Neuromuscular training to target deficits associated with second anterior cruciate ligament injury

Effects of transcranial direct current stimulation and sensorimotor training in anterior cruciate ligament patients: a sham-controlled pilot study

BACKGROUND

Studies showed changes in the central nervous system in patients who sustained an anterior cruciate ligament tear. There is a lack of evidence regarding the effectiveness of transcranial direct-current stimulation in such patients.

METHODS

A sham-controlled randomised study. One group of patients (n = 6) underwent 6 weeks of sensorimotor training after an anterior cruciate ligament tear during transcranial direct-current stimulation. The stimulation consisted of 20 minutes (3 sessions/week; 2 weeks) of 2 mA anodal transcranial direct-current stimulation over the primary motor and premotor cortex. The second group (n = 6) received sham stimulation with 6 weeks of sensorimotor training. Centre of pressure deviations in the medio-lateral and anterior-posterior direction and centre of pressure velocity were measured.

RESULTS

The results demonstrated a significant effect of sensorimotor training on the centre of pressure in medio-lateral and anterior-posterior direction (p=0.025) (p=0.03) in the leg in which an anterior cruciate ligament tear occurred. The type of training did not affect the results. Post-hoc tests showed no significant effect of training in the subgroups (p≥0.115).

CONCLUSION

Sensorimotor training led to a decrease in sway of the centre of pressure in patients who sustained an anterior cruciate ligament tear, but the addition of anodal transcranial direct-current stimulation placed over the primary motor cortex did not potentiate the adaptive responses of the sensorimotor training.

Kinematics but not kinetics alterations to single-leg drop jump movements following a subject-tailored fatiguing protocol suggest an increased risk of ACL injury

Introduction

Neuromuscular fatigue causes a transient reduction of muscle force, and alters the mechanisms of motor control. Whether these alterations increase the risk of anterior cruciate ligament (ACL) injury is still debated. Here we compare the biomechanics of single-leg drop jumps before and after the execution of a fatiguing exercise, evaluating whether this exercise causes biomechanical alterations typically associated with an increased risk of ACL lesion. The intensity of the fatiguing protocol was tailored to the aerobic capacity of each participant, minimizing potential differential effects due to inter-individual variability in fitness.

Methods

Twenty-four healthy male volunteers performed single leg drop jumps, before and after a single-set fatiguing session on a cycle ergometer until exhaustion (cadence: 65-70 revolutions per minute). For each participant, the intensity of the fatiguing exercise was set to 110% of the power achieved at their anaerobic threshold, previously identified by means of a cardiopulmonary exercise test. Joint angles and moments, as well as ground reaction forces (GRF) before and after the fatiguing exercise were compared for both the dominant and the non-dominant leg.

Results

Following the fatiguing exercise, the hip joint was more extended (landing: Δ=-2.17°, p = 0.005; propulsion: Δ=-1.83°, p = 0.032) and more abducted (landing: Δ=-0.72°, p = 0.01; propulsion: Δ=-1.12°, p = 0.009). Similarly, the knee joint was more extended at landing (non-dominant leg: Δ=-2.67°, p < 0.001; dominant: Δ=-1.4°, p = 0.023), and more abducted at propulsion (both legs: Δ=-0.99°, p < 0.001) and stabilization (both legs: Δ=-1.71°, p < 0.001) hence increasing knee valgus. Fatigue also caused a significant reduction of vertical GRF upon landing (Δ=-0.21 N/kg, p = 0.003), but not during propulsion. Fatigue did not affect joint moments significantly.

Conclusion

The increased hip and knee extension, as well as the increased knee abduction we observed after the execution of the fatiguing exercise have been previously identified as risk factors for ACL injury. These results therefore suggest an increased risk of ACL injury after the execution of the participant-tailored fatiguing protocol proposed here. However, the reduced vertical GRF upon landing and the preservation of joint moments are intriguing, as they may suggest the adoption of protective strategies in the fatigued condition to be evaluated in future studied.

A clinical practice review of therapeutic movement-based anterior cruciate ligament reconstruction return to sports bridge program: the biological, biomechanical and behavioral rationale

This clinical practice review describes the biological, biomechanical and behavioral rationale behind a return to sport bridge program used predominantly with non-elite, youth and adolescent high school and college athletes following anterior cruciate ligament (ACL) reconstruction. Post-physiotherapy, this program has produced outcomes that meet or exceed previous reports. With consideration for athletic identity and the Specific Adaptations to Imposed Demands (SAID) principle, the early program focus was on restoring non-impaired bilateral lower extremity joint mobility and bi-articular musculotendinous extensibility. Building on this foundation, movement training education, fundamental bilateral lower extremity strength and power, and motor learning was emphasized with use of external focus cues and ecological dynamics-social cognition considerations. Plyometric and agility tasks were integrated to enhance fast twitch muscle fiber recruitment, anaerobic metabolic energy system function, and fatigue resistance. The ultimate goal was to achieve the lower extremity neuromuscular control and activation responsiveness needed for bilateral dynamic knee joint stability. The rationale and conceptual basis of selected movement tasks and general philosophy of care concepts are described and discussed in detail. Based on the previously reported efficacy of this movement-based therapeutic exercise program we recommend that supplemental programs such as this become standard practice following release from post-surgical physiotherapy and before return to sports decision-making.

Using a target as external focus of attention results in a better jump-landing technique in patients after anterior cruciate ligament reconstruction - A cross-over study

BACKGROUND

Improving jump-landing technique during rehabilitation is important and may be achieved through different feedback techniques, i.e., internal focus of attention (IF) or external focus of attention using a target (EF). However, there is a lack of evidence on the most effective feedback technique after anterior cruciate ligament reconstruction (ACLR). The purpose of this study was to investigate the potential difference in jump-landing techniques between IF and EF instructions in patients after ACLR.

