medial shift of the hip center was significantly correlated with a lower postoperative contralateral/ipsilateral knee adduction moment ratio (R = 0.462, p = 0.035). Based on these relationships, we concluded that implant positioning could influence the biomechanical risk of knee OA progression after THR. Although implant positioning decisions are necessarily driven by other factors, it may be appropriate to assess individual THR candidate's knee OA risk and adjust perioperative management accordingly. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:1187–1194, 2013     

Increased knee joint loads during walking are present in subjects with knee osteoarthritis

OBJECTIVE: This study tests the hypothesis that the peak external knee adduction moment during gait is increased in a group of ambulatory subjects with knee osteoarthritis (OA) of varying radiographic severity who are being managed with medical therapy. Tibiofemoral knee OA more commonly affects the medial compartment. The external knee adduction moment can be used to assess the load distribution between the medial and lateral compartments of the knee joint. Additionally, this study tests if changes in the knee angles, such as a reduced midstance knee flexion angle, or reduced sagittal plane moments previously identified by others as load reducing mechanisms are present in this OA group. DESIGN: Thirty-one subjects with radiographic evidence of knee OA and medial compartment cartilage damage were gait tested after a 2-week drug washout period. Thirty-one normal subjects (asymptomatic control subjects) with a comparable age, weight and height distribution were also tested. Significant differences in the sagittal plane knee motion and peak external moments between the normal and knee OA groups were identified using t tests. RESULTS: Subjects with knee OA walked with a greater than normal peak external knee adduction moment (P=0.003). The midstance knee flexion angle was not significantly different between the two groups (P=0.625) nor were the peak flexion and extension moments (P> 0.037). CONCLUSIONS: Load reducing mechanisms, such as a decreased midstance knee flexion angle, identified by others in subjects with endstage knee OA or reduced external flexion or extension moments were not present in this group of subjects with knee OA who were being managed by conservative treatment. The finding of a significantly greater than normal external knee adduction moment in the knee OA group lends support to the hypothesis that an increased knee adduction moment during gait is associated with knee OA.     

Abnormal loading of the hip and knee joints in unilateral hip osteoarthritis persists two years after total hip replacement

A total hip replacement (THR) is a common and routine procedure to reduce pain and restore normal activity. Gait analysis can provide insights into functional characteristics and dynamic joint loading situation not identifiable by clinical examination or static radiographic measures. The present prospective longitudinal study tested whether 2 years after surgery a THR would restore dynamic loading of the knee and hip joints in the frontal plane to normal. Instrumented gait analysis was performed shortly before surgery and approximately 2 years after THR on 15 unilateral hip osteoarthritis (OA) patients. 15 asymptomatic matched individuals were recruited as healthy controls. Results showed that abnormal joint loading persisted 2 years after THR. The 2nd external knee adduction moment in terminal stance in the affected (?34%, p = 0.002, d = 1.22) and non‐affected limb (?25%, p = 0.035, d = 0.81) was lower compared to controls and thus indicated a shift in the knee joint load distribution from medial to lateral. A correlation analysis revealed that a smaller hip range of motion explained 46% of 2nd knee adduction moment alterations. In contrast, the 2nd external hip adduction moment in terminal stance was postoperatively higher in the affected (+22%, p = 0.007, d = 1.04) and non‐affected limb (+22%, p = 0.005, d = 1.05). Here, 51% of 2nd hip adduction moment alterations can be explained with a greater hip adduction angle. Patients with a THR may therefore be at higher risk for abnormal joint loading and thus for the development of OA in other joints of the lower extremities. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2167–2177, 2018.

