Anterior Cruciate Ligament Reconstruction Participants Research Articles

Knee proprioception four months after anterior cruciate ligament reconstruction: impact of limb dominance, anterolateral procedure, and association with readiness to return to sport.

BackgroundKnee proprioception may be compromised after anterior cruciate ligament reconstruction (ACLR), but associated factors and impact remain unclear. This study evaluated knee proprioception 4 months after primary ACLR, compared with healthy controls, and explored the impacts of leg dominance, anterolateral procedures (AEAPs), and their association with psychological readiness to return to sports. MethodsThis prospective cohort study included 30 ACLR participants and 20 healthy controls. Isokinetic testing measured knee strength and proprioception, using passive joint position sense (JPS1: detection, JPS2: repositioning) and kinesthesia (threshold to detection of passive motion). At 8 months, ACLR participants completed the ACL-RSI scale to assess psychological readiness to return to sports. ResultsAt 4 months postoperative, kinesthesia was better in the operated limb than the non-operated limb (p= 0.008), but position sense did not differ significantly. There were no significant differences in kinesthesia or position sense between ACLR participants and controls. The operated limb had worse JPS2 if the ACLR was on the non-dominant side. Proprioception was unaffected by AEAPs, and only repositioning showed a moderate, non-significant correlation with ACL-RSI (r= -0.377). ConclusionAt 4 months post-ACLR, kinesthesia improved in the operated leg; dominance influenced position sense, highlighting the need for personalized rehabilitation.

Longitudinal assessment of knee joint proprioception using weight-bearing and non-weight-bearing tests throughout rehabilitation after anterior cruciate ligament reconstruction

ObjectiveEvaluate active knee joint position sense (JPS) throughout rehabilitation after anterior cruciate ligament reconstruction (ACLR). DesignLongitudinal. SettingMotion laboratory. ParticipantsTwenty-two individuals post-ACLR and 22 activity-matched non-injured controls performed weight-bearing and non-weight-bearing knee JPS tests. The ACLR participants performed at three functional timepoints: T1, able to perform single-leg sit-to-stand; T2, able to hop maximally; T3, cleared for return to sports. Controls performed on one occasion. Main outcome measuresConstant, absolute, variable errors (CE, AE, VE) and interlimb symmetry estimates (100% signifying perfect symmetry), for 40° and 65° knee flexion target angles. ResultsFor the weight-bearing 40° condition, CE and AE of the ACLR knee significantly increased from T1 to T2 (P = 0.010) and T1 to T3 (P = 0.002). Consequently, interlimb asymmetry for AE significantly increased from T1 (AEsym% = 101.2% ± 55.4%) to T3 (AEsym% = 139.7% ± 54.8%). Compared to controls, AE for the ACLR knee was significantly smaller at T1 (P = 0.016). No other significant differences were observed. ConclusionsSmaller JPS errors at early rehabilitation while weight-bearing may have been due to heightened quadriceps activation and increased γ motor neuron sensitivity, compensating for deficient ACL mechanoreceptors. In contrast, non-weight-bearing testing did not reveal changes over time. Clinicians are advised to consider these distinctions when assessing proprioception at different rehabilitation stages.

Lower limb coordination patterns following anterior cruciate ligament reconstruction:A longitudinal study: Longitudinal lower limb coordination patterns following ACLR

