Frontal Plane Knee Mechanics and Early Cartilage Degeneration in People With Anterior Cruciate Ligament Reconstruction: A Longitudinal Study

Reliability and changes in knee cartilage T2 relaxation time from 6 to 24 months after anatomic anterior cruciate ligament reconstruction

The objectives of this study were to evaluate the reliability of cartilage T2 relaxation time measurements and to identify focal changes in T2 relaxation on the affected knee from 6 to 24 months after anatomic anterior cruciate ligament reconstruction (ACLR). Data from 41 patients who received anatomic ACLR were analyzed. A bilateral 3.0-T MRI was acquired 6 and 24 months after ACLR. T2 relaxation time was measured in subregions of the femoral condyle and the tibial plateau. The root-mean-square coefficient of variation (RMSCV) was calculated to evaluate the reliability of T2 relaxation time in the contralateral knee. Subregion changes in the affected knee T2 relaxation time were identified using the contralateral knee as a reference. The superficial and full thickness layers of the central and inner regions showed good reliability. Conversely, the outer regions on the femoral side and regions in the deep layers showed poor reliability. T2 relaxation time increased in only 3 regions on the affected knee when controlling for changes in the contralateral knee, while changes in T2 relaxation time were identified in 14 regions when not using the contralateral knee as a reference. In conclusion, evaluation of cartilage degeneration by T2 relaxation time after ACLR is most reliable for central and inner cartilage regions. Cartilage degeneration occurs in the central and outer regions of the lateral femoral condyle from 6 to 24 months after anatomic ACLR.

Cartilage compositional MRI-a narrative review of technical development and clinical applications over the past three decades

Articular cartilage damage and degeneration are among hallmark manifestations of joint injuries and arthritis, classically osteoarthritis. Cartilage compositional MRI (Cart-C MRI), a quantitative technique, which aims to detect early-stage cartilage matrix changes that precede macroscopic alterations, began development in the 1990s. However, despite the significant advancements over the past three decades, Cart-C MRI remains predominantly a research tool, hindered by various technical and clinical hurdles. This paper will review the technical evolution of Cart-C MRI, delve into its clinical applications, and conclude by identifying the existing gaps and challenges that need to be addressed to enable even broader clinical application of Cart-C MRI.

Regular Running Is Related to the Knee Joint Cartilage Structure in Healthy Adults

PURPOSE

The purpose of this study was to determine whether regular running distance and biomechanics are related to medial central femur cartilage (MCFC) structure.

METHODS

The cross-sectional study sample consisted of 1164 runners and nonrunners aged 18-65 yr. Participants completed questionnaires on physical activity and their running history. We performed quantitative magnetic resonance imaging of knee cartilage-T2 relaxation time (T2) mapping (high T2 indicates cartilage degeneration)-and a running biomechanical analysis using a three-dimensional motion capture system. A 14-d monitoring of the physical activity was conducted.

RESULTS

Those aged 35-49 yr were at 84% higher odds of having MCFC T2 in the highest level (85th percentile, P < 0.05) compared with youngest adults indicating that MCFC structures may be altered with aging. Being male was associated with 34% lower odds of having T2 at the highest level ( P < 0.05) compared with females. Nonrunners and runners with the highest weekly running distance were more likely to have a high T2 compared with runners with running distance of 6-20 km·wk -1 ( P < 0.05). In addition, the maximal knee internal adduction moment was associated with a 19% lower odds of having T2 at the highest level ( P < 0.05).

CONCLUSIONS

Females compared with males and a middle-aged cohort compared with the younger cohort seemed to be associated with the degeneration of MCFC structures. Runners who ran 6-20 km·wk -1 were associated with a higher quality of their MCFC compared with highly active individuals and nonrunners. Knee frontal plane biomechanics was related to MCFC structure indicating a possibility of modifying the medial knee collagen fibril network through regular running.

Effect of sensor number and location on accelerometry-based vertical ground reaction force estimation during walking

Knee osteoarthritis is a major cause of global disability and is a major cost for the healthcare system. Lower extremity loading is a determinant of knee osteoarthritis onset and progression; however, technology that assists rehabilitative clinicians in optimizing key metrics of lower extremity loading is significantly limited. The peak vertical component of the ground reaction force (vGRF) in the first 50% of stance is highly associated with biological and patient-reported outcomes linked to knee osteoarthritis symptoms. Monitoring and maintaining typical vGRF profiles may support healthy gait biomechanics and joint tissue loading to prevent the onset and progression of knee osteoarthritis. Yet, the optimal number of sensors and sensor placements for predicting accurate vGRF from accelerometry remains unknown. Our goals were to: 1) determine how many sensors and what sensor locations yielded the most accurate vGRF loading peak estimates during walking; and 2) characterize how prescribing different loading conditions affected vGRF loading peak estimates. We asked 20 young adult participants to wear 5 accelerometers on their waist, shanks, and feet and walk on a force-instrumented treadmill during control and targeted biofeedback conditions prompting 5% underloading and overloading vGRFs. We trained and tested machine learning models to estimate vGRF from the various sensor accelerometer inputs and identified which combinations were most accurate. We found that a neural network using one accelerometer at the waist yielded the most accurate loading peak vGRF estimates during walking, with average errors of 4.4% body weight. The waist-only configuration was able to distinguish between control and overloading conditions prescribed using biofeedback, matching measured vGRF outcomes. Including foot or shank acceleration signals in the model reduced accuracy, particularly for the overloading condition. Our results suggest that a system designed to monitor changes in walking vGRF or to deploy targeted biofeedback may only need a single accelerometer located at the waist for healthy participants.

Sustained Limb-Level Loading: A Ground Reaction Force Phenotype Common to Individuals at High Risk for and Those With Knee Osteoarthritis

OBJECTIVE

The objective of this study was to compare the vertical (vGRF), anterior-posterior (apGRF), and medial-lateral (mlGRF) ground reaction force (GRF) profiles throughout the stance phase of gait (1) between individuals 6 to 12 months post-anterior cruciate ligament reconstruction (ACLR) and uninjured matched controls and (2) between ACLR and individuals with differing radiographic severities of knee osteoarthritis (KOA), defined as Kellgren and Lawrence (KL) grades KL2, KL3, and KL4.

METHODS

A total of 196 participants were included in this retrospective cross-sectional analysis. Gait biomechanics were collected from individuals 6 to 12 months post-ACLR (n = 36), uninjured controls matched to the ACLR group (n = 36), and individuals with KL2 (n = 31), KL3 (n = 67), and KL4 osteoarthritis (OA) (n = 26). Between-group differences in vGRF, apGRF, and mlGRF were assessed in reference to the ACLR group throughout each percentage of stance phase using a functional linear model.

RESULTS

The ACLR group demonstrated lower vGRF and apGRF in early and late stance compared to the uninjured controls, with large effects (Cohen's d range: 1.35-1.66). Conversely, the ACLR group exhibited greater vGRF (87%-90%; 4.88% body weight [BW]; d = 0.75) and apGRF (84%-94%; 2.41% BW; d = 0.79) than the KL2 group in a small portion of late stance. No differences in mlGRF profiles were observed between the ACLR and either the uninjured controls or the KL2 group. The magnitude of difference in GRF profiles between the ACLR and OA groups increased with OA disease severity.

CONCLUSION

Individuals 6 to 12 months post-ACLR exhibit strikingly similar GRF profiles as individuals with KL2 KOA, suggesting both patient groups may benefit from targeted interventions to address aberrant GRF profiles.

Quadriceps composition and function influence downhill gait biomechanics >1 year following anterior cruciate ligament reconstruction

BACKGROUND

Quadriceps dysfunction is common following anterior cruciate ligament reconstruction and contributes to aberrant gait biomechanics. Changes in quadriceps composition also occur in these patients including greater concentrations of non-contractile tissue. The purpose of this study was to evaluate associations between quadriceps composition, function, and gait biomechanics in individuals with anterior cruciate ligament reconstruction.

METHODS

Forty-eight volunteers with anterior cruciate ligament reconstruction completed gait biomechanics and quadriceps function and composition assessments. Gait biomechanics were sampled during downhill walking (-10° slope) on an instrumented treadmill. Quadriceps function (peak torque and rate of torque development) was assessed via maximal isometric contractions, while composition was evaluated via ultrasound echo intensity.

FINDINGS

Greater quadriceps peak torque was associated with a greater peak knee extension moment (r = 0.365, p = 0.015). Greater vastus lateralis echo intensity (i.e. poorer muscle quality) was associated with less knee flexion displacement (r = -0.316, p = 0.032). Greater echo intensity of the vastus lateralis (r = -0.298, p = 0.044) and rectus femoris (r = -0.322, p = 0.029) was associated with a more abducted knee angle at heel strike. Quadriceps peak torque explained 11-16% of the variance in echo intensity.

INTERPRETATION

Both quadriceps function and composition influence aberrant gait biomechanics following anterior cruciate ligament reconstruction. Quadriceps composition appears to provide insight into quadriceps dysfunction independent of muscle strength, as they associated with different gait biomechanics outcomes and shared minimal variance. Future research is necessary to determine the influence of changes in quadriceps composition on joint health outcomes.

Acutely Normalizing Walking Speed Does Not Normalize Gait Biomechanics Post-Anterior Cruciate Ligament Reconstruction

PURPOSE

To determine the effect of acutely increasing walking speed on gait biomechanics in ACLR individuals compared with their habitual speed and uninjured matched-controls.

METHODS

Gait biomechanics were collected on 30 ACLR individuals (20 females; age, 22.0 ± 4.2 yr; body mass index, 24.0 ± 3.0 kg·m -2 ) at their habitual speed and at 1.3 m·s -1 , a speed similar to controls, and 30 uninjured matched-controls (age: 21.9 ± 3.8, body mass index: 23.6 ± 2.5) at their habitual speed. Functional waveform analyses compared biomechanics between: i) walking at habitual speed vs 1.3 m·s -1 in ACLR individuals; and ii) ACLR individuals at 1.3 m·s -1 vs controls.