     

Gait alterations to effectively reduce hip contact forces

Patients with hip pathology present alterations in gait which have an effect on joint moments and loading. In knee osteoarthritic patients, the relation between medial knee contact forces and the knee adduction moment are currently being exploited to define gait retraining strategies to effectively reduce pain and disease progression. However, the relation between hip contact forces and joint moments has not been clearly established. Therefore, this study aims to investigate the effect of changes in hip and pelvis kinematics during gait on internal hip moments and contact forces which is calculated using muscle driven simulations. The results showed that frontal plane kinetics have the largest effect on hip contact forces. Given the high correlation between the change in hip adduction moment and contact force at initial stance (R² = 0.87), this parameter can be used to alter kinematics and predict changes in contact force. At terminal stance the hip adduction and flexion moment can be used to predict changes in contact force (R² = 0.76). Therefore, gait training that focuses on decreasing hip adduction moments, a wide base gait pattern, has the largest potential to reduce hip contact forces. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1094–1102, 2015.     

Control of frontal plane knee laxity during gait in patients with medial compartment knee osteoarthritis

OBJECTIVE: Patients with medial compartment knee osteoarthritis (OA) adopt an abnormal gait pattern, and often develop frontal plane laxity at the knee. The purpose of this study was to quantify the extent of frontal plane knee joint laxity in patients with medial knee OA and genu varum and to assess the effect of joint laxity on knee joint kinetics, kinematics and muscle activity during gait. DESIGN: Twelve subjects with genu varum and medial compartment knee osteoarthritis (OA group) and 12 age-matched uninjured subjects underwent stress radiography to determine the presence and magnitude of frontal plane laxity. All subjects also went through gait analysis with surface electromyography of the medial and lateral quadriceps, hamstrings, and gastrocnemius to calculate knee joint kinematics and kinetics and co-contraction levels during gait. RESULTS: The OA group showed significantly greater knee instability (P = 0.002), medial joint laxity (P = 0.001), greater medial quadriceps-medial gastrocnemius (VMMG) co-contraction (P = 0.043), and greater knee adduction moments (P = 0.019) than the control group. Medial joint laxity contributed significantly to the variance in both VMMG and the knee adduction moment during early stance. CONCLUSION: The presence of medial laxity in patients with knee OA is likely contributing to the altered gait patterns observed in those with medial knee OA. Greater medial co-contraction and knee adduction moments bodes poorly for the long-term integrity of the articular cartilage, suggesting that medial joint laxity should be a focus of interventions aimed at slowing the progression of disease in individuals with medial compartment knee OA.     

Verification of biomechanical factors of gait related to medial knee loading in patients 6 Months after total knee arthroplasty

BackgroundThe knee adduction moment (KAM) is considered an index for estimating the knee mechanical load, and increased KAM peak and KAM impulse are related to increased medial knee load and progression of knee joint degeneration. We aimed to verify the biomechanical factors of gait related to medial knee loading in patients 6 months after TKA.MethodsThirty-nine women who underwent TKA were enrolled. A three-dimensional gait analysis was performed 6 months postoperatively to generate data on the lower limb joint angle, moment, and power at the backward component (braking phase) and forward component (propulsion phase) peaks of the ground reaction force. Medial knee loading was evaluated using the time-integrated value of KAM during the stance period (KAM impulse). The higher the value of the KAM impulse, the higher the medial knee joint load. The relationships between the KAM impulse and the data for biomechanical factors were evaluated using partial correlation analysis with gait speed as a control factor.ResultsIn the braking phase, the KAM impulse positively correlated with the knee adduction angle (r = 0.377) and negatively correlated with the toe-out angle (r = −0.355). The KAM impulse positively correlated with the knee adduction angle (r = 0.402), the hip flexion moment (r = 0.335), and the hip adduction moment (r = 0.565) and negatively correlated with the toe-out angle (r = −0.357) in the propulsive phase.ConclusionThe KAM impulse 6 months after TKA was related to the knee adduction angle, hip flexion moment, hip adduction moment, and toe-out angle. These findings may provide fundamental data for controlling variable medial knee joint load after TKA and implementing patient management strategies to ensure implant durability.     

