CONTEXT:Chronic ankle instability is associated with persistent biomechanical changes including a lateral center of pressure (COP) location during stance. Gait retraining studies generally show COP location improvements. Multiple COP processing techniques are available which may impact results. Therefore, the purpose of this study is to identify the impact of processing technique on the COP location during baseline walking and in response to intervention in people with chronic ankle instability. DESIGN:Cohort Study. METHODS:Participants with chronic ankle instability walked on an instrumented treadmill for 2 minutes (baseline), completed a vibration feedback gait retraining session, and then completed a posttest treadmill trial with no feedback. The COP location was filtered using a fourth-order Butterworth filter with a 10-Hz low-pass cutoff. Processing techniques included bounding COP data within the foot: (1) relative to the border of the lateral foot in the medial-lateral plane (Straight-Plane Technique) and (2) relative to the midline of the foot which changes with foot progression angle (Foot-Progression-Angle Technique). 1D statistical parametric mapping paired t tests were completed on absolute change scores at baseline between techniques and between baseline and posttest for each of the techniques. RESULTS:Absolute COP change scores at baseline between processing techniques were statistically different from 5% to 44% of stance phase while walking. Baseline to posttest COP locations were statistically different from 4% to 62% of stance phase (P ≤ .01) when processed with the Straight-Plane Technique. No statistically significant difference was identified using the Foot-Progression-Angle Technique. CONCLUSIONS:Interpretations of COP location and COP location changes could be impacted by processing techniques with differing reference coordinate systems. New insights into processing techniques could impact interpretations of previously published work and should be considered before comparing across studies to make broad generalizations related to the COP location.

Aberrant gait biomechanics following ACL reconstruction (ACLR) are linked to knee osteoarthritis development in adult patients. However, limited research exists to characterize walking biomechanics profiles of pediatric ACLR patients. The study purpose was to determine (1) differences in biomechanical profiles between pediatric ACLR patients (Tanner Stage I-IV) and two comparison-control groups (i.e., uninjured, matched pediatrics, adult-matched ACLR); (2) associations between biomechanical and Knee Osteoarthritis Outcomes Score (KOOS)-Child outcomes in pediatric ACLR patients. Gait biomechanics were collected in pediatric ACLR (n = 25), pediatric controls (n = 25), and adult ACLR groups (n = 25). Pediatric patients completed the KOOS-Child at the same session. A functional mixed effects model determined between-group differences in biomechanical variables. Uncorrected partial correlations, controlling for gait speed, were utilized to determine the association between discrete biomechanics and KOOS-Child scores. Pediatric ACLR patients demonstrated lesser first and second peak vertical ground reaction force (vGRF) and greater midstance vGRF than pediatric controls. Pediatric ACLR patients exhibited lesser midstance and greater late stance vGRF compared to the adult ACLR group. Pediatric ACLR patients demonstrated lesser knee flexion angle, knee extension moment, and knee abduction moment profiles compared to pediatric controls and adult ACLR patients throughout the majority of the stance phase. Greater midstance vGRF was associated with greater KOOS-Child Quality of Life scores in the contralateral limb (r = 0.54, p = 0.006). Pediatric ACLR patients exhibit unique biomechanical profiles compared to pediatric controls and adult ACLR patients; however, the associations with patient-reported outcomes remain unclear. Pediatrics may experience an exaggerated response to ACLR that may impact knee joint health.

