Fewer daily steps are associated with greater cartilage oligomeric matrix protein response to loading post-ACL reconstruction

Aberrant joint loading contributes to the development of posttraumatic knee osteoarthritis (PTOA) following anterior cruciate ligament reconstruction (ACLR); yet little is known about the association between joint loading due to daily walking and cartilage health post-ACLR. Accelerometer-based measures of daily steps and cadence (i.e., rate of steps/min) provide information regarding daily walking in a real-world setting. The purpose of this study was to determine the association between changes in serum cartilage oligomeric matrix protein (COMP; %∆COMP), a mechanosensitive biomarker that is associated with osteoarthritis progression, following a standardized walking protocol and daily walking in individuals with ACLR and uninjured controls. Daily walking was assessed over 7 days using an accelerometer worn on the right hip in 31 individuals with ACLR and 21 controls and quantified as mean steps/day and time spent in ≥100 steps/min. Serum COMP was measured before and following a 3000-step walking protocol at a preferred speed. %∆COMP was calculated as a change in COMP relative to the prewalking value. Linear regressions were used to examine associations between daily walking and %∆COMP after adjusting for preferred speed. Fewer daily steps (ΔR²  = 0.18, p = 0.02) and fewer minutes spent in ≥100 steps/min (ΔR²  = 0.16, p = 0.03) were associated with greater %∆COMP following walking in individuals with ACLR; no statistically significant associations existed in controls (daily steps: ΔR²  = 0.03, p = 0.47; time ≥100 steps/min: ΔR²  < 0.01, p = 0.81). Clinical significance: Individuals with ACLR who engage in less daily walking undergo greater %ΔCOMP, which may represent greater cartilage degradation or turnover in response to walking.

Differences in Gait Biomechanics Between Adolescents and Young Adults With Anterior Cruciate Ligament Reconstruction

CONTEXT

Adolescents and adults are treated similarly in rehabilitation and research despite differences in clinical recovery after anterior cruciate ligament reconstruction (ACLR). Aberrant gait is a clinical outcome associated with poor long-term health post-ACLR but has not been compared between adolescents and adults.

OBJECTIVE

To compare gait biomechanical waveforms throughout stance between adolescents (<18 years old) and young adults (≥18 years old) post-ACLR.

DESIGN

Case-control study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

Adolescents (n = 13, girls = 77%, age = 16.7 ± 0.6 years, height = 1.7 ± 0.1 m, weight = 22.2 ± 3.7 kg/m2) were identified from a cross-sectional cohort assessing clinical outcomes 6 to 12 months post-ACLR. Young adults (n = 13, women = 77%, age = 22.3 ± 4.0 years, height = 1.7 ± 0.1 m, weight = 22.9 ± 3.3 kg/m2) were matched based on sex, time since surgery (±2 months), and body mass index (±3 kg/m2).

INTERVENTION(S)

Participants performed 5 gait trials at their habitual speed.

MAIN OUTCOME MEASURE(S)

Three-dimensional gait biomechanics and forces were collected. Vertical ground reaction force normalized to body weight (xBW), knee-flexion angle (°), knee-abduction moment (xBW × height), and knee-extension moment (BW × height) waveforms were calculated during the stance phase of gait (0%-100%). Habitual walking speed was compared using independent t tests. We used functional waveforms to compare gait biomechanics throughout stance with and without controlling for habitual walking speed by calculating mean differences between groups with 95% CIs.

RESULTS

Adolescents walked with slower habitual speeds compared with adults (adolescents = 1.1 ± 0.1 m/s, adults = 1.3 ± 0.1 m/s, P < .001). When gait speed was not controlled, adolescents walked with less vertical ground reaction force (9%-15% of stance) and knee-abduction moment (12%-25% of stance) during early stance and less knee-extension moment during late stance (80%-99% of stance). Regardless of their habitual walking speed, adolescents walked with greater knee-flexion angle throughout most stances (0%-21% and 29%-100% of stance).

CONCLUSIONS

Adolescents and adults demonstrated different gait patterns post-ACLR, suggesting that age may play a role in altered gait biomechanics.

