Biomechanical Threshold Values for Identifying Clinically Significant Knee-Related Symptoms Six Months Following Anterior Cruciate Ligament Reconstruction.

CONTEXT: Slower habitual walking speed and aberrant gait biomechanics are linked to clinically significant knee-related symptoms and articular cartilage composition changes linked to posttraumatic osteoarthritis (PTOA) following anterior cruciate ligament reconstruction (ACLR). OBJECTIVE: To determine specific gait biomechanical variables that can accurately identify individuals with clinically significant knee-related symptoms post-ACLR, and the corresponding threshold values, sensitivity, specificity, and odds ratios for each biomechanical variable. DESIGN: Cross-sectional analysis. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Seventy-one individuals (n=38 female; age=21±4 years; height=1.76±0.11 m; mass=75.38±13.79 kg) who were 6 months post-primary unilateral ACLR (6.2±0.4 months). MAIN OUTCOME MEASURES: 3D motion capture of 5 overground walking trials was used to calculate discrete gait biomechanical variables of interest during stance phase (1st and 2nd peak vertical ground reaction force [vGRF]; midstance minimum vGRF; peak internal knee abduction and extension moments; and peak knee flexion angle), along with habitual walking speed. Knee Injury and Osteoarthritis Outcome Scores (KOOS) was used to dichotomize patients as symptomatic (n=51) or asymptomatic (n=20) using the Englund et al. 2003 KOOS guidelines for defining clinically significant knee-related symptoms. Separate receiver operating characteristic (ROC) curves and respective areas under the curve (AUC) were used to evaluate the capability of each biomechanical variable of interest for identifying individuals with clinically significant knee-related symptoms. RESULTS: Habitual walking speed (AUC=0.66), vGRF at midstance (AUC=0.69), and 2nd peak vGRF (AUC=0.76), demonstrated low-to-moderate accuracy for identifying individuals with clinically significant knee-related symptoms. Individuals who exhibited habitual walking speeds ≤1.27 m/s, midstance vGRF ≥0.82 BW, and 2nd peak vGRF ≤1.11 BW, demonstrated 3.13, 6.36, and 9.57 times higher odds of experiencing clinically significant knee-related symptoms, respectively. CONCLUSIONS: Critical thresholds for gait variables may be utilized to identify individuals with increased odds of clinically significant knee-related symptoms and potential targets for future interventions.

Early Gait Biomechanics Linked to Daily Steps Following Anterior Cruciate Ligament Reconstruction.

CONTEXT: Gait biomechanics and daily steps are important aspects of knee joint loading that change following anterior cruciate ligament reconstruction (ACLR). Understanding their relationship during the first 6 months post-ACLR could help develop comprehensive rehabilitation interventions that promote optimal joint loading following injury, thereby improving long-term knee joint health. OBJECTIVE: Our primary objective was to compare biomechanical gait waveforms throughout stance at early timepoints post-ACLR in individuals with different daily step behaviors at 6 months post-ACLR. The secondary aim was to examine how these gait waveforms compare to those of uninjured controls. DESIGN: Case-Control Study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Individuals with primary ACLR assigned to a low (LSG) (n=13) or high step group (HSG) (n=19) based on their average daily steps at 6 months post- ACLR, and uninjured matched controls (n=32). MAIN OUTCOME MEASURE(S): Gait biomechanics were collected at 2, 4, and 6 months post-ACLR in ACLR individuals and at a single session for controls. Knee adduction moment (KAM), knee extension moment (KEM), and knee flexion angle (KFA) waveforms were calculated during gait stance and then compared via functional waveform analyses. Mean differences and corresponding 95% confident intervals between groups were reported. RESULTS: Primary results demonstrated lesser KFA (1-45%, 79-92% of stance) and greater KEM (65-93% of stance) at 2 months and greater KAM (14-20%, 68-92% of stance) at 4 months post-ACLR for the HSG compared to the LSG. KEM, KAM, and KFA waveforms differed across various proportions of stance at all timepoints between step groups and controls. CONCLUSION: Differences in gait biomechanics are present at 2 and 4 months post-ACLR between step groups, with the LSG demonstrating an overall more flexed knee and more profound stepwise underloading throughout stance than the HSG. The results indicate a relation between early gait biomechanics and later daily steps behaviors following ACLR.