BackgroundChanges in lower limb joint coordination have been shown to increase localized stress on knee joint soft tissue—a known precursor of osteoarthritis. While 50% of individuals who undergo anterior cruciate ligament reconstruction (ACLR) develop radiographic osteoarthritis, it is unclear how underlying joint coordination during gait changes post-ACLR. The purpose of this study was twofold: to determine differences in lower limb coordination patterns during gait in ACLR individuals 2, 4, and 6 months post-ACLR and to compare the coordination profiles of the ACLR participants at each timepoint post-ACLR to uninjured matched controls. MethodsWe conducted a longitudinal assessment to quantify lower limb coordination at 3 timepoints post-ACLR and compared the ACLR coordination profiles to uninjured controls. Thirty-four ACLR (age = 21.43 ± 4.24 years, mean ± SD; 70.59% female) and 34 controls (age = 21.42 ± 3.43 years; 70.59% female) participated. The ACLR group completed 3 overground gait assessments (2,4, and 6 months post-ACLR), and the controls completed 1 assessment, at which lower limb kinematics were collected. Cross-recurrence quantification analysis was used to characterize sagittal and frontal plane ankle-knee, ankle-hip, and knee-hip coordination dynamics. Comprehensive general linear mixed models were constructed to compare between-limb and within-limb coordination outcomes over time post-ACLR and a between-group comparison across timepoints. ResultsThe ACLR limb demonstrated a more “stuck” sagittal plane knee-hip coordination profile (greater trapping time (TT); p = 0.004) compared bilaterally. Between groups, the ACLR participants exhibited a more predictable ankle-knee coordination pattern (percent determinism (%DET); p < 0.05), stronger coupling between joints (meanline (MNLine)) across all segments (p < 0.05), and greater knee-hip TT (more “stuck”; p < 0.05) compared to the controls at each timepoint in the sagittal plane. Stronger frontal plane knee-hip joint coupling (MNLine) persisted across timepoints within the ACLR group compared to the controls (p < 0.05). ConclusionThe results indicate ACLR individuals exhibit a distinct and rigid coordination pattern during gait compared to controls within 6-month post-ACLR, which may have long-term implications for knee-joint health.

Lower extremity joint contact force symmetry during walking and running, 2-7 years post-ACL reconstruction.

Premature osteoarthritis after anterior cruciate ligament reconstruction (ACLR) is common among athletes. Reduced knee contact forces after ACLR likely contribute to the multifactorial etiology of the disease. Whether this reduction is accompanied by compensatory increases in joint contact forces (JCF) at adjacent or contralateral joints is unclear. It is also unclear if compensatory effects depend on the task demands. Thus, we compared hip, knee, and ankle JCF symmetry between individuals with reconstruction and a matched control group during walking and running. Thirty participants (19 females), 2-7 years post-unilateral ACLR (mean = 47.8 months), and 30 controls matched on sex, mass, and activity level were recruited. Limb symmetry indices of peak contact forces and force impulses were calculated for each joint during walking and running, and analyzed using two-factor (group, activity) analysis of variances. Lower ACLR group peak knee JCF (p = 0.009) and knee JCF impulse (p = 0.034) during walking and running were observed. An interaction of group and activity was observed for peak hip JCF, with ACLR participants demonstrating greater involved limb peak hip JCF during running (p = 0.012). Ankle JCF and ground reaction force symmetry indices were not different between groups or across tasks. Decreased knee and increased ipsilateral peak hip JCF during running suggests that proximal adaptations exist at 2-7 years after ACLR, particularly during activities with increased task demand. Clinical significance: Knee and hip JCF asymmetry at 2-7 years after ACLR may underscore a need for clinical strategies and follow-up assessments to identify and target such outcomes.

Comparison of Impairments, Activity Limitations, Balance, and Quality of Life between Patients with and without Meniscus Repair or Partial Meniscectomy Post-ACL Reconstruction

(1) Background: The anterior cruciate ligament (ACL) is a crucial ligament in the knee joint. This study compares the differences in knee range of motion (ROM), knee proprioception error, balance, function, and quality of life (QOL) among participants with and without meniscus repair or partial meniscectomy nine months post ACL reconstruction. (2) Methods: In this cross-sectional study, 57 male participants were selected through convenience sampling from a tertiary care hospital. Knee flexion and extension ROM were assessed using a digital goniometer; a digital inclinometer was used to assess knee proprioception error; the Y balance test was used to evaluate balance; the lower extremity functional scale (LEFS) was used to assess activity; and QOL was assessed using the ACLQOL questionnaire. (3) Results: There were no significant differences in outcomes except balance. The YB composite score had a moderate negative correlation with knee proprioception error with an R-value of −0.372 **. (4) Conclusions: Nine to 12 months post ACL reconstruction, the isolated ACL reconstruction participants had better lower-quarter single-leg balance than those who underwent ACL reconstruction and meniscal repair or partial meniscectomy. The remaining parameters, like knee ROM, knee proprioception error, LEFS score, and ACLQOL scores, were similar between these two groups.

