After Anterior Cruciate Ligament Injury Research Articles

Altered Knee Laxity and Stiffness in Response to a Soccer Match Simulation in Players Returning to Sport Within 12 Months After Anterior Cruciate Ligament Reconstruction

Background: The acute effects of exercise on anterior knee laxity (AKL) and anterior knee stiffness (AKS) have been documented in healthy participants, but only limited evidence has been provided for athletes cleared to return to sports after anterior cruciate ligament (ACL) reconstruction (ACLR). Purpose/Hypothesis: The purpose was to determine if 45 minutes of a soccer match simulation lead to acute changes in AKL and AKS in soccer players returning to sport within 12 months after ACLR. We hypothesized that the reconstructed knee of the ACLR group would exhibit an altered response to sport-specific exercise. Study Design: Controlled laboratory study. Methods: A total of 13 soccer players cleared to return to sport after ACLR and 13 healthy control soccer players matched for age, physical activity level, limb dominance, and anthropometric characteristics were recruited. To assess the effects of a standardized soccer match simulation (Soccer Aerobic Field Test [SAFT45]) on AKL and AKS, an arthrometric evaluation was carried out bilaterally before and immediately after SAFT45. To conduct a comprehensive examination of the force-displacement curve, the absolute and side-to-side difference (SSD) values of both AKL and AKS were extracted at 67, 134, and 200 N. Results: The ACLR and control groups showed similar AKL and AKS at baseline (P > .05). In response to SAFT45, laxity increased bilaterally at all force levels by 14% to 17% only in the control group (P < .025). Similarly, AKS at 134 and 200 N decreased in response to SAFT45 only in the control group (10.5% and 20.5%, respectively; P < .025). After SAFT45, the ACLR group had 1.9 and 2.5 times higher SSDs of AKS at 67 and 134 N compared with the control group, respectively (P < .025), as well as a 1.9 times higher SSD of AKS at 134 N compared with baseline (P = .014). Conclusion: Soccer players at the time of return to sport after ACLR showed an altered mechanical response to a sport-specific match simulation consisting of bilaterally unchanged AKL and AKS. Clinical Relevance: Soccer players showing altered AKL and AKS in response to exercise after ACLR may not be ready to sustain their preinjury levels of sport, thus potentially increasing the risk of second ACL injuries.

Confidence, ability to meet return to sport criteria, and second ACL injury risk associations after ACL-reconstruction.

This study tested the hypotheses that participants with high knee-related confidence at the time of return to sport (RTS) after anterior cruciate ligament (ACL) reconstruction (ACLR) would have a greater likelihood of meeting RTS criteria and would have a higher likelihood of second ACL injury. Participants completed RTS testing when cleared to RTS. Success was defined as an IKDC score more than or equal to 90 and all limb symmetry index (LSI) scores more than or equal to 90%. Confidence groups were created based on response to the KOOS Quality of Life subscale. Incidence of second ACL injury was tracked for 24 months after RTS. Associations among confidence, success in meeting RTS criteria, and second ACL injury were evaluated. At RTS, 37.7% were classified with high knee-related confidence, 26.4% met RTS criteria and 22.0% sustained a second ACL injury post-RTS. A higher proportion of confident participants met all RTS criteria (p = 0.001). Confident participants were over two times more likely to suffer a second ACL injury (odds ratio [OR] = 2.40; 95% confidence interval [CI]:1.21-5.20) (p = 0.02) and participants who were both confident and met all RTS criteria were 10 times more likely to suffer a second ACL injury (OR = 9.6; 95% CI:1.1, 84.2) (p = 0.02) than those who passed all RTS criteria but lacked knee-related confidence. Clinical significance: Confident, young athletes at the time of RTS after ACLR are more likely to meet all RTS criteria and more likely to sustain a second ACL injury after RTS. Future work must consider how the inclusion of additional factors into RTS criteria may better identify those at high risk for poor outcome after ACLR.

Return to sport after anterior cruciate ligament injury: Panther Symposium ACL Injury Return to Sport Consensus Group

ObjectivesA precise and consistent definition of return to sport (RTS) after anterior cruciate ligament (ACL) injury is lacking, and there is controversy surrounding the process of returning patients to sports and their previous activity level. The aim of the Panther Symposium ACL Injury RTS Consensus Group was to provide a clear definition of RTS after ACL injury and description of the RTS continuum, as well as provide clinical guidance on RTS testing and decision-making.MethodsAn international, multidisciplinary group of ACL experts convened as part of a consensus meeting. Consensus statements were developed using a modified Delphi method. Literature review was performed to report the supporting evidence.ResultsKey points include that RTS is characterised by achievement of the preinjury level of sport and involves a criteria-based progression from return to participation to RTS, and ultimately return to performance. Purely time-based RTS decision-making should be abandoned. Progression occurs along an RTS continuum with decision-making by a multidisciplinary group that incorporates objective physical examination data and validated and peer-reviewed RTS tests, which should involve functional assessment as well as psychological readiness. Consideration should be given to biological healing, contextual factors and concomitant injuries.ConclusionThe resultant consensus statements and scientific rationale aim to inform the reader of the complex process of RTS after ACL injury that occurs along a dynamic continuum. Research is needed to determine the ideal RTS test battery, the best implementation of psychological readiness testing and methods for the biological assessment of healing and recovery.

