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Background: Anterior cruciate ligament (ACL) injury increases risk for posttraumatic knee osteoarthritis (OA). Quantitative ultrashort echo time enhanced T2* (UTE-T2*) mapping shows promise for early detection of potentially reversible subsurface cartilage abnormalities after ACL reconstruction (ACLR) but needs further validation against established clinical metrics of OA risk such as knee adduction moment (KAM) and mechanical alignment. Hypothesis: Elevated UTE-T2* values in medial knee cartilage 2 years after ACLR correlate with varus alignment and higher KAM during walking. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: Twenty patients (mean age, 33.1 ± 10.5 years; 11 female) 2 years after ACLR underwent 3.0-T knee magnetic resonance imaging (MRI), radiography, and gait analysis, after which mechanical alignment was measured, KAM during walking was calculated, and UTE-T2* maps were generated. The mechanical axis and the first and second peaks of KAM (KAM1 and KAM2, respectively) were tested using linear regressions for correlations with deep UTE-T2* values in the central and posterior medial femoral condyle (cMFC and pMFC, respectively) and central medial tibial plateau (cMTP). UTE-T2* values from ACL-reconstructed patients were additionally compared with those of 14 uninjured participants (mean age, 30.9 ± 8.9 years; 6 female) using Mann-Whitney U and standard t tests. Results: Central weightbearing medial compartment cartilage of ACL-reconstructed knees was intact on morphological MRI. Mean UTE-T2* values were elevated in both the cMFC and pMFC of ACL-reconstructed knees compared with those of uninjured knees (P = .003 and P = .012, respectively). In ACL-reconstructed knees, UTE-T2* values of cMFC cartilage positively correlated with increasing varus alignment (R = 0.568). Higher UTE-T2* values in cMFC and cMTP cartilage of ACL-reconstructed knees also correlated with greater KAM1 (R = 0.452 and R = 0.463, respectively) and KAM2 (R = 0.465 and R = 0.764, respectively) and with KAM2 in pMFC cartilage (R = 0.602). Conclusion: Elevated deep UTE-T2* values of medial knee cartilage 2 years after ACLR correlate with 2 clinical markers of increased risk of medial knee OA. These results support the clinical utility of MRI UTE-T2* for early diagnosis of subsurface cartilage abnormalities. Longitudinal follow-up of larger cohorts is needed to determine the predictive and staging potential of UTE-T2* for posttraumatic OA. [ABSTRACT FROM AUTHOR]

Background: Altered knee kinematics after anterior cruciate ligament injury and reconstruction (ACLR) have been implicated in the development of posttraumatic osteoarthritis (PTOA), leading to poor long-term clinical outcomes. Purpose: This study was conducted to determine (1) whether the average knee center of rotation (KCOR), a multidimensional metric of knee kinematics, of the ACL-reconstructed knee during walking differs from that of the uninjured contralateral knee; (2) whether KCOR changes between 2 and 4 years after surgery; and (3) whether early KCOR changes predict patient-reported outcomes 8 years after ACLR. Study Design: Descriptive laboratory study. Methods: Twenty-six human participants underwent gait analysis with calculation of bilateral KCOR during walking at 2 and 4 years after unilateral ACLR. Knee injury and Osteoarthritis Outcome Score (KOOS) and Lysholm score results were collected at 2, 4, and 8 years after ACLR in 13 of these participants. Results: The ACL-reconstructed knee showed greater medial compartment motion because of pivoting about a more lateral KCOR (P = .03) than the contralateral knee at 2 years. KCOR became less lateral over time (P = .047), with values approaching those of the uninjured knee by 4 years (P = .55). KCOR was also more anterior in the ACL-reconstructed knee at 2 years (P = .02). Between 2 and 4 years, KCOR moved posteriorly in 16 (62%) and anteriorly in 10 (38%) participants. Increasing the anterior position of KCOR in the ACL-reconstructed knee from 2 to 4 years correlated with worsening clinical outcomes at 4 years (KOOS–Quality of Life, R2 = 0.172) and more strongly at 8 years (Lysholm score, R2 = 0.41; KOOS-Pain, R2 = 0.37; KOOS-Symptoms, R2 = 0.58; and KOOS–Quality of Life, R2 = 0.50). Conclusion: The observed changes to KCOR during walking between 2 and 4 years after ACLR show progressive improvement toward kinematic symmetry over the 2-year follow-up. The correlation between increasingly abnormal kinematics and worsening clinical outcomes years later in a subset of participants provides a potential explanation for the incidence of PTOA after ACLR. [ABSTRACT FROM AUTHOR]