CONTEXT:Relationships between continuous measures of walking biomechanics and post anterior cruciate ligament reconstruction (ACLR) outcomes are unclear. The purposes of this study were to: (1) determine whether continuous measures of walking vertical ground reaction force (vGRF) and knee-flexion angle (KFA) can be used to cluster patients post-ACLR and (2) compare symptom status and discrete measures of walking biomechanics between resulting clusters. DESIGN:Cross-sectional. METHODS:A Bayesian hierarchical model was used to cluster 196 patients post-ACLR (118 females; age = 21 ± 4 y; height = 1.71 ± 0.10 cm; mass = 73 ± 15 kg; time post-ACLR = 25 ± 26 mo) on involved-leg vGRF and KFA waveforms during walking. Symptom status (asymptomatic or symptomatic) was derived from Knee injury and Osteoarthritis Outcome Scores. Symptom status and discrete walking vGRF and KFA characteristics were compared between resulting patient clusters. RESULTS:Five distinct patient clusters resulted and exhibited different representative vGRF and KFA waveforms. Clusters 1 to 4 consisted of mostly asymptomatic patients (63%, n = 47; 53%, n = 49; 58%, n = 24; 74%, n = 31) and were combined to form an aggregate group. Cluster 5 consisted of mostly symptomatic patients (58%; n = 45). The aggregate group exhibited 5% greater impact peak vGRF, 42% greater excursion between impact peak and midstance vGRF minimum, greater average (18%) and instantaneous (15%) vGRF rates during early stance, and 62% greater KFA excursion between peak KFA in early stance and subsequent peak knee extension than Cluster 5. CONCLUSION:Continuous vGRF and KFA were able to cluster patients post-ACLR into distinct groups that exhibited differing symptom status and biomechanics. These results offer new insight regarding relationships between walking biomechanics and post-ACLR symptoms and can guide future research designed to manipulate walking biomechanics to improve post-ACLR outcomes.

BACKGROUND:Chronic ankle instability (CAI) is associated with abnormal joint loading and an increased risk of early joint degeneration, yet the underlying biomechanical mechanisms remain unclear. It is unknown whether altered ankle loading reflects chronic effects of repeated ankle sprains rather than a single traumatic event, and how muscle forces contribute to these differences. METHODS:Ankle joint contact forces (JCF) and muscle contributions during walking were compared among 21 uninjured controls, 21 copers (individuals with a prior ankle sprain but no persistent symptoms), and 21 individuals with CAI. Participants completed treadmill gait analysis at a self-selected speed. Musculoskeletal modeling was used to estimate muscle contributions to tri-axial ankle JCF. RESULTS:Individuals with CAI exhibited significantly lower compressive JCF compared with both uninjured controls and copers (p = 0.007), primarily due to reduced triceps surae force. Participants with CAI also demonstrated higher posteriorly directed shear JCF relative to controls and copers (p ≤ 0.008), driven mainly by increased tibialis anterior force during early stance. Additionally, individuals with CAI showed higher laterally directed shear JCF compared with uninjured controls, attributable to altered contributions from shank muscles and ground reaction forces (p ≤ 0.041). CONCLUSION:Altered ankle joint loading during walking appears specific to CAI rather than a history of ankle sprain alone. Differences in muscle force contributions distinguish CAI from successful post-sprain adaptation and suggest that rehabilitation strategies targeting muscle coordination may help restore more coper-like joint loading patterns.

Background: Gait analyses are performed following anterior cruciate ligament reconstruction (ACLR) to identify aberrant biomechanics that accelerate osteoarthritis development. However, it is unclear whether differences in participants' footwear contribute to discrepancies in findings, thus making studies incomparable. Research Question: The purpose of this study was to compare ACLR and contralateral limb walking biomechanics while individuals walked barefoot, in lab standard footwear, and in their personal footwear. Methods: Thirty-six individuals with primary unilateral ACLR underwent walking assessments while barefoot, in laboratory standard footwear, and in personal footwear. Peak sagittal and frontal plane knee moments and angles, and vertical ground reaction force (vGRF) and its accompanying loading rates (i.e., instantaneous and linear) were evaluated via 2 (limb) x 3 (footwear) repeated measure ANOVAs. Significant main or interaction effects were followed by Bonferroni-corrected paired t-tests. Results: The ACLR limb displayed smaller sagittal plane moments and angles, larger frontal plane moments, and smaller vGRF compared to the contralateral limb across all footwear conditions. Barefoot walking resulted in smaller frontal plane moments and vGRF but larger vGRF instantaneous loading rate than lab or personal footwear walking. Lab footwear resulted in smaller peak vGRF but larger vGRF instantaneous loading rate than personal footwear. Barefoot walking resulted in smaller vGRF linear loading rate than personal footwear. The ACLR limb displayed smaller vGRF linear loading rate while barefoot compared to the contralateral limb while barefoot and the ACLR limb while in personal footwear. Significance: Except for the vGRF linear loading rate, footwear did not differentially influence inter-limb gait biomechanics, thus studies that investigate inter-limb differences but utilize different footwear are comparable. However, the main effects of footwear suggest caution is warranted when comparing biomechanics from studies that utilize different footwear protocols.