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.

Femoral cartilage ultrasound echo-intensity is a valid measure of cartilage composition.

This study aimed to create a conversion equation that accurately predicts cartilage magnetic resonance imaging (MRI) T2 relaxation times using ultrasound echo-intensity and common participant demographics. We recruited 15 participants with a primary anterior cruciate ligament reconstruction between the ages of 18 and 35 years at 1-5 years after surgery. A single investigator completed a transverse suprapatellar scan with the ACLR limb in max knee flexion to image the femoral trochlea cartilage. A single reader manually segmented the femoral cartilage cross-sectional area to assess the echo-intensity (i.e., mean gray-scale pixel value). At a separate visit, a T2 mapping sequence with the MRI beam set to an oblique angle was used to image the femoral trochlea cartilage. A single reader manually segmented the cartilage cross-sectional area on a single MRI slice to assess the T2 relaxation time. A stepwise, multiple linear regression was used to predict T2 relaxation time from cartilage echo-intensity and common demographic variables. We created a conversion equation using the regression betas and then used an ICC and Bland-Altman plot to assess agreement between the estimated and true T2 relaxation time. Cartilage ultrasound echo-intensity and age significantly predicted T2 relaxation time (F = 7.33, p = 0.008, R2 = 0.55). When using the new conversion equation to estimate T2 relaxation time from cartilage echo-intensity and age, there was strong agreement between the estimated and true T2 relaxation time (ICC2,k = 0.84). This study provides promising preliminary data that cartilage echo-intensity combined with age can be used as a clinically accessible tool for evaluating cartilage composition.

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.

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.

Knee kinetics and the medial femoral cartilage cross-sectional area response to loading in indviduals with anterior cruciate ligament reconstruction.

BACKGROUND: Ultrasonography is capable of detecting morphological changes in femoral articular cartilage cross-sectional area in response to an acute bout of walking; yet, the response of femoral cartilage cross-sectional area varies between individuals. It is hypothesized that differences in joint kinetics may influence the response of cartilage to a standardized walking protocol. Therefore, the study purpose was to compare internal knee abduction and extension moments between individuals with anterior cruciate ligament reconstruction who demonstrate an acute increase, decrease, or unchanged medial femoral cross-sectional area response following 3000 steps. METHODS: The medial femoral cartilage in the anterior cruciate ligament reconstructed limb was assessed with ultrasonography before and immediately following 3000 steps of treadmill walking. Knee joint moments were calculated in the anterior cruciate ligament reconstructed limb and compared between groups throughout the stance phase of gait using linear regression and functional, mixed effects waveform analyses. FINDINGS: No associations between peak knee joint moments and the cross-sectional area response were observed. The group that demonstrated an acute cross-sectional area increase exhibited 1) lower knee abduction moments in early stance in comparison to the group that exhibited a decreased cross-sectional area response; and 2) greater knee extension moments in early stance in comparison to the group with an unchanged cross-sectional area response. INTERPRETATION: The propensity of femoral cartilage to acutely increase cross-sectional area in response to walking is consistent with less-dynamic knee abduction and knee extension moment profiles.

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.

Changes in biomechanics, strength, physical function, and daily steps after extended-release corticosteroid injections in knee osteoarthritis: a responder analysis.