Background: There is increasing evidence that kinematic changes after anterior cruciate ligament (ACL) injury can influence the risk for premature osteoarthritis. However, kinematics can change over time, and the factors influencing those changes remain unknown but potentially important. Hypothesis/Purpose: The purpose of this study was to perform gait analysis on a population of ACL-deficient (ACLD) subjects without knee osteoarthritis after considerable time had elapsed since their injuries. The following hypotheses were tested: (1) ACLD knees will have greater anterior femoral translation, external femoral rotation, and flexion moment as compared with healthy contralateral knees with increased time since injury; (2) side-to-side differences in anterior femoral translation and external femoral rotation are positively associated with side-to-side differences in knee flexion moment. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Nineteen subjects with unilateral ACLD (time since injury, 1-384 months) underwent gait testing. Linear regression testing was performed for significant relationships between side-to-side differences in tibial translation and rotation during stance and the amount of time since injury, as well as the relationship between differences in peak flexion moment and differences in translation and rotation. Results: There was a time dependency in side-to-side differences. Subjects with shorter times since injury had the femur of the ACLD knee more posteriorly translated and internally rotated than the femur of the contralateral knee, and subjects with longer times since injury had the femur of the ACLD knee more anteriorly translated (R2 = 0.33) and externally rotated (R2 = 0.53) than the femur of the contralateral knee. Additionally, when the population was stratified into 2 subgroups based on time after injury (shortterm: 1.4-18.7 months; long-term: 58-383.5 months), a relationship between side-to-side differences in knee flexion moment and side-to-side differences in knee translation and rotation was found for the long-term subgroup. Conclusion: The results of this study provide an understanding of the relationship between kinematics and kinetics of the ACLD knee and the amount of time since injury. They suggest that elapsed time since injury might be an important factor when the function of ACL-injured knees is interpreted as it relates to osteoarthritis. [ABSTRACT FROM AUTHOR]

Background: The incidence of anterior cruciate ligament (ACL) injury can be decreased through the use of intervention programs. However, the success of these programs is dependent on access to a skilled trainer who provides feedback; as such, these programs would benefit from a simple device with the capacity to provide high-quality feedback.Hypothesis: Feedback based on kinematic measurements from a simple inertial sensor-based system can be used to modify key ACL injury risk metrics (knee flexion angle, trunk lean, knee abduction moment) during jump landing.Study Design: Controlled laboratory study.Methods: Seventeen subjects (7 male) were tested during drop jump tasks. Their movements were measured simultaneously with inertial, optoelectronic, and force platform systems. Feedback provided to the subjects was based only on measurements from the inertial sensor-based system (knee flexion angle, trunk lean, and thigh coronal velocity). The subjects conducted a baseline session (without landing instructions), then a training session (with immediate feedback), and finally an evaluation session (without feedback). The baseline and evaluation sessions were then tested for changes in the key risk metrics.Results: The subjects increased their knee flexion angle (16.2°) and trunk lean (17.4°) after the training. They also altered their thigh coronal angular velocity by 29.4 deg/s and reduced their knee abduction moment by 0.5 %BW·Ht. There was a significant correlation (R2 = 0.55) between the change in thigh coronal angular velocity and the change in knee abduction moment.Conclusion: Subjects reduced key risk metrics for ACL injury after training with the system, suggesting the potential benefit of instrumented feedback for interventional training.Clinical Relevance: Interventional training for reducing the risk of ACL injury could be improved with a simple device that provides immediate feedback. [ABSTRACT FROM PUBLISHER]

Background: Femoroacetabular impingement (FAI) has been linked to osteoarthritis. Treatment options range from nonoperative to operative, and current outcome measures are generally subjective or not conducted under actual activities of daily living. Thus, there is a need for the use of motion capture techniques to quantitatively assess the outcome of surgical intervention for those treated for FAI.Hypothesis: The gait of FAI patients 1 year after operative treatment (arthroscopic hip reshaping) will be significantly closer to the normal range and pattern of hip flexion motion, relative to pretreatment.Study Design: Case series; Level of evidence, 4.Methods: Eleven patients between 18 and 44 years of age with diagnosed FAI were enrolled in this study. Kinematics and kinetics for this group of patients were collected using motion capture techniques before arthroscopic bone-reshaping surgery and again 1 year after surgery. Pain and perceived activity level (Tegner scale) were also collected. All collected data were compared using a paired t test.Results: Overall hip sagittal plane range of motion increased on the affected side from 27.6° ± 5.0° to 30.7° ± 4.3° (P = .02). The presence of abnormal reversals (second-order change in the slope in the hip flexion/extension curve) that was present in 5 patients preoperatively disappeared or was reduced in prevalence and magnitude in 4 of the patients postoperatively. Additionally, pain decreased and activity level increased postoperatively.Conclusion: The results supported the hypothesis that surgical intervention for FAI restores more normal patterns of gait and provides objective support that the surgical procedure is useful. The results help establish motion capture as a potential method for quantitatively assessing the outcome in FAI surgical interventions. The presence of abnormal reversals in hip flexion has been reported in end-stage hip osteoarthritis, and the presence of these reversals in FAI patients reinforces the idea of FAI being a precursor to hip osteoarthritis. [ABSTRACT FROM AUTHOR]