RESULTS

In the ACLR group, there were no statistically significant biomechanical differences between walking at habitual speed (1.18 ± 0.12 m·s -1 ) and 1.3 m·s -1 (1.29 ± 0.05 m·s -1 ). Compared with controls (habitual speed: 1.34 ± 0.12 m·s -1 ), the ACLR group while walking at 1.3 m·s -1 exhibited smaller vertical ground reaction force (vGRF) during early and late stance (13-28, 78-90% stance phase), greater midstance vGRF (47-61%), smaller early-to-midstance knee flexion angle (KFA; 1-44%), greater mid-to-late stance KFA (68-73, 96-101%), greater internal knee abduction moment (69-101%), and smaller internal knee extension moment (4-51, 88-96%).

CONCLUSIONS

Increasing walking speed to a speed similar to uninjured controls did not elicit significant changes to gait biomechanics, and ACLR individuals continued to demonstrate biomechanical profiles that are associated with PTOA development and differ from controls.

Physical Activity Associates with T1rho MRI of Femoral Cartilage After Anterior Cruciate Ligament Reconstruction

PURPOSE

Less physical activity has been associated with systemic biomarkers of cartilage breakdown after anterior cruciate ligament reconstruction (ACLR). However, previous research lacks analysis of deleterious cartilage compositional changes and objective physical activity after ACLR. The purpose of this study was to determine the association between physical activity quantified via accelerometer-based measures of daily steps and time in moderate-to-vigorous physical activity (MVPA), and T1rho magnetic resonance imaging (MRI) of the femoral articular cartilage, a marker of proteoglycan density in individuals with ACLR.

METHODS

Daily steps and MVPA were assessed over 7 d using an accelerometer worn on the hip in 26 individuals between 6 and 12 months after primary unilateral ACLR. Resting T1rho MRI was collected bilaterally, and T1rho MRI interlimb ratios (ILR: ACLR limb/contralateral limb) were calculated for lateral and medial femoral condyle regions of interest. We conducted univariate linear regression analyses to determine associations between T1rho MRI ILRs and daily steps and MVPA with and without controlling for sex.

RESULTS

Greater T1rho MRI ILR of the central lateral femoral condyle, indicative of less proteoglycan density in the ACLR limb, was associated with greater time in MVPA ( R2 = 0.178, P = 0.032). Sex-adjusted models showed significant interaction terms between daily steps and sex in the anterior ( P = 0.025), central ( P = 0.002), and posterior ( P = 0.002) medial femoral condyle.

CONCLUSIONS

Lesser physical activity may be a risk factor for maintaining cartilage health after ACLR; additionally, the relationship between physical activity and cartilage health may be different between males and females.

Cartilage deformation following a walking bout in individuals with anterior cruciate ligament reconstruction

The purpose was to (1) compare the effect of a walking bout on femoral cartilage deformation between limbs with and without anterior cruciate ligament reconstruction (ACLR) and (2) examine the association between gait kinetics and the magnitude of cartilage deformation. A total of 30 individuals with primary unilateral ACLR completed this study [14 male, 16 female; age = 22.57 (3.78) years; body mass index (BMI) = 25.88 (5.68) kg/m2 ; time since ACLR = 61.00 (16.43) months]. Overground walking biomechanics were assessed on day 1, and a 30-min walking bout or 30-min resting bout (control) were completed on days 2 and 3 (counterbalanced order). Femoral cartilage thickness was measured using ultrasound before, immediately following, and 30-min following each intervention. Linear mixed effects models compared the effect of walking on cartilage thickness between the ACLR and contralateral limbs after adjusting for sex, BMI, speed, and the number of steps. Stepwise regression examined the association between the external knee flexion and adduction moments and cartilage deformation following walking. There was a significant limb × time interaction for medial cartilage thickness. Post hoc analyses indicated that cartilage thickness decreased immediately following walking in the contralateral but not ACLR limb. Main effects of limb were observed for medial, central, and lateral cartilage thickness indicating thicker cartilage in the ACLR compared with contralateral limb. A higher knee adduction moment was associated with greater cartilage deformation in the ACLR limb. Femoral cartilage in the ACLR limb exhibited a less dynamic response to walking than the uninvolved limb, which may be due to habitual underloading during gait.

Patellar Dislocation in Adolescent Patients: Influence on Cartilage Properties Based on T1ρ Relaxation Times

BACKGROUND

Adolescents who experience a patellar dislocation have an elevated risk of patellofemoral posttraumatic osteoarthritis. Magnetic resonance imaging (MRI)-based T1ρ relaxation times were measured for adolescents to evaluate patellofemoral cartilage after patellar dislocation. Long T1ρ relaxation times are an indicator of cartilage degradation.

HYPOTHESIS

The primary hypothesis is that patellofemoral cartilage T1ρ relaxation times will be elevated in the acute phase after patellar dislocation. The secondary hypothesis is that T1ρ relaxation times will be higher for knees with multiple rather than single dislocations due to repeated traumatic injury.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

In total, 23 adolescents being treated for a recent patellar dislocation, 13 for a first-time dislocation (47 ± 38 days since most recent dislocation) and 10 for multiple dislocations (55 ± 24 days since most recent dislocation), and 10 healthy controls participated in MRI-based T1ρ relaxation time mapping. For multiple regions of the patellofemoral joint, mean T1ρ values were compared between the 3 groups with multiple group comparisons and post hoc tests. T1ρ relaxation times were also correlated against measures of patellofemoral anatomy and alignment for single and multiple dislocations. Statistical significance was set at P < .05.

RESULTS

T1ρ relaxation times were significantly longer for injured knees (single and multiple dislocations) than controls at the medial and central patella and central trochlear groove. For the regions on the patella, significant differences between injured and control knees exceeded 15%. No significant differences were identified between single and multiple dislocations. For the initial dislocation group, T1ρ relaxation times within multiple regions of the patellofemoral joint were significantly correlated with lateral patellar alignment or patellar height.

CONCLUSION

Elevated patellofemoral cartilage T1ρ relaxation times are consistent with a high risk of long-term patellofemoral osteoarthritis for adolescents who experience patellar dislocations. T1ρ relaxation times were elevated for multiple regions of patellofemoral cartilage. T1ρ relaxation times were expected to increase with additional dislocation episodes, but relaxation times after single and multiple dislocations were similar. After a first dislocation, parameters related to patellar maltracking were correlated with cartilage degradation.

Delayed cartilage oligomeric matrix protein response to loading is associated with femoral cartilage composition post-ACLR

PURPOSE

To determine associations between immediate and delayed response of serum cartilage oligomeric matrix protein (sCOMP) to loading (i.e., 3000 walking steps) and femoral cartilage interlimb T1ρ relaxation times in individual's post-anterior cruciate ligament reconstruction (ACLR).

METHODS

This cross-sectional study included 20 individuals 6-12 months following primary ACLR (65% female, 20.5 ± 4.0 years old, 24.9 ± 3.0 kg/m2, 7.3 ± 1.5 months post-ACLR). Serum samples were collected prior to, immediately following, and 3.5 h following walking 3000 steps on a treadmill at habitual walking speed. sCOMP concentrations were processed using enzyme-linked immunosorbent assays. Immediate and delayed absolute sCOMP responses to loading were evaluated immediately and 3.5 h post-walking, respectively. Participants underwent bilateral magnetic resonance imaging with T1ρ sequences to calculate resting femoral cartilage interlimb T1ρ relaxation time ratios between limbs (i.e., ACLR/Uninjured limb). Linear regression models were fitted to determine associations between sCOMP response to loading and femoral cartilage T1ρ outcomes controlling for pre-loading sCOMP concentrations.

RESULTS

Greater increases in delayed sCOMP response to loading were associated with greater lateral (∆R2 = 0.29, p = 0.02) but not medial (∆R2 < 0.01, p = 0.99) femoral cartilage interlimb T1ρ ratios. Associations between immediate sCOMP response to loading with femoral cartilage interlimb T1ρ ratios were weak and non-significant (∆R2 range = 0.02-0.09, p range = 0.21-0.58).

CONCLUSION

Greater delayed sCOMP response to loading, a biomarker of cartilage breakdown, is associated with worse lateral femoral cartilage composition in the ACLR limb compared to the uninjured limb. Delayed sCOMP response to loading may be a more indicative metabolic indicator linked to deleterious changes in composition than immediate sCOMP response.

Gait Variability Structure Linked to Worse Cartilage Composition Post-ACL Reconstruction

INTRODUCTION

Aberrant gait variability has been observed after anterior cruciate ligament reconstruction (ACLR), yet it remains unknown if gait variability is associated with early changes in cartilage composition linked to osteoarthritis development. Our purpose was to determine the association between femoral articular cartilage T1ρ magnetic resonance imaging relaxation times and gait variability.

METHODS

T1ρ magnetic resonance imaging and gait kinematics were collected in 22 ACLR participants (13 women; 21 ± 4 yr old; 7.52 ± 1.43 months post-ACLR). Femoral articular cartilage from the ACLR and uninjured limbs were segmented into anterior, central, and posterior regions from the weight-bearing portions of the medial and lateral condyles. Mean T1ρ relaxation times were extracted from each region and interlimb ratios (ILR) were calculated (i.e., ACLR/uninjured limb). Greater T1ρ ILR values were interpreted as less proteoglycan density (worse cartilage composition) in the injured limb compared with the uninjured limb. Knee kinematics were collected at a self-selected comfortable walking speed on a treadmill with an eight-camera three-dimensional motion capture system. Frontal and sagittal plane kinematics were extracted, and sample entropy was used to calculate kinematic variability structure (KV structure ). Pearson's product-moment correlations were conducted to determine the associations between T1ρ and KV structure variables.