METHODS

Thirty patients (12 females, mean age 23.26 ± 4.91 years) participated after ACLR. Patients were randomly assigned into two groups that each followed a different testing sequence. Patients performed a drop vertical jump-landing test after receiving instructions with varying types of focus of attention. The Landing Error Scoring System (LESS) assessed the jump-landing technique.

RESULTS

EF was associated with a significantly better LESS score (P < 0.001) compared with IF. Only EF instructions led to improvements in jump-landing technique.

CONCLUSION

Using a target as EF resulted in a significantly better jump-landing technique than IF in patients after ACLR. This indicates that increased use of EF could or might result in a better treatment outcome during ACLR rehabilitation.

Comparison of Psychological Readiness to Return to Sport After Primary Versus Revision Anterior Cruciate Ligament Reconstruction

Background

Rates of return to preinjury level of play after anterior cruciate ligament (ACL) reconstruction (ACLR) remain unsatisfactory, particularly for patients who undergo revision surgery. Psychological readiness is associated with successful return to sport (RTS) and self-perceived preinjury sport performance.

Purpose

To compare psychological readiness at RTS between patients who underwent revision ACL autograft reconstruction and matched controls who underwent primary ACL autograft reconstruction.

Study Design

Cohort study; Level of evidence, 3.

Methods

Data were gathered using a single orthopaedic surgeon database of patients who underwent ACLR between 2015 and 2018. Patients who underwent revision ACLR and met the study criteria (N = 92) were matched by age, sex, graft type, and rehabilitation protocol to a control group of patients who underwent primary ACLR (n = 92). Functional assessment at release to play was examined using passive knee range of motion, single-leg squat, and single-leg hop testing. Self-reported outcomes included the International Knee Documentation Committee subjective function survey and the ACL-Return to Sport after Injury (ACL-RSI) psychological readiness scale. Time to release to play was recorded as the number of months needed to reach a ≥90% limb symmetry index from the date of the index ACLR. Data were assessed for normality using the Shapiro-Wilk test, and univariate general linear models were utilized with an alpha level of .05.

Results

The overall mean patient age was 29.9 ± 10 years, and 40% of patients were women. No significant differences between groups were noted in any of the baseline patient characteristics or surgical findings. At RTS, the mean ACL-RSI score was significantly lower in the revision surgery group (77.4 ± 19.4 vs 85.3 ± 17.4; P = .011). In addition, the revision surgery group returned to play significantly later than the primary surgery group (9.4 ± 2 vs 8.1 ± 1.3 months, respectively; P < .001).

Conclusion

When compared with primary ACL autograft reconstruction, revision reconstruction patients exhibited lower psychological readiness scores and a longer time to meet the objective criteria for RTS.

Registration

NCT03704376 (ClinicalTrials.gov identifier).

Recurrence quantification analysis of isokinetic strength tests: A comparison of the anterior cruciate ligament reconstructed and the uninjured limb

BACKGROUND

Despite widespread use of return to sport testing following anterior cruciate ligament reconstruction, studies suggest inadequacy in current testing criteria, such as limb symmetry index calculations, to determine athletes' readiness to return to play. Recurrence quantification analysis, an emerging non-linear data analysis tool, may reveal subtle neuromuscular differences between the injured and uninjured limb that are not captured by traditional testing. We hypothesized that isokinetic torque curve data of the injured limb would demonstrate lower determinism and entropy as compared to the uninjured limb.

METHODS

102 patients (44 M, 58F, 10 ± 1 months post-anterior cruciate ligament reconstruction) underwent isokinetic quadriceps strength testing using a HumacNorm dynamometer. Patients completed maximum effort knee extension and flexion at 60°/sec. Data were post-processed with a MATLAB CRQA Graphical User Interface and determinism and entropy values were extracted. Paired-sample t-tests (α = 0.05) were used to compare data from the injured and uninjured limb.

FINDINGS

Determinism and entropy values in the torque curves were lower in the injured limb than the uninjured limb (p < 0.001). Our findings indicate there is less predictability and complexity present in the torque signals of injured limbs.

INTERPRETATION

Recurrence quantification analysis can be used to assess neuromuscular differences between limbs in patients who have undergone anterior cruciate ligament reconstruction. Our findings offer further evidence that there are changes to the neuromuscular system which persist following reconstruction. Further investigation is needed to establish thresholds of determinism and entropy values needed for safe return to sport and to evaluate the utility of recurrence quantification analysis as a return to sport criterion.

Functional Outcomes of Motor Learning Interventions in Anterior Cruciate Ligament Injuries

Anterior cruciate ligament injury is one of the pathologies that affect the daily and professional life of the majority of athletes. When the treatment options are examined, there are two options surgical treatment and conservative treatment. Rehabilitation is essential in both cases, with or without surgery. Especially for returning to sports, long-term rehabilitation after surgery has become essential. While many different exercise methods have been tried in the prevention of anterior cruciate ligament injury and rehabilitation after reconstructive surgery, many have focused on strength training. The abnormal movement pattern that occurs with the somatosensory loss seen after anterior cruciate ligament injury results in a functional loss in the injured extremity and the contralateral extremity in the long term. Considering the incidence of injury, studies to establish the normal movement pattern and restore motor control are very important. For this reason, motor learning-based interventions that support neuroplasticity are of great interest today. This review aims to examine the functional results of current motor learning-based interventions in anterior cruciate ligament rehabilitation in line with the literature.