Return to Play After Patellar Tendon Autograft for Primary Anterior Cruciate Ligament Reconstruction in Rugby Players.

Background:There is scant literature on outcomes after anterior cruciate ligament (ACL) reconstruction in rugby players, and no prior study has evaluated the outcomes of bone–patellar tendon–bone (BTB) autograft ACL reconstruction.Purpose:To assess the rate of return to play, the timing of that return, and the subsequent graft reinjury rate among rugby players after ACL reconstruction with BTB autograft.Methods:The ACL registry at a single hospital was screened for professional and amateur rugby players who had undergone a primary ACL reconstruction with BTB autograft. Professional rugby players were those playing for one of the professional provincial teams in Ireland. Outcomes were analyzed for the rate and timing of return to play, functional outcomes, and subsequent graft ruptures. Additionally, outcomes were compared between professional and amateur athletes.Study Design:Case series; Level of evidence, 4.Results:A total of 126 patients with 24 months of follow-up were enrolled. The overall rate of return to play was 84.9%, with 75.4% returning to the same level of play; 8.7% of patients did not return to play secondary to non–knee-related issues. The mean time to return was 10.9 ± 4.9 months. Among professional rugby players, 93.3% were able to return at a mean time of 9.7 ± 4.4 months; 80% returned to the same level. The mean Anterior Cruciate Ligament–Return to Sport after Injury score was 78.4 ± 20.2, the Cincinnati knee score was 92.5 ± 8.0, the International Knee Documentation Committee score was 88.2 ± 8.1, and the Marx score was 9.7 ± 5.3. Two patients sustained a subsequent rerupture of the reconstructed ACL, and 4 players sustained a contralateral ACL injury within the follow-up interval of 2 years.Conclusion:Rugby players receiving BTB ACL reconstruction demonstrated good clinical outcomes with a high rate of return to sport, with the majority returning before 12 months. The rate of a subsequent ACL injury was low among the authors’ cohort at short-term follow-up.

Knee Muscle Activity During Jump Landing Tasks Following Anterior Cruciate Ligament Reconstruction: A Review Study

Background: Changes in knee muscle activity remain years after Anterior Cruciate Ligament (ACL) surgery. However, the literature on the successful or unsuccessful recovery of lower limb muscle activation during jump landing is controversial. Objectives: The present review intended to compare the surface Electromyography (EMG) of knee muscle activity in healthy and Anterior Cruciate Ligament Reconstruction (ACLR) groups in jump landing tasks. Methods: PubMed, Embase, and Web of Science databases were searched papers from 1990 to 2020 using the keywords “anterior cruciate ligament or ACL, EMG or Electromyography or Muscle activation, Landing or Jumping or Hopping”. After screening the titles, abstracts, and full text of the collected articles, 7 studies met the inclusion criteria of this review. The Critical Appraisal Skills Program tool was used for the quality assessment of the included papers. Results: The present research results suggested earlier onset muscle activity for quadriceps and hamstring in ACLR subjects, compared to healthy subjects. Furthermore, the ratio of activation of quadriceps/hamstring in the ACLR group was higher than that in the healthy individuals considering the type of rehabilitation, the time elapsed from surgery, and gender. The methodological quality of the observational studies ranged from 6 to 8 out of 12 that reflects the overall quality of the methodology. Conclusion: According to this review, we can conclude that the ACLR group exhibited different neuromuscular strategies in the pre-landing phase that might increase the recurrent risk of ACL injury.

Knee joint unloading and daily physical activity associate with cartilage T2 relaxation times one month after acl injury

Purpose: The risk of osteoarthritis (OA) is high after anterior cruciate ligament (ACL) injury, but mechanisms underlying its development are poorly understood. The purpose of this study was to determine if gait biomechanics and daily physical activity (PA) are associated with cartilage T2 relaxation times, a marker of cartilage quality, one month after ACL injury. We hypothesized that lower measures of knee joint loading would be associated with longer T2 relaxation times (less organized collagen orientation and higher water content).