Gait Asymmetry Variation in Kinematics,Kinetics, and Muscle Force along with the Severity Levels of Knee Osteoarthritis

Objective

Knee osteoarthritis (OA) patients exhibit greater gait asymmetry than healthy controls. However, gait asymmetry in kinematics, kinetics and muscle forces across patients with different severity levels of knee OA is still unknown. The study aimed to investigate the changes of gait asymmetry in lower limb kinematics, kinetics, and muscle force across patients with different severity levels of knee OA.

Methods

This is a cross-sectional study. From January 2020 to January 2021, 118 patients with symptomatic and radiographic medial knee OA were categorized into three groups using the Kellgren and Lawrence scale (mild: grade 1 and 2, n = 37; moderate: grade 3, n = 31; severe: grade 4, n = 50). During self-paced walking, marker trajectories and ground reaction forces data were recorded. Musculoskeletal simulations were used to determine gait kinematics, kinetics, and muscle force. One-way analysis of variance with Tukey's post-hoc test was used to evaluate group difference. Paired-sample t-test was used to compared the between-limb difference.

Results

In the Severe group, significantly greater asymmetry index in knee flexion/extension range of motion (45%) was observed with a greater value on the contralateral side (p < 0.01), compared to the Mild (15%) and Moderate (15%) groups. Significantly higher peak hip contact force (JCF) on the contralateral side was found in the Mild (more affected side: 3.80 ± 0.67 BW, contralateral side: 4.01 ± 0.58 BW), Moderate (more affected side: 3.67 ± 0.56 BW, contralateral side: 4.07 ± 0.81 BW), and Severe groups (more affected side: 3.66 ± 0.79 BW, contralateral side: 3.94 ± 0.64 BW) (p < 0.05). Significantly greater gluteus medius muscle force on the contralateral side was found in Mild (more affected side: 0.48 ± 0.09 BW, contralateral side: 0.52 ± 0.12 BW), Moderate (more affected side: 0.45 ± 0.10 BW, contralateral side: 0.51 ± 0.15 BW), and Severe groups (more affected side: 0.42 ± 0.15 BW, contralateral side: 0.47 ± 0.12 BW) (p < 0.05). The contralateral side showing significantly higher peak knee adduction moment and medial knee JCF was only observed in the Mild group (p < 0.05).

Conclusions

Gait asymmetry in kinematics and muscle forces increased from mild to severe knee OA. Asymmetrical gait pattern tends to transfer loads from the more affected side to the contralateral side. Peak hip JCF and gluteus medius muscle force can be used to detect this asymmetrical gait pattern in patients with knee OA, regardless of severity levels.     

The knee adduction moment during gait in subjects with knee osteoarthritis is more closely correlated with static alignment than radiographic disease severity, toe out angle and pain.

This study tested whether the peak external knee adduction moments during walking in subjects with knee osteoarthritis (OA) were correlated with the mechanical axis of the leg, radiographic measures of OA severity, toe out angle or clinical assessments of pain, stiffness or function. Gait analysis was performed on 62 subjects with knee OA and 49 asymptomatic control subjects (normal subjects). The subjects with OA walked with a greater than normal peak adduction moment during early stance (p = 0.027). In the OA group, the mechanical axis was the best single predictor of the peak adduction moment during both early and late stance (R = 0.74, p < 0.001). The radiographic measures of OA severity in the medial compartment were also predictive of both peak adduction moments (R = 0.43 to 0.48, p < 0.001) along with the sum of the WOMAC subscales (R = -0.33 to -0.31, p < 0.017). The toe out angle was predictive of the peak adduction moment only during late stance (R = -0.45, p < 0.001). Once mechanical axis was accounted for, other factors only increased the ability to predict the peak knee adduction moments by 10 18%. While the mechanical axis was indicative of the peak adduction moments, it only accounted for about 50% of its variation, emphasizing the need for a dynamic evaluation of the knee joint loading environment. Understanding which clinical measures of OA are most closely associated with the dynamic knee joint loads may ultimately result in a better understanding of the disease process and the development of therapeutic interventions.     