Sex-Specific Changes in Physical Risk Factors for Anterior Cruciate Ligament Injury by Chronological Age and Stages of Growth and Maturation From 8 to 18 Years of Age

OBJECTIVE

To critically assess the literature focused on sex-specific trajectories in physical characteristics associated with anterior cruciate ligament (ACL) injury risk by age and maturational stage.

DATA SOURCES

PubMed, CINAHL, Scopus, and SPORTDiscus databases were searched through December 2021.

STUDY SELECTION

Longitudinal and cross-sectional studies of healthy 8- to 18-year-olds, stratified by sex and age or maturation on ≥1 measure of body composition, lower extremity strength, ACL size, joint laxity, knee-joint geometry, lower extremity alignment, balance, or lower extremity biomechanics were included.

DATA EXTRACTION

Extracted data included study design, participant characteristics, maturational metrics, and outcome measures. We used random-effects meta-analyses to examine sex differences in trajectory over time. For each variable, standardized differences in means between sexes were calculated.

DATA SYNTHESIS

The search yielded 216 primary and 22 secondary articles. Less fat-free mass, leg strength, and power and greater general joint laxity were evident in girls by 8 to 10 years of age and Tanner stage I. Sex differences in body composition, strength, power, general joint laxity, and balance were more evident by 11 to 13 years of age and when transitioning from the prepubertal to pubertal stages. Sex differences in ACL size (smaller in girls), anterior knee laxity and tibiofemoral angle (greater in girls), and higher-risk biomechanics (in girls) were observed at later ages and when transitioning from the pubertal to postpubertal stages. Inconsistent study designs and data reporting limited the number of included studies.

CONCLUSIONS

Critical gaps remain in our knowledge and highlight the need to improve our understanding of the relative timing and tempo of ACL risk factor development.

Dorsiflexion and Hop Biomechanics Associate with Greater Talar Cartilage Deformation in Those with Chronic Ankle Instability

PURPOSE

This study aimed to identify associations between dorsiflexion range of motion (DFROM), functional hop test performance, and hopping biomechanics with the magnitude of talar cartilage deformation after a standardized hopping protocol in individuals with and without chronic ankle instability (CAI).

METHODS

Thirty CAI and 30 healthy individuals participated. Ankle DFROM was assessed using the weight-bearing lunge test. Four different functional hop tests were assessed. Three-dimensional kinematics and kinetics were sampled during a 60-cm single-leg hop. We calculated cartilage deformation after a dynamic loading protocol consisting of sixty 60-cm single-leg forward hops by assessing the change in average thickness for the overall, medial, and lateral talar cartilage. Linear regressions examined the associations between cartilage deformation magnitude and DFROM, functional hop tests, and hop biomechanical variables after accounting for body weight and time since the initial ankle sprain.

RESULTS

In CAI group, lesser static DFROM (ΔR2 = 0.22) and smaller peak ankle dorsiflexion angle (ΔR2 = 0.17) was associated with greater medial deformation. Greater peak vertical ground reaction force (vGRF) (ΔR2 = 0.26-0.28) was associated with greater medial and overall deformation. Greater vGRF loading rate (ΔR2 = 0.23-0.35) was associated with greater lateral and overall deformation. Greater side hop test times (ΔR2 = 0.31-0.36) and ankle plantarflexion at initial contact (ΔR2 = 0.23-0.38) were associated with greater medial, lateral, and overall deformation. In the control group, lesser side hop test times (ΔR2 = 0.14), greater crossover hop distances (ΔR2 = 0.14), and greater single-hop distances (ΔR2 = 0.21) were associated with greater overall deformation.

CONCLUSIONS

Our results indicate that lesser static DFROM, poorer functional hop test performance, and hop biomechanics associate with greater talar cartilage deformation after a dynamic loading protocol in those with CAI. These factors may represent targets for therapeutic interventions within this population to slow ankle posttraumatic osteoarthritis progression.

Gait Biomechanics and Balance Associate with Talar and Subtalar T1ρ Relaxation Times in Those with Chronic Ankle Instability

PURPOSE

This study aimed to determine associations between T1ρ relaxation times of talar and subtalar articular cartilage and commonly altered gait biomechanics and postural control outcomes in those with chronic ankle instability (CAI).