The Clinical Radiographic Incidence of Posttraumatic Osteoarthritis 10 Years After Anterior Cruciate Ligament Reconstruction: Data From the MOON Nested Cohort

Background: The incidence of posttraumatic osteoarthritis (PTOA) based on clinical radiographic grading criteria at 10 years after anterior cruciate ligament (ACL) reconstruction (ACLR) has not been well-defined in a prospective cohort of young athletic patients. Hypothesis: Among young athletic patients, there is a high incidence of clinical radiographic PTOA at 10 years after ACLR. Additionally, there is a significant difference in clinical radiographic osteoarthritis (OA) changes (joint space narrowing and osteophyte formation) between ACL-reconstructed and contralateral knees at 10 years. Study Design: Case series; Level of evidence, 4. Methods: The first 146 patients in an ongoing nested cohort study of the Multicenter Orthopaedic Outcomes Network (MOON) prospective cohort presented for a minimum 10-year follow-up. Included patients had a sports-related ACL injury, were aged <33 years at the time of ACLR, had no history of ipsilateral or contralateral knee surgery, and did not undergo revision ACLR before follow-up. Bilateral knee metatarsophalangeal view radiographs were obtained and graded according to International Knee Documentation Committee (IKDC), Osteoarthritis Research Society International (OARSI), and modified Kellgren-Lawrence (KL) criteria by 2 blinded reviewers. The incidence and severity of ipsilateral and contralateral radiographic OA were determined among patients without a contralateral ACL injury before 10-year follow-up (N = 133). Results: Interrater reliability was substantial for the IKDC (Gwet Agreement Coefficient [AC] 1 = 0.71), moderate for the KL (0.48), and almost perfect for the OARSI (0.84) grading systems. Among patients with a contralateral radiographically normal knee, the 10-year incidence of clinical radiographic PTOA after ACLR was 37% as defined by osteophytes and 23% as defined by joint space narrowing. The maximum side-to-side difference in the OARSI osteophyte grade in the medial or lateral compartment was 0 in 65% of patients, 1 in 20%, and ≥2 in 15%. The maximum side-to-side difference in the OARSI joint space narrowing grade was 0 in 77% of patients, 1 in 19%, and ≥2 in 4%. Conclusion: In young active patients, the 10-year incidence of clinical radiographic PTOA after ACLR was 37% as defined by osteophytes and 23% as defined by joint space narrowing. The mean difference in the degree of osteophyte formation (≤1 grade in 85%) and joint space narrowing (≤1 grade in 96%) between the ACL-reconstructed and contralateral knees was small. Registration: NCT02717559 (ClinicalTrials.gov identifier)

Knee joint unloading and daily physical activity associate with cartilage T2 relaxation times 1 month after ACL injury.

Osteoarthritis (OA) is prevalent after anterior cruciate ligament (ACL) injury, but mechanismsunderlying its development are poorly understood. The purpose of this study was to determine if gait biomechanics and daily physical activity (PA) associate with cartilage T2 relaxation times, a marker of collagen organization and water content, 1 month after ACL injury. Twenty-seven participants (15-35 years old) without chondral lesions completed magnetic resonance imaging, three-dimensional gait analysis, and 1 week of PA accelerometry. Interlimb differences and ratios were calculated for gait biomechanics and T2 relaxation times, respectively. Multiple linear regression models adjusted for age, sex, and concomitant meniscus injury were used to determine the association between gait biomechanics and PA with T2 relaxation times, respectively. Altered knee adduction moment (KAM) impulse, less knee flexion excursion (kEXC) and higher daily step counts accounted for 35.8%-65.8% of T2 relaxation time variation in the weightbearing and posterior cartilage of the medial and lateral compartment (all p ≤ .011). KAM impulse was the strongest factor for T2 relaxation times in all models (all p ≤ .001). Lower KAM impulse associated with longer T2 relaxation times in the injured medial compartment (β = -.720 to -.901) and shorter T2 relaxation in the lateral compartment (β = .713 to.956). At 1 month after ACL injury, altered KAM impulse, less kEXC, and higher PA associated with longer T2 relaxation times, which may indicate poorer cartilage health. Statement of Clinical Significance: Gait biomechanics and daily PA are modifiable targets that may improve cartilage health acutely after ACL injury and slow progression to OA.

Rehabilitation and Return to Sport Assessment after Anterior Cruciate Ligament Injury: Quantifying Joint Kinematics during Complex High-Speed Tasks through Wearable Sensors.