INTRODUCTION/OBJECTIVE: To determine changes in gait biomechanics, quadricep strength, physical function, and daily steps after an extended-release corticosteroid knee injection at 4 and 8 weeks post-injection in individuals with knee osteoarthritis as well as between responders and non-responders based on changes in self-reported knee function. METHOD: The single-arm, clinical trial included three study visits (baseline, 4 weeks, and 8 weeks post-injection), where participants received an extended-release corticosteroid injection following the baseline visit. Time-normalized vertical ground reaction force (vGRF), knee flexion angle (KFA), knee abduction moment (KAM), and knee extension moment (KEM) waveforms throughout stance were collected during gait biomechanical assessments. Participants also completed quadricep strength, physical function (chair-stand, stair-climb, 20-m fast-paced walk) testing, and free-living daily step assessment for 7 days following each visit. RESULTS: All participants demonstrated increased KFA excursion (i.e., greater knee extension angle at heel strike and KFA at toe-off), increased KEM during early stance, improved physical function (all p < 0.001), and increased quadricep strength at 4 and 8 weeks. KAM increased throughout most of stance at 4 and 8 weeks post-injection (p < 0.001) but appears to be driven by gait changes in non-responders. Non-responders demonstrated lesser vGRF during late stance and lesser KEM and KFA throughout stance compared to responders at baseline. CONCLUSIONS: Extended-release corticosteroid injections demonstrated short-term improvements in gait biomechanics, quadricep strength, and physical function for up to 4 weeks. However, non-responders demonstrated gait biomechanics associated with osteoarthritis progression prior to the corticosteroid injection, suggesting that non-responders demonstrate more deleterious gait biomechanics prior to corticosteroid injection. Key Points • Individuals with knee osteoarthritis who were treated with extended-release corticosteroid injections demonstrated improvements in gait biomechanics and physical function for 8 weeks. • Individuals with knee osteoarthritis, who walked with aberrant walking biomechanics before treatment, failed to respond to extended-release corticosteroid treatment. • Future research should determine the mechanisms contributing to the short-term changes in gait biomechanics and physical function such as reduced inflammation.

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.

Age-, Sex-, and Graft-Specific Reference Values From 783 Adolescent Patients at 5 to 7 Months After ACL Reconstruction: IKDC, Pedi-IKDC, KOOS, ACL-RSI, Single-Leg Hop, and Thigh Strength.

OBJECTIVE: To describe age-, sex-, and graft source-specific reference values for patient-reported, physical function, and strength outcome measures in adolescents at 5 to 7 months after anterior cruciate ligament reconstruction. DESIGN: Cross-sectional study. METHODS: Data were collected at 3 universities and 2 children's hospitals. The participants completed at least one of the International Knee Documentation Committee (IKDC) Subjective Evaluation Form, Pediatric IKDC (Pedi-IKDC), Knee Injury and Osteoarthritis Outcomes Score (KOOS), and Anterior Cruciate Ligament Return to Sport After Injury (ACL-RSI) Scale. Participants also completed single-leg hop tests and/or isokinetic quadriceps and hamstrings strength assessments (at 60°/s). Reference values were summarized using descriptive statistics and stratified for age, sex, and graft source. RESULTS: Reference values were reported for common patient-reported outcomes and measures of physical function and strength from 783 participants (56% females, age = 16. 4 ± 2.0 years) who were in early adolescence (12-14 years, N = 183, 52% females), middle adolescence (15-17 years, N = 456, 58% females), or late adolescence (18-20 years, N = 144, 55% females). Three hundred seventy-nine participants (48.4%) received a bone-patellar tendon-bone autograft, 292 participants (37.3%) received hamstring tendon autograft, and 112 participants (14.3%) received autograft or allograft from an alternative source. CONCLUSION: Reference values for common patient-reported outcomes and measures of physical function and strength differed depending on a patient's age, sex, and graft source. Using patient-specific reference values, in addition to previously described age-appropriate cutoff values, may help clinicians monitor and progress patients through rehabilitation and return to physical activity after anterior cruciate ligament reconstruction. J Orthop Sports Phys Ther 2023;53(4):1-8. Epub: 23 January 2023. doi:10.2519/jospt.2023.11389.

Improvement Trajectories in Patient-Reported Outcomes Between Males and Females After Anterior Cruciate Ligament Reconstruction.