Walking and running roll-off characteristics in patients with ACL reconstruction history

BackgroundGait mechanics alternation is one of side effects after anterior cruciate ligament reconstruction (ACLR). Foot roll-off characteristics shows whole gait mechanics and is not well known in ACLR patients. The purpose of present study was to investigate the roll-off process characteristics while walking and running in patients with ACLR history. Research questionIs there any difference in walking and running roll-off characteristics between patients with ACLR history and healthy individuals? Methods48 physically active males (24 healthy and 24 with ACLR history) participated in this study. Participants walked and ran on a footscan (Rsscan International) which was mounted in the midway of a 18 m runway at the speeds of 2 m·s−1 and 3.3 m·s−1. Center of pressure (COP) trajectory, timing of stance subphases, foot progression angle and contact time were calculated bilaterally in walking and running. Mixed-design MANOVA was used to examine effect of ACLR on the outcomes. ResultsThe results showed that ACLR participants had greater foot progression angle (p = .001) and more medially oriented COP trajectory in forefoot push-off phase (FFPOP) of waking (p = .001) and running (p = .001), but showed shorter contact time in running compared to healthy group (p = .02). Involved leg in ACLR group showed greater foot progression angle (p = .001) and more medially directed COP trajectory in FFPOP of walking (p = .001) and running (p = .01) compared to uninvolved side. Also, involved leg had shorter contact time (p = .04) and shorter relative time in the forefoot contact phase (p = .001), and longer relative time in forefoot flat phase (p = .001) during running. SignificanceBased on the results, it can be concluded that ACLR affects running and walking roll-off characteristics which can show altered mechanics. Running shows remarkable differences in roll-off process than walking. So, it is recommended to use running in post-ACLR assessments rather than walking.

Biomechanical Effects of Manipulating Preferred Cadence During Treadmill Walking in Patients With ACL Reconstruction.

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. Cueing larger steps will facilitate larger knee angles and moments, while cueing smaller steps would induce smaller knee angles and moments. Randomized cross-sectional design. Level 3. 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. 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). 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. 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.

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

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. 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. 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). 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.

Quadriceps muscle strength at 2years following anterior cruciate ligament reconstruction is associated with tibiofemoral joint cartilage volume.

Quadriceps strength deficits following anterior cruciate ligament reconstruction (ACLR) are linked to altered lower extremity biomechanics, tibiofemoral joint (TFJ) space narrowing and cartilage composition changes. It is unknown, however, if quadriceps strength is associated with cartilage volume in the early years following ACLR prior to the onset of posttraumatic osteoarthritis (OA) development. The purpose of this cross-sectional study was to examine the relationship between quadriceps muscle strength (peak and across the functional range of knee flexion) and cartilage volume at ~ 2years following ACLR and determine the influence of concomitant meniscal pathology. The involved limb of 51 ACLR participants (31 isolated ACLR; 20 combined meniscal pathology) aged 18-40years were tested at 2.4 ± 0.4years post-surgery. Isokinetic knee extension torque generated in 10° intervals between 60° and 10° knee flexion (i.e. 60°-50°, 50°-40°, 40°-30°, 30°-20°, 20°-10°) together with peak extension torque were measured. Tibial and patellar cartilage volumes were measured using magnetic resonance imaging (MRI). The relationships between peak and angle-specific knee extension torque and MRI-derived cartilage volumes were evaluated using multiple linear regression. In ACLR participants with and without meniscal pathology, higher knee extension torques at 60°-50° and 50°-40° knee flexion were negatively associated with medial tibial cartilage volume (p < 0.05). No significant associations were identified between peak concentric or angle-specific knee extension torques and patellar cartilage volume. Higher quadriceps strength at knee flexion angles of 60°-40° was associated with lower cartilage volume on the medial tibia ~ 2years following ACLR with and without concomitant meniscal injury. Regaining quadriceps strength across important functional ranges of knee flexion after ACLR may reduce the likelihood of developing early TFJ cartilage degenerative changes. III.

Few young athletes meet newly derived age- and activity-relevant functional recovery targets after ACL reconstruction.