RESULTS

Lesser frontal plane KV structure was associated with greater mean T1ρ ILR in the anterior lateral ( r = - 0.44, P = 0.04) and anterior medial condyles ( r = - 0.47, P = 0 .03). Lesser sagittal plane KV structure was associated with greater mean T1ρ ILR in the anterior lateral condyle ( r = - 0.47, P = 0.03).

CONCLUSIONS

The association between less KV structure and worse femoral articular cartilage proteoglycan density suggests a link between less variable knee kinematics and deleterious changes joint tissue changes. The findings suggest that less knee kinematic variability structure is a mechanism linking aberrant gait to early osteoarthritis development.

Patellofemoral joint loading and early osteoarthritis after ACL reconstruction

Patellofemoral joint (PFJ) osteoarthritis is common following anterior cruciate ligament reconstruction (ACLR) and may be linked with altered joint loading. However, little is known about the cross-sectional and longitudinal relationship between PFJ loading and osteoarthritis post-ACLR. This study tested if altered PFJ loading is associated with prevalent and worsening early PFJ osteoarthritis post-ACLR. Forty-six participants (mean ± 1 SD age 26 ± 5 years) approximately 1-year post-ACLR underwent magnetic resonance imaging (MRI) and biomechanical assessment of their reconstructed knee. Trunk and lower-limb kinematics plus ground reaction forces were recorded during the landing phase of a standardized forward hop. These data were input into a musculoskeletal model to calculate the PFJ contact force. Follow-up MRI was completed on 32 participants at 5-years post-ACLR. Generalized linear models (Poisson regression) assessed the relationship between PFJ loading and prevalent early PFJ osteoarthritis (i.e., presence of a PFJ cartilage lesion at 1-year post-ACLR) and worsening PFJ osteoarthritis (i.e., incident/progressive PFJ cartilage lesion between 1- and 5-years post-ACLR). A lower peak PFJ contact force was associated with prevalent early PFJ osteoarthritis at 1-year post-ACLR (n = 14 [30.4%]; prevalence ratio: 1.37; 95% confidence interval [CI]: 1.02-1.85) and a higher risk of worsening PFJ osteoarthritis between 1- and 5-years post-ACLR (n = 9 [28.1%]; risk ratio: 1.55, 95% CI: 1.13-2.11). Young adults post-ACLR who exhibited lower PFJ loading during hopping were more likely to have early PFJ osteoarthritis at 1-year and worsening PFJ osteoarthritis between 1- and 5-years. Clinical interventions aimed at mitigating osteoarthritis progression may be beneficial for those with signs of lower PFJ loading post-ACLR.

Baseline cartilage T1ρ and T2 predicted patellofemoral joint cartilage lesion progression and patient-reported outcomes after ACL reconstruction

This study aims to determine if baseline T1ρ and T2 will predict cartilage morphological lesion progression in the patellofemoral joint (PFJ) and patient-reported outcomes at 2-year after anterior cruciate ligament (ACL) reconstruction (ACLR). Thirty-nine ACL-injured patients were studied at baseline and two-year after ACLR. 3 T MR T1ρ and T2 images and Knee Injury and Osteoarthritis Outcome Score (KOOS) were acquired at both time points. Voxel-based relaxometry (VBR) technique was used to detect local cartilage abnormalities. Patients were divided into progression and non-progression groups based on changes of the whole-organ magnetic resonance imaging scoring (WORMS) grading of cartilage in PFJ from baseline to 2-year, and into lower (more pain) and higher (less pain) KOOS pain groups based on 2-year KOOS pain scores, separately. Voxel-based analyses of covariance were used to compare T1ρ and T2 values at baseline between the defined groups. Using VBR analysis, the progression group at 2-year showed higher T1ρ and T2 compared with the non-progression group at baseline, with the medial femoral condyle showing the largest areas with significant differences. At two-year, 56% of patients were able to recover with respect to KOOS pain. The lower KOOS pain group at 2-year showed significantly elevated T1ρ and T2 in the patella at baseline compared with the higher KOOS pain group. In conclusion, baseline T1ρ and T2 mapping, combined with VBR analysis, may help identify ACLR patients at high risk of developing progressive PFJ cartilage lesions and worse clinical symptoms 2-year after surgery.

Evidence Review for Preventing Osteoarthritis After an Anterior Cruciate Ligament Injury: An Osteoarthritis Action Alliance Consensus Statement

CONTEXT

The Osteoarthritis Action Alliance formed a secondary prevention task group to develop a consensus on secondary prevention recommendations to reduce the risk of osteoarthritis after a knee injury.

OBJECTIVE

Our goal was to provide clinicians with secondary prevention recommendations that are intended to reduce the risk of osteoarthritis after a person has sustained an anterior cruciate ligament injury. Specifically, this manuscript describes our methods, literature reviews, and dissenting opinions to elaborate on the rationale for our recommendations and to identify critical gaps.

DESIGN

Consensus process.

SETTING

Virtual video conference calls and online voting.

PATIENTS OR OTHER PARTICIPANTS

The Secondary Prevention Task Group consisted of 29 members from various clinical backgrounds.

MAIN OUTCOME MEASURE(S)

The group initially convened online in August 2020 to discuss the target population, goals, and key topics. After a second call, the task group divided into 9 subgroups to draft the recommendations and supportive text for crucial content areas. Twenty-one members completed 2 rounds of voting and revising the recommendations and supportive text between February and April 2021. A virtual meeting was held to review the wording of the recommendations and obtain final votes. We defined consensus as >80% of voting members supporting a proposed recommendation.

RESULTS

The group achieved consensus on 15 of 16 recommendations. The recommendations address patient education, exercise and rehabilitation, psychological skills training, graded-exposure therapy, cognitive-behavioral counseling (lacked consensus), outcomes to monitor, secondary injury prevention, system-level social support, leveraging technology, and coordinated care models.

CONCLUSIONS

This consensus statement reflects information synthesized from an interdisciplinary group of experts based on the best available evidence from the literature or personal experience. We hope this document raises awareness among clinicians and researchers to take steps to mitigate the risk of osteoarthritis after an anterior cruciate ligament injury.

Interlimb differences in T1ρ MRI relaxation times linked with symptomatic knee osteoarthritis following anterior cruciate ligament reconstruction

BACKGROUND

Lower proteoglycan density, as estimated by greater T1ρ magnetic resonance imaging (MRI) relaxation times, may be an indicator of early osteoarthritis development. We examined associations between femoral cartilage inter-limb T1ρ MRI relaxation time ratios and clinically relevant knee symptoms at 12 months following anterior crucial ligament reconstruction (ACLR).

METHODS

Twenty-nine individuals completed the Knee Osteoarthritis Outcome Score (KOOS) and underwent MRI 12 months following ACLR for this cross-sectional study. Participants were categorized as symptomatic or asymptomatic for clinically relevant knee symptoms consistent with osteoarthritis based on a standard KOOS classification. T1ρ MRI relaxation times were segmented in the weightbearing regions of lateral and medial femoral condyle (LFC and MFC). Inter-limb T1ρ MRI relaxation time ratios were calculated by normalizing the ACLR to the uninjured knee. T-tests were used to compare LFC and MFC interlimb T1ρ relaxation time ratios between individuals with and without knee symptoms. A Receiver Operating Characteristic (ROC) Curve analysis was used to determine a critical inter-limb T1ρ relaxation time ratio identifying symptomatic patients. Odds ratios (OR) and 95% confidence intervals (CI) estimated the association between the critical value and clinically relevant knee symptoms.

RESULTS

Symptomatic individuals had significantly higher LFC inter-limb T1ρ MRI relaxation time ratios compared to asymptomatic individuals (p = 0.04). Individuals with an LFC inter-limb T1ρ MRI relaxation time ratio >1.11 were more likely to have symptoms (OR 8.5; 95%CI = 1.25-57.93).

CONCLUSION

Individuals with greater inter-limb LFC T1ρ MRI relaxation time ratios 12 months post-ACLR may be more likely to exhibit symptoms consistent with knee OA.

Knee Osteoarthritis Following Anterior Cruciate Ligament Reconstruction: Frequency, Contributory Elements, and Recent Interventions to Modify the Route of Degeneration

Half of the individuals who experience an anterior cruciate ligament reconstruction (ACLR) suffer from knee osteoarthritis (OA) 12-14 years later. Elements that make a contribution to the appearance of OA following ACLR are anomalous anterior tibial displacement and anomalous tibial rotation in the course of the stance phase of walking (exhibited in 85% of operated knees). Individuals who undergo an early ACLR (5 days on average following anterior cruciate ligament [ACL] breakage) have an inferior frequency of radiographically apparent tibiofemoral OA at 32-37 years of follow-up than individuals with ACL rupture who did not experience the procedure. Nevertheless, the percentage of symptomatic OA, radiographically apparent patellofemoral OA and knee symptoms are alike in both groups. At 15 years of follow-up, 23% of knees that experienced an anatomic ACLR suffer from OA, while this percentage augments to 44% if the ACLR was non-anatomic. Knees of individuals who experience ACLR need total knee arthroplasty at an earlier age than healthy knees. Intra-articular injections of interleukin-1 receptor antagonist and corticosteroids may reduce the risk of OA after ACLR.

Environmental Risk Factors for Osteoarthritis: The Impact on Individuals with Knee Joint Injury

Osteoarthritis is a debilitating chronic condition involving joint degeneration, impacting over 300 million people worldwide. This places a high social and economic burden on society. The knee is the most common joint impacted by osteoarthritis. A common cause of osteoarthritis is traumatic joint injury, specifically injury to the anterior cruciate ligament. The purpose of this review is to detail the non-modifiable and modifiable risk factors for osteoarthritis with particular focus on individuals after anterior cruciate ligament injury. After reading this, health care providers will better comprehend the wide variety of factors linked to osteoarthritis.