METHODS

Fifteen individuals with CAI (21.13 ± 1.81 yr) completed a T1ρ magnetic resonance imaging as well as a postural control and an overground gait assessment. Talocrural and subtalar cartilage was segmented manually to calculate T1ρ relaxation times. Greater T1ρ relaxation times were interpreted as decreased proteoglycan content. Pearson product-moment bivariate correlations examined the relationships between T1ρ relaxation times and the gait biomechanics and postural control outcomes.

RESULTS

Across multiple variables, worse postural control demonstrated moderate to strong associations (range, 0.433-0.642 and -0.713) with greater talar T1ρ relaxation times. At the subtalar joint, greater T1ρ relaxation times were associated with lower peak vertical ground reaction forces, lower average vertical ground reaction force loading rates, and lower peak loading rates (range, -0.438 to -0.622). At the talar dome, greater talar T1ρ relaxation times were associated with increased knee extensor moments (r = 0.457), as well as greater knee flexion (r = 0.482) and knee adduction (r = 0.407) at initial contact. Larger step spatiotemporal gait parameters also associated with greater talar and subtalar T1ρ relaxation times (range, 0.434-0.697).

CONCLUSIONS

In individuals with CAI, worse postural control and altered kinematic, kinetic, and spatiotemporal outcomes demonstrate moderate to strong associations with greater talar T1ρ and/or subtalar relaxation times (i.e., less proteoglycan content). Associations between modifiable neuromechanical variables and greater T1ρ relaxation times may represent potential therapeutic interventions to mitigate ankle joint degeneration in those with CAI.

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.

Cueing Changes in Peak Vertical Ground Reaction Force to Improve Coordination Dynamics in Walking

AbstractsBiofeedback has been effectively implemented to improve the mediation and distribution of joint loads during gait, however, the inability to effectively coordinate lower limb movement by altering loading patterns may increase pathological stress and risk of injury and deleterious joint changes. This study examined the influence cueing an increase or decrease in lower extremity loading has on inter- and intralimb joint coordination during gait, applied herein for 12 persons following anterior cruciate ligament reconstruction across three loading conditions (control, high, and low). Visual biofeedback was presented on a screen via a force-measuring treadmill with targeted changes prescribed based on stride-to-stride peak vertical ground reaction forces bilaterally. The pattern and stability of coordination dynamics among each of the ankle, hip and knee joint pairs were assessed via discrete relative phase and cross-recurrence quantification analyses for each condition. High and low loading altered the pattern and stability of intralimb coordination; low loading led to decreased coordination stability (20° greater than control condition) and high loading resulted in a more tightly coupled coordination pattern (higher %CDET). With thoughtful consideration for movement control, biofeedback can be used to target mechanisms leading to long-term deleterious joint adaptations.

Talar and Subtalar T1ρ Relaxation Times in Limbs with and without Chronic Ankle Instability

OBJECTIVE

The primary aim was to determine differences in talocrural and subtalar joint (STJ) articular cartilage composition, using T1ρ magnetic resonance imaging (MRI) relaxation times, between limbs in individuals with unilateral chronic ankle instability (CAI) and compare with an uninjured control. Our secondary purpose was to determine the association between talocrural and STJ composition in limbs with and without CAI.

DESIGN

T1ρ MRI relaxation times were collected on 15 CAI (11 females, 21.13 ± 1.81 years, body mass index [BMI] = 23.96 ± 2.74 kg/m²) and 15 uninjured control individuals (11 females, 21.07 ± 2.55 years, BMI = 24.59 ± 3.44 kg/m²). Talocrural cartilage was segmented manually to identify the overall talar dome. The SJT cartilage was segmented manually to identify the anterior, medial, and posterior regions of interest consistent with STJ anatomical articulations. For each segmented area, a T1ρ relaxation time mean and variability value was calculated. Greater T1ρ relaxation times were interpreted as decreased proteoglycan content.

RESULTS

Individuals with CAI demonstrated a higher involved limb talocrural T1ρ mean and variability relative to their contralateral limb (P < 0.05) and the healthy control limb (P < 0.05). The CAI-involved limb also had a higher posterior STJ T1ρ mean relative to the healthy control limb (P < 0.05). In healthy controls (P < 0.05), but not the CAI-involved or contralateral limbs (p>0.05), talocrural and posterior STJ composition measures were positively associated.