National registry data have established Knee injury and Osteoarthritis Outcome Score (KOOS) functional recovery target values for adults after anterior cruciate ligament (ACL) reconstruction. However, the specificity of these target values for young athletes after ACL reconstruction is unclear. The purpose of this analysis was to (1) derive age- and activity-relevant KOOS functional recovery target values from uninjured young athlete data and (2) determine clinical measures at the time of RTS clearance associated with meeting the newly-derived functional recovery target values in young athletes following ACLR. Two hundred and twenty-two young athletes (56 uninjured controls, 17.2 ± 2.4years, 73% female; 166 after ACL reconstruction, 16.9 ± 2.2years, 68% female) were included in this cross-sectional analysis from a larger cohort study. Uninjured control participants completed the KOOS, and functional recovery target values were defined as the lower bound of the 95% confidence interval for KOOS subscales. ACL reconstruction participants completed testing within 4weeks of return-to-sport clearance, including the KOOS, single-leg hop tests, and isometric quadriceps strength. In ACL reconstruction participants, logistic regression was used to determine predictors of meeting all KOOS functional recovery target values (primary outcome) among demographic/injury, hop, and strength data (α ≤ 0.05). KOOS functional recovery target values for each subscale from uninjured athlete data were: Pain ≥ 94, Symptoms ≥ 92, Activities of Daily Living ≥ 97, Sport ≥ 92, and Quality-of-Life ≥ 92. At the time of return-to-sport clearance, ACL reconstruction participants met the KOOS functional recovery targets in the following proportions: Pain, 63%; Symptoms, 42%; Activities of Daily Living, 80%; Sport, 45%; Quality-of-Life, 24%; overall functional recovery (met all subscale targets), 17%. In ACL reconstruction participants, significant predictors of overall functional recovery (primary outcome) were: younger age, hamstring graft, pediatric ACL reconstruction, quadriceps strength limb-symmetry index > 90%, single-hop limb-symmetry index > 90%, and crossover-hop limb-symmetry index > 90%. KOOS functional recovery target values derived from uninjured young athletes were higher than those previously reported. Small proportions of young athletes following recent RTS clearance after ACLR met these newly-derived functional recovery target values, and factors associated with meeting functional recovery target values included younger age, hamstring autograft and pediatric ACLR, and having > 90% LSI for quadriceps strength and single-leg hop tests. I.

Comparing myofascial meridian activation during single leg vertical drop jump in patients with anterior cruciate ligament reconstruction and healthy participants.

Muscles work synergistically to support the body during landing. Myofascial meridians have been described to classify muscles into functional synergies. The role that these functional lines plays in positioning the trunk and lower extremity of patients with anterior cruciate ligament reconstruction (ACLR) and healthy athletes during drop landing tasks remains unclear. The purpose of this study was to compare the front and back functional lines (FFL and BFL) muscle activation in patients with ACLR and healthy participants during single leg vertical drop jump (SLVDJ). Thirty-two male athletes (post-ACLR = 16, healthy = 16) participated (age = 23.3 ± 2.3 years). Superficial electromyography of FFL (adductor longus [AL], rectus abdominis [RA], pectoralis major) and BFL (vastus lateralis [VL], gluteus maximus [GMax], latissimus dorsi [LD]) was collected during the SLVDJ and compared at initial contact and maximum knee flexion between groups using t-tests and limbs using paired-samples t-tests. In the FFL, the AL (p < 0.05) and RA (p < 0.05) muscles were more active in the healthy group compared to the ACLR group at initial contact and maximum knee flexion. PM demonstrated greater activation in the healthy group only at maximum knee flexion (p < 0.05). In the BFL, the VL (p < 0.05) and GMax (p < 0.05) muscles were more active in the ACLR group, whereas the LD (p < 0.05) muscles demonstrated greater activation in the healthy group at initial contact and maximum knee flexion. There were no healthy group inter-limb differences in FFL and BFL activation. ACLR participants demonstrated greater non-injured limb VL, AL, GMax and LD activation (p < 0.05) and greater injured limb PM and RA activation (p < 0.05). Based on the present data, patients after ACLR may present with an alteration in BFL and FFL muscles activation during a drop jump task. Functional line muscles during dynamic activities may change lower extremity positioning and lead to increase ACL injury risk.

Visual cognition associated with knee proprioception, time to stability, and sensory integration neural activity after ACL reconstruction.