Kinesiophobia Is Associated with Peak Knee Abduction Angle during Jump Landing after ACL Reconstruction

INTRODUCTION

This study aimed to investigate the associations between kinesiophobia, knee abduction angle (KAA) during the first 100 ms of landing, and knee flexion excursion (KFE) in individuals 5-12 months after anterior cruciate ligament reconstruction (ACLR). We hypothesized that greater kinesiophobia would be associated with greater peak KAA and lesser KFE during landing on the ACLR limb, but not on the contralateral limb.

METHODS

Thirty-six participants between 14 and 35 yr old (females = 19, age = 19.9 ± 5.1 yr, height = 172.5 ± 9.4 cm, weight = 76.7 ± 20.0 kg, time since surgery =7.2 ± 1.7 months) were recruited from a sports medicine clinic at 5-12 months after primary unilateral ACLR. Participants completed the Tampa Scale of Kinesiophobia-11 (TSK-11) to measure kinesiophobia and three successful trials of a standard drop vertical jump task. A 10-camera three-dimensional motion capture system synchronized with two embedded force plate platforms was used to capture jump-landing kinematics. Separate stepwise linear regression models were used to examine the associations between kinesiophobia, peak KAA, and KFE on the ACLR and contralateral limbs after accounting for time since surgery and biological sex.

RESULTS

When accounting for time since surgery and biological sex, every 1-point increase on the TSK-11 (i.e., increase in kinesiophobia) associated with a 0.37° increase (i.e., a 7.1% increase) in ACLR limb KAA ( P = 0.02). Kinesiophobia was not associated with contralateral limb KAA, ACLR limb KFE, or contralateral limb KFE.

CONCLUSIONS

Higher kinesiophobia was related to greater amounts of peak KAA during landing in individuals 5-12 months post-ACLR. Modifying kinesiophobia may help to decrease KAA and lead to reduced secondary ACL injury risk. Future research should investigate feasible psychological interventions to reduce kinesiophobia and improve KAA in patients post-ACLR.

Video Analysis of 26 Cases of Second ACL Injury Events in Collegiate and Professional Athletes

Background

Significant effort has gone into the identification and quantification of the underlying mechanisms of primary ACL injury. Secondary ACL injury is observed in approximately 1/4 to 1/3 of athletes who return to sport following ACL reconstruction. However, little has been done to evaluate the mechanisms and playing circumstances surrounding these repeat injuries.

Hypothesis/Purpose

The purpose of this study was to characterize the mechanisms of non-contact secondary ACL injuries using video analysis. It was hypothesized that in video recordings of secondary ACL injury, athletes would exhibit greater frontal plane hip and knee angles, but not greater hip and knee flexion, at 66 ms following initial contact (IC) as compared to at IC and 33ms following IC.

Study Design

Cross-Sectional Study.

Methods

Twenty-six video recordings of competitive athletes experiencing secondary ACL ruptures via noncontact mechanisms were analyzed for lower extremity joint kinematics, playing situation, and player attention. Kinematics were assessed at IC as well as 33 ms (1 broadcast frame) and 66 ms (2 broadcast frames) following IC.

Results

Knee flexion and knee frontal plane angles were greater at 66 ms than IC (p ≤ 0.03). Hip, trunk, and ankle frontal plane angles were not greater at 66 ms than IC (p ≥ 0.22). Injuries were distributed between attacking play (n=14) and defending (n=8). Player attention was most commonly focused on the ball (n=12) or an opponent (n=7). A single-leg landing accounted for just over half of the injuries (54%), while a cutting motion accounted for the remainder of the injuries (46%).

Conclusion

Secondary ACL injury was most likely to occur during landing or a sidestep cut with player attention external to their own body. Knee valgus collapse combined with limited hip motion was identified in the majority of secondary injuries.

Level of Evidence

Level IIIb.

Application of Shear-Wave Elastography in the Evaluation of Hamstring Stiffness in Young Basketball Athletes

Background

Previous literature has postulated a relationship between greater hamstring stiffness and a higher risk of sustaining injury. Shear wave elastography (SWE) presents a relatively new means for non-invasive evaluation of soft tissue elasticity pre- and post- injury or intervention.

Purpose

1. To establish baseline hamstring stiffness measures for young competitive athletes and (2) determine effect of targeted neuromuscular training (TNMT) on shear wave stiffness of the hamstring.

Study Design

Un-blinded, prospective, non-randomized, cohort study.

Methods

Six-hundred forty-two lower extremities from 321 high school and collegiate basketball athletes (177 F: 139 M) were examined for hamstring stiffness prior to the start of their competitive basketball season. Teams were cluster assigned to either the control or intervention (TNMT) group. Subjects in the control group underwent regular season activities as directed, with no influence from the research team. For the TNMT group, the research team introduced a hamstring targeted dynamic warm-up program as an intervention focused on activating the hamstring musculature.

Results

Collegiate status was significant to hamstring stiffness for both sexes (p ≤ 0.02), but hamstring stiffness did not correlate to age or sex (r2 ≤ 0.08). Intervention was a significant factor to hamstring stiffness when the hip was positioned in extension (p ≤ 0.01), but not in deeper flexion (p = 0.12). This effect was sex-specific as TNMT influenced hamstring stiffness in females (p = 0.03), but not in males (p ≥ 0.13). Control athletes suffered three HAM injuries; TNMT athletes suffered 0 hamstring injuries.

Conclusion

Higher SWE measurements correlated with increased risk of injury, male sex, and collegiate athletics. TNMT intervention can lessen muscle stiffness which may reduce relate to injury incidence. Intervention effectiveness may be sex specific.

Level of Evidence

II.