Knee Cartilage Change within 5 Years after Aclr Using Hamstring Tendons with Preserved Tibial-Insertion: A Prospective Randomized Controlled Study Based on Magnetic Resonance Imaging

Background: Comparing to anterior cruciate ligament reconstructions (ACLR) with free hamstring tendon (FHT), ACLR with preserved tibial-insertion hamstring tendon (HT-PTI) could ensure the blood supply of the graft and avoid graft necrosis. Yet, whether HT-PTI could protect the cartilage and clinical outcomes in mid-long period after ACLR was still unclear. Purpose: To compare the cartilage change and clinical results between the HT-PTI and FHT in 5 years after ACLR. Study design: Randomized controlled trial; Level of evidence, 2. Methods: A total of 45 patients who underwent isolated ACLR with the autograft of hamstring tendons were enrolled and randomized into 2 groups. The study group undertook ACLR with HT-PTI, whereas the control group had FHT. At pre-operation, and 6, 12, 24, and 60 months post-operation, all cases underwent evaluation with Knee Injury and Osteoarthritis Outcome Score (KOOS), and MR examination. The knee cartilage was divided into 8 sub-regions of which the T2 value and cartilage volume on MRI were measured and documented. The data of two groups were compared and their correlations were analyzed. Results: A total of 18 patients in the HT-PTI group and 19 patients in the FHT group completed the follow-up. The KOOS scores were improved at each follow-up time point (p < 0.001), reached the most superior at 12 months and maintained until 60 months but had no significant difference between the two groups. At 60 months, the cartilage in most subregions in FHT group had higher T2 values than those of pre-operation (p < 0.05) and also higher than HT-PTI group; The cartilage volume changes (CV%) are positive at 6 months and negative from 12 to 60 months in the FHT group, while being negative at all time points in the HT-PTI group. The values of absolute CV% in most subregions in FHT group were significantly higher than those in the HT-PTI group at 6 and 60 months (p < 0.05). Conclusion: The improvement of KOOS score peaked at 12 months in all cases and had no difference between the two groups. The cartilage in the FHT group had more volume loss, earlier and wider damage than that in the HT-PTI group within 5 years. No significant correlation was found among KOOS score, CV%, and T2 value.

Worse Tibiofemoral Cartilage Composition Is Associated with Insufficient Gait Kinetics After ACL Reconstruction

PURPOSE

Greater articular cartilage T1ρ magnetic resonance imaging relaxation times indicate less proteoglycan density and are linked to posttraumatic osteoarthritis development after anterior cruciate ligament reconstruction (ACLR). Although changes in T1ρ relaxation times are associated with gait biomechanics, it is unclear if excessive or insufficient knee joint loading is linked to greater T1ρ relaxation times 12 months post-ACLR. The purpose of this study was to compare external knee adduction (KAM) and flexion (KFM) moments in individuals after ACLR with high versus low tibiofemoral T1ρ relaxation profiles and uninjured controls.

METHODS

Gait biomechanics were collected in 26 uninjured controls (50% females; age, 22 ± 4 yr; body mass index, 23.9 ± 2.8 kg·m -2 ) and 26 individuals after ACLR (50% females; age, 22 ± 4 yr; body mass index, 24.2 ± 3.5 kg·m -2 ) at 6 and 12 months post-ACLR. ACLR-T1ρ High ( n = 9) and ACLR-T1ρ Low ( n = 17) groups were created based on 12-month post-ACLR T1ρ relaxation times using a k-means cluster analysis. Functional analyses of variance were used to compare KAM and KFM.

RESULTS

ACLR-T1ρ High exhibited lesser KAM than ACLR-T1ρ Low and uninjured controls 6 months post-ACLR. ACLR-T1ρ Low exhibited greater KAM than uninjured controls 6 and 12 months post-ACLR. KAM increased in ACLR-T1ρ High and decreased in ACLR-T1ρ Low between 6 and 12 months, both groups becoming more similar to uninjured controls. There were scant differences in KFM between ACLR-T1ρ High and ACLR-T1ρ Low 6 or 12 months post-ACLR, but both groups demonstrated lesser KFM compared with uninjured controls.

CONCLUSIONS

Associations between worse T1ρ profiles and increases in KAM may be driven by the normalization of KAM in individuals who initially exhibit insufficient KAM 6 months post-ACLR.

Fewer daily steps are associated with greater cartilage oligomeric matrix protein response to loading post-ACL reconstruction

Aberrant joint loading contributes to the development of posttraumatic knee osteoarthritis (PTOA) following anterior cruciate ligament reconstruction (ACLR); yet little is known about the association between joint loading due to daily walking and cartilage health post-ACLR. Accelerometer-based measures of daily steps and cadence (i.e., rate of steps/min) provide information regarding daily walking in a real-world setting. The purpose of this study was to determine the association between changes in serum cartilage oligomeric matrix protein (COMP; %∆COMP), a mechanosensitive biomarker that is associated with osteoarthritis progression, following a standardized walking protocol and daily walking in individuals with ACLR and uninjured controls. Daily walking was assessed over 7 days using an accelerometer worn on the right hip in 31 individuals with ACLR and 21 controls and quantified as mean steps/day and time spent in ≥100 steps/min. Serum COMP was measured before and following a 3000-step walking protocol at a preferred speed. %∆COMP was calculated as a change in COMP relative to the prewalking value. Linear regressions were used to examine associations between daily walking and %∆COMP after adjusting for preferred speed. Fewer daily steps (ΔR²  = 0.18, p = 0.02) and fewer minutes spent in ≥100 steps/min (ΔR²  = 0.16, p = 0.03) were associated with greater %∆COMP following walking in individuals with ACLR; no statistically significant associations existed in controls (daily steps: ΔR²  = 0.03, p = 0.47; time ≥100 steps/min: ΔR²  < 0.01, p = 0.81). Clinical significance: Individuals with ACLR who engage in less daily walking undergo greater %ΔCOMP, which may represent greater cartilage degradation or turnover in response to walking.

Elevated Patellofemoral and Tibiofemoral T1ρ Relaxation Times Following a First Time Patellar Dislocation

OBJECTIVE

The study was performed to evaluate cartilage within the knee following a first-time patellar dislocation, using elevated MRI-based T1ρ relaxation times as an indicator of low proteoglycan concentration. The hypothesis is that MRI-based T1ρ relaxation times for patellofemoral and tibiofemoral cartilage are significantly longer for knees being treated for patellar dislocation than for healthy control knees.

DESIGN

Twenty-one subjects being treated for a first-time, unilateral dislocation of the patella and 16 healthy controls participated in MRI-based T1ρ relaxation time mapping. Mean relaxation times were quantified for patellofemoral and tibiofemoral regions for injured knees, the contralateral knees, and healthy controls. T1ρ values for each region were compared between the 3 groups with generalized estimating equations. Linear regressions were also performed to correlate T1ρ relaxation times with time from injury.

RESULTS

The knees with a disloction had longer T1ρ relaxation times than the contralateral knees and control group at the medial patella and longer relaxation times than the control group at the lateral tibia (P < 0.05). T1ρ relaxation times at the medial patella also decreased with time from injury (r² = 0.21, P = 0.037).

CONCLUSIONS

Compositional changes to cartilage on the medial patella are related to traumatic impact during a dislocation. Potential exists for cartilage properties at the medial patella to improve with time. Cartilage degradation at the lateral tibia is not directly related to traumatic impact. The current baseline data are a starting point to characterize the pathway from a first-time dislocation to progressive cartilage degradation and osteoarthritis.

Cartilage oligomeric matrix protein responses to a mechanical stimulus associate with ambulatory loading in individuals with anterior cruciate ligament reconstruction

Mechanical factors have been implicated in the development of osteoarthritis after anterior cruciate ligament (ACL) reconstruction. This study tested for associations between ambulatory joint loading (total joint moment [TJM] and vertical ground reaction force [vGRF]) and changes in serum levels of cartilage oligomeric matrix protein (COMP) in response to a mechanical stimulus (30-min walk) in individuals with ACL reconstruction. Twenty-five subjects (mean age: 34.5 ± 9.8 years; 2.2 ± 0.2 years post-surgery) with primary unilateral ACL reconstruction underwent gait analysis for assessment of peak vGRF and TJM first (TJM1) and second (TJM2) peaks. Serum COMP concentrations were measured by enzyme-linked immunosorbent assay immediately before, 3.5 h, and 5.5 h after a 30-min walk. Pearson correlation coefficients and backward stepwise multiple linear regression analysis, with adjustments for age, sex, body mass index, and between-limb speed difference, assessed associations between changes in COMP and between-limb differences in joint loading parameters. Greater TJM1 (R = 0.542, p = 0.005), TJM2 (R = 0.460, p = 0.021), and vGRF (R = 0.577, p = 0.003) in the ACL-reconstructed limb as compared to the contralateral limb were associated with higher COMP values 3.5 h following the 30-min walk. Change in COMP at 5.5 h became a significant predictor of the between-limb difference in TJM1 and vGRF in multivariate analyses after accounting for the between-limb speed difference. These results demonstrate that higher TJM and vGRF in the ACLR limb as compared to the contralateral limb are associated with higher relative COMP levels 3.5 and 5.5 h after a 30-min walk. Future work should investigate the effect of therapies to alter joint loading on the biological response in individuals after ACL reconstruction.

Loading during Midstance of Gait Is Associated with Magnetic Resonance Imaging of Cartilage Composition Following Anterior Cruciate Ligament Reconstruction

OBJECTIVE

A complex association exists between aberrant gait biomechanics and posttraumatic knee osteoarthritis (PTOA) development. Previous research has primarily focused on the link between peak loading during the loading phase of stance and joint tissue changes following anterior cruciate ligament reconstruction (ACLR). However, the associations between loading and cartilage composition at other portions of stance, including midstance and late stance, is unclear. The objective of this study was to explore associations between vertical ground reaction force (vGRF) at each 1% increment of stance phase and tibiofemoral articular cartilage magnetic resonance imaging (MRI) T1ρ relaxation times following ACLR.