Visual cognitive ability has previously been associated with anterior cruciate ligament injury and injury risk biomechanics in healthy athletes. Neuroimaging reports have identified increased neural activity in regions corresponding to visual-spatial processing, sensory integration, and visual cognition in individuals after anterior cruciate ligament reconstruction (ACLR), indicating potential neural compensatory strategies for motor control. However, it remains unclear whether there is a relationship between visual cognition, neural activity, and metrics of neuromuscular ability after ACLR. The purpose of this study was to (1) evaluate the relationship between visual cognitive function and measurements of neuromuscular control (proprioception and time to stability [TTS]), isokinetic strength, and subjective function, and (2) examine the neural correlates of visual cognition between ACLR (n = 16; time since surgery 41.4 ± 33.0 months) and demographically similar controls (n = 15). Visual cognition was assessed by the ImPACT visual motor and visual memory subscales. Outcome variables of proprioception to target knee angle 20°, landing TTS, strength, and subjective function were compared between groups, and visual cognition was correlated within groups to determine the relationship between visual cognition and outcome variables controlled for time from surgery (ACLR group). The control group had better IKDC scores and strength. Visual memory and visual motor ability were negatively associated with proprioception error (r = -0.63)and TTS (r = -0.61), respectively, in the ACLR group but not controls. Visual cognition was associated with increased neural activity in the precuneus and posterior cingulate cortex in the ACLR group but not control participants. These data suggest the neural strategy in which ACLR participants maintain proprioception and stability varies, and may depend on visual cognition and sensory integration neural activity.

Rationale for a Parsimonious Measure of Subjective Knee Function Among Individuals With Anterior Cruciate Ligament Reconstruction: A Rasch Analysis.

The International Knee Documentation Committee Subjective Knee Evaluation Form (IKDC) is the most frequently used patient-reported measure of subjective knee function among individuals with anterior cruciate ligament reconstruction (ACLR). Yet, due to the limitations of traditional validation approaches, whether the IKDC measures knee function as intended is unclear. Rasch analysis offers a robust validation approach, which may enhance the clinical interpretation of the IKDC. To assess the psychometric properties, ability to classify health status, and relationships between the IKDC and objective measures of strength and functional performance relative to a newly proposed reduced-item instrument. Cross-sectional study. Laboratory. A total of 77 individuals with primary unilateral ACLR (age = 21.9 ± 7.8 years, time postsurgery = 6.2 ± 1.0 months) and 76 age-matched control individuals (age = 22.0 ± 4.2 years). Rasch analysis was used to assess the psychometric properties of the IKDC. Receiver operator characteristic curves and logistic regression were calculated to assess the accuracy of classifying participants with ACLR versus control participants. Pearson product moment and Spearman rank order correlation analyses were conducted to evaluate relationships among subjective knee function, quadriceps torque, and single-limb hop performance. Rasch analysis aided the development of a reduced 8-item instrument (IKDC-8), which yielded improved psychometric properties in the rating scale performance (IKDC-8 = 0, IKDC = 3 nonmonotonic "misbehaving" items), percentage of variance accounted for by 1 dimension (IKDC-8 = 71.5%, IKDC = 56.7%), and precision in item separation (IKDC-8 = 9.79, IKDC = 5.02). The IKDC was an outstanding diagnostic tool, and the IKDC-8 was excellent, correctly classifying 87.2% and 82.7% of cases, respectively. Using the Hanley-McNeil formula, we found no difference in the areas under the respective receiver operator characteristic curves. Equivalent associations between subjective and objective knee function were observed regardless of the instrument used. We demonstrated evidence of enhanced reliability and validity for a parsimonious measure of subjective knee function. The proposed instrument reduces the number of items, increases the score interpretability as measuring a single construct, and improves the rating scale functioning while not diminishing its ability to classify participants with ACLR versus control participants or changing existing relationships with objective measures of recovery. We suggest the IKDC-8 may enhance clinical use by reducing administration time, improving the interpretation of the subjective knee function score, and clarifying functional ability.

Impaired Regulation of Submaximal Force after ACL Reconstruction: Role of Muscle Spindles.