Rehabilitation Guidelines for Use Following a Periacetabular Osteotomy (PAO): A North American Based Delphi Consensus

Background

Treatment of acetabular dysplasia with a periacetabular osteotomy (PAO) has been shown to improve long term outcomes and is considered the gold standard in the setting of symptomatic hip dysplasia in patients younger than 35 years of age. Post-operative rehabilitation following a PAO plays an important role in helping patients return to their prior level of function and reduce the impact of strength deficits that may persist. Currently, there is a paucity of research supporting post-operative rehabilitation guidelines. The purpose of this study is to present expert-driven rehabilitation guidelines to reduce practice variation following a PAO.

Methods

A panel of 16 physiotherapists from across the United States and Canada who were identified as experts in PAO rehabilitation by high-volume hip preservation surgeons participated in this Delphi study. Panelists were presented with 11 questions pertaining to rehabilitation guidelines following a PAO. Three iterative survey rounds were presented to the panelists based on responses to these questions. This three-step Delphi method was utilized to establish consensus on post-operative rehabilitation guidelines following a PAO.

Results

Total (100%) participation was achieved for all three survey rounds. Consensus (>75%) was reached for 11/11 questions pertaining to the following areas: 1) weight-bearing and range of motion (ROM) precautions, 2) therapeutic exercise prescription including neuromuscular control, cardiovascular exercise, and flexibility, and 3) objective measures for return to straight line running and return to full participation in sports.

Conclusion

This Delphi study established expert-driven rehabilitation guidelines for use following a PAO. The standardization of rehabilitative care following PAO is essential for achieving optimal outcomes despite other factors such as geographical location and socioeconomic status. Further research on patient-reported outcomes is necessary to confirm successful rehabilitation following the guidelines outlined in this study.

Interventions for increasing return to sport rates after an anterior cruciate ligament reconstruction surgery: A systematic review

Background

An injury followed by surgery poses many challenges to an athlete, one of which is rehabilitation, with the goal of returning to sport. While total restoration of physical abilities is a primary goal for most athletes, psychosocial factors also play an important role in the success of an athlete's return to sport (RTS). The purpose of this review was to examine the effectiveness of exercise and psychosocial interventions on RTS rates, which might be one of the most important outcomes for elite athletes.

Methods

To carry out this review, PubMed, SAGE Journals, Web of Science, SPORTDiscus, ScienceDirect, and Google Scholar databases were searched from inception to July 2022. The inclusion criteria consisted exercise or psychosocial intervention for athletes after anterior cruciate ligament reconstruction (ACLR), with reporting RTS rates as an outcome.

Results

From 1032 identified articles, four reports (N = 130) met inclusion criteria, all of which examined the recovery after ACLR. The mean MINORS score for the included studies was 16.3 ± 6.1, of which non-comparative studies scored 11.0 ± 1.4, while comparative studies scored 21.5 ± 0.7. There were consistent findings for benefits of exercise and psychosocial interventions on RTS rates. Return to preinjury rates in the reviewed studies vary between 63 and 95% with lower % observed in female athletes and with shorter follow-up. Interventional studies reporting RTS rates with a larger sample size and longer follow-up are needed.

Conclusion

Physical and psychological function, as well as social support can be influenced by appropriate interventions, indicating future work on rehabilitation programs for return to preinjury might consider taking the holistic approach addressing those.

Return to sports after ACL injury 5 years from now: 10 things we must do

Background

The outcome after ACL reconstruction (ACLR) is in general disappointing with unacceptable number of athletes that do not return to pre-injury level of sports, high re-injury rates, early development of osteoarthritis and shorter careers. Athletes after ACLR have high expectation to return to sports which is in contrast with the current outcomes. The aim of this manuscript is to present an overview of factors that are needed to be incorporated and to personalize the rehabilitation process for an athlete who has undergone an ACLR.

Level of evidence

4.

Influence of Rehabilitation Aid with Biofeedback on the Rehabilitation Process during Remote Home-Based Rehabilitation

Ensuring the regularity and correctness of rehabilitation exercises in the home environment is a prerequisite for successful treatment. This clinical study compares balance therapy in the home environment on a conventional balance mat and an instrumented wobble board, with biofeedback supported by a rehabilitation scheme realized as web-based software that controls the course of rehabilitation remotely. The study included 55 patients with knee injuries. The control group consisted of 25 patients (12 females and 13 males, mean age 39 ± 12 years) and the study group of 30 patients (19 females and 11 males, mean age 40 ± 12 years). Treatment effects were compared using the ICS Balance Platform measurement system. Measurements showed significant differences in the change in ICS Balance platform parameters representing the dynamic stability of the patients. The dynamic stability improved more with the instrumented wobble board. The study did not show an influence of different methods of communication with patients during home-based rehabilitation.

Can MRI knee joint measurements predict the population at risk of ACL injury?

BACKGROUND

Anterior cruciate ligament (ACL) injuries have been increasing significantly over time. The relationship between the ACL injury and the knee joint structures is poorly understood. The purpose of this study is to examine whether the measurements of different structures in the knee joint are linked with ACL injury in affected patients.

METHODS

This retrospective case-control study included patients who suffered from ACL tears and underwent magnetic resonance imaging (MRI). A control group of patients with no knee pathologies on MRI was included. Fourteen knee variables, including lateral meniscus (LM) posterior horn height, length, depth, and volume; medial meniscus (MM) posterior horn height, length, depth, and volume; lateral and medial (MFC) femoral condyle sphere diameter; lateral and medial tibial plateau length; and patella tendon horizontal and vertical diameter, were collected. A multivariate logistic regression including LM posterior horn depth, MM posterior horn length, MM volume, MFC sphere diameter, and patella tendon horizontal diameter and receiver operating characteristic curve, was used to compare the two groups.