The aim of the present study was to quantify joint kinematics through a wearable sensor system in multidirectional high-speed complex movements used in a protocol for rehabilitation and return to sport assessment after Anterior Cruciate Ligament (ACL) injury, and to validate it against a gold standard optoelectronic marker-based system. Thirty-four healthy athletes were evaluated through a full-body wearable sensor (MTw Awinda, Xsens) and a marker-based optoelectronic (Vicon Nexus, Vicon) system during the execution of three tasks: drop jump, forward sprint, and 90° change of direction. Clinically relevant joint angles of lower limbs and trunk were compared through Pearson’s correlation coefficient (r), and the Coefficient of Multiple Correlation (CMC). An excellent agreement (r > 0.94, CMC > 0.96) was found for knee and hip sagittal plane kinematics in all the movements. A fair-to-excellent agreement was found for frontal (r 0.55–0.96, CMC 0.63–0.96) and transverse (r 0.45–0.84, CMC 0.59–0.90) plane kinematics. Movement complexity slightly affected the agreement between the systems. The system based on wearable sensors showed fair-to-excellent concurrent validity in the evaluation of the specific joint parameters commonly used in rehabilitation and return to sport assessment after ACL injury for complex movements. The ACL professionals could benefit from full-body wearable technology in the on-field rehabilitation of athletes.

Anterior Cruciate Ligament Injury and Knee Osteoarthritis: An Umbrella Systematic Review and Meta-analysis.

To conduct a systematic review of reviews to summarize the (1) risk for development and (2) prevalence of knee osteoarthritis (OA) after anterior cruciate ligament (ACL) injury and surgical treatment and (3) compare prevalence rates between surgical and nonsurgical treatment of ACL injury. Five electronic databases were searched using medical subject heading and text words up to February 2020 to identify English language reviews. Studies were included if they were a systematic review or meta-analysis. Thirteen eligible reviews were included, and the main outcome extracted was knee OA prevalence or risk data and any meta-analysis results. Results from reviews were combined with a summary meta-analysis based on odds ratios (ORs) or proportions. There was a near 7-fold and 8-fold increase in the odds for the development of knee OA post ACL injury [OR = 6.81 (5.70-8.13)] and ACL reconstruction [OR = 7.7, (6.05-9.79)]. Data were too heterogenous to specify a point estimate prevalence for OA after ACL injury, but OA prevalence was estimated at 36% (19.70-53.01) at near 10 years after reconstruction surgery. A significantly higher prevalence of OA was found for those who received surgical treatment at a minimum 10-year follow-up [OR = 1.40 (1.17-1.68)]. This study combines all data from previous systematic reviews into a single source to show that ACL injury markedly increases the risk for development of knee OA, which is likely to be present in the long term in approximately a third of patients who have reconstruction surgery. Surgical treatment does not reduce OA prevalence in the longer term compared with nonsurgical treatment.

The Influence of Mode-of-Injury on Psychological Readiness for Return-To-Sport Following Anterior Cruciate Ligament Reconstruction: A Matched-Controlled Study

BackgroundSelf-efficacy and fear of re-injury have been documented as factors related to an athlete’s ability to return-to-sport after anterior cruciate ligament (ACL) reconstruction. The purpose of this study was to compare psychological readiness between athletes injured in their primary mode of sport versus those injured outside of their primary sport following ACL reconstruction.HypothesisAthletes sustaining ‘in-sport’ injuries will demonstrate poorer psychological readiness when compared their matched counterparts injured outside of their primary sport.Study DesignCase-Control StudyMethodsA single-surgeon database of 638 patients following ACL reconstruction was used to conduct a matched case-control analysis. Psychological readiness was examined 16-weeks postoperatively using the ACL-Return to Sport after Injury (ACL-RSI) questionnaire with subgroup analyses for the ‘emotional’, ‘confidence’ and ‘injury-risk’ subscales. Subject matching was performed for baseline patient and surgical demographics. All statistical comparisons were performed using a one-way (group) analysis variance (ANOVA) at a significance level of α = .05.ResultsNinety-two matched patients (49 ‘in-sport’ injuries, 43 ‘out-of-sport’ injuries) were included in the final analysis. The ‘in-sport’ group exhibited significantly lower total ACL-RSI scores (55.3 ±12.9 versus 60.8 ±11.6, t = 2.747, P < .001) when compared to the ‘out-of-sport’ group. Subscale comparisons indicated lower ‘emotional’ (P < .016) and higher ‘injury risk’ (P < .001) psychological constructs for ‘in-sport’ athletes versus ‘out-of-sport’ athletes. No differences were found between groups for the ‘confidence’ subscale (P = .987).ConclusionsAthletes sustaining ‘in-sport’ ACL injuries demonstrated poorer psychological readiness when compared to athletes injured outside their primary sport when in preparation for return-to-sport activities following ACL reconstruction.Clinical RelevanceClinicians should consider the potential impact of mode of injury on psychological readiness when returning athletes to sport after ACL reconstruction.