CONTEXT: Patient-reported outcomes (PROs) are used to track recovery and inform clinical decision-making after anterior cruciate ligament reconstruction (ACLR). Whether sex influences the trajectory of improvements in PROs over time post-ACLR remains unclear. OBJECTIVES: To (1) examine the effect of sex on the association between months post-ACLR and Knee injury and Osteoarthritis Outcome Score (KOOS) Quality of Life (QOL) scores in individuals with ACLR and (2) assess sex differences in the KOOS QOL score at selected timepoints post-ACLR. DESIGN: Cross-sectional study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 133 females (20± 3 years) and 85 males (22 ± 4 years) within 6 to 60 months of primary, unilateral ACLR. MAIN OUTCOME MEASURE(S): The KOOS QOL was completed at a single follow-up timepoint post-ACLR. A multivariate linear regression model was calculated to assess the interaction of sex on the association between months post-ACLR and KOOS QOL score. Sex-specific linear regression models were then used to predict KOOS QOL estimated marginal means at each clinical timepoint (6, 12, 24, 36, 48, and 60 months post-ACLR) and compare the sexes. RESULTS: In the primary model (R2 = 0.16, P < .0001), a significant interaction existed between sex and time post-ACLR (ß = -0.46, P < .01). Greater months post-ACLR were associated with better KOOS QOL scores for males (R2 = 0.29, ß = 0.69, P < .001); months post-ACLR was a weaker predictor of KOOS QOL scores for females (R2 = 0.04, ß = 0.23, P < .02). Estimated marginal means for KOOS QOL scores were greater for males than females at 36 months (t210 = 2.76, P < .01), 48 months (t210 = 3.02, P < .01), and 60 months (t210 = 3.09, P = .02) post-ACLR. CONCLUSIONS: Males exhibited PRO improvement post-ACLR as the months post-ACLR increased, whereas females did not demonstrate the same magnitude of linear increase in KOOS QOL score. Females may require extended intervention to improve clinical outcomes post-ACLR and address a plateau in QOL score.

Validation of a Survey to Characterize Barriers to Physical Activity After Anterior Cruciate Ligament Reconstruction.

CONTEXT: Although 84% of patients expected to return to activity within 1 year of anterior cruciate ligament (ACL) reconstruction (ACLR), as few as 24% will return to their preinjury level of activity. By considering a patient's perceptions of reengagement in activity after ACLR, clinicians and researchers may be better equipped to implement interventions that are patient centered. OBJECTIVE: To describe the validation of the ACL Reasons survey, a tool to aid clinicians and researchers in understanding patient perceptions of barriers to physical activity (PA) engagement after ACLR. DESIGN: Cross-sectional study. PATIENTS OR OTHER PARTICIPANTS: The ACL Reasons survey was administered via Qualtrics to 78 patients 6 to 24 months after primary, unilateral ACLR. Patients were categorized as active, more challenging, or less active based on their responses to the ACL Reasons. MAIN OUTCOME MEASURE(S): Development of the ACL Reasons survey occurred via an iterative process of drafting and revising based on feedback from a team of external expert reviewers. Tegner activity level, Marx activity score, the Knee injury and Osteoarthritis Outcomes Score (KOOS), ACL Return to Sport after Injury score, and Tampa Scale of Kinesiophobia score were compared among groups using analysis-of-variance and Kruskal Wallis tests. RESULTS: Groups differed based on Tegner activity level (P < .001), Marx activity score (P = .01), KOOS pain score (P = .02), KOOS symptom score (P = .04), KOOS sports and recreation score (P < .001), KOOS quality of life score (P < .001), ACL Return to Sport after Injury score (P < .001), and Tampa Scale of Kinesiophobia score (P < .001), with the less active group performing worse on each. Knee symptoms, fear of knee symptoms or movement, and fear of injury were the most common reasons for the change in PA engagement. CONCLUSIONS: These results support the validity of the ACL Reasons survey as a tool for identifying barriers to PA engagement after ACLR. This tool may help facilitate communication between patients with ACLR and their health care providers to enhance patient-centered care.

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.