Investigating the loading environment of the tibiofemoral joint is critical following anterior cruciate ligament reconstruction (ACLR), given these individuals incur a high risk of post-traumatic osteoarthritis (PTOA). Whole-body vibration (WBV) and local muscle (LMV) vibration acutely improve isometric quadriceps function and gait biomechanics linked to PTOA development, but it is unclear how vibration affects tibiofemoral contact and quadriceps forces during walking. Participants with unilateral, primary ACLR were randomized to control (n = 21, time since ACLR = 23 ± 15), WBV (n = 25, time since ACLR = 27 ± 15), or LMV (n = 23, time since ACLR = 31 ± 16) groups, and walking biomechanics were assessed before and immediately following the respective interventions. Peak medial, lateral, and total tibiofemoral contact forces, as well as rectus femoris, vastus medialis, vastus intermedius, and vastus lateralis forces, were compared between groups and across time with 2 × 3 repeated measure ANCOVAs while controlling for gait speed and time since ACLR. Medial contact force decreased following WBV (mean difference = -0.219, p = 0.001, d = -0.643) but was unaltered by LMV. Peak lateral contact, total contact, and quadriceps forces were unaltered by WBV or LMV (p > 0.05). Greater medial contact forces during gait have been implicated in the development of idiopathic osteoarthritis, and individuals with ACLR often exhibit signs of limb overloading in the later stages of recovery (e.g., > 2 years post-ACLR). WBV may offer a targeted strategy to reduce PTOA risk in those who overload the ACLR limb by decreasing medial knee compartment loading.

CONTEXT:Those with chronic ankle instability (CAI) rely more on visual information to maintain postural control. Plantar massage and ankle joint mobilization are moderately successful at improving CAI-associated postural control impairments. Manual therapies may have a larger influence on the underlying sensory strategy used to maintain postural control, but their effect on these strategies remains unknown. OBJECTIVE:To evaluate the effects of separate 2-week plantar massage and ankle joint mobilization interventions on estimates of visual reliance during single-limb stance in those with CAI and determine whether changes in visual reliance estimates were driven by concurrent changes in peripheral- or spinal-level sensorimotor function. DESIGN:Randomized controlled clinical trial. SETTING:Research laboratory. PATIENTS:Sixty participants with CAI. INTERVENTIONS:Participants were equally randomized into plantar massage, ankle joint mobilization, and control (no intervention) groups. The manual therapy groups received six 5-minute treatments of their respective interventions over a 2-week period. MAIN OUTCOME MEASURE:A percentage modulation outcome quantified an individual's reliance on visual information by estimating the weight given to visual information during eyes-open stance based on the magnitude of postural instability that occurs with vision removed. Secondary measures included joint position sense, plantar light-touch thresholds, and the H-reflex. Outcomes were captured before (baseline), immediately after (post), and 1-month (follow-up) after the 2-week intervention. RESULTS:Plantar massage resulted in significant percentage modulation changes in sagittal (P ≤ .046) but not frontal plane outcomes (P ≥ .069) relative to the control group. Joint mobilization did not alter percentage modulation changes (P ≥ .413). Significant correlations between percentage modulation changes and peripheral sensorimotor function were noted primarily at the 1-month follow-up. CONCLUSIONS:A 2-week plantar massage but not an ankle joint mobilization intervention alters sagittal plane percentage modulation values during single-limb stance in those with CAI. These changes may be driven by changes in peripheral sensorimotor function.