RESULTS

A total of 85 patients were included in our study; 54 suffered from ACL injuries and 31 as a control group with normal knee MRI. Logistic regression revealed that increased LM posterior horn depth (OR = 1.27; 95% CI = 1.03-1.56; p = 0.028), decreased MM posterior horn length (OR = 0.71; 95% CI = 0.55-0.93; p = 0.013), and MFC sphere diameter (OR = 1.20; 95% CI = 1.01-1.43; p = 0.035) were independent risk factors for ACL rupture. The MFC sphere diameter yielded the highest area under the curve: 0.747 (95% CI, 0.632-0.862). No difference was found in the other measurements between the two groups.

CONCLUSIONS

Concerning the difference in anatomical variations, the lateral meniscus posterior horn depth and medial femoral condyle sphere diameter were higher, while medial meniscus posterior horn length was lower in patients with an ACL injury. These structural knee measurements could have a possible increase in the likelihood of sustaining an ACL injury and can be used by clinicians to predict ACL injury.

Comparison between movement pattern training and strengthening on muscle volume, muscle fat, and strength in patients with hip-related groin pain: An exploratory analysis

The purpose of this exploratory analysis was to compare the impact of movement pattern training (MoveTrain) and standard strength and flexibility training (Standard) on muscle volume, strength and fatty infiltration in patients with hip-related groin pain (HRGP). We completed a secondary analysis of data collected during an assessor-blinded randomized control trial. Data were used from 27 patients with HRGP, 15-40 years, who were randomized into MoveTrain or Standard groups. Both groups participated in their training protocol (MoveTrain, n = 14 or Standard, n = 13) which included 10 supervised sessions over 12 weeks and a daily home exercise program. Outcome measures were collected at baseline and immediately after treatment. Magnetic resonance images data were used to determine muscle fat index (MFI) and muscle volume. A hand-held dynamometer was used to assess isometric hip abductor and extensor strength. The Standard group demonstrated a significant posttreatment increase in gluteus medius muscle volume compared to the MoveTrain group. Both groups demonstrated an increase in hip abductor strength and reduction in gluteus minimus and gluteus maximus MFI. The magnitude of change for all outcomes were modest. Statement of Clinical Significance: Movement pattern training or a program of strength/flexibility training may be effective at improving hipabductor strength and reducing fatty infiltration in the gluteal musculature among those with HRGP. Further research is needed to betterunderstand etiology of strength changes and impact of muscle volume and MFI in HRGP and the effect of exercise on muscle structure andfunction.

Reliability of three-dimensional motion analysis during single-leg side drop landing test after anterior cruciate ligament reconstruction: An in vivo motion analysis study

Background:

Anterior cruciate ligament (ACL) injury is a common sport injury and investigation of landing biomechanics is helpful in injury prevention and rehabilitation. Recent study found a lateral single-leg drop landing test resulted in the highest peak knee valgus angle (PKVA), but its reliability on patients who received ACL reconstruction (ACLR) is unknown.

Objective:

This study aimed to investigate the reliability in both within and between days on the normalized vertical ground reaction force (NVGRF) and kinematics of lower limbs after receiving ACLR. The findings can form the cornerstone for further study related to lateral jumping-and-landing biomechanics in patients with ACLR.

Methods:

This was a test-retest reliability study. Twelve patients (four females and eight males) who received ACLR with mean age of 29.4 (SD ± 1.66) were recruited. The subjects were instructed to jump laterally from 30 cm height and landed with single-leg for five times. The procedure was conducted on both legs for comparison. The NVGRF and local maxima of the hip, knee and ankle angles during the first 100 ms in all three planes were analyzed. The measurement was conducted by the same assessor to evaluate the within-session reliability, and the whole procedure was repeated one week later for the evaluation of the between-session reliability. Intra-class correlation coefficient (ICC) test was used to assess the within- and between-session reliability by ICC (3, 1) and ICC (3, K) respectively.

Results:

The within-session reliability of NVGRF [ICC (3, 1)] was 0.899–0.936, and its between-session reliability [ICC (3, K)] was 0.947–0.923. Overall reliability for kinematics within-session [ICC (3, 1)] was 0.948–0.988, and the between-session reliability [ICC (3, K)] was 0.618–0.982, respectively. Good to excellent reliability for the lateral single-leg drop landing test was observed in most of the outcome measures for within- and between-session. The ICC value of NVGRF of ACLR leg was lower than that of the good leg in the within-session which may associate with lower neuromuscular control in ACLR leg than that of the good leg.

Conclusion:

The results of this study support the use of a lateral single-leg drop landing test to evaluate lower limb biomechanics for ACLR.

EFFECTS OF A PROPHYLACTIC KNEE SLEEVE ON THE ANTERIOR CRUCIATE LIGAMENT AND LOWER EXTREMITY BIOMECHANICS: AN EXAMINATION USING MUSCULOSKELETAL SIMULATION

The current study aimed using a two-experiment musculoskeletal simulation-based approach, measuring anterior cruciate ligament (ACL) biomechanics, knee joint kinematics, and lower extremity joint loading to examine the effects of both a prophylactic knee sleeve on (1) a sport-specific change of direction movement in female footballers and (2) a single leg landing in male footballers. Experiment 1 examined 12 female university first team level footballers (age [Formula: see text] years, height [Formula: see text][Formula: see text]m, body mass [Formula: see text][Formula: see text]kg) undertaking a [Formula: see text] cutting movement in sleeve and no-sleeve conditions. Experiment 2 examined 10 male university first team level footballers (age [Formula: see text] years, height [Formula: see text][Formula: see text]m, body mass [Formula: see text][Formula: see text]kg) undertaking a single leg drop jump landing in sleeve and no-sleeve conditions. In each experiment, data was collected in a biomechanics laboratory and three-dimensional (3D) motion capture and ground reaction force (GRF) information was collected. 3D kinematics, 3D knee kinetics, and ACL ligament forces/strains were measured using musculoskeletal simulation, and participants were also asked to subjectively rate the knee sleeve in terms of both comfort and stability. Experiment 1 showed that the sleeve condition was associated with greater ACL strain ([Formula: see text]% and no-[Formula: see text]%) and forces ([Formula: see text] BW and no-[Formula: see text] BW). In addition, the brace condition also enhanced lateral compressive tibiofemoral ([Formula: see text] BW and no-[Formula: see text] BW) and total compressive tibiofemoral force ([Formula: see text] BW and no-[Formula: see text] BW). Finally, for the subjective ratings, participants indicated that the knee sleeve significantly improved perceived comfort and stability. Experiment 2 did not reveal any statistical differences between knee sleeve and no-sleeve conditions nor any effects of the knee sleeve on subjective ratings of comfort or stability. Therefore, the findings from the current investigation suggest that the prophylactic knee sleeve examined in the current investigation does not appear to reduce the biomechanical parameters linked to the aetiology of knee pathologies in male/female footballers.