Adolescents Are Less Physically Active Than Adults After Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Sources of physical activity (PA) and motivation for return to sport after anterior cruciate ligament reconstruction (ACLR) differ between adolescents and adults. It is unclear whether these differences influence participation in PA during the first year after ACLR when individuals are transitioning from rehabilitative care to unrestricted activity. PURPOSE: To compare device-assessed measures of PA between adolescents and adults at 6 to 12 months after ACLR. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Included were 22 adolescents (age, 15.9 ± 1.2 years; time since surgery = 8.0 ± 2.1 months) and 23 adults (age, 22.5 ± 5.0 years; time since surgery = 8.2 ± 2.1 months) who were cleared for unrestricted PA after primary unilateral ACLR. Participants were considered physically active if they met their age-specific United States Department of Health and Human Services PA guidelines. Participants wore an accelerometer-based PA monitor for at least 7 days. Daily minutes of moderate to vigorous-PA (MVPA) and daily step counts were reported and compared between age groups using analysis of covariance, with monitor wear time and sex included as covariates. The association between age group and meeting age-specific PA guidelines was assessed using binary logistic regression and reported as an odds ratio. RESULTS: Adults with ACLR participated in 16 minutes more MVPA per day (49 ± 22 vs 33 ± 16 minutes per day; P < .001) and took 2212 more steps per day (8365 ± 2294 vs 6153 ± 1765 steps per day; P < .001) when compared with adolescent participants. In addition, 83% of adults were physically active, compared with 9% of adolescents (odds ratio = 60.2; 95% CI, 7.6-493.4). CONCLUSION: Adolescents with ACLR were less physically active than adults with ACLR, and only 9% of adolescents met aerobic PA guidelines. This is concerning because PA patterns adopted early in life are predictive of PA patterns in adulthood. Our findings indicate a need to better understand underlying causes of reduced PA among adolescents with ACLR and to develop intervention strategies that promote engagement in adequate PA after rehabilitation.

Adolescent Patient, Parent, and Clinician Perceptions of Rehabilitation After Anterior Cruciate Ligament Reconstruction: A Qualitative Study.

CONTEXT: Rehabilitation after anterior cruciate ligament reconstruction (ACLR) is challenging for adolescent patients concurrently experiencing growth and development, changes in attitudes and social interactions, and a gradual shift toward independence. OBJECTIVE: To examine the perceptions of information sharing and interpersonal communication among adolescent patients going through ACLR, their parents, and physical therapists (PTs) treating adolescent patients with ACLR. DESIGN: Cross-sectional study. SETTING: University-affiliated sports medicine clinic. PATIENTS OR OTHER PARTICIPANTS: Nine adolescent patients who had recently completed physical rehabilitation after ACLR, one of their parents, and PTs who treated adolescent patients with ACLR were recruited and enrolled. MAIN OUTCOME MEASURE(S): Participants completed semistructured interviews. The interview scripts for patients, parents, and PTs intentionally addressed the same topics, with only minor modifications in wording as appropriate for each role. All interviews were recorded, transcribed verbatim, and analyzed using a hybrid of deductive and inductive coding by trained members of the study team. RESULTS: Patients, parents, and PTs perceived that interpersonal dynamics (eg, communication, external motivation) and stakeholder knowledge (eg, understanding of the psychological consequences of injury) influenced intrapersonal experiences (eg, emotional response, intrinsic motivation) during rehabilitation after ACLR. Additionally, patients and parents indicated that a lack of information about the rehabilitation process hindered their ability to obtain additional information from the PT and surgeon. CONCLUSIONS: Participants from all stakeholder groups reported that orthopaedic surgeons and other members of the health care team may consider being more consistent when setting expectations, physical restrictions, and recovery timelines.

Knee symptoms do not affect walking biomechanics among women 6 months after anterior cruciate ligament reconstruction.

Women with anterior cruciate ligament reconstruction report worse pain and knee-related symptoms, and also exhibit biomechanical changes that may be related to knee osteoarthritis (OA) development. This is particularly concerning as symptom state has been previously associated with knee OA development. The purpose of this study was to compare lower extremity walking biomechanics between women (age: 21.40 ± 8.54 years) experiencing clinically significant knee-related symptoms and women with acceptable symptoms 6 months following surgery. Twenty-eight women with history of primary, unilateral anterior cruciate ligament reconstruction who completed a lower extremity walking biomechanics assessment 6 months following surgery were included in this analysis. Women were dichotomized as experiencing acceptable or clinically significant knee symptoms according to Knee injury and OA Outcomes Score cut-offs described by Englund et al. Walking biomechanics were compared between women with clinically significant and acceptable symptoms using one-way analysis of covariances for involved limb biomechanics. Biomechanical variables of interest were: peak vertical ground reaction forces (vGRFs), vGRF loading rates, knee flexion angles, knee extension moments, knee adduction angles, and knee adduction moments, and gait speed. Nearly 60% of women reported clinically significant knee symptoms 6 months postoperative. There were no statistically significant differences between symptom groups for walking biomechanics and gait speed outcomes. These findings suggest patient reported knee symptoms may not be a primary influence on walking biomechanics 6 months following anterior cruciate ligament reconstruction. Though, longitudinal assessment of changes in symptom state and walking biomechanics may be warranted as poorer walking biomechanics and symptoms are indicators of knee OA.