BACKGROUND:Altered gait biomechanics following anterior cruciate ligament reconstruction (ACLR) contribute to the 3-6 times greater risk of osteoarthritis development in this population compared to those without a knee injury. To mitigate the onset of osteoarthritis, it is necessary to understand gait recovery during the first year post-ACLR when patients have access to rehabilitative care. The purpose of this review was to compare ACLR limb gait biomechanics to the uninjured limb and healthy controls during the first year of recovery. METHODS:Online database searches of PubMed, CINAHL, Scopus, and SportDiscus were conducted from inception to January 2025. Eligibility criteria included longitudinal studies of individuals with ACL injury who underwent ACLR (≤35 years of age) with a baseline gait assessment between pre-ACLR and 6 months post-ACLR and a follow up assessment <12 months post-surgical; and cross-sectional studies that met the same criteria except for study design. Methodological quality was assessed with the Black and Downs scale. Demographic and surgical characteristics and biomechanical outcomes were extracted from each study. FINDINGS:Nine studies were included in the review. The ACLR limb gait biomechanics incrementally improved in the first year of recovery. However, the ACLR limb displayed smaller sagittal plane knee angles and internal moments and was underloaded in the first 50 % stance compared to the uninjured limb and healthy controls throughout the first year post-ACLR. Differences in frontal plane loading were inconsistent. INTERPRETATION:Aberrant gait biomechanics associated with osteoarthritis development are not resolved during the time when patients have access to care.

Aberrant gait biomechanics following anterior cruciate ligament (ACL) injury and ACL reconstruction (ACLR) are critical factors contributing to the development of knee osteoarthritis (KOA). However, it remains unknown how ACLR impacts lower extremity joint energetics and each joint's contribution to total limb energetics during walking. To compare mechanical energetics at the ankle, knee, and hip joints between ACLR limbs, contralateral, and control limbs during walking. Forty-four participants with primary unilateral ACLR (post-ACLR: 6.0 ± 0.2 months) and 44 uninjured controls were studied. Ankle, knee, and hip joint work were calculated as the time integral of the negative (energy dissipation) or positive (energy generation) regions of the respective stance-phase joint power curves. The joint-specific contribution to total limb energy dissipation and generation was calculated. ANCOVA was used to assess differences in energy dissipation and generation at the ankle, knee, and hip between ACLR, contralateral, and matched control limbs, respectively. Compared to contralateral and matched control limbs, ACLR limbs exhibited lesser energy dissipation (ACLR: -0.06 ± 0.03 J/kg; vs. contralateral: -0.12 ± 0.07; vs. control: -0.12 ± 0.04; p < 0.001, all) and generation (0.08 ± 0.03 vs. 0.11 ± 0.06 vs. 0.10 ± 0.04; p < 0.001, all) about the knee joint and lesser contribution from the knee (66.8 ± 33.0 vs. 79.8 ± 26.7 vs. 79.9 ± 23.1; p = 0.01, all) and greater contribution from the hip (30.5 ± 33.1 vs. 14.5 ± 23.5 vs. 14.7 ± 19.8; p = 0.004 and p = 0.003, respectively) to total limb generation during mid-stance. Compared to contralateral limbs and matched controls, individuals at 6 months post ACLR exhibit altered lower extremity mechanical energetics, with decreased knee contributions and a greater hip contribution during walking.