Ongoing motor deficits are routinely present following anterior cruciate ligament (ACL) reconstruction, including the ability to regulate muscle force. While such deficits are known, it is unclear why this occurs. The goal of the current study was to investigate the potential influence of muscle spindle input on submaximal force regulation and muscle activity at the knee in people following ACL reconstruction. Fourteen participants (8 female) who were 6-24 months post-ACL reconstruction and 15 control participants (8 female) undertook submaximal force matching and force modulation tasks before and after 20 min of vibration applied to the patella tendon. Across all tasks, the ACL reconstruction participants were poorer at force matching (P=0.007). The effect of vibration was not significant in either group for the force matching tasks (P=0.06), although there was a reduction in maximum voluntary contraction post-vibration in the control group (P<0.001). The ACL reconstruction group also showed evidence of greater activation of the medial hamstring muscles in comparison to controls (P=0.04). Individuals who have undergone ACL reconstruction have a diminished ability to accurately match and regulate submaximal muscle force, but this does not appear to be related to impaired muscle spindle input. Neuromuscular retraining programs that involve force regulation tasks may be necessary to optimize rehabilitation after ACL reconstruction.

Decreased Loading During Gait Alters Intralimb Coordination In Anterior Cruciate Ligament Reconstructed Individuals

Aberrant lower extremity loading following anterior cruciate ligament reconstruction (ACLR) is theorized to play a role in posttraumatic osteoarthritis (PTOA) development. Cueing an increase or decrease in loading could potentially optimize gait biomechanics and slow progression to PTOA. Stable coordination is fundamental for functional gait as a mediating process for the distribution of joint loads. Accordingly, examining how joint loading impacts coordination during gait may elucidate compensatory movement strategies following ACLR. PURPOSE: Determine the effect of cueing an increase or decrease in lower extremity loading on intralimb coordination between the knee-hip joints in ACLR participants. METHODS: Coordination was assessed in 10 individuals (age: 21±4 years; 9±1 months post-surgery; 4F) with unilateral ACLR during three separate loading conditions. Loading was manipulated via real-time feedback using a force measuring treadmill that cued a change in peak vertical ground reaction force (vGRF). Three conditions were conducted on separate days in a random order: 1) preferred (no feedback), 2) overload (cue 5% body weight [BW] increase in vGRF), and 3) underload (cue 5% BW decrease in vGRF). The intralimb coordination between sagittal plane knee-hip angles was assessed via measures of coordination dynamics (mean [M] and standard deviation [SD] of relative phase [RP] and percent determinism [%DET] from cross-recurrence quantification analysis) for each condition. One-way repeated-measures analyses of variance were used to determine differences among conditions. RESULTS: A main effect of loading was observed for M RP (F2,26=6.9, p<.05) and SD RP (F2,26=9.5, p<.05). The underloaded condition exhibited significantly different coordination stability (lower M and higher SD of RP) compared to the preferred and overloaded conditions (p<.05). A significant effect of loading on %DET (F2,26=2.7 p<.05) was also observed; the underloaded condition led to tighter coupling than the preferred condition. (p<.05). CONCLUSIONS: Overall, underloading changed the pattern and multi-scale stability of knee-hip coordination. These findings indicate manipulations in joint loading result in altered movement strategies that concern the development of PTOA.

Altered Corticospinal Tract Structure And Excitability In Patients With Anterior Cruciate Ligament Reconstruction

Underlying neural factors contribute to poor outcomes following anterior cruciate ligament reconstruction (ACLR). Neurophysiological adaptations have been identified in motor cortex activation and corticospinal tract excitability, however limited evidence exists on neurostructural changes that may influence motor recovery in ACLR patients. PURPOSE: To 1) quantify hemispheric differences in structural properties of the corticospinal tract in patients with a history of ACLR, and 2) assess the relationship between excitability and corticospinal tract structure. METHODS: Ten ACLR participants (age: 22.6 ± 1.9yrs; height: 166.3 ± 7.5cm; mass: 65.4 ± 12.6kg, months from surgery: 70.0 ± 23.6) volunteered for this cross-sectional study. Corticospinal tract structure (volume; fractional anisotropy [FA]; axial diffusivity [AD]; radial diffusivity [RD]; mean diffusivity [MD]) was assessed using diffusion tensor imaging, and excitability was assessed using transcranial magnetic stimulation (motor evoked potentials [MEP]) for each hemisphere. Hemispheric differences were evaluated using paired samples t-tests. Pearson product moment correlational analyses were conducted on structural and excitability outcomes. Alpha level was set at p ≤ 0.05. RESULTS: The hemisphere of the ACLR injured limb demonstrated lower volume (567.1 ± 75.3voxels; p = 0.005), lower FA (0.49 ± 0.01; p = 0.02), higher MD (7.58 x10-4 ± 0.35 x10-4; p = 0.01), and smaller MEPs (0.013 ± 0.007; p = 0.04) compared to the hemisphere of the non-injured limb (659.7 ± 64.3voxels; 0.53 ± 0.02; 7.23 x10-4 ± 0.10 x10-4; 0.028 ± 0.010), indicating disrupted white matter structure and a reduction in excitability of the corticospinal tract. Correlation analyses revealed a strong, positive correlation between corticospinal tract volume and MEP of the ACLR injured limb (r=0.890; p=0.001). CONCLUSIONS: ACLR patients demonstrated asymmetry in structural properties of the corticospinal tract that may influence the recovery of motor function following surgical reconstruction. More research is warranted to establish the influence of neurostructural measures on patient outcomes and response to treatment in ACLR populations.