CONCLUSIONS

Individuals with CAI have lower proteoglycan content in both the talocrural and posterior STJ in their involved limbs relative to the contralateral and a healthy control limb. Cartilage composition findings may be consistent with the early development of posttraumatic osteoarthritis.

Sex-Specific Associations between Cartilage Structure and Metabolism at Rest and Acutely Following Walking and Drop-Landing

OBJECTIVE

Cartilage health is thought to be dependent on the relationship between mechanics, structure, and metabolism, rather than these individual components in isolation. Due to sex differences in cartilage health, there is need to determine if the relationships between these cartilage components separately for males and females. Therefore, we sought to determine the sex-specific associations between cartilage structure and metabolism at rest and their acute response following walking and drop-landing in healthy individuals.

DESIGN

A cartilage ultrasound assessment and an ante-cubital blood draw were performed before and after walking and drop-landing conditions in 20 males and 20 females. Cartilage structure was assessed via medial and lateral femoral cartilage cross-sectional area. Cartilage metabolism was quantified with serum cartilage oligomeric matrix protein (COMP) concentration. Percent change scores from pre- to postloading were used to calculate acute alterations in cross-sectional area and COMP. Correlational analyses were used to assess the association between cartilage structure and metabolism measures separately for males and females.

RESULTS

In females, greater resting COMP concentration was associated with less cartilage cross-sectional area in the medial(ρ = -0.50, P = 0.03) and lateral (ρ = -0.69, P = 0.001) femur. Resting cartilage measures were not associated among males. Following walking and drop-landing, percent change scores in cartilage structure and metabolism were not associated.

CONCLUSIONS

This study highlights that, in females, thinner anterior femoral cartilage is associated with greater resting serum COMP concentrations, a biomarker often linked to cartilage breakdown. Future studies into the relationships between various cartilage components should consider sex-specific analyses as these relationships are sex dependent.

Tibiofemoral articular cartilage composition differs based on serum biochemical profiles following anterior cruciate ligament reconstruction

OBJECTIVE

Biochemical joint changes contribute to posttraumatic osteoarthritis (PTOA) development following anterior cruciate ligament reconstruction (ACLR). The purpose of this longitudinal cohort study was to compare tibiofemoral cartilage composition between ACLR patients with different serum biochemical profiles. We hypothesized that profiles of increased inflammation (monocyte chemoattractant protein-1 [MCP-1]), type-II collagen turnover (type-II collagen breakdown [C2C]:synthesis [CPII]), matrix degradation (matrix metalloproteinase-3 [MMP-3] and cartilage oligomeric matrix protein [COMP]) preoperatively to 6-months post-ACLR would be associated with greater tibiofemoral cartilage T1ρ relaxation times 12-months post-ACLR.

DESIGN

Serum was collected from 24 patients (46% female, 22.1 ± 4.2 years old, 24.0 ± 2.6 kg/m2 body mass index [BMI]) preoperatively (6.4 ± 3.6 days post injury) and 6-months post-ACLR. T1ρ Magnetic Resonance Imaging (MRI) was collected for medial and lateral tibiofemoral articular cartilage at 12-months post-ACLR. A k-means cluster analysis was used to identify profiles based on biomarker changes over time and T1ρ relaxation times were compared between cluster groups controlling for sex, age, BMI, concomitant injury (either meniscal or chondral pathology), and Marx Score.

RESULTS

One cluster exhibited increases in MCP-1 and COMP while the other demonstrated decreases in MCP-1 and COMP preoperatively to 6-months post-ACLR. The cluster group with increases in MCP-1 and COMP demonstrated greater lateral tibial (adjusted mean difference = 3.88, 95% confidence intervals [1.97-5.78]) and femoral (adjusted mean difference = 12.71, 95% confidence intervals [0.41-23.81]) T1ρ relaxation times.

CONCLUSION

Profiles of increased serum levels of inflammation and matrix degradation markers preoperatively to 6-months post-ACLR are associated with MRI changes consistent with lesser lateral tibiofemoral cartilage proteoglycan density 12-months post-ACLR.

Changes in Infrapatellar Fat Pad Volume 6 to 12 Months After Anterior Cruciate Ligament Reconstruction and Associations With Patient-Reported Knee Function

CONTEXT

Hypertrophy of the infrapatellar fat pad (IFP) in idiopathic knee osteoarthritis has been linked to deleterious synovial changes and joint pain related to mechanical tissue impingement. Yet little is known regarding the IFP's volumetric changes after anterior cruciate ligament reconstruction (ACLR).