Context: Gait biomechanics and daily steps are important aspects of knee-joint loading that change after anterior cruciate ligament reconstruction (ACLR). Understanding their relationship during the first 6 months post-ACLR could help clinicians develop comprehensive rehabilitation interventions that promote optimal joint loading after injury, thereby improving longterm knee-joint health. Objectives: To compare biomechanical gait waveforms throughout stance at early time points post-ACLR in individuals with different daily step behaviors at 6 months post-ACLR and to examine how these gait waveforms compare with those of uninjured controls. Design: Case-control study. Setting: Laboratory. Patients or Other Participants: A total of 32 individuals with primary ACLR assigned to the low-step group (LSG; n = 13) or the high-step group (HSG; n = 19) based on their average daily steps at 6 months post-ACLR and 32 uninjured matched controls. Main Outcome Measure(s): Gait biomechanics were collected at 2, 4, and 6 months post-ACLR for the ACLR groups and at a single session for the control group. Knee-adduction moment, 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% CIs between groups were reported. Results: Primary results demonstrated less KFA (1%-45% versus 79%-92% of stance) and greater KEM (65%-93% of stance) at 2 months and greater knee-adduction moment (14%-20% versus 68%-92% of stance) at 4 months postACLR for the HSG compared with the LSG. Knee-adduction moment, KEM, and KFA waveforms differed across various proportions of stance at all time points between the step and control groups. Conclusions: Differences in gait biomechanics were 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 step behaviors post-ACLR.

A history of anterior cruciate ligament reconstruction (ACLR) and high body mass index (BMI) are strong risk factors for incident knee osteoarthritis. Limited research has evaluated the interaction between ACLR and high BMI on limb-level loading and early deleterious changes in cartilage health. The purpose of this study was to separately investigate the association between vertical ground reaction force (vGRF) loading profiles during gait and tibiofemoral cartilage composition in ACLR patients with high and normal BMI. Forty-three participants with primary unilateral ACLR (17 ± 14 months post-ACLR) were categorized as high (≥ 25 kg/m2; n = 18) or normal (< 25 kg/m2; n = 25) BMI and performed an overground gait at self-selected speed. For biomechanical outcomes, we calculated the differences between first peak and midstance minimum (∆vGRF1) and between the second peak and midstance minimum (∆vGRF2). T1ρ relaxation time interlimb ratios (ILR), calculated as the T1ρ relaxation time in the ACLR relative to the uninjured limb, were calculated for the medial and lateral tibia and femur. Stepwise linear regressions were used to determine associations between biomechanical outcomes and T1ρ relaxation time ILR for each region of interest. Lesser ∆vGRF1 and ∆vGRF2 in the high-BMI group significantly associated with greater T1ρ relaxation time ILR for the medial femoral condyle (ΔR2 = 0.28, p = 0.03; ΔR2 = 0.25, p = 0.04, respectively) and tibial plateau (ΔR2 = 0.55, p < 0.001; ΔR2 = 0.25, p = 0.004, respectively). Aberrant limb-level loading, characterized by less dynamic limb loading, is linked to deleterious changes in tibiofemoral cartilage in ACLR patients with high BMI, suggesting that gait retraining may be more critical for ACLR with a BMI ≥ 25 kg/m2.

Post-traumatic knee osteoarthritis (PTOA) develops rapidly after anterior cruciate ligament reconstruction (ACLR) and both high and low vertical ground reaction force (vGRF) loading rates are associated with cartilage degeneration. However, the gait characteristics that influence vGRF linear and instantaneous loading rates after ACLR are unknown. Sixty-nine individuals with ACLR (sex: 72 % female, age: 20 ± 3 years, and time since ACLR: 26 ± 16 months) walked at a self-selected pace from which the vGRF linear (slope from heel strike to peak) and instantaneous (peak of the first time derivative) loading rates were calculated. Lasso regressions were utilized to objectively identify a subset of predictor variables that influence vGRF linear and instantaneous loading rates. The identified predictors were then utilized in multiple regressions to determine the unique variance attributable to each predictor by computing Δr2 when that predictor was removed from the model. Greater gait speed (Δr2=0.019), greater medial hamstring preparatory amplitude (Δr2=0.022), and lesser peak posterior ground reaction force (pGRF) (Δr2=0.103) were associated with greater vGRF linear loading rate. Greater gait speed (Δr2=0.072), greater medial hamstring preparatory amplitude (Δ r2 = 0.016), greater anterior ground reaction force (aGRF) immediately after heel strike (Δr2=0.054), and lesser peak pGRF (Δr2=0.019) were associated with greater vGRF instantaneous loading rates. Lesser pGRF and greater aGRF immediately after heel strike explain additional variance in vGRF linear and instantaneous loading rates beyond that explained by gait speed. Future investigations should evaluate the relationship between the aGRF immediately after heel strike and pGRF with indicators of cartilage degeneration.