A Nonproprietary Movement Analysis System (MoJoXlab) Based on Wearable Inertial Measurement Units Applicable to Healthy Participants and Those With Anterior Cruciate Ligament Reconstruction Across a Range of Complex Tasks: Validation Study.

BackgroundMovement analysis in a clinical setting is frequently restricted to observational methods to inform clinical decision making, which has limited accuracy. Fixed-site, optical, expensive movement analysis laboratories provide gold standard kinematic measurements; however, they are rarely accessed for routine clinical use. Wearable inertial measurement units (IMUs) have been demonstrated as comparable, inexpensive, and portable movement analysis toolkits. MoJoXlab has therefore been developed to work with generic wearable IMUs. However, before using MoJoXlab in clinical practice, there is a need to establish its validity in participants with and without knee conditions across a range of tasks with varying complexity.ObjectiveThis paper aimed to present the validation of MoJoXlab software for using generic wearable IMUs for calculating hip, knee, and ankle joint angle measurements in the sagittal, frontal, and transverse planes for walking, squatting, and jumping in healthy participants and those with anterior cruciate ligament (ACL) reconstruction.MethodsMovement data were collected from 27 healthy participants and 20 participants with ACL reconstruction. In each case, the participants wore seven MTw2 IMUs (Xsens Technologies) to monitor their movement in walking, jumping, and squatting tasks. The hip, knee, and ankle joint angles were calculated in the sagittal, frontal, and transverse planes using two different software packages: Xsens’ validated proprietary MVN Analyze and MoJoXlab. The results were validated by comparing the generated waveforms, cross-correlation (CC), and normalized root mean square error (NRMSE) values.ResultsAcross all joints and activities, for data of both healthy and ACL reconstruction participants, the CC and NRMSE values for the sagittal plane are 0.99 (SD 0.01) and 0.042 (SD 0.025); 0.88 (SD 0.048) and 0.18 (SD 0.078) for the frontal plane; and 0.85 (SD 0.027) and 0.23 (SD 0.065) for the transverse plane (hip and knee joints only). On comparing the results from the two different software systems, the sagittal plane was very highly correlated, with frontal and transverse planes showing strong correlation.ConclusionsThis study demonstrates that nonproprietary software such as MoJoXlab can accurately calculate joint angles for movement analysis applications comparable with proprietary software for walking, squatting, and jumping in healthy individuals and those following ACL reconstruction. MoJoXlab can be used with generic wearable IMUs that can provide clinicians accurate objective data when assessing patients’ movement, even when changes are too small to be observed visually. The availability of easy-to-setup, nonproprietary software for calibration, data collection, and joint angle calculation has the potential to increase the adoption of wearable IMU sensors in clinical practice, as well as in free living conditions, and may provide wider access to accurate, objective assessment of patients’ progress over time.