DESIGN

Twenty-three individuals (47.82% female, 22.1 ±4.1 years old) with unilateral ACLR participated in a gait assessment and T1ρ MRI collection at 12.25 ± 0.61 months post-ACLR. T1ρ relaxation times were calculated for the articular cartilage of the weightbearing medial and lateral femoral (MFC, LFC) and tibial (MTC, LTC) condyles. Separate bivariate, Pearson product moment correlation coefficients (r) were used to estimate strength of associations between T1ρ MRI relaxation times in the medial and lateral tibiofemoral articular cartilage with vGRF across the entire stance phase.

RESULTS

Greater vGRF during midstance (46%-56% of stance phase) was associated with greater T1ρ MRI relaxation times in the MFC (r ranging between 0.43 and 0.46).

CONCLUSIONS

Biomechanical gait profiles that include greater vGRF during midstance are associated with MRI estimates of lesser proteoglycan density in the MFC. Inability to unload the ACLR limb during midstance may be linked to joint tissue changes associated with PTOA development.

Knee joint unloading and daily physical activity associate with cartilage T2 relaxation times 1 month after ACL injury

Osteoarthritis (OA) is prevalent after anterior cruciate ligament (ACL) injury, but mechanismsunderlying its development are poorly understood. The purpose of this study was to determine if gait biomechanics and daily physical activity (PA) associate with cartilage T2 relaxation times, a marker of collagen organization and water content, 1 month after ACL injury. Twenty-seven participants (15-35 years old) without chondral lesions completed magnetic resonance imaging, three-dimensional gait analysis, and 1 week of PA accelerometry. Interlimb differences and ratios were calculated for gait biomechanics and T2 relaxation times, respectively. Multiple linear regression models adjusted for age, sex, and concomitant meniscus injury were used to determine the association between gait biomechanics and PA with T2 relaxation times, respectively. Altered knee adduction moment (KAM) impulse, less knee flexion excursion (kEXC) and higher daily step counts accounted for 35.8%-65.8% of T2 relaxation time variation in the weightbearing and posterior cartilage of the medial and lateral compartment (all p ≤ .011). KAM impulse was the strongest factor for T2 relaxation times in all models (all p ≤ .001). Lower KAM impulse associated with longer T2 relaxation times in the injured medial compartment (β = -.720 to -.901) and shorter T2 relaxation in the lateral compartment (β = .713 to .956). At 1 month after ACL injury, altered KAM impulse, less kEXC, and higher PA associated with longer T2 relaxation times, which may indicate poorer cartilage health. Statement of Clinical Significance: Gait biomechanics and daily PA are modifiable targets that may improve cartilage health acutely after ACL injury and slow progression to OA.

A Review of the Relationships Between Knee Pain and Movement Neuromechanics

CONTEXT

Knee injury and disease are common, debilitating, and expensive. Pain is a chief symptom of knee injury and disease and likely contributes to arthrogenic muscle inhibition. Joint pain alters isolated motor function, muscular strength, and movement biomechanics. Because knee pain influences biomechanics, it likely also influences long-term knee joint health.

OBJECTIVE

The purpose of this article is 2-fold: (1) review effects of knee pain on lower-extremity muscular activation and corresponding biomechanics and (2) consider potential implications of neuromechanical alterations associated with knee pain for long-term knee joint health. Experimental knee pain is emphasized because it has been used to mimic clinical knee pain and clarify independent effects of knee pain. Three common sources of clinical knee pain are also discussed: patellofemoral pain, anterior cruciate ligament injury and reconstruction, and knee osteoarthritis.

DATA SOURCES

The PubMed, Web of Science, and SPORTDiscus databases were searched for articles relating to the purpose of this article.

CONCLUSION

Researchers have consistently reported that knee pain alters neuromuscular activation, often in the form of inhibition that likely occurs via voluntary and involuntary neural pathways. The effects of knee pain on quadriceps activation have been studied extensively. Knee pain decreases voluntary and involuntary quadriceps activation and strength and alters the biomechanics of various movement tasks. If allowed to persist, these neuromechanical alterations might change the response of articular cartilage to joint loads during movement and detrimentally affect long-term knee joint health. Physical rehabilitation professionals should consider neuromechanical effects of knee pain when treating knee injury and disease. Resolution of joint pain can likely help to restore normal movement neuromechanics and potentially improve long-term knee joint health and should be a top priority.

A Multi-Systems Approach to Human Movement after ACL Reconstruction: The Musculoskeletal System

Several negative adaptations to the musculoskeletal system occur following anterior cruciate ligament (ACL) injury and ACL reconstruction (ACLR) such as arthrogenic muscle inhibition, decreased lower extremity muscle size, strength, power, as well as alterations to bone and cartilage. These changes have been associated with worse functional outcomes, altered biomechanics, and increased risk for re-injury and post-traumatic osteoarthritis. After ACL injury and subsequent ACLR, examination and evaluation of the musculoskeletal system is paramount to guiding clinical decision making during the rehabilitation and the return to sport process. The lack of access many clinicians have to devices necessary for gold standard assessment of muscle capacities and force profiles is often perceived as a significant barrier to best practices. Fortunately, testing for deficits can be accomplished with methods available to the clinician without access to costly equipment or time-intensive procedures. Interventions to address musculoskeletal system deficits can be implemented with a periodized program. This allows for restoration of physical capacities by adequately developing and emphasizing physical qualities beginning with mobility and movement, and progressing to work capacity and neuromuscular re-education, strength, explosive strength, and elastic or reactive strength. Additional considerations to aid in addressing strength deficits will be discussed such as neuromuscular electrical stimulation, volume and intensity, eccentric training, training to failure, cross-education, and biomechanical considerations. The American Physical Therapy Association adopted a new vision statement in 2013 which supported further development of the profession's identity by promoting the movement system, yet validation of the movement system has remained a challenge. Application of a multi-physiologic systems approach may offer a unique understanding of the musculoskeletal system and its integration with other body systems after ACLR. The purpose of this clinical commentary is to highlight important musculoskeletal system considerations within a multi-physiologic system approach to human movement following ACLR.

LEVEL OF EVIDENCE

5.

Longitudinal Changes in Ultrasound-Assessed Femoral Cartilage Thickness in Individuals from 4 to 6 Months Following Anterior Cruciate Ligament Reconstruction

OBJECTIVE

Diagnostic ultrasound provides a valid assessment of cartilage health that has been used to observe cross-sectional cartilage thickness differences post-ACLR (anterior cruciate ligament reconstruction), but has not been used longitudinally during early recovery post-ACLR.

DESIGN

The purpose of this study was to assess longitudinal changes in femoral cartilage thickness via ultrasound in individuals at 4 to 6 months post-ACLR and compared to healthy controls. Twenty participants (50% female, age = 21.1 ± 5.7 years) completed testing sessions 4 and 6 months post-ACLR. Thirty healthy controls (57% female, age = 20.8 ± 3.8 years) without knee injury history completed 2 testing sessions (>72 hours apart). Femoral cartilage ultrasound images were captured bilaterally in ACLR participants and in the dominant limb of healthy controls during all sessions. Average cartilage thicknesses in the medial, intercondylar, and lateral femoral regions were determined using a semi-automated processing technique.

RESULTS

When comparing cartilage thickness mean differences or changes over time, individuals post-ACLR did not demonstrate between limb differences (P-range = 0.50-0.92), limb differences compared to healthy controls (P-range = 0.19-0.94), or changes over time (P-range = 0.22-0.72) for any femoral cartilage thickness region. However, participants demonstrated cartilage thickening (45%) or thinning (35%) that exceeded minimal detectable change (MDC) from 4 to 6 months post-ACLR, respectively.

CONCLUSIONS

Using MDC scores may help better identify within-subject femoral cartilage thickness changes longitudinally post-ACLR due to bidirectional cartilage thickness changes.

Long-term outcomes of anterior cruciate ligament reconstruction surgery: 2020 OREF clinical research award paper

ACL injuries place the knee at risk for post-traumatic osteoarthritis (PTOA) despite surgical anterior cruciate ligament (ACL) reconstruction. One parameter thought to affect PTOA risk is the initial graft tension. This randomized controlled trial (RCT) was designed to compare outcomes between two graft tensioning protocols that bracket the range commonly used. At 7 years postsurgery, we determined that most outcomes between the two tension groups were not significantly different, that they were inferior to an uninjured matched control group, and that PTOA was progressing in both groups relative to controls. The trial database was also leveraged to gain insight into mechanisms of PTOA following ACL injury. We determined that the inflammatory response at the time of injury undermines one of the joint's lubricating mechanisms. We learned that patients continue to protect their surgical knee 5 years postinjury compared to controls during a jump-pivot activity. We also established that presurgical knee function and mental health were correlated with symptomatic PTOA at 7 years, that there were specific anatomical factors associated with poor outcomes, and that there were no changes in outcomes due to tunnel widening in patients receiving hamstring tendon autografts. We also validated a magnetic resonance imaging technique to noninvasively assess graft strength. In conclusion, the RCT determined that initial graft tensioning does not have a major influence on 7-year outcomes. Therefore, surgeons can reconstruct the ACL using a graft tensioning protocol that is within the window of the two graft tensioning techniques evaluated in this RCT.

Limb dominance influences energy absorption contribution (EAC) during landing after anterior cruciate ligament reconstruction

OBJECTIVE

To determine the role of limb dominance on energy absorption contribution (EAC) during a jump landing (JL) task at return to sport (RTS) after ACL-R.

DESIGN

Cross-sectional study.

SETTING

Clinical Research Laboratory.