Comparison of muscle strength and neuromuscular control up to 1 year after anterior cruciate ligament reconstruction between patients with dominant leg and non-dominant leg injuries

BackgroundThere has not been an investigation to determine whether leg dominance affects the recovery of quadriceps and hamstring strength, muscle reaction time (acceleration time, AT), and postural stability after anterior cruciate ligament (ACL) reconstruction in recreational-level athletic patients. MethodsA total of 100 patients with isolated ACL injuries (58 patients had dominant leg injuries; 42 patients had non-dominant leg injuries) participated. All patients received an anatomical single-bundle ACL reconstruction using an auto-hamstring tendon graft without preoperative rehabilitation. Leg dominance was defined as the kicking leg. The quadriceps and hamstring strength, AT, and postural stability (overall stability index (OSI)) of both legs were assessed at three different time points (preoperative, 6 months, 12 months), using an isokinetic dynamometer and postural stabilometry system. ResultsAll patients in both groups showed gradual improvement in quadriceps and hamstring muscle strength in the operated legs up to 1 year postoperatively. However, the mean value of quadriceps strength was lower in the operated non-dominant leg than the operated dominant leg 6 months postoperatively (P = 0.048). The AT and OSI of the operated legs in both groups recovered significantly 6 months postoperatively compared with their preoperative values; however, the AT and OSI values after 6 and 12 months were similar. ConclusionQuadriceps strength of the operated non-dominant leg was lower than that of the operated dominant leg 6 months postoperatively; however, the strength of the quadriceps and hamstring muscles was not different after 12 months between the operated dominant and non-dominant legs. Clinicians and physical therapists should consider these results during early rehabilitation and identify effective protocols to enhance quadriceps strength, especially in patients with non-dominant leg injuries.

Explosive Quadriceps Strength Symmetry and Landing Mechanics Limb Symmetry After Anterior Cruciate Ligament Reconstruction in Females.

Emerging evidence suggests that a lower quadriceps rate of torque development (RTD) after anterior cruciate ligament (ACL) reconstruction (ACLR) may be associated with altered landing mechanics. However, the influence of quadriceps RTD magnitude and limb symmetry on landing mechanics limb symmetry remains unknown. To assess the influence of quadriceps RTD magnitude and limb symmetry on limb symmetry in sagittal-plane landing mechanics during functional landing tasks in females with or without ACLR. Cross-sectional study. Laboratory. A total of 19 females with ACLR (age = 19.21 ± 1.81 years, height = 164.12 ± 6.97 cm, mass = 63.79 ± 7.59 kg, time after surgery = 20.05 ± 9.50 months) and 19 females serving as controls (age = 21.11 ± 3.28 years, height = 167.26 ± 7.26 cm, mass = 67.28 ± 9.25 kg). Landing mechanics were assessed during a double-legged (DL) jump-landing task, a single-legged jump-landing task, and a side-cutting task. Quadriceps RTD was collected during isometric muscle contractions. Separate stepwise multiple linear regression models were used to determine the variance in limb symmetry in the sagittal-plane knee moment at initial contact, peak vertical ground reaction force, and loading rate that could be explained by quadriceps RTD magnitude or limb symmetry, group (ACLR or control), and their interaction. In the ACLR group, greater limb symmetry in quadriceps RTD was associated with greater symmetry in sagittal-plane knee moment at initial contact during the DL task (P = .004). Peak vertical ground reaction force and loading rate could not be predicted by quadriceps RTD magnitude or limb symmetry, group, or their interaction during any task. Developing greater symmetry but not magnitude in quadriceps RTD likely enabled more symmetric sagittal-plane knee landing mechanics during the DL task in the ACLR group and thus may reduce the risk of a second ACL injury. Such a protective effect was not found during the single-legged or side-cutting tasks, which may indicate that these tasks do not allow for the compensatory landing mechanism of shifting load to the uninvolved limb that was possible during the DL task.

Healthy Pediatric Athletes Have Significant Baseline Limb Asymmetries on Common Return-to-Sport Physical Performance Tests.