Biomechanical changes at the hip,knee, and ankle joints during gait are associated with knee osteoarthritis severity

Mechanical factors have been implicated in the progression of knee osteoarthritis (OA). Understanding how these factors change as the condition progresses would elucidate their role and help in developing interventions that could delay the progress of knee OA. In this cross‐sectional study, we identified kinematic and kinetic variables at the hip, knee, and ankle joints that change between three clinically distinct levels of knee OA disease severity: asymptomatic, moderate OA, and severe OA. The severity level was based on a combined radiographic/symptomatic clinical decision for treatment with (severe) or without (moderate) total knee replacement surgery. Gait variables that changed between groups were categorized as: those that differed between the asymptomatic group and both OA groups, those that differed between the asymptomatic group and the severe OA group only, or those that changed progressively, that is, the asymptomatic differed from the moderate OA, and the moderate OA differed from the severe OA group. Changes seen in both OA subject groups compared to asymptomatic included increased mid‐stance knee adduction moments, decreased peak knee flexion moments, decreased peak hip adduction moments, and decreased peak hip extension moments. Changes found only in the severe knee OA group included multiple kinematic and kinetic differences at the hip, knee, and ankle joints. Gait differences that progressed with OA severity included decreased stance phase knee flexion angles, decreased early stance knee extension moments, decreased peak stance phase hip internal rotation moments, and decreased peak ankle dorsiflexion moments. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:332–341, 2008     

Hip and knee joint rotations differ between patients with medial and lateral knee osteoarthritis: gait analysis of 30 patients and 15 controls.

The motions and moments in the hip and knee in female patients on the waiting list for knee prosthesis surgery with medial (n = 15) or lateral (n = 15) osteoarthritis (OA) were compared with a control group (n = 15). We hypothesized that not only the kinematics and kinetics of the knee but also of the hip would differ between patients the medial and lateral groups. At midstance, patients with lateral OA showed slightly (2 degrees) more maximal (peak) adduction (p = 0.015) of the hip joint and patients with medial OA had 7 degrees more abduction (p < 0.001) than did controls. In patients with lateral OA, the femur was positioned in about 7 degrees more maximum external rotation (p = 0.001), but femur position did not differ between medial OA and controls (p > or = 0.8). There was a tendency to higher internal hip rotation moment in lateral OA compared to controls (p = 0.021). The maximum values of the internal knee abduction moments were 52% higher in medial OA (p = 0.005) and 63% lower in lateral OA (p < 0.001) compared to controls. Cases with medial OA had 9 degrees more, whereas those with lateral OA had 6 degrees less external tibial rotation than controls (medial vs. lateral OA, p = 0.001). We found an association between presence of lateral OA of the knee and the biomechanics of the hip joint. It remains to be evaluated if the changed biomechanics of the hip joint is a reason for development of lateral OA or an observation that is a result of this disease.     

Lower extremity walking mechanics of young individuals with asymptomatic varus knee alignment

Varus knee alignment is associated with an increased risk for developing medial knee osteoarthritis (OA). Medial knee OA is commonly associated with altered walking mechanics in the frontal and sagittal planes, as well as altered ground reaction forces. It is unknown whether these mechanics are present in young, asymptomatic individuals with varus knees. We expected that varus‐aligned individuals would generally present with frontal plane mechanics that were similar to those reported for individuals with medial knee OA. The gait mechanics of 17 asymptomatic individuals with varus knees and 17 healthy, normally aligned controls were recorded. Gait parameters associated with medial knee OA were compared between groups. The individuals with varus knees exhibited greater knee external adduction moments, knee adduction, eversion, and lateral ground reaction force than the normally aligned individuals. In addition, those with varus knees also demonstrated increased knee flexion and external knee flexor moments during midstance. These results suggest that individuals with varus knees exhibit some, but not all, of the altered mechanics seen in medial knee OA. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1414–1419, 2009     