OBJECTIVES

To examine changes in IFP volume between 6 and 12 months after ACLR and determine associations between patient-reported outcomes and IFP volume at each time point as well as the volume change over time. In a subset of individuals, we examined interlimb IFP volume differences 12 months post-ACLR.

STUDY DESIGN

Prospective cohort study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

We studied 26 participants (13 women, 13 men, age = 21.88 ± 3.58 years, body mass index = 23.82 ± 2.21 kg/m2) for our primary aims and 13 of those participants (8 women, 5 men, age = 21.15 ± 3.85 years, body mass index = 23.01 ± 2.01 kg/m2) for our exploratory aim.

MAIN OUTCOME MEASURE(S)

Using magnetic resonance imaging, we evaluated the IFP volume change between 6 and 12 months post-ACLR in the ACLR limb and between-limbs differences at 12 months in a subset of participants. International Knee Documentation Committee subjective knee evaluation (IKDC) scores were collected at 6-month and 12-month follow-ups, and associations between IFP volume and patient-reported outcomes were determined.

RESULTS

The IFP volume in the ACLR limb increased from 6 months (19.67 ± 6.30 cm3) to 12 months (21.26 ± 6.91 cm3) post-ACLR. Greater increases of IFP volume between 6 and 12 months were significantly associated with better 6-month IKDC scores (r = .44, P = .03). The IFP volume was greater in the uninjured limb (22.71 ± 7.87 cm3) than in the ACLR limb (20.75 ± 9.03 cm3) 12 months post-ACLR.

CONCLUSIONS

The IFP volume increased between 6 and 12 months post-ACLR; however, the IFP volume of the ACLR limb remained smaller than that of the uninjured limb at 12 months. In addition, those with better knee function 6 months post-ACLR demonstrated greater increases in IFP volume between 6 and 12 months post-ACLR. This suggests that greater IFP volumes may play a role in long-term joint health after ACLR.

Feasibility of a Wearable-Based Physical Activity Goal-Setting Intervention Among Individuals With Anterior Cruciate Ligament Reconstruction

CONTEXT

Individuals with a history of anterior cruciate ligament reconstruction (ACLR) demonstrate persistent reductions in physical activity (PA) volume that are not being addressed during rehabilitation. Currently, it is challenging for clinicians to prescribe exercise interventions that extend beyond in-person rehabilitative care in a manner that is responsive and acceptable to patients.

OBJECTIVE

To investigate the feasibility of using a novel, technology-driven, personalized goal-setting intervention over a 2-month period among young individuals with a history of primary unilateral ACLR.

DESIGN

Single-blinded feasibility study.

SETTING

University community.

PATIENTS OR OTHER PARTICIPANTS

Ten women and 2 men (age = 22.0 ± 3.0 years, time since surgery = 56.0 ± 36.3 months) with a history of primary unilateral ACLR.

INTERVENTION(S)

All participants completed a 28-day PA observation period immediately followed by a 28-day individualized PA goal-setting intervention period delivered via a commercially available PA monitor.

MAIN OUTCOME MEASURE(S)

Primary feasibility outcomes were days of PA monitor wear compliance and days of goal achievement during the intervention period. Participants also completed the Knee Osteoarthritis Outcome Score (KOOS) at study enrollment and after the intervention period, and the individual change in the KOOS Quality of Life subscale was compared with the minimal detectable change (7.2 points).

RESULTS

Average PA monitor wear compliance was 95.5% ± 7.3% during the observation period and 97.7% ± 2.9% during the intervention period. Median goal achievement was 31.5% ± 6.8% during the intervention period. Five participants demonstrated meaningful improvements in the KOOS Quality of Life subscale during the study period.

CONCLUSIONS

Individualized goal setting via mobile technology appears to be a feasible approach to PA promotion. However, based on the low rate of daily goal attainment during the intervention period, continued refinement of this intervention aproach would be beneficial before broad clinical implementation.