PARTICIPANTS

One hundred eight participants (age = 16.19 ± 1.74, Height = 172.25 ± 9.96 cm, Weight = 72.61 ± 15.48 kg).

MAIN OUTCOME MEASURES

Participants were grouped into two groups: those who injured their dominant limb ACL (D-ACL) and those who injured their non-dominant limb ACL (ND-ACL). A multiple analysis of variance (MANOVA) was used to assess for between group differences in EAC across the three joints.

RESULTS

In the surgical limb, D-ACL demonstrated smaller hip (D-ACL = 32.23 ± 10.44%, ND-ACL = 69.68 ± 8.51%, p < 0.008) and greater knee (D-ACL = 45.86 ± 10.36%, ND-ACL = 9.41 ± 5.68%, p < 0.008) EAC than ND-ACL. In the non-surgical limb, D-ACL demonstrated greater hip (D-ACL = 62.59 ± 9.03%, ND-ACL = 25.95 ± 7.15%, p < 0.008), and smaller knee (D-ACL = 13.79 ± 5.57%, ND-ACL = 58.01 ± 7.86%, p < 0.008), EAC than ND-ACL.

CONCLUSION

After ACL-R, eccentric loading strategies during a JL task at RTS are different depending upon limb dominance. D-ACL demonstrated a greater knee loading strategy on the surgical side compared to ND-ACL.

Operative and nonoperative management of anterior cruciate ligament injury: Differences in gait biomechanics at 5 years

Gait biomechanics after anterior cruciate ligament (ACL) injury are associated with functional outcomes and the development of posttraumatic knee osteoarthritis. However, biomechanical outcomes between patients treated nonoperatively compared with operatively are not well understood. The primary purpose of this study was to compare knee joint contact forces, angles, and moments during loading response of gait between individuals treated with operative compared with nonoperative management at 5 years after ACL injury. Forty athletes treated operatively and 17 athletes treated nonoperatively completed gait analysis at 5 years after ACL reconstruction or completion of nonoperative rehabilitation. Medial compartment joint contact forces were estimated using a previously validated, patient-specific electromyography-driven musculoskeletal model. Knee joint contact forces, angles, and moments were compared between the operative and nonoperative group using mixed model 2 × 2 analyses of variance. Peak medial compartment contact forces were larger in the involved limb of the nonoperative group (Op: 2.37 ± 0.47 BW, Non-Op: 3.03 ± 0.53 BW; effect size: 1.36). Peak external knee adduction moment was also larger in the involved limb of the nonoperative group (Op: 0.25 ± 0.08 Nm/kg·m, Non-Op: 0.32 ± 0.09 Nm/kg·m; effect size: 0.89). No differences in radiographic tibiofemoral osteoarthritis were present between the operative and nonoperative groups. Overall, participants treated nonoperatively walked with greater measures of medial compartment joint loading than those treated operatively, while sagittal plane group differences were not present. Statement of clinical relevance: The differences in medial knee joint loading at 5 years after operative and nonoperative management of ACL injury may have implications on the development of posttraumatic knee osteoarthritis.

Lower limb biomechanics before and after anterior cruciate ligament reconstruction: A systematic review

This review aimed to synthesise the findings of literature that have assessed the changes in lower limb biomechanics following anterior cruciate ligament (ACL) reconstructive surgery. Systematic searches of CINHAL, MEDLINE, SCOPUS, and SPORTDiscus databases were run. All included studies had presented biomechanical variables pre- and post-surgery for the same participants. Articles were categorised by the analysed movement, and effect sizes were calculated. Fifty-four studies met the inclusion criteria, providing data on gait (n = 31), balance (n = 12), joint position sense (n = 5), stair ambulation (n = 4), pivoting (n = 6), and landing (n = 5). Measures of balance performance and joint position sense showed improvements from pre- to post-surgery. Changes in joint kinematics were inconsistent between studies, however increased knee flexion excursion, and reduced tibial anterior translation and internal rotation post reconstruction were identified. Joint kinetics reduced in magnitude in the early stages after surgery (≤5 weeks), then increased later in recovery (≥24 weeks). Risk of bias assessment identified most articles had a moderate or high risk (low = 5; moderate = 21; high = 11) resulting from participant retention and surgical intervention differences. The results of the review identified that although lower limb biomechanics did alter following reconstruction, few variables provided consistent results across studies and tasks. The low methodological quality of some articles may have contributed to these inconsistent findings. Alternatively, differences across studies may have resulted from individual coping strategies of participants that have previously been suggested to be present before reconstructive surgery, and future research should look to explore individual coping strategies to ACL reconstruction.

Single-leg hop mechanics are correlated with self-reported knee function early after anterior cruciate ligament reconstruction

BACKGROUND

Biomechanical changes that persist after anterior cruciate ligament (ACL) injury may impact short- and long-term outcomes. Understanding the relationship of biomechanics during a dynamic task and patient reported function can better identify patients who are most vulnerable to sub-optimal long-term outcomes, such as osteoarthritis (OA). The purpose of this study was to determine whether hip and knee biomechanics during single-leg hop landing were significantly correlated with the Knee injury and Osteoarthritis Outcome Score (KOOS), and whether symptomatic knees displayed altered biomechanics relative to asymptomatic knees.

METHODS

Hip and knee biomechanics during the landing phase of a single-leg hop of thirty subjects with ACLR were analyzed. Subjects were also classified as symptomatic or asymptomatic based on their KOOS results. Correlation analyses and group comparisons between symptomatic and asymptomatic subjects were conducted.

FINDINGS

KOOS Symptoms, Pain, and Sport subscales were significantly correlated with frontal and sagittal plane hip and knee biomechanics. Furthermore, those with symptomatic knees demonstrated greater hip and knee flexion angles, and greater hip flexion moments.

INTERPRETATION

These results indicate that biomechanics associated with ACLR during a single-leg hop are correlated with worse KOOS outcomes. However, these correlations may be due to symptoms of the recovery from ACLR rather than those of OA. The results of this study may help to identify rehabilitation opportunities for patients at risk for worse long-term outcomes after ACLR.

Osteoarthritis year in review 2019: imaging

OBJECTIVE

To provide a narrative review of original articles on osteoarthritis (OA) imaging published between April 1, 2018 and March 30, 2019.

METHODS

All original research articles on OA imaging published in English between April 1, 2018 and March 30, 2019 were identified using a PubMed database search. The search terms of "Osteoarthritis" or "OA" were combined with the search terms "Radiography", "X-Rays", "Magnetic Resonance Imaging", "MRI", "Ultrasound", "US", "Computed Tomography", "Dual Energy X-Ray Absorptiometry", "DXA", "DEXA", "CT", "Nuclear Medicine", "Scintigraphy", "Single-Photon Emission Computed Tomography", "SPECT", "Positron Emission Tomography", "PET", "PET-CT", or "PET-MRI". Articles were reviewed to determine relevance based upon the following criteria: 1) study involved human subjects with OA or risk factors for OA and 2) study involved imaging to evaluate OA disease status or OA treatment response. Relevant articles were ranked according to scientific merit, with the best publications selected for inclusion in the narrative report.

RESULTS

The PubMed search revealed a total of 1257 articles, of which 256 (20.4%) were considered relevant to OA imaging. Two-hundred twenty-six (87.1%) articles involved the knee joint, while 195 (76.2%) articles involved the use of magnetic resonance imaging (MRI). The proportion of published studies involving the use of MRI was higher than previous years. An increasing number of articles were also published on imaging of subjects with joint injury and on deep learning application in OA imaging.

CONCLUSION

MRI and other imaging modalities continue to play an important role in research studies designed to better understand the pathogenesis, progression, and treatment of OA.

Somatosensory Function Influences Aberrant Gait Biomechanics Following Anterior Cruciate Ligament Reconstruction

Osteoarthritis is common following anterior cruciate ligament reconstruction (ALCR), and aberrant gait biomechanics are considered a primary contributor. Somatosensory dysfunction potentially alters gait biomechanics, but this association is unclear. Therefore, the purposes of this investigation were to compare somatosensory function between limbs and evaluate associations between somatosensory function and gait biomechanics linked to osteoarthritis development in individuals with ALCR. Seventy-three volunteers with ALCR participated. Gait biomechanics (peak vertical ground reaction force magnitude and loading rate, peak internal knee extension and valgus moments, peak knee flexion and varus angles, and quadriceps/hamstrings co-activation) were assessed as subjects walked at their preferred speed. The somatosensory function was assessed via joint position sense error (knee flexion) and vibratory perception threshold (femoral epicondyles, malleoli, and first metatarsal). Though somatosensory function did not differ between the ACLR and contralateral limbs, poorer joint position sense in the ACLR limb was associated with lower loading rates and internal knee extension moments, and greater co-activation. Poorer vibratory perception at the medial and lateral malleoli and first metatarsal head in the ACLR limb was associated with lower loading rates, greater internal knee valgus moments and varus angles, and greater co-activation. Poorer vibratory perception at the medial malleolus and first metatarsal head in the contralateral limb was associated with greater peak knee varus angles and internal knee valgus moments. These results suggest that future research evaluating rehabilitation approaches for improving somatosensory function is warranted as a potential approach for restoring normal gait biomechanics and reducing osteoarthritis risk. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:620-628, 2020.

Patients With Abnormal Limb Kinetics at 6 Months After Anterior Cruciate Ligament Reconstruction Have an Increased Risk of Persistent Medial Meniscal Abnormality at 3 Years

Background:

Several reports have shown that altered biomechanics after anterior cruciate ligament reconstruction (ACLR) are associated with the development of posttraumatic osteoarthritis. However, it is not fully understood whether altered biomechanics are associated with meniscal changes after ACLR.

Purpose:

To investigate changes in gait and landing biomechanics over a 3-year period and their correlation with meniscal matrix alterations present before and after ACLR through use of magnetic resonance T1ρ/T2 mapping, which can allow detection of early meniscal degeneration.