Adduction moment increases with age in healthy obese individuals

There is a need to understand how obesity and aging interact to cause an increased risk of medial knee osteoarthritis (OA). This study tested whether the knee adduction and flexion moments increase with age in healthy normal‐weight and obese adults, as well as the mechanism of this increase. We analyzed whether ground reaction force magnitude, knee alignment, step width, toe‐out angle, body volume distribution, and limb position (knee position relative to the pelvis center) are associated with the adduction moment and whether these variables also change with age. Ninety‐six healthy volunteers (60 normal‐weight and 36 obese) were tested using marker‐based gait analysis; knee alignment was based on marker positions during quiet standing. Adduction moment increased with age in obese (R² = 0.19), but not in normal‐weight individuals (R² = 0.01); knee flexion moment did not change with age in either group. In the obese, only knee alignment and limb position were related to the adduction moment (R² = 0.19 and 0.51), but only limb position changed with age (R² = 0.26). The resulting increase in adduction moment suggests greater medial compartment loads, which may combine with elevated levels of inflammation to contribute to the increased risk of medial OA in this population. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:1414–1422, 2013     

Gait abnormalities following slipped capital femoral epiphysis

The authors evaluated 30 subjects with treated unilateral slipped capital femoral epiphysis and a range of severity from mild to severe to characterize gait and strength abnormalities using instrumented three-dimensional gait analysis and isokinetic muscle testing. For slip angles less than 30 degrees, kinematic, kinetic, and strength variables were not significantly different from age- and weight-matched controls. For moderate to severe slips, as slip angle increased, passive hip flexion, hip abduction, and internal rotation in the flexed and extended positions decreased significantly. Persistent pelvic obliquity, medial lateral trunk sway, and trunk obliquity in stance increased, as did extension, adduction, and external rotation during gait. Gait velocity and step length decreased with increased amount of time spent in double limb stance. Hip abductor moment, hip extension moment, knee flexion moment, and ankle dorsiflexion moment were all decreased on the involved side. Hip and knee strength also decreased with increasing slip severity. All of these changes were present on the affected and to a lesser degree the unaffected side. Body center of mass translation or pelvic obliquity in mid-stance greater than one standard deviation above normal correlated well with the impression of compensated or uncompensated Trendelenburg gait.     

Repeatability of gait analysis for measuring knee osteoarthritis pain in patients with severe chronic pain

Gait measures are receiving increased attention in the evaluation of patients with knee osteoarthritis (OA). Yet, there remains a need to assess variability of gait analysis in patients with knee osteoarthritis over time and how pain affects variation in these gait parameters. The purpose of this study was to determine if important gait parameters, such as the knee adduction moment, knee flexion moment, peak vertical ground reaction force, and speed, were repeatable in patients with mild‐to‐moderate knee OA over a trial period of 12 weeks. Six patients were enrolled in this cross‐over study design after meeting strict inclusion criteria. Gait tests were conducted three times at 4 week intervals and once after the placebo arm of a randomized treatment sequence; each gait test followed a 2‐week period of receiving a placebo for a pain modifying drug. Repeatability for each gait variable was found using intraclass correlation coefficients (ICC) with a two‐way random model. This study found that the knee adduction moment was repeatable throughout the four gait tests. However, normalized peak vertical ground reaction force and knee flexion moment were not as repeatable, varying with pain. This suggests that these gait outcomes could offer a more objective way to measure a patient's level of pain. © 2012 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 31:1007–1012, 2013     

Changes in the total knee joint moment in patients with medial compartment knee osteoarthritis over 5 years

Progression of medial compartment knee osteoarthritis (OA) has been associated with repetitive mechanical loading during walking, often characterized by the peak knee adduction (KAM) and knee flexion moments (KFM). However, the relative contributions of these components to the knee total joint moment (TJM) can change as the disease progresses since KAM and KFM are influenced by different factors that change over time. This study tested the hypothesis that the relative contributions of KAM, KFM, and the rotational moment (KRM) to the TJM change over time in subjects with medial compartment knee OA. Patients with medial compartment knee OA (n = 19) were tested walking at their self‐selected speed at baseline and a 5‐year follow‐up. For each frame during stance, the TJM was calculated using the KAM, KFM, and KRM. The peaks of the TJM and the relative contributions of the moment components at the time of the peaks of the TJM were tested for changes between baseline and follow‐up. The percent contribution of KFM to the first peak of the TJM (TJM1) significantly decreased (p < 0.001) and the percent contribution of KAM to TJM1 significantly increased (p < 0.001), while the magnitude of the TJM1 did not significantly change over the 5‐year follow‐up. These gait changes with disease progression appear to maintain a constant TJM1, but the transition from a KFM to a KAM dominance appears to reflect gait changes associated with progressing OA and pain. Thus, the TJM and its component analysis captures a comprehensive metric for total loading on the knee over time. Published 2018. This article is a U.S. Government work and is in the public domain in the USA. 36:2373–2379, 2018.