Quality of Life Associates With Moderate to Vigorous Physical Activity Following Anterior Cruciate Ligament Reconstruction

CONTEXT

Higher knee function is linked to psychological readiness to return to sport following anterior cruciate ligament reconstruction (ACLR). Individuals with ACLR participate in less physical activity compared to matched uninjured controls, yet the association between knee function and physical activity following ACLR remains unclear.

OBJECTIVE

To determine the association between patient-reported knee function measured with the Knee Injury and Osteoarthritis Outcomes Score Quality of Life (KOOS-QOL), daily steps, and minutes spent in moderate to vigorous physical activity (MVPA) in individuals with ACLR. Secondarily, we determined associations between KOOS-QOL, daily steps, and MVPA in individuals with ACLR who presented with (symptomatic) and without (asymptomatic) clinically meaningful knee related symptoms.

DESIGN

Cross-sectional study.

SETTING

Laboratory, Free-living conditions.

PATIENTS OR OTHER PARTICIPANTS

Sixty-six individuals with primary unilateral ACLR (55% female, 22±4 years, 28±33 months post-ACLR, BMI: 24.2±2.9 kg/m2).

OUTCOME MEASURE(S)

We collected KOOS and retrospectively stratified participants into those with (symptomatic [n=30]) or without (asymptomatic [n=36]) clinically meaningful knee related symptoms based on previously defined KOOS cutoffs. We assessed daily steps and MVPA from ActiGraph GT9X Link accelerometers which each participant wore on the right hip for 7 days. We conducted linear regressions to determine associations between KOOS-QOL, daily steps, and MVPA.

RESULTS

No significant associations existed in the entire sample between KOOS-QOL and daily steps (ΔR2=0.01, P=0.50) or MVPA (ΔR2=0.01, P=0.36). In symptomatic individuals, greater KOOS-QOL associated with greater MVPA (ΔR2=0.12, P=0.05,). No significant associations existed between KOOS-QOL, daily steps, and MVPA in the asymptomatic group.

CONCLUSIONS

Symptomatic individuals with ACLR who spent more time in MVPA reported higher quality of life.

Synovial fluid concentrations of matrix Metalloproteinase-3 and Interluekin-6 following anterior cruciate ligament injury associate with gait biomechanics 6 months following reconstruction

OBJECTIVE

To compare gait biomechanics 6 months following anterior cruciate ligament (ACL) reconstruction (ACLR) between patients with the highest and lowest concentrations of synovial fluid (SF) interleukin-6 (IL-6) and matrix metalloproteinase-3 (MMP-3), as well as compared to uninjured controls.

DESIGN

SF concentrations of IL-6 and MMP-3 were collected 7 ± 4 days post injury in 38 ACL injured patients (55% female, 21±4yrs, 25.3 ± 5.2BMI). ACL injured individuals were stratified into the lowest and highest quartiles based on IL-6 (IL-6_Lowest and IL-6_Highest) and MMP-3 (MMP-3_Lowest and MMP-3_Highest) concentrations. Gait biomechanics were collected on the injured limb 6 months post-ACLR and in 38 uninjured controls (50% female, 21±3yrs, 23.8 ± 2.8BMI). Functional analyses of variance were used to compare vertical ground reaction force (vGRF), knee flexion angle (KFA), and internal knee extension moment (KEM) waveforms throughout stance phase of gait to determine the proportions of stance differing between limbs and groups.

RESULTS

Compared to uninjured controls, IL-6_High and MMP-3_High ACL subgroups demonstrated lesser vGRF (largest differences: IL-6, 7.88%BW; MMP-3, 11.05%BW) during early-stance and greater vGRF (largest differences: IL-6, 6.21%BW; MMP-3, 5.85%BW) in mid-stance, lesser KFA (largest differences: IL-6, 3.11°; MMP-3, 3.72°) and lesser KEM (largest differences: IL-6, 0.96%BW•m; MMP-3, 1.07%BW•m) in early-stance, as well as greater KFA in mid-stance (largest differences: IL-6, 1.5°; MMP-3, 2.95°).

CONCLUSIONS

High SF concentrations of a proinflammatory cytokine and a degradative enzyme early post-ACL injury are associated with aberrant gait biomechanics in the injured limb at 6 months post-ACLR (i.e., lesser vGRF, KFA and KEM) linked to posttraumatic osteoarthritis development.