Study Design:

Cohort study; Level of evidence, 2.

Methods:

A total of 36 patients with ACLR and 14 healthy controls were included in this study. All patients underwent magnetic resonance imaging and biomechanical analysis during gait of the injured knee and contralateral knee preoperatively and at 6 months, 1 year, 2 years, and 3 years after ACLR, as well as biomechanical analysis during drop-landing from 6 months to 3 years postoperatively. To evaluate biochemical changes of the mensical matrix, T1ρ/T2 relaxation times of the meniscus were calculated.

Results:

Mean T1ρ/T2 values of ACLR knees were significantly higher than values in the contralateral and control knees in the posterior lateral and medial horns up to 1 year after surgery; however, the differences were not seen at 3 years after surgery. The ACLR knee exhibited significantly lower peak knee flexion moment and angle during gait at 6 months compared with baseline and continued to decrease until 3 years. The ACLR knee exhibited significantly lower peak vertical ground-reaction force and peak knee flexion moment and angle during landing at 6 months. However, the differences were no longer present at 3 years. Biomechanics at 6 months had significant correlations with changes of mean T1ρ/T2 values in the medial posterior horn from 6 months to 3 years after ACLR.

Conclusion:

Although mean T1ρ/T2 values of meniscus seen before ACLR improved after 3 years, approximately 30% of patients with ACLR did not show decreases from 6 months to 3 years. Patients with abnormal lower limb kinetics of the ACLR knee at 6 months showed less recovery in the medial posterior horn from 6 months to 3 years, suggesting that biomechanical parameters during the early stage of recovery might be potential biomarkers for predicting persistent medial meniscal abnormality after ACLR.

Osteoarthritis and ACL Reconstruction-Myths and Risks

PURPOSE OF REVIEW

Anterior cruciate ligament (ACL) injury is one of the most common ligamentous injuries suffered by athletes participating in cutting sports. A common misperception is that ACL reconstruction can prevent osteoarthritis (OA). The goal of this paper is to review and discuss the contributing factors for the development of OA following ACL injury.

RECENT FINDINGS

There has been interesting new research related to ACL reconstruction. As understanding of knee biomechanics following ACL injury and reconstruction has changed over time, many surgeons have changed their surgical techniques to low anterior drilling to position their femoral tunnel in an attempt to place the ACL in a more anatomic position. Even with this change in the femoral tunnel position, 85% of knees following ACL reconstruction have abnormal tibial motion compared to contralateral non-injured knees. Studies have shown increases in inflammatory cytokines in the knee following ACL injury, and newer MRI sequences have allowed for earlier objective detection of degenerative changes to cartilage following injury. Recent studies have shown that injecting IL-1 receptor antagonist and corticosteroids can modulate the post-injury inflammatory cascade. ACL reconstruction does not prevent the development of OA but can improve knee kinematics and reduce secondary injury to the cartilage and meniscus. Advancements in imaging studies has allowed for earlier detection of degenerative changes in the knee, which has allowed researchers to study how new interventions can alter the course of degenerative change in the knee following ACL injury.

Gait Mechanics and T1ρ MRI of Tibiofemoral Cartilage 6 Months after ACL Reconstruction

PURPOSE

Aberrant walking biomechanics after anterior cruciate ligament reconstruction (ACLR) are hypothesized to be associated with deleterious changes in knee cartilage. T1ρ magnetic resonance imaging (MRI) is sensitive to decreased proteoglycan density of cartilage. Our purpose was to determine associations between T1ρ MRI interlimb ratios (ILR) and walking biomechanics 6 months after ACLR.

METHODS

Walking biomechanics (peak vertical ground reaction force (vGRF), vGRF loading rate, knee extension moment, knee abduction moment) were extracted from the first 50% of stance phase in 29 individuals with unilateral ACLR. T1ρ MRI ILR (ACLR limb/uninjured limb) was calculated for regions of interest in both medial and lateral femoral (LFC) and medial and lateral tibial condyles. Separate, stepwise linear regressions were used to determine associations between biomechanical outcomes and T1ρ MRI ILR after accounting for walking speed and meniscal/chondral injury (P ≤ 0.05).

RESULTS

Lesser peak vGRF in the ACLR limb was associated with greater T1ρ MRI ILR for the LFC (posterior ΔR = 0.14, P = 0.05; central ΔR = 0.15, P = 0.05) and medial femoral condyle (central ΔR = 0.24, P = 0.01). Lesser peak vGRF loading rate in the ACLR limb (ΔR = 0.21, P = 0.02) and the uninjured limb (ΔR = 0.27, P = 0.01) was associated with greater T1ρ MRI ILR for the anterior LFC. Lesser knee abduction moment for the injured limb was associated with greater T1ρ MRI ILR for the anterior LFC (ΔR = 0.16, P = 0.04) as well as the posterior medial tibial condyle (ΔR = 0.13, P = 0.04).

CONCLUSION

Associations between outcomes related to lesser mechanical loading during walking and greater T1ρ MRI ILR were found 6 months after ACLR. Although preliminary, our results suggest that underloading of the ACLR limb at 6 months after ACLR may be associated with lesser proteoglycan density in the ACLR limb compared with the uninjured limb.

Knee Loading After ACL-R Is Related to Quadriceps Strength and Knee Extension Differences Across the Continuum of Care

Background:

Quadriceps strength and knee extension are believed to be important in the ability to effectively load the knee after anterior cruciate ligament (ACL) reconstruction (ACL-R).

Purpose:

To compare quadriceps strength (QUADS), side-to-side knee extension difference (ExtDiff), and knee energy absorption contribution (EAC) in patients preoperatively, 12 weeks postoperatively, and at return to sport (RTS). A secondary aim was to determine how the factors of QUADS and ExtDiff contributed to the ability to load the knee (knee EAC) at each of the 3 time points.

Study Design:

Case series; Level of evidence, 4.

Methods:

Overall, 41 individuals (mean ± SD age, 15.95 ± 1.63 years) were enrolled in this study. QUADS, ExtDiff, and knee EAC during a double-limb squat were collected preoperatively, 12 weeks postoperatively, and at RTS. Isokinetic QUADS was collected at 60 deg/s, normalized to body mass, and averaged across 5 trials. Knee extension was measured with a goniometer, and ExtDiff was calculated for analyses. Knee EAC was measured during double-limb squat descent and was calculated as a percentage of total energy absorption for the limb. Observations were obtained from both the surgical and nonsurgical limbs at the 3 time points. A mixed regression model with random intercept to compare change over the 3 time points was used, and a model selection was conducted with Akaike information criteria. Significance was set at P < .05.

Results:

Surgical limb QUADS was significantly lower preoperatively (mean ± SD, 1.37 ± 0.49 N·m/kg; P = .0023) and at 12 weeks (1.11 ± 0.38 N·m/kg; P < .0001) than at RTS (1.58 ± 0.47 N·m/kg). Nonsurgical limb QUADS was also significantly lower preoperatively (2.01 ± 0.54 N·m/kg; P < .0256) and at 12 weeks (2.03 ± 0.48 N·m/kg; P < .0233) than at RTS (2.18 ± 0.54 N·m/kg). Knee EAC for the surgical limb was significantly lower at 12 weeks than at RTS (40.98% ± 13.73% vs 47.50% ± 12.04%; P < .0032), and ExtDiff was significantly greater preoperatively than at RTS (–2.68° ± 3.19° vs –0.63° ± 1.43°; P < .0001). Preoperatively, QUADS for both the surgical (P < .0003) and nonsurgical (P = .0023) limbs was a significant predictor of surgical limb knee EAC, explaining 33.99% of the variance. At 12 weeks, surgical limb QUADS was a significant predictor (P < .0051) of surgical limb knee EAC, explaining 18.83% of the variance. At RTS, ExtDiff was a significant predictor (P = .0201) of surgical limb knee EAC, explaining 12.92% of the variance.

Conclusion:

The ability to load the knee after ACL injury changes across the continuum of care and is related to QUADS and ExtDiff. These results provide clinicians with insight into potential contributing factors that may limit knee loading during the rehabilitation process.

Quadriceps weakness associates with greater T1ρ relaxation time in the medial femoral articular cartilage 6 months following anterior cruciate ligament reconstruction

PURPOSE

Quadriceps weakness following anterior cruciate ligament reconstruction (ACLR) is linked to decreased patient-reported function, altered lower extremity biomechanics and tibiofemoral joint space narrowing. It remains unknown if quadriceps weakness is associated with early deleterious changes to femoral cartilage composition that are suggestive of posttraumatic osteoarthritis development. The purpose of the cross-sectional study was to determine if quadriceps strength was associated with T1ρ relaxation times, a marker of proteoglycan density, of the articular cartilage in the medial and lateral femoral condyles 6 months following ACLR. It is hypothesized that individuals with weaker quadriceps would demonstrate lesser proteoglycan density.

METHODS

Twenty-seven individuals (15 females, 12 males) with a patellar tendon autograft ACLR underwent isometric quadriceps strength assessments in 90°of knee flexion during a 6-month follow-up exam. Magnetic resonance images (MRI) were collected bilaterally and voxel by voxel T1ρ relaxation times were calculated using a five-image sequence and a monoexponential equation. Following image registration, the articular cartilage for the weight-bearing surfaces of the medial and lateral femoral condyles (MFC and LFC) were manually segmented and further sub-sectioned into posterior, central and anterior regions of interest (ROI) based on the corresponding meniscal anatomy viewed in the sagittal plane. Univariate linear regression models were used to determine the association between quadriceps strength and T1ρ relaxation times in the entire weight-bearing MFC and LFC, as well as the ROI in each respective limb.

