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Following anterior cruciate ligament reconstruction (ACLR), patients exhibit abnormal walking mechanics and quadriceps dysfunction. Quadriceps dysfunction has been largely attributed to muscle atrophy and weakness. While important, these factors do not capture intrinsic properties of muscle that govern its ability to generate force and withstand load. While fascicle abnormalities after ACLR have been documented in early stages of recovery (<12 mo), long-term effects of ACLR on fascicle mechanics remain unexplored. We evaluated quadriceps fascicle mechanics during walking 3 years post-ACLR and examined the relationship with knee mechanics. Participants included 24 individuals with ACLR and 24 Controls. Linear mixed models compared the ACLR, Contralateral, and Controls limbs for (1) quadriceps strength, (2) fascicle architecture and mechanics, and (3) knee mechanics. No difference in strength or overall fascicle length excursions was found between limbs. The ACLR limb exhibited longer fascicles at heel strike and peak knee extension moment (P <.001–.004), and smaller fascicle angles at heel strike, peak knee extension moment, and overall suppressed fascicle angle excursions (P <.001–.049) relative to the Contralateral and/or Control limb. This indicates an abnormality in fascicle architecture and mechanics following ACLR and suggests abnormalities in contractile function that cannot be explained by muscle weakness and may contribute to long-term gait irregularities. [ABSTRACT FROM AUTHOR]

Electrically evoked torque at rest (i.e., the torque produced from supramaximal stimuli applied to a resting muscle) has been shown to be related to muscle size in healthy adults, but this relationship has not been evaluated in pathological populations where atrophy is present. This study aims to evaluate the relationship between the electrically evoked torque at rest and vastus lateralis cross-sectional area (CSA) in individuals with anterior cruciate ligament (ACL) reconstruction. Eighteen individuals with ACL reconstruction participated. Quadriceps electrically evoked torque at rest was elicited bilaterally via sex-specific, standardized supramaximal triplet stimulations. Vastus lateralis CSA was measured at 50% of thigh length using ultrasound. Pearson's r and partial correlations were used to evaluate associations between outcomes. Evoked torque at rest was positively associated with vastus lateralis CSA in the ACL reconstructed limb (r = 0.865, partial r = 0.816, P < 0.01), non-reconstructed limb (r = 0.628, partial r = 0.575, P < 0.05), and side-to-side ratios (r = 0.670, partial r = 0.659, P < 0.01). These results indicate that electrically evoked torque at rest may indirectly assess side-to-side differences in quadriceps muscle size after ACL reconstruction.

Background: Abnormal gait is common after anterior cruciate ligament reconstruction (ACLR) which may influence osteoarthritis risk in this population. Yet few gait retraining options currently exist in ACLR rehabilitation. Cueing cadence changes is a simple, low-cost method that can alter walking mechanics in healthy adults, but few studies have tested its effectiveness in an ACLR population. Here, we evaluated the acute effects of altering cadence on knee mechanics in patients 9 to 12 months post ACLR. Hypothesis: Cueing larger steps will facilitate larger knee angles and moments, while cueing smaller steps would induce smaller knee angles and moments. Study Design: Randomized cross-sectional design. Level of Evidence: Level 3. Methods: Twenty-eight patients with unilateral ACLR underwent gait assessments on a treadmill at preferred pace. Preferred walking gait was assessed first to obtain preferred cadence. Participants then completed trials while matching an audible beat set to 90% and 110% of preferred cadence in a randomized order. Three-dimensional sagittal and frontal plane biomechanics were evaluated bilaterally. Results: Compared with preferred cadence, cueing larger steps induced larger peak knee flexion moments (KFMs) and knee extension excursions bilaterally (P < 0.01), whereas cueing smaller steps only reduced knee flexion excursions (P < 0.01). Knee adduction moments remain unchanged across conditions and were similar between limbs (P > 0.05). Peak KFMs and excursions were smaller in the injured compared with uninjured limb (P < 0.01). Conclusion: Frontal plane gait outcomes were unchanged across conditions suggesting acute cadence manipulations result in mainly sagittal plane adaptations. Follow-up studies using a longitudinal cadence biofeedback paradigm may be warranted to elucidate the utility of this gait retraining strategy after ACLR. Clinical Relevance: Cueing changes in walking cadence can target sagittal plane knee loading and joint range of motion in ACLR participants. This strategy may offer high clinical translatability given it requires relatively minimal equipment (ie, free metronome app) outside of a treadmill. [ABSTRACT FROM AUTHOR]