Vertical ground reaction force (vGRF) is a promising target for modifying aberrant gait biomechanics in individuals post-anterior cruciate ligament reconstruction (ACLR). However, an adequate sample size and arandomized, mechanistic study is needed to determine acute effects of vGRF biofeedback on biomechanical outcomes. The purpose of the study is to determine differences in discrete gait biomechanical variables (i.e., first and second peak vGRF, midstance vGRF, peak knee flexion angle (KFA), KFA range-of-motion (ROM), peak knee extension moment (KEM), and peak knee abduction moment (KAM) following a treadmill walking protocol between limbs and across four separate conditions in individuals 6-12 months post-ACLR. We utilized a randomized, cross-over mechanistic trial where participants walked for 3000 steps for three visual feedback conditions (i.e., HIGH, LOW, and SYMMETRICAL vGRF loading) and a control condition on a dual-belt treadmill. We constructed a mixed effects linear model to determine within-subject biomechanical changes between limbs and conditions. The HIGH condition elicited greater first peak vGRF, sagittal plane motion (i.e., peak KFA, KFA ROM), and peak KEM compared to the control condition (p < 0.01). The LOW condition observed first peak vGRF and KFA ROM decreases but increased peak KFA and KEM (p < 0.01) compared to the control condition. No notable biomechanical changes were observed between the SYMMETRICAL and control conditions. The HIGH condition produced acute, sagittal plane kinematic and kinetic profile improvements in ACLR individuals. vGRF is a viable target for modifying gait biomechanics; future work should determine the long-term health effects of vGRF-driven feedback treatment to improve gait profiles post-ACLR.

Context:Recurrent trauma and altered biomechanics in those with chronic ankle instability (CAI) have been linked to altered joint loading. Previous studies revealed that patients with CAI exhibit altered joint contact force (JCF) profiles relative to uninjured individuals during walking and landing. Identifying more easily obtainable outcomes that are associated with ankle JCF in those with CAI would reduce the knowledge gap between loading profiles at the ankle joint and outcomes related to CAI. Objective:To quantify how ankle JCF, structural measures, postural control, and walking biomechanics interrelate in patients with CAI and how CAI variables predict ankle JCF. Design:Cross-sectional study. Setting:Research laboratory. Patients or Other Participants:A total of 21 patients with CAI (7 men, 15 women; age = 23 ± 4 years, height = 171.6 ± 8.3 cm, mass = 71.7 ± 12.1 kg). Main Outcome Measures:Triaxial peaks, impulses, and loading rates of ankle JCF were captured. Rearfoot alignment, Star Excursion Balance Test reach distances, weight-bearing lunge test score, and peak ankle angles and moments during the stance phase of walking were also recorded. Partial Pearson r correlations and forward stepwise regressions were used to examine the relationships among the ankle JCF variables and traditional CAI-related impairments. Results:Less compressive JCF variables were associated with more rearfoot varus alignment (r = -0.53, P = .02) and greater peak inversion moment while walking (r = -0.46, P = .041). Greater posterior JCF was associated with greater peak eversion (r = 0.55, P = .01) and dorsiflexion moments while walking (r = -0.48, P = .03) as well as less rearfoot varus alignment (r = 0.51, P = .02). Similarly, greater lateral JCF variables were associated with greater dorsiflexion moment while walking (r = 0.49, P = .03) as well as less rearfoot varus alignment (r = -0.52, P = .02). Multivariate regression models partially explained ankle JCF while walking in those with CAI. Conclusions:Although our results suggest potential associations between gait biomechanics, structural measures, and postural control with ankle JCF, further research is needed to determine if targeting these factors during therapeutic interventions would modify mechanical loading at the ankle joint during walking.