Familial Predisposition to Anterior Cruciate Ligament Injury: A Systematic Review with Meta-analysis

BACKGROUND

Having a family history of anterior cruciate ligament (ACL) injury has been investigated in the literature but few studies have focused on this factor specifically or reported their outcomes by sex.

OBJECTIVE

We aimed to systematically review family history as a risk factor for sustaining a primary ACL injury and the impact it has on ACL graft rupture or contralateral ACL injury in male and female individuals.

METHODS

A literature search was completed in seven databases from inception until March 2021 to investigate primary and subsequent ACL injuries in those with a family history of ACL injury. Articles were screened by prespecified inclusion criteria, and the methodological quality of each study was determined. Study results were combined using an odds ratio (OR) meta-analysis. Subgroup analysis was also completed by sex for primary ACL injury, as well as by graft rupture and contralateral ACL injury for subsequent ACL injuries.

RESULTS

Twelve studies were acquired for systematic review and meta-analysis. Four studies that investigated primary ACL injury, seven that investigated ACL graft and/or contralateral ACL ruptures and one study that investigated both primary and subsequent ACL injury. Having a family history of ACL injury increased the odds of injury across all outcomes. Those with a family history had a 2.5 times greater odds for sustaining a primary ACL injury (OR 2.53 [95% confidence interval [CI] 1.96-3.28, p < 0.001)]. There was no significant difference of injury odds for primary ACL injury when analysed by sex. Family history of ACL injury was found to increase the odds of subsequent ACL injury by 2.38 (95% CI 1.64-3.46, p < 0.001) and was significant for both graft ruptures (OR 1.80 [95% CI 1.20-2.71, p = 0.005]) and contralateral ACL injuries (OR 2.28 [95% CI 1.28-4.04, p = 0.005]). When compared directly, the odds of sustaining a graft rupture versus a contralateral ACL injury were similar for those with a family history. Outcomes were not frequently reported by sex for subsequent ACL injuries.

CONCLUSIONS

Having a family history of ACL injury more than doubles the odds of sustaining a primary or subsequent ACL injury. However, if a family history of ACL injury is present, the sex of the athlete does not increase the risk for primary injury nor is there a difference in the risk for a subsequent graft rupture compared to a contralateral ACL injury.

CLINICAL TRIAL REGISTRATION

PROSPERO: CRD42020186472.

Effect of an Anterior Cruciate Ligament Rupture on Knee Proprioception Within 2 Years After Conservative and Operative Treatment: A Systematic Review with Meta-Analysis

BACKGROUND

The anterior cruciate ligament (ACL) plays a major role in knee proprioception and is thus responsible for maintaining knee joint stability and functionality. The available evidence suggests that ACL reconstruction diminishes somatosensory feedback and proprioceptive functioning, which are vital for adequate joint positioning and movement control.

OBJECTIVE

The aim of this systematic review and meta-analysis was to investigate the effect of an ACL rupture on knee proprioception after arthroscopic ACL repair surgery or conservative treatment.

METHODS

A systematic review with meta-analysis was conducted according to the Preferred Reporting Guidelines for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The literature search was performed in the following databases from inception to 10th October 2020: PubMed, Web of Science, SPORTDiscus, Cochrane Library and Scopus. Randomized and non-randomized studies that evaluated proprioception using the joint position sense (JPS) and threshold to detection of passive motion (TTDPM) techniques at 15°-30° knee flexion with an external healthy control group in a time period between 6 and 24 months post injury or operation were included in the analysis.

RESULTS

In total, 4857 studies were identified, from which 11 were included in the final quantitative analysis. The results demonstrated that proprioception after arthroscopic ACL repair surgery was significantly lower than in the healthy control group (JPS: standardized mean difference [SMD] 0.57, 95% confidence interval [CI] 0.27-0.87, p < 0.01, n = 6 studies; TTDPM: SMD 0.77, 95% CI 0.20-1.34, p < 0.01, n = 4 studies). There were no significant differences in proprioception between the conservative treatment group and the healthy control group (JPS: SMD 0.57, 95% CI - 0.69 to 1.84, p = 0.37, n = 4 studies; TTDPM: SMD 0.82, 95% CI - 0.02 to 1.65, p = 0.05, n = 2 studies), although measures for TTDPM were close to statistical significance.

CONCLUSION

The findings of the present systematic review and meta-analysis revealed that knee proprioception is persistently compromised 6-24 months following surgical treatment of ACL tears compared with healthy controls. The reduced kinesthetic awareness after ACL surgery is of high relevance for optimizing individual treatment plans in these patients. As the current literature is still scarce about the exact underlying mechanisms, further research is needed.

TRIAL REGISTRATION

The present systematic review was registered in PROSPERO (CRD42021198617).