     

Lateral wedges alter mediolateral load distributions at the knee joint in obese individuals

Obesity is the primary risk factor for knee osteoarthritis (OA). Greater external knee adduction moments, surrogate measures for medial compartment loading, are present in Obese individuals and may predispose them to knee OA. Laterally wedged insoles decrease the magnitude of the external adduction moment in Obese individuals but it is unknown how they alter the center of pressure on the tibial plateau. A gait analysis was performed on 14 Obese (avg. 29.3 years; BMI range: 30.3–51.6 kg/m²) and 14 lean women (avg. 26.1 years; BMI range: 20.9–24.6 kg/m²) with and without a full‐length, wedged insole. Computed joint angles, joint moments, and knee extensor strength values were input into a musculoskeletal model to estimate center of pressure of the contact force on the tibial plateau. Statistical significance was assessed using a two‐way ANOVA to compare the main effects of group and insole condition (α = 0.05). The insole resulted in a significant (p < 0.01) lateral shift in the center of pressure location in both the Obese and Control groups (mean: 2.9 ± 0.7 and 1.5 ± 0.7 mm, respectively). The insole also significantly reduced the peak external knee adduction moment 1.88 ± 1.82 N m in the Control group (p < 0.01) and 3.62 ± 3.90 N m in the Obese group (p < 0.01). The results of this study indicate the effects of a prophylactic wedged insole for reducing the magnitude of the load on the knee's medial compartment in Obese women who are at risk for knee OA development. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31: 665–671, 2013     

The effect of different types of insoles or shoe modifications on medial loading of the knee in persons with medial knee osteoarthritis: a randomised trial

Many conservative treatments exist for medial knee osteoarthritis (OA) which aims to reduce the external knee adduction moment (EKAM). The objective of this study was to determine the difference between different shoes and lateral wedge insoles on EKAM, knee adduction angular impulse (KAAI), external knee flexion moment, pain, and comfort when walking in individuals with medial knee OA. Seventy individuals with medial knee OA underwent three‐dimensional walking gait analysis in five conditions (barefoot, control shoe, typical wedge, supported wedge, and mobility shoe) with pain and comfort recorded concurrently. The change in EKAM, KAAI, external knee flexion moment, pain, and comfort were assessed using multiple linear regressions and pairwise comparisons. Compared with the control shoe, lateral wedge insoles and barefoot walking significantly reduced early stance EKAM and KAAI. The mobility shoe showed no effect. A significant reduction in latter stance EKAM was seen in the lateral wedge insoles compared to the other conditions, with only the barefoot condition reducing the external knee flexion moment. However, the mobility shoe showed significant immediate knee pain reduction and improved comfort scores. Different lateral wedge insoles show comparable reductions in medial knee loading and in our study, the mobility shoe did not affect medial loading. © 2015 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. J Orthop Res 33:1646–1654, 2015.     