RESULTS

Lesser quadriceps strength was significantly associated with greater T1ρ relaxation times in the entire weight-bearing MFC (R² = 0.14, P = 0.05) and the anterior-MFC ROI (R² = 0.22, P = 0.02) of the ACLR limb. A post hoc analysis found lesser strength and greater T1ρ relaxation times were significantly associated in a subsection of participants (n = 18) without a concomitant medial tibiofemoral compartment meniscal or chondral injury in the entire weight-bearing MFC, as well as anterior-MFC and central-MFC ROI of the ACLR and uninjured limb.

CONCLUSIONS

The association between weaker quadriceps and greater T1ρ relaxation times in the MFC suggests deficits in lower extremity muscle strength may be related to cartilage composition as early as 6 months following ACLR. Maximizing quadriceps strength in the first 6 months following ACLR may be critical for promoting cartilage health early following ACLR.

LEVEL OF EVIDENCE

Prognostic level 1.

Longitudinal Changes in the Total Knee Joint Moment After Anterior Cruciate Ligament Reconstruction Correlate With Cartilage Thickness Changes

This study investigated associations between changes in the total joint moment (TJM) at the knee and changes in cartilage thickness after anterior cruciate ligament reconstruction (ACLR). Seventeen subjects (five males; age: 29.6 ± 7.3 years) with unilateral ACLR underwent gait analysis and magnetic resonance imaging at baseline (2.2 ± 0.3 years post-ACLR) and at long-term follow-up (7.7 ± 0.7 years post-ACLR). Knee loading was assessed using the TJM, and differences in loading were analyzed using repeated measures analysis of variance. Pearson correlation coefficients assessed associations between changes in TJM and changes in (medial-to-lateral) M/L femoral cartilage thickness ratios in the ACLR limb. Bilaterally, there was no significant change in the magnitude of the TJM first peak (TJM1), however, there was a significant increase in the percent contribution of the knee flexion moment (KFM) (p < 0.001) and decrease in the percent contribution of the knee adduction moment (KAM) to TJM1 (p < 0.001). The change in the percent contributions of KFM and KAM to TJM1 were associated with changes in M/L femoral cartilage thickness in the ACLR limb. Specifically, subjects with smaller increases in KFM contribution (R = 0.521, p = 0.032) and smaller decreases in KAM contribution (R = -0.521, p = 0.032) had a reduction in the M/L ratio in the central femoral subregion over the follow-up period, with similar trends in the external femoral subregion. The study results provide new insight into changes in the loading environment at the knee joint prospectively following ACL reconstruction and give evidence that there are modifiable gait metrics that are associated with cartilage changes after ACLR. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1546-1554, 2019.

Abnormal Biomechanics at 6 Months Are Associated With Cartilage Degeneration at 3 Years After Anterior Cruciate Ligament Reconstruction

PURPOSE

To investigate the changes in landing biomechanics over a 3-year period and their correlation with cartilage degenerative changes in the medial tibiofemoral joint of the knee after anterior cruciate ligament reconstruction (ACLR) using magnetic resonance T1ρ mapping.

METHODS

Thirty-one anterior cruciate ligament-injured patients underwent magnetic resonance imaging of the injured knee before ACLR and 3 years after ACLR, as well as biomechanical analysis of a drop-landing task at 6 months and 3 years after ACLR. Sixteen healthy individuals were recruited and underwent knee magnetic resonance imaging and biomechanical assessment during a drop-landing task. T1ρ cartilage relaxation times were calculated for the medial femur and tibia.

RESULTS

ACLR patients exhibited increased peak vertical ground reaction force (VGRF), VGRF impulse, peak knee flexion moment (KFM), and KFM impulse from 6 months to 3 years (P < .001 for each). Although the ACLR knees showed significantly lower peak VGRF and KFM at 6 months (P < .001 for both) when compared with the controls, there were no significant differences at 3 years. At 3 years, ACLR patients showed higher T1ρ values over the medial femur (P < .001) and tibia (P = .012) when compared with their preoperative values and with healthy control values. Within the ACLR group, side-to-side differences in peak VGRF and sagittal knee biomechanics at 6 months were associated with increased T1ρ values from baseline to 3 years.

CONCLUSIONS

The results of this longitudinal study show that landing biomechanics are altered after ACLR but biomechanical abnormalities tend to recover at 3 years after ACLR. Differences in lower-extremity mechanics during a landing task at 6 months may be associated with cartilage degeneration at 3 years after anterior cruciate ligament injury and reconstruction.

LEVEL OF EVIDENCE

Level II, prospective trial.

Acute Effects of Barefoot and Minimalist Footwear on Medial Tibiofemoral Compartment Loading During Running: A Statistical Parametric Mapping Approach

The current investigation examined the effects of running barefoot and in minimalist footwear on medial tibiofemoral compartment loading, compared to conventional running trainers. Fifteen male runners ran over a force platform in five different footwear conditions (barefoot, Vibram five-fingers (Footwear A), Inov-8 (Footwear B) Nike-Free (Footwear C), and running trainer) whilst lower extremity kinematics were examined using a three-dimensional camera system. Medial compartment loading during the stance phase was explored using the knee adduction moment (KAM). In addition, the KAM instantaneous load rate was also calculated. Differences between footwear across the entire stance phase were examined using 1-dimensional statistical parametric mapping, whereas differences in discrete parameters were explored using one-way repeated measures ANOVA. Statistical parametric mapping revealed that Footwear B was associated with a significantly larger KAM compared to the running trainer from 15-20 and 25-30% of the stance phase and also Footwear C from 15-20% of the stance phase. The KAM instantaneous load rate was significantly larger in the barefoot (210.69 Nm/kg/s), Footwear A (200.23 Nm/kg/s) and Footwear B (186.03 Nm/kg/s) conditions in comparison to Footwear C (100.88 Nm/kg/s) and running trainers (92.70 Nm/kg/s). The findings from this study indicate that running barefoot and in minimalist footwear with the least midsole interface may place runners at increased risk of medial compartment knee OA, although further exploration using habitual barefoot / minimalist footwear users is required.

Poor Performance on Single-Legged Hop Tests Associated With Development of Posttraumatic Knee Osteoarthritis After Anterior Cruciate Ligament Injury

Background

The risk for knee osteoarthritis (OA) is substantially increased after anterior cruciate ligament (ACL) injury. Tools are needed to identify characteristics of patients after ACL injury who are most at risk for posttraumatic OA.

Purpose

To determine whether clinical measures of knee function after ACL injury are associated with the development of radiographic knee OA 5 years after injury.

Study Design

Cohort study; Level of evidence, 2.

Methods

A total of 76 athletes (mean age, 28.7 ± 11.3 years; 35.5% female) with ACL injury were included. Clinical measures of knee function (quadriceps strength, single-legged hop tests, patient-reported outcomes) were assessed after initial impairment resolution (baseline), after 10 additional preoperative or nonoperative rehabilitation sessions (posttraining), and 6 months after ACL reconstruction or nonoperative rehabilitation. Posterior-anterior bent-knee radiographs were completed at 5 years and graded in the medial compartment by use of the Kellgren-Lawrence system. Logistic regression models were used at each of the 3 time points to determine the ability of clinical measures to predict knee OA at 5 years.

Results

Of the 76 patients, 9 (11.8%) had knee OA at 5 years. After adjustment for ACL reconstruction compared with nonoperative management, ipsilateral second ACL injuries, and the presence of contralateral knee OA, clinical measures of knee function at posttraining (6-m timed hop, Knee Outcomes Survey-Activities of Daily Living Scale) explained the most variance in posttraumatic OA development at 5 years (P = .006; ▵R ², 27.5%). The 6-m hop test was the only significant posttraining predictor of OA at 5 years (P = .023; patients without OA, 96.6% ± 5.4%; patients with OA, 84.9% ± 14.1%). Similar significant group differences in hop scores and subjective knee function were present at baseline. No significant group differences in clinical measures existed at 6 months after ACL reconstruction or nonoperative rehabilitation.

Conclusion

Poor performance in single-legged hop tests early after ACL injury but not after reconstruction or nonoperative rehabilitation is associated with the development of radiographic posttraumatic knee OA 5 years after injury. Clinical measures of knee function were most predictive of subsequent OA development following an extended period of rehabilitation early after ACL injury.

Knee Joint Kinematics and Kinetics During Walking and Running After Surgical Achilles Tendon Repair

BACKGROUND

Despite the increasing incidence of Achilles tendon (AT) ruptures, there is a lack of information on the possible risks associated with regular running and walking for exercise after an injury. There are some known kinematic gait changes after an AT rupture, especially at the knee. However, it is not clear whether runners with AT ruptures may be at risk for secondary knee injuries during shod or barefoot running/walking.

PURPOSE/HYPOTHESIS

The purpose of this study was to compare the kinematics and kinetics of barefoot walking and barefoot and shod running between athletes with a history of AT ruptures and a healthy control group. We hypothesized that there would be increased knee joint loads in the affected limb of the AT rupture group, especially during shod running.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten patients who had undergone surgical treatment of a unilateral acute AT rupture (6.1 ± 3.7 years postoperatively ) and 10 control participants were matched according to age, sex, physical activity, weight, height, and footfall type. The kinematics and kinetics of barefoot walking and barefoot and shod running were recorded using a high-speed motion capture system synchronized with force platforms.

RESULTS

The main outcome measures were lower extremity joint angles and moments during the stance phase of walking and running. After AT repair, athletes had increased internal knee abduction moments during shod and barefoot running compared with the healthy control group (P < .05, η2 > 0.14). There were no significant differences in kinematics and kinetics during walking between the AT rupture and healthy control groups (P ≥ .05).

CONCLUSION

After an AT rupture, athletes had increased internal knee abduction moments during running compared with the healthy control group.

CLINICAL RELEVANCE

The increased abduction loads on the knee in patients with an AT rupture could lead to further running-related injuries. However, barefoot walking may be used as a proprioceptive exercise without an increased risk of overuse injuries in these patients.