A cross-sectional study to assess variability in knee frontal plane movement during single leg squat in patients with anterior cruciate ligament injury

BACKGROUND

Single leg squat (SLS) tests help predict anterior cruciate ligament injuries. However, the variability in joint movement during this test has not been fully investigated. The aim of this study was to examine the knee frontal plane movement variability during SLS in patients with anterior cruciate ligament (ACL) injury.

METHODS

In this cross-sectional study, we enrolled 56 patients with ACL injury (28 males; 28 females) and 46 healthy subjects (23 males; 23 females). All participants underwent SLS tests. All kinematic variables were joint angle of trunk, pelvis and lower limb, center of gravity (COG), center of pressure (COP). These data were obtained at the frontal plane and the coefficient of variation (CV) were calculated. Multiple comparisons were performed between healthy subjects and the injured leg and uninjured leg of patients with ACL injury. The correlation of the CV in knee varus/valgus range of motion (ROM) with the CV in other kinematic variables were investigated in patients with ACL injury.

RESULTS

Compared with healthy subjects, patients with ACL injury exhibited significantly larger the CV in knee varus/valgus ROM. A positive correlation was observed between the CV in knee varus/valgus ROM and the CV in pelvic lateral inclination ROM in patients with ACL injury.

CONCLUSIONS

Knee frontal plane movement variability during SLS may help evaluate the risk of ACL injury/re-injury. In addition, pelvic lateral inclination variability during SLS may need to be evaluated in conjunction with knee frontal plane movement variability.

Knee Biomechanical Deficits During a Single-Leg Landing Task Are Addressed With Neuromuscular Training in Anterior Cruciate Ligament-Reconstructed Athletes

OBJECTIVE

Faulty neuromuscular and biomechanical deficits of the knee are nearly ubiquitous in athletes after anterior cruciate ligament (ACL) reconstruction (ACLR). Knee biomechanical deficits are directly associated with an increased risk of second ACL injury, which typically occurs during a sports-related movement on a single limb. To date, the biomechanical effects of a neuromuscular training (NMT) program on knee biomechanics during a single-leg landing task have not been investigated.

DESIGN

Prospective Cohort Study.

SETTING

Controlled laboratory setting.

PARTICIPANTS

Eighteen ACLR and 10 control athletes.

INTERVENTIONS

Neuromuscular training.

MAIN OUTCOME MEASURES

Knee kinematics and kinetics.

RESULTS

There were no significant interactions of session and limb (P > 0.05) for the athletes with ACLR after training. However, there were several significant main effects of session (P < 0.05) for knee kinematics and kinetics during the single-leg landing task. After training, the athletes with ACLR landed with greater knee flexion angles, decreased knee abduction angles, increased knee flexion range of motion, and decreased knee excursion. Also, the ACLR athletes landed with lower knee flexion moments, greater knee adduction moments, and lower peak vertical ground reaction force. Post-training comparison of the ACLR and control cohorts found no significant interactions of group and limb (P > 0.05) and only a significant main effect of group (P < 0.05) for frontal plane knee angle at initial contact. The athletes with ACLR landed with greater knee adduction angles than the control group.

CONCLUSIONS

Deficits in knee biomechanics that are associated with an increased risk of ACL injury are attenuated after completion of this NMT program.

Functional and Anthropometrical Screening Test among High Performance Female Football Players: A Descriptive Study with Injury Incidence Analysis, the Basque Female Football Cohort (BFFC) Study

The main objectives of the present study were to describe the injury incidence and to analyze the anthropometric and physical characteristics of players from three high-level women's football teams. The present study involved 54 female football players (21.9 ± 4.9 years old) from three different teams competing in the Spanish Reto Iberdrola-Segunda División PRO league. A battery of tests was carried out to determine the anthropometric and physical performance characteristics of the players along with an injury incidence record during a full competitive season. The obtained results showed that there was a high incidence of injury, as 38% of the players suffered some type of injury during the season (range 1-5; 1.75 ± 1.02 injuries per player). Injuries occurred in both matches and during training at a similar percentage (48.6 vs. 51.4%), and the majority of the registered episodes were graded as moderate or severe injury types (60%). Players suffering from an injury accumulated a total of 1587 chronological days off work due to injury during the season, with a recurrence rate of 55%. Considering the high incidence of injury, and the injury burden and the reinjure rate observed in this research, it seems necessary to apply the most efficient prevention and recovery measures possible in these female football teams. These descriptive data could serve athletic trainers and medical staff of female football teams to better understand their own screening procedure-derived data.

Altered trunk and lower extremity movement coordination after neuromuscular training with and without external focus instruction: a randomized controlled trial

Background

This study sought to determine the effects of a 6-week neuromuscular training (NMT) and NMT plus external focus (NMT plus EF) programs on trunk and lower extremity inter-segmental movement coordination in active individuals at risk of injury.

Methods

Forty-six active male athletes (controls = 15, NMT = 16, NMT plus EF = 15) participated (age = 23.26 ± 2.31 years) in this controlled, laboratory study. Three-dimensional kinematics were collected during a drop vertical jump (DVJ). A continuous relative phase (CRP) analysis quantified inter-segmental coordination of the: (1) thigh (flexion/extension)—shank (flexion/extension), (2) thigh (abduction/adduction)—shank (flexion/extension), (3) thigh (abduction/adduction)—trunk (flexion/extension), and (4) trunk (flexion/extension)—pelvis (posterior tilt/anterior tilt). Analysis of covariance compared biomechanical data between groups.

Results

After 6 weeks, inter-segmental coordination patterns were significantly different between the NMT and NMT plus EF groups (p < 0.05). No significant differences were observed in CRP for trunk-pelvis coupling comparing between NMT and NMT plus EF groups (p = 0.134), while significant differences were observed CRP angle of the thigh-shank, thigh-trunk couplings (p < 0.05).