Linking Gait Biomechanics and Daily Steps After ACL Reconstruction.

PURPOSE: Aberrant biomechanics and altered loading frequency are associated with poor knee joint health in osteoarthritis development. After anterior cruciate ligament reconstruction (ACLR), individuals demonstrate underloading (lesser vertical ground reaction force (vGRF)) with stiffened knee gait biomechanics (lesser knee extension moment (KEM) and knee flexion angle) and take fewer daily steps as early as 6 months after surgery. The purpose of this cross-sectional laboratory study is to compare gait biomechanics throughout stance between individuals 6-12 months after ACLR who take the lowest, moderate, and highest daily steps. METHODS: Individuals with primary, unilateral history of ACLR between the ages of 16 and 35 yr were included (n = 36, 47% females; age, 21 ± 5 yr; months since ACLR, 8 ± 2). Barefoot gait biomechanics of vGRF (body weight), KEM (body weight × height), and knee flexion angle during stance were collected and time normalized. Average daily steps were collected via a waist-mounted accelerometer in free-living settings over 7 d. Participants were separated into tertiles based on lowest daily steps (3326-6042 daily steps), moderate (6043-8198 daily steps), and highest (8199-12,680 daily steps). Biomechanical outcomes of the ACLR limb during stance were compared between daily step groups using functional waveform gait analyses. RESULTS: There were no significant differences in sex, body mass index, age, or gait speed between daily step groups. Individuals with the lowest daily steps walk with lesser vGRF and lesser KEM during weight acceptance, and lesser knee flexion angle throughout stance in the ACLR limb compared with individuals with highest and moderate daily steps. CONCLUSIONS: After ACLR, individuals who take the fewest daily steps also walk with lesser vGRF during weight acceptance and a stiffened knee strategy throughout stance. These results highlight complex interactions between joint loading parameters after ACLR.

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.

Assessing Physical Activity After ACL Injury: Moving Beyond Return to Sport.

CONTEXT: Return to sport is widely utilized by sports medicine researchers and clinicians as a primary outcome of interest for successful recovery when working with young patients who have undergone anterior cruciate ligament (ACL) reconstruction (ACLR). While return-to-sport outcomes are effective at tracking progress post-ACLR, they are limited because they do not necessarily capture physical activity (PA) engagement, which is important to maintain knee joint health and reduce the risk of noncommunicable diseases. Therefore, there is a critical need (1) to describe current PA participation and measurement recommendations; (2) to appraise common PA measurement approaches, including patient-reported outcomes and device-based methodologies; and (3) to provide clinical recommendations for future evaluation. EVIDENCE ACQUISITION: Reports of patient-reported or device-based PA in patients with ACL injury were acquired and summarized based on a PubMed search (2000 through July 2020). Search terms included physical activity OR activity AND anterior cruciate ligament OR ACL. STUDY DESIGN: Clinical review. LEVEL OF EVIDENCE: Level 5. RESULTS: We highlight that (1) individuals with ACLR are 2.36 times less likely to meet the US Department of Health and Human Services PA recommendations even when reporting successful return to sport, (2) common patient-reported PA assessments have significant limitations in the data that can be derived, and (3) alternative patient-reported and device-based assessments may provide improved assessment of PA in this patient population. CONCLUSION: Clinicians and researchers have relied on return to sport status or self-reported PA participation via surveys. These approaches are not consistent with current recommendations for PA assessment and do not allow for comparison with contemporary PA recommendations or guidelines. Return to sport, patient-reported outcome measures, and device-based assessment approaches should be used in complementary manners to comprehensively assess PA participation after ACLR. However, appropriate techniques should be used when assessing PA in adult and adolescent populations.