Background:Return to sport (RTS) after anterior cruciate ligament (ACL) reconstruction in children is associated with a much higher risk (∼30%) of subsequent ACL injury than in adults. Most RTS testing protocols use a limb symmetry index (LSI) ≥90% on physical performance tests (PPTs) to assess an athlete’s readiness for sport. This assumes that, in a healthy state, the physical performances across both lower extremities are and should be equal.Purpose:To determine the prevalence of limb asymmetries >10% in the uninjured pediatric population on common PPTs as well as to explore the relationship between athlete variables, limb preference, and LSI values.Study Design:Cross-sectional study; Level of evidence, 3.Methods:This study included healthy volunteers (N = 100) evenly distributed between the ages of 6 and 18 years (mean age, 11.7 ± 3.6 years; 52% female). Participants performed 9 common PPTs. For analysis, we developed a composite score for each limb by averaging trials. We then calculated the LSI for each test. Univariable and multivariable linear regression analyses were performed to assess the relationship between athlete variables (age, sex, height, and weight) and LSI for each PPT.Results:Instances of poor baseline limb symmetry (<90% LSI) were common across all PPTs. The single-leg timed hop had the highest percentage of participants, with LSI ≥90% at 73%, while the stork on a Bosu ball had the lowest percentage at 23%. After adjusting for age, female sex showed a significant association with LSI for the stork test (P = .010) and the quadrant hop–counterclockwise (P = .021). Additionally, after adjusting for sex, increasing age showed a significant association with LSI for the stork test (P < .001), single-leg squat on a Bosu ball (P = .010), quadrant hop–clockwise (P = .016), and quadrant hop–counterclockwise (P = .009).Conclusion:The majority of healthy athletes 18 years and younger demonstrated significant (<90%) limb asymmetries. Limb symmetry was not consistently affected by participant age or sex, and the effect sizes of these relationships were small. These findings should encourage clinicians and coaches to exercise caution in using the LSI as an isolated measure of RTS readiness after injury in pediatric athletes.

Relationship between altered knee kinematics and subchondral bone remodeling in a clinically translational model of ACL injury.

Abnormal joint kinematics are commonly reported in the acute and chronic stages of recovery after anterior cruciate ligament (ACL) injury and have long been mechanistically implicated as a primary driver in the development of posttraumatic osteoarthritis (PTOA). Though strongly theorized, it is unclear to what extent biomechanical adaptations after ACL injury culminate in the development of PTOA, as data that directly connects these factors does not exist. Using a preclinical, noninvasive ACL injury rodent model, our objective was to explore the direct effect of an isolated ACL injury on joint kinematics and the pathogenetic mechanisms involved in the development of PTOA. A total of 32, 16-week-old Long-Evans rats were exposed to a noninvasive ACL injury. Marker-less deep learning software (DeepLabCut) was used to track animal movement for sagittal-plane kinematic analyses and micro computed tomography was used to evaluate subchondral bone architecture at days 7, 14, 28, and 56 following injury. There was a significant decrease in peak knee flexion during walking (p < .05), which had a moderate-to-strong negative correlation (r = -.59 to -.71; p < .001) with subchondral bone plate porosity in all load bearing regions of the femur and tibia. Additional comprehensive analyses of knee flexion profiles revealed dramatic alterations throughout the step cycle. This occurred alongside considerable loss of epiphyseal trabecular bone and substantial changes in anatomical orientation. Knee flexion angle and subchondral bone microarchitecture are severely impacted after ACL injury. Reductions in peak knee flexion angle after ACL injury are directly associated with subchondral bone plate remodeling.

Patient-Reported Outcomes, Return-to-Sport Status, and Reinjury Rates After Anterior Cruciate Ligament Reconstruction in Adolescent Athletes: Minimum 2-Year Follow-up.

Background:Significant variation exists in the published rates of return to sport after anterior cruciate ligament (ACL) reconstruction (ACLR). Functional outcomes and psychological response to injury have been implicated as factors that influence return to sport. Most studies focus on patients aged in the mid-20s, and less is known about this topic in adolescents.Purpose:To report midterm ACLR results for adolescent patients with regard to return to primary sport, patient-reported outcomes, and reinjury rate.Study Design:Case-control study; Level of evidence, 3.Methods:Adolescent athletes were contacted at a minimum of 2 years after ACLR. Patients completed 2 patient-reported outcome measures, the ACL--Return to Sport After Injury (ACL-RSI) and the International Knee Documentation Committee (IKDC) subjective form, and responded to questions regarding preinjury primary sport and level of competition, post-ACLR return to primary sport status, and reinjury.Results:A total of 74 patients (mean ± SD surgical age, 15.9 ± 1.5 years; follow-up age, 19.9 ± 2.0 years; response rate, 24.5%) completed the surveys at a mean of 4.0 ± 2.0 years after primary ACLR. Outcome scores averaged 90.3 ± 12.3 for IKDC and 81.6 ± 20.4 for ACL-RSI. Questionnaire responses indicated that 27.0% of patients did not return to or sustain primary sport participation after ACLR; the principal reasons were poor knee function, team/training change, and fear of another injury. Both IKDC and ACL-RSI scores were statistically lower in patients who did not successfully return to their primary sport in contrast to patients who successfully resumed their primary sport (IKDC, P = .026; ACL-RSI, P < .001). IKDC and ACL-RSI scores were moderately positively correlated with one another (r Spearman = 0.60). There were 18 patients (reinjury rate, 24.3%) who suffered another ACL injury; 8 of these injuries included ipsilateral ACL graft tear (retear rate, 10.8%).Conclusion:In our cohort, 73% of adolescent patients successfully returned to their primary preinjury sport at a minimum of 2 years after ACLR. Both knee function and psychological responses to injury were important in determining an adolescent athlete’s return to sport. The findings support the use of the IKDC and ACL-RSI at midterm follow-up, with higher scores associated with a greater likelihood of adolescent patients returning to sport after ACLR.