Estimates of voluntary activation in individuals with anterior cruciate ligament reconstruction: Effects of type of stimulator, number of stimuli, and quantification technique

BackgroundAccurate quantification of voluntary activation is important for understanding the extent of quadriceps dysfunction in individuals with anterior cruciate ligament reconstruction (ACLR). Voluntary activation has been quantified using both percent activation derived from the interpolated twitch technique and central activation ratio (CAR) derived from the burst superimposition technique, as well as by using different types of electrical stimulators and pulse train conditions. However, it is unclear how these parameters affect voluntary activation estimates in individuals with ACLR. This study was performed to fill this important knowledge gap in the anterior cruciate ligament literature. MethodsQuadriceps strength and voluntary activation were examined in 18 ACLR participants (12 quadriceps/patellar tendon graft, 6 hamstring tendon graft; time since ACLR: 1.06 ± 0.82 years, mean ± SD) at 90° of knee flexion using 2 stimulators (Digitimer and Grass) and pulse train conditions (3-pulse and 10-pulse). Voluntary activation was quantified by calculating both CAR and percent activation. ResultsResults indicated that voluntary activation was significantly overestimated by CAR when compared with percent activation (p < 0.001). Voluntary activation estimates were not affected by pulse train conditions when using percent activation; however, 3-pulse stimuli resulted in greater overestimation than 10-pulse stimuli when using CAR (p = 0.003). Voluntary activation did not differ between stimulators (p > 0.05); however, the Digitimer evoked greater torque at rest than the Grass (p < 0.001). ConclusionThese results indicate that percent activation derived from the interpolated twitch technique provides superior estimates of voluntary activation than CAR derived from burst superimposition and is less affected by pulse train conditions or stimulators in individuals with ACLR.

ACL Size and Notch Width Between ACLR and Healthy Individuals: A Pilot Study.

Given the relatively high risk of contralateral anterior cruciate ligament (ACL) injury in patients with ACL reconstruction (ACLR), there is a need to understand intrinsic risk factors that may contribute to contralateral injury. The ACLR group would have smaller ACL volume and a narrower femoral notch width than healthy individuals after accounting for relevant anthropometrics. Cross-sectional study. Level 3. Magnetic resonance imaging data of the left knee were obtained from uninjured (N = 11) and unilateral ACL-reconstructed (N = 10) active, female, collegiate-level recreational athletes. ACL volume was obtained from T2-weighted images. Femoral notch width and notch width index were measured from T1-weighted images. Independent-samples t tests examined differences in all measures between healthy and ACLR participants. The ACLR group had a smaller notch width index (0.22 ± 0.02 vs 0.25 ± 0.01; P = 0.004; effect size, 1.41) and ACL volume (25.6 ± 4.0 vs 32.6 ± 8.2 mm3/(kg·m)-1; P = 0.025; effect size, 1.08) after normalizing by body size. Only after normalizing for relevant anthropometrics, the contralateral ACLR limb had smaller ACL size and narrower relative femoral notch size than healthy individuals. These findings suggest that risk factor studies of ACL size and femoral notch size should account for relevant body size when determining their association with contralateral ACL injury. The present study shows that the method of the identified intrinsic risk factors for contralateral ACL injury could be used in future clinical screening settings.

Exercise with Blood Flow Restriction to Improve Quadriceps Function Long After ACL Reconstruction.

Quadriceps atrophy and weakness can persist for years after anterior cruciate ligament reconstruction (ACLR). We evaluated the effectiveness of a home-based blood flow restriction (BFR) exercise program to increase quadriceps size and strength several years after ACLR. Nine adults with ACLR (5±2 yrs post-surgery, ≤90% symmetry in quadriceps size and strength) and nine uninjured controls volunteered. ACLR participants exercised at home for 25 min, 5×/wk for 4 wks (single-leg knee extension, bodyweight half-squats, walking). Blood flow in only the involved leg was restricted using a thigh cuff inflated to 50% of limb occlusion pressure. Rectus femoris and vastus lateralis thickness and knee extensor strength were measured before and after training. Baseline and post-training symmetry (involved leg/uninvolved leg) indices were compared to uninjured controls. Rectus femoris and vastus lateralis thickness and knee extensor strength in the involved leg increased by 11±5%, 10±6%, and 20±14%, respectively (all P<0.01). Compared to baseline, post-training knee extensor strength symmetry increased from 88±4 to 99±5% (P<0.01) and did not differ from uninjured controls (99±5%, P=0.95). Implementation of BFR exercise at home was feasible, safe and effective. Results extend upon early post-operative application of BFR exercise for ACLR recovery and demonstrate that BFR can improve quadriceps function long after ACLR.