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 after anterior cruciate ligament reconstruction (ACLR). Objectives To (1) determine whether specific gait biomechanical variables can accurately identify individuals with clinically significant knee-related symptoms post-ACLR and (2) determine the corresponding threshold values, sensitivity, specificity, and odds ratios for each biomechanical variable. Design Cross-sectional study. Setting Laboratory. Patients or Other Participants A total of 71 individuals (38 female, 33 male; age = 21 ± 4 years, height = 1.76 ± 0.11 m, mass = 75.38 ± 13.79 kg, time after primary unilateral ACLR = 6.2 ± 0.4 months). Main Outcome Measure(s) Three-dimensional motion capture of 5 overground walking trials was used to calculate discrete gait biomechanical variables of interest during stance phase (first and second 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. Previously established Knee Injury and Osteoarthritis Outcome Score cutoff scores were used to define patients with (ie, symptomatic; n = 51) and those without (ie, asymptomatic; n = 20) clinically significant knee-related symptoms. Separate receiver operating characteristic curves and respective areas under the curve (AUCs) were used to evaluate the capability of each biomechanical variable of interest to identify individuals with clinically significant knee-related symptoms. Results Habitual walking speed (AUC = 0.66), vGRF at midstance (AUC = 0.69), and second 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 minimum vGRF ≥ 0.82 body weights, and second peak vGRF ≤ 1.11 body weights 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 used to identify individuals with increased odds of clinically significant knee-related symptoms and potential targets for future interventions.

Background:Aberrant gait biomechanics-ie, lower knee abduction moment (KAM) impulse- are linked to the development of posttraumatic osteoarthritis after anterior cruciate ligament (ACL) injury and ACL reconstruction (ACLR). There is a clinical need to identify modifiable factors, such as kinesiophobia and pain, that may contribute to aberrant gait development after ACLR to advance multimodal rehabilitation strategies. Purpose/Hypothesis:This study aimed to determine associations between preoperative kinesiophobia and pain and gait biomechanics linked to posttraumatic osteoarthritis development at 2 and 4 months after ACLR. We hypothesized that worse preoperative kinesiophobia and pain would be associated with lower KAM impulses in the ACLR limb but not the uninjured limb at 2 and 4 months after ACLR. Study Design:Cohort study; Level of evidence, 2. Methods:Patients within 6 weeks of ACL injury and planning to undergo ACLR with bone-patellar tendon-bone autografts were recruited for the study. Preoperatively, participants completed the Tampa Scale of Kinesiophobia (TSK-11) and Knee injury and Osteoarthritis Outcome Score Pain (KOOS Pain) subscale surveys to assess kinesiophobia (ie, psychological component to pain) and knee pain, respectively. Participants returned at 2 and 4 months after ACLR to complete a 3-dimensional gait biomechanics analysis. KAM impulses during the stance phase were calculated (N*m*s/N*m) for both limbs. Associations of preoperative TSK-11 and KOOS Pain scores with KAM impulses in ACLR and uninjured limbs were analyzed using separate linear regressions. Results:A total of 36 participants (58% women; mean age, 21.4 ± 4.31 years; body mass index, 24.1 ± 3.59 kg/m2 ) completed 3 study visits. Higher preoperative kinesiophobia was associated with lower KAM impulses in the ACLR limb (R 2 = 0.14; P = .02) but not the uninjured limb (R 2 = 0.01; P = .58) at 4 months after ACLR. Preoperative KOOS Pain scores were not associated with KAM impulses in the ACLR and uninjured limbs at 2 and 4 months after ACLR (ΔR 2 range, <0.01-0.02; P range = .53-.90). Conclusion:Preoperative kinesiophobia, but not pain, was weakly associated with lower KAM impulses during early to midphases of clinical recovery at 4 months after ACLR.