Neuromuscular Training Improves Self-Reported Function and Single-Leg Landing Hip Biomechanics in Athletes After Anterior Cruciate Ligament Reconstruction.

Background:Neuromuscular training (NMT) has been shown to attenuate high-risk biomechanics in uninjured athletes. At the time that athletes return to sport after anterior cruciate ligament (ACL) reconstruction (ACLR), they demonstrate hip biomechanical deficits associated with injury to the reconstructed knee versus the uninjured contralateral knee.Purpose:The primary purpose of the study was to examine whether an NMT program can improve single-leg drop (SLD) landing hip biomechanics for athletes after ACLR. Secondarily, we compared the posttraining SLD hip biomechanics of athletes after ACLR with a control group of athletes who also completed the NMT program.Study Design:Controlled laboratory study.Methods:A total of 18 ACLR and 10 uninjured athletes were recruited and completed a 12-session NMT program. A knee-specific questionnaire and biomechanics of an SLD task was evaluated for each athlete before and after NMT. Paired t tests were used to compare pre- and posttraining International Knee Documentation Committee (IKDC) scores. Repeated-measures analysis of variance (ANOVA) was performed to assess the main effects and interactions of testing session × limb for the ACLR athletes. A 2-way ANOVA was conducted to quantify the interactions and main effects of group × limb.Results:There was a significant increase (P = .03) in IKDC scores from pre- to posttraining. For the ACLR athletes, there was a significant session × limb interaction for hip external rotation moment (P = .02) and hip abduction angle (P = .013). Despite increases in hip external rotation moment, no significant changes from pre- to posttraining were observed for the involved limbs. No significant changes were observed for hip abduction angle of the involved limbs between training sessions. Significant main effects of session (P < .05) revealed that athletes landed with greater hip excursion, lower hip flexion moment, and lower ground-reaction force after training. The posttraining comparison between the ACLR and control groups found no significant group × limb interactions for any of the hip kinematic or kinetic variables. A significant main effect of group (P < .05) revealed that the ACLR athletes landed with greater hip flexion angle and hip external rotation moment.Conclusion:ACLR athletes demonstrated an improvement in SLD hip biomechanics and neuromuscular control after participating in an NMT program.Clinical Relevance:This evidence indicates a potential role for NMT to improve hip biomechanics during an SLD task so as to reduce ACL injury risk.

A Translational Porcine Model for Human Cell–Based Therapies in the Treatment of Posttraumatic Osteoarthritis After Anterior Cruciate Ligament Injury

Background: There is a high incidence of posttraumatic osteoarthritis (PTOA) after anterior cruciate ligament (ACL) injury, and these injuries represent an enormous health care economic burden. In an effort to address this unmet clinical need, there has been increasing interest in cell-based therapies. Purpose: To establish a translational large animal model of PTOA and demonstrate the feasibility of intra-articular human cell–based interventions. Study Design: Descriptive laboratory study. Methods: Nine Yucatan mini-pigs underwent unilateral ACL transection and were monitored for up to 12 weeks after injury. Interleukin 1 beta (IL-1β) levels and collagen breakdown were evaluated longitudinally using enzyme-linked immunosorbent assays of synovial fluid, serum, and urine. Animals were euthanized at 4 weeks (n = 3) or 12 weeks (n = 3) after injury, and injured and uninjured limbs underwent magnetic resonance imaging (MRI) and histologic analysis. At 2 days after ACL injury, an additional 3 animals received an intra-articular injection of 107 human bone marrow–derived mesenchymal stem cells (hBM-MSCs) combined with a fibrin carrier. These cells were labeled with the luciferase reporter gene (hBM-MSCs-Luc) as well as fluorescent markers and intracellular iron nanoparticles. These animals were euthanized on day 0 (n = 1) or day 14 (n = 2) after injection. hBM-MSC-Luc viability and localization were assessed using ex vivo bioluminescence imaging, fluorescence imaging, and MRI. Results: PTOA was detected as early as 4 weeks after injury. At 12 weeks after injury, osteoarthritis could be detected grossly as well as on histologic analysis. Synovial fluid analysis showed elevation of IL-1β shortly after ACL injury, with subsequent resolution by 2 weeks after injury. Collagen type II protein fragments were elevated in the synovial fluid and serum after injury. hBM-MSCs-Luc were detected immediately after injection and at 2 weeks after injection using fluorescence imaging, MRI, and bioluminescence imaging. Conclusion: This study demonstrates the feasibility of reproducing the chondral changes, intra-articular cytokine alterations, and body fluid biomarker findings consistent with PTOA after ACL injury in a large animal model. Furthermore, we have demonstrated the ability of hBM-MSCs to survive and express transgene within the knee joint of porcine hosts without immunosuppression for at least 2 weeks. Clinical Relevance: This model holds great potential to significantly contribute to investigations focused on the development of cell-based therapies for human ACL injury–associated PTOA in the future (see Appendix Figure A1, available online).