Association of Jump-Landing Biomechanics With Tibiofemoral Articular Cartilage Composition 12 Months After ACL Reconstruction

BACKGROUND

Excessively high joint loading during dynamic movements may negatively influence articular cartilage health and contribute to the development of posttraumatic osteoarthritis after anterior cruciate ligament reconstruction (ACLR). Little is known regarding the link between aberrant jump-landing biomechanics and articular cartilage health after ACLR.

PURPOSE/HYPOTHESIS

The purpose of this study was to determine the associations between jump-landing biomechanics and tibiofemoral articular cartilage composition measured using T1ρ magnetic resonance imaging (MRI) relaxation times 12 months postoperatively. We hypothesized that individuals who demonstrate alterations in jump-landing biomechanics, commonly observed after ACLR, would have longer T1ρ MRI relaxation times (longer T1ρ relaxation times associated with less proteoglycan density).

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A total of 27 individuals with unilateral ACLR participated in this cross-sectional study. Jump-landing biomechanics (peak vertical ground-reaction force [vGRF], peak internal knee extension moment [KEM], peak internal knee adduction moment [KAM]) and T1ρ MRI were collected 12 months postoperatively. Mean T1ρ relaxation times for the entire weightbearing medial femoral condyle, lateral femoral condyle (global LFC), medial tibial condyle, and lateral tibial condyle (global LTC) were calculated bilaterally. Global regions of interest were further subsectioned into posterior, central, and anterior regions of interest. All T1ρ relaxation times in the ACLR limb were normalized to the uninjured contralateral limb. Linear regressions were used to determine associations between T1ρ relaxation times and biomechanics after accounting for meniscal/chondral injury.

RESULTS

Lower ACLR limb KEM was associated with longer T1ρ relaxation times for the global LTC (ΔR 2 = 0.24; P = .02), posterior LTC (ΔR 2 = 0.21; P = .03), and anterior LTC (ΔR 2 = 0.18; P = .04). Greater ACLR limb peak vGRF was associated with longer T1ρ relaxation times for the global LFC (ΔR 2 = 0.20; P = .02) and central LFC (ΔR 2 = 0.15; P = .05). Peak KAM was not associated with T1ρ outcomes.

CONCLUSION

At 12 months postoperatively, lower peak KEM and greater peak vGRF during jump landing were related to longer T1ρ relaxation times, suggesting worse articular cartilage composition.

Acute Talar Cartilage Deformation in Those with and without Chronic Ankle Instability

PURPOSE

This study aimed 1) to determine whether talar cartilage deformation measured via ultrasonography (US) after standing and hopping loading protocols differs between chronic ankle instability (CAI) patients and healthy controls and 2) to determine whether the US measurement of cartilage deformation reflects viscoelasticity between standing and hopping protocols.

METHODS

A total of 30 CAI and 30 controls participated. After a 60-min off-loading period, US images of the talar cartilage were acquired before and after static (2-min single-leg standing) and dynamic (60 single-leg forward hops) loading conditions. We calculated cartilage deformation by assessing the change in average thickness (mm) for overall, medial, and lateral talar cartilage. The independent variables include time (Pre60 and postloading), condition (standing and dynamic loading), and group (CAI and control). A three-way mixed-model repeated-measures ANCOVA and appropriate post hoc tests were used to compare cartilage deformation between the groups after static and dynamic loading.

RESULTS

After the static loading condition, those with CAI had greater talar cartilage deformation compared with healthy individuals for overall (-10.87% vs -6.84%, P = 0.032) and medial (-12.98% vs -5.80%, P = 0.006) talar cartilage. Similarly, the CAI group had greater deformation relative to the control group for overall (-8.59% vs -3.46%, P = 0.038) and medial (-8.51% vs -3.31%, P = 0.043) talar cartilage after the dynamic loading condition. In the combined cohort, cartilage deformation was greater after static loading compared with dynamic in overall (-8.85% vs -6.03%, P = 0.003), medial (-9.38% vs -5.91%, P = 0.043), and lateral (-7.90% vs -5.65%, P = 0.009) cartilage.

CONCLUSION

US is capable of detecting differences in cartilage deformation between those with CAI and uninjured controls after standardized physiologic loads. Across both groups, our results demonstrate that static loading results in greater cartilage deformation compared with dynamic loading.