We developed an open-sourced program that accounts for the current limitations of B-mode ultrasound and extends the clinical utility of ultrasound for assessing femoral trochlear cartilage thickness. Images were collected on 18 patients with a history of knee surgery. By failing to account for ultrasound acoustics and beam refraction, cartilage thickness was underestimated by 26% and overestimated by 0–4%, respectively (p < 0.001). Comprehensive thickness measurements achieved by measuring the Euclidean distance between every point were significantly different than traditional single-location measurements or by using the area/length (p = 0.004–0.006). Sub-regions were significantly different than all whole regions of interest (p = 0.001–0.012). [ABSTRACT FROM AUTHOR]

Background: Quadriceps weakness is common after anterior cruciate ligament (ACL) reconstruction and can alter gait mechanics. Functional resistance training (FRT) is a novel approach to retraining strength after injury, but it is unclear how it alters gait mechanics. Therefore, we tested how 3 different types of FRT devices: a knee brace resisting extension (unidirectional brace), a knee brace resisting extension and flexion (bidirectional brace), and an elastic band pulling backwards on the ankle (elastic band)–acutely alter gait kinetics in this population. Hypothesis: The type of FRT device will affect ground-reaction forces (GRFs) during and after the training. Specifically, the uni- and bidirectional braces will increase GRFs when compared with the elastic band. Study Design: Crossover study. Level of Evidence: Level 2. Methods: A total of 15 individuals with ACL reconstruction received FRT with each device over 3 separate randomized sessions. During training, participants walked on a treadmill while performing a tracking task with visual feedback. Sessions contained 5 training trials (180 seconds each) with rest between. Vertical and anterior-posterior GRFs were assessed on the ACL-reconstructed leg before, during, and after training. Changes in GRFs were compared across devices using 1-dimensional statistical parametric mapping. Results: Resistance applied via bidirectional brace acutely increased gait kinetics during terminal stance/pre-swing (ie, push-off), while resistance applied via elastic band acutely increased gait kinetics during initial contact/loading (ie, braking). Both braces behaved similarly, but the unidirectional brace was less effective for increasing push-off GRFs. Conclusion: FRT after ACL reconstruction can acutely alter gait kinetics during training. Devices can be applied to selectively alter gait kinetics. However, the long-term effects of FRT after ACL reconstruction with these devices are still unknown. Clinical Relevance: FRT may be applied to alter gait kinetics of the involved limb after ACL reconstruction, depending on the device used. [ABSTRACT FROM AUTHOR]