Tibial tubercle–trochlear groove (TT–TG) distance is a reliable measurement of increased rotational laxity in the knee with an anterior cruciate ligament injury

BackgroundThe aims of this study were: 1. To evaluate the use of the tibial tubercle–trochlear groove (TT–TG) distance as a measurement showing rotational instability after anterior cruciate ligament (ACL) injury. 2. To determine the effect of concomitant anterolateral ligament (ALL) injury on TT–TG distance. MethodsKnee magnetic resonance (MR) images of 251 patients were retrospectively evaluated to compare the study group (131 patients) who underwent ACL reconstruction due to acute complete ACL injury and the control group (120 patients) without any trauma and/or patellofemoral instability. The rate of secondary signs of ACL injury (Anterolateral ligament injury, Kissing lesion, Anterior tibial translocation, Buckling of the posterior cruciate ligament (PCL)) in the study group was noted. The relationship between the TT–TG distance and other secondary signs was examined. ResultsTT–TG distance was measured as 10.83 ± 1.2 mm, 12.88 ± 1.1 mm, 14.17 ± 1.5 mm in control, isolated ACL and ACL + ALL groups, respectively (p < 0.05). TT–TG distance was significantly higher in the patients with ALL injury and kissing lesions than the patients without these lesions (p ˂ 0.05). TT–TG distance did not differ significantly between the patients with and without anterior tibial translocation or buckling of the PCL (p ˃ 0.05). TT–TG distance measurements showed significant interobserver 0.994 (0.992–0.996) and intraobserver 0.997 (0.996–0.998) correlation. ConclusionsTT–TG distance measurement can be used as a reliable quantitative measure of the increased rotational instability after ACL injury. TT–TG distance increases significantly if there is an ALL injury accompanying the ACL injury.

Radiographic and Symptomatic Knee Osteoarthritis 32 to 37 Years After Acute Anterior Cruciate Ligament Rupture

Background: The long-term prevalence of knee osteoarthritis (OA) after anterior cruciate ligament (ACL) injury is unknown, especially in patients without a history of ACL surgery. Purpose: To (1) describe the prevalence of radiographic OA, symptomatic OA, and knee replacement surgery 32 to 37 years after acute ACL injury and to (2) compare the prevalence of radiographic OA, symptomatic OA, and knee symptoms between patients allocated to early ACL surgery or no ACL surgery and patients who crossed over to ACL surgery. Study Design: Cohort study; Level of evidence, 2. Methods: Participants aged 15 to 40 years at the time of ACL injury were allocated to surgical (augmented or nonaugmented ACL repair) or nonsurgical ACL treatment within 14 days of injury. At 32 to 37 years after the initial injury, 153 participants were followed up with plain weightbearing radiographs and completed 4 subscales from the Knee injury and Osteoarthritis Outcome Score (KOOS). Radiographic OA was defined as Kellgren and Lawrence grade 2 or higher. Symptomatic OA was defined as radiographic OA plus knee symptoms measured with the KOOS. Results: Participants allocated to ACL surgery (n = 64) underwent surgery at a mean ± SD of 5 ± 4 days (range, 0-11 days) after injury. Of the 89 participants allocated to no ACL surgery, 53 remained nonsurgically treated, 27 had ACL surgery within 2 years, and 9 had ACL surgery between 3 and 21 years after injury. In the total sample, 95 participants (62%) had radiographic tibiofemoral OA, including 11 (7%) who had knee replacement. The prevalence of radiographic tibiofemoral OA was lower in the group allocated to ACL surgery compared with the group who never had ACL surgery (50% vs 75%; P = .005). The prevalence of symptomatic OA (50% in the total sample) and patellofemoral radiographic OA (35% in the total sample) was similar between groups. Conclusion: Patients allocated to early ACL surgery, performed a mean 5 days after injury, had a lower prevalence of tibiofemoral radiographic OA at 32 to 37 years after injury compared with patients who never had ACL surgery. The prevalences of symptomatic OA, radiographic patellofemoral OA, and knee symptoms were similar irrespective of ACL treatment. Overall, the prevalence of OA after ACL injury was high. Registration: NCT03182647 (ClinicalTrials.gov identifier)