Longitudinal changes in knee gait mechanics between 2 and 8 years after anterior cruciate ligament reconstruction

The purpose of this study was to longitudinally investigate changes in knee joint kinematics and kinetics from 2 to 8 years post‐ACLR. Seventeen subjects with primary unilateral transtibial ACLR performed bilateral gait analysis approximately 2 years and 8 years post‐ACLR. Seventeen matched healthy control subjects were also analyzed. Kinematic and kinetic comparisons between the ACLR and contralateral limbs over time were completed using a 2 × 2 (time, limb) repeated‐measures ANOVA. Unpaired Student's t‐tests were used to compare the ACLR and contralateral kinematics and kinetics to the control group. The ACLR and contralateral limbs had similar gait changes over time. Kinetic changes over time included a reduction in first (p = 0.048) and second (p < 0.001) peak extension moments, internal rotation moment (p < 0.001), adduction moment (first peak: p = 0.002, second peak: p = 0.009, impulse: p = 0.004) and an increase in peak knee flexion moment (p = 0.002). Kinematic changes over time included increases in peak knee flexion angle in the first half of stance (p = 0.026), minimum knee flexion angle in the second half of stance (p < 0.001), and average external rotation angle during stance (p = 0.007), and a reduction in average anterior femoral displacement during stance (p = 0.006). Comparison to healthy controls demonstrated improvement in some gait metrics over time. The results demonstrated longitudinal changes from 2 to 8 years after ACLR in knee joint kinetics and kinematics that have been related to clinical outcome after ACLR and the progression of knee OA, and support future larger and comprehensive investigations into long‐term changes in joint mechanics in the ACLR population. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1478–1486, 2018.

     

Unilateral hip osteoarthritis: The effect of compensation strategies and anatomic measurements on frontal plane joint loading

In order to reduce pain caused by the affected hip joint, unilateral hip osteoarthritis patients (HOAP) adopt characteristic gait patterns. However, it is unknown if the knee and hip joint loading in the non‐affected (limb_{non‐affected}) and the affected (limb_affected) limb differ from healthy controls (HC) and which gait parameters correlate with potential abnormal joint loading. Instrumented 3D‐gait analysis was performed on 18 HOAP and 18 sex, age, and height matched HC. The limb_{non‐affected} showed greater first and second peak external hip adduction moments (first HAM: +15%, p = 0.014; second HAM: +15%, p = 0.021, respectively), than seen in HC. In contrast, the second peak external knee adduction moment (KAM) in the limb_affected is reduced by about 23% and 30% compared to the limb_{non‐affected} and HC, respectively. Furthermore, our patients showed characteristic gait compensation strategies including reduced peak vertical forces (pvF), a greater foot progression angle (FPA), and reduced knee range of motion (ROM) in the limb_affected. The limb_affected was 5.6 ± 3.8 mm shorter than the limb_{non‐affected}. Results of stepwise regression analyses showed that increased first pvF explain 16% of first HAM alterations, whereas knee ROM and FPA explain 39% of second KAM alterations. We therefore expect an increased rate of progression of OA in the hip joint of the limb_{non‐affected} and suggest that the shift in the medial‐to‐lateral knee joint load distribution may impact the rate of progression of OA in the limb_affected. The level of evidence is III. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1764–1773, 2017.

     

Muscles that do not cross the knee contribute to the knee adduction moment and tibiofemoral compartment loading during gait

The aims of this study were to evaluate and explain the individual muscle contributions to the medial and lateral knee compartment forces during gait, and to determine whether these quantities could be inferred from their contributions to the external knee adduction moment. Gait data from eight healthy male subjects were used to compute each individual muscle contribution to the external knee adduction moment, the net tibiofemoral joint reaction force, and reaction moment. The individual muscle contributions to the medial and lateral compartment forces were then found using a least‐squares approach. While knee‐spanning muscles were the primary contributors, non‐knee‐spanning muscles (e.g., the gluteus medius) also contributed substantially to the medial compartment compressive force. Furthermore, knee‐spanning muscles tended to compress both compartments, while most non‐knee‐spanning muscles tended to compress the medial compartment but unload the lateral compartment. Muscle contributions to the external knee adduction moment, particularly those from knee‐spanning muscles, did not accurately reflect their tendencies to compress or unload the medial compartment. This finding may further explain why gait modifications may reduce the knee adduction moment without necessarily decreasing the medial compartment force. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1586–1595, 2012