Context: Modifiable and nonmodifiable risk factors have been identified for sustaining a primary anterior cruciate ligament (ACL) injury; however, less research is available examining risk factors for a second injury. Identifying whether bony morphological factors are different (or more exaggerated) among those that experience a secondary ACL injury is critical to understanding if nonmodifiable risk factors are associated with a second injury. Objective: To determine if bony morphology is different among those that experience a secondary ACL reinjury as compared with those that do not. Design: Case-control. Setting: University laboratory. Participants and Interventions: ACL participants were tracked after return to play following primary reconstruction, and if individuals experienced a second ipsilateral injury (ACLx2; n = 14, 8f/6m, 17.9 ± 4.0 y), the primary clinical MRI was analyzed for bony morphological risk factors. ACLx2 participants were matched to individuals (sex, age, height, graft, gender, and activity level) that had undergone reconstruction but did not experience reinjury (ACLx1, n = 14, 8f/6m, 18.7 ± 4.0 y). Ten controls were also enrolled (5m/5f, 20.8 ±3.9 y) for the purposes of comparing the authors' ACL data against healthy knees. Main Outcome Measures: Lateral and medial posterior tibial slopes (LPTS, MPTS), notch shape index (NSI), and medial tibial plateau depth of concavity (MDC). Results: All ACL-reconstructed patients (combined ACLx1 and ACLx2 group) had a steeper LPTS than controls (d = 0.87, 95% CI 0.11-1.60, P = .023); however, no difference in LPTS was found between ACLx1 and ACLx2 (P > .05). No differences in MPTS, NSI, and MDC were found between all ACL participants (combined ACLx2 and ACLx1) and controls or between ACLx1 and ACLx2 (P > .05). Conclusions: Compared to healthy individuals, a steeper LPTS is a common bony abnormality in all ACL-injured participants. Individuals that go on to experience a second ipsilateral ACL injury do not have more exaggerated bony morphology than those that do not suggesting that differences in modifiable risk factors at return to play may contribute to reinjury. [ABSTRACT FROM AUTHOR]

Electrically evoked torque at rest (i.e., the torque produced from supramaximal stimuli applied to a resting muscle) has been shown to be related to muscle size in healthy adults, but this relationship has not been evaluated in pathological populations where atrophy is present. This study aims to evaluate the relationship between the electrically evoked torque at rest and vastus lateralis cross-sectional area (CSA) in individuals with anterior cruciate ligament (ACL) reconstruction. Eighteen individuals with ACL reconstruction participated. Quadriceps electrically evoked torque at rest was elicited bilaterally via sex-specific, standardized supramaximal triplet stimulations. Vastus lateralis CSA was measured at 50% of thigh length using ultrasound. Pearson's r and partial correlations were used to evaluate associations between outcomes. Evoked torque at rest was positively associated with vastus lateralis CSA in the ACL reconstructed limb (r = 0.865, partial r = 0.816, P <.01), non-reconstructed limb (r = 0.628, partial r = 0.575, P <.05), and side-to-side ratios (r = 0.670, partial r = 0.659, P <.01). These results indicate that electrically evoked torque at rest may indirectly assess side-to-side differences in quadriceps muscle size after ACL reconstruction. [ABSTRACT FROM AUTHOR]

Serum biomarkers may allow for the early identification of posttraumatic osteoarthritis after anterior cruciate ligament (ACL) injury and reconstruction. Homeostasis of matrix-metalloproteinase-3 (MMP-3) and type II collagen turnover biomarkers (C2C:CPII ratio) is believed to be compromised in individuals with ACL injury, yet the influence of sex, body mass index (BMI), and age on these biomarkers before and after ACL reconstruction remains unknown. To determine the relationship of sex, BMI, and age with serum levels of MMP-3 and C2C:CPII before and after ACL reconstruction. Descriptive laboratory study. Laboratory. Thirty-two (females = 18, males = 14) individuals with ACL injuries. Demographic variables and blood samples were collected before surgery and at return to activity. Serum was extracted from the blood and assays were used to quantify MMP-3 and C2C:CPII. Generalized linear mixed-effects regression models were used to assess the relationships between sex, BMI, age, time, and participant on the outcome variables. A significant time × sex interaction was identified for MMP-3 levels (P =.021), whereby MMP-3 levels were higher in males at return to activity (males, 2.71 ± 0.59 ng/mL; females, 1.92 ± 0.60 ng/mL; P =.017). Males also had higher MMP-3 levels at return to activity when compared with presurgery levels (P =.009). A main effect for age demonstrated that older age was associated with higher MMP-3 levels. No significant main or interaction effects were noted for C2C:CPII levels. Upregulation of MMP-3 serum levels may occur after ACL reconstruction, particularly in males, which may have deleterious consequences for the cartilage matrix. Sex, BMI, and time did not influence C2C:CPII ratios, but further research with larger sample sizes is needed to confirm these findings. [ABSTRACT FROM AUTHOR]