Conclusions

Trunk and lower extremity movement coordination were more in-phase during DVJ in the NMT plus EF compared to NMT in active individuals at risk of anterior cruciate ligament injury.

Trial registration: The protocol was prospectively registered at UMIN_RCT website with ID number: UMIN000035050, Date of provisional registration 2018/11/27.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13102-021-00326-9.

Lower limb kinematics differ at the time of foot contact between successful and unsuccessful single limb landings following anterior cruciate ligament reconstruction

OBJECTIVES

To investigate differences in lower extremity kinematics at initial ground contact between successful and unsuccessful single limb landings following anterior cruciate ligament (ACL) reconstruction.

DESIGN

Observational study.

SETTING

Controlled laboratory environment.

PARTICIPANTS

22 male participants (aged 17-40 years) who had undergone unilateral ACL reconstruction attended a single test session.

MAIN OUTCOME MEASURES

Within-subjects comparisons was performed for pelvis, hip, knee and ankle kinematics using paired t-tests.

RESULTS

When unsuccessful at landing on the ACL reconstructed limb, participants had significantly increased knee flexion (P = 0.04) and reduced ankle plantarflexion (P = 0.03) compared to their successful landings. In contrast, when unsuccessful at landing on the unaffected limb, participants had significantly increased pelvic contralateral hitch (P < 0.01) and increased hip abduction (P < 0.01) compared to successful landings.

CONCLUSION

Body position at the time of initial contact was different for landings that were successful compared to landings that were unsuccessful. These differences were limb-specific: altered position in sagittal plane preceded unsuccessful landings on the reconstructed limb whereas altered position in the coronal plane body position that preceded unsuccessful landings on the unaffected limb. These findings suggest that limb specific landing strategies may be required to improve athletes' performance following ACL reconstruction.

LEVEL OF EVIDENCE

IV.

Integrating neurocognitive challenges into injury prevention training: A clinical commentary

Despite the efforts of many traditional lower extremity injury prevention programs (IPP), the incidence of anterior cruciate ligament injuries in young athletes continues to rise. Current best practices for IPPs include training lower extremity neuromuscular control and movement quality during cutting, jumping, and pivoting. Emerging evidence indicates neurocognition may contribute to injury incidence and injury risk biomechanics. Therefore, IPP outcomes may improve if clinicians also consider neurocognitive contributions to neuromuscular control and athletic performance. A substantial barrier to neurocognitive challenge integration during injury prevention training in the group setting is the lack of structured neuromuscular and neurocognitive progressions. Therefore, our aim is to provide clinicians with a defined framework and recommendations from clinical experience for how to implement neurocognitive challenges within group IPPs that requires minimal extra time and resources. This clinical commentary proposes a three-phase model adopted from motor learning literature to simultaneously progress neuromuscular and neurocognitive challenges through a structured IPP.

Visual Perturbation to Enhance Return to Sport Rehabilitation after Anterior Cruciate Ligament Injury: A Clinical Commentary

Anterior cruciate ligament (ACL) tears are common traumatic knee injuries causing joint instability, quadriceps muscle weakness and impaired motor coordination. The neuromuscular consequences of injury are not limited to the joint and surrounding musculature, but may modulate central nervous system reorganization. Neuroimaging data suggest patients with ACL injuries may require greater levels of visual-motor and neurocognitive processing activity to sustain lower limb control relative to healthy matched counterparts. Therapy currently fails to adequately address these nuanced consequences of ACL injury, which likely contributes to impaired neuromuscular control when visually or cognitively challenged and high rates of re-injury. This gap in rehabilitation may be filled by visual perturbation training, which may reweight sensory neural processing toward proprioception and reduce the dependency on vision to perform lower extremity motor tasks and/or increase visuomotor processing efficiency. This clinical commentary details a novel approach to supplement the current standard of care for ACL injury by incorporating stroboscopic glasses with key motor learning principles customized to target visual and cognitive dependence for motor control after ACL injury.

LEVEL OF EVIDENCE

5.

Risk Factors for Failure After Anterior Cruciate Ligament Reconstruction in a Pediatric Population: A Prediction Algorithm

Background:

Anterior cruciate ligament reconstruction (ACLR) in pediatric patients is becoming increasingly common. There is growing yet limited literature on the risk factors for revision in this demographic.

Purpose:

To (1) determine the rate of pediatric revision ACLR in a nationally representative sample, (2) ascertain the associated patient- and injury-specific risk factors for revision ACLR, and (3) examine the differences in the rate and risks of revision ACLR between pediatric and adult patients.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

The PearlDiver patient record database was used to identify adult patients (age ≥20 years) and pediatric patients (age <20 years) who underwent primary ACLR between 2010 and 2015. At 5 years postoperatively, the risk of revision ACLR was compared between the adult and pediatric groups. ACLR to the contralateral side was also compared. Multivariate logistic regression was used to determine the significant risk factors for revision ACLR and the overall reoperation rates in pediatric and adult patients; from these risk factors, an algorithm was developed to predict the risk of revision ACLR in pediatric patients.

Results:

Included were 2055 pediatric patients, 1778 adult patients aged 20 to 29 years, and 1646 adult patients aged 30 to 39 years who underwent ACLR. At 5 years postoperatively, pediatric patients faced a higher risk of revision surgery when compared with adults (18.0 % vs 9.2% [adults 20-29 years] and 7.1% [adults 30-39 years]; P < .0001), with significantly decreased survivorship of the index ACLR (P < .0001; log-rank test). Pediatric patients were also at higher risk of undergoing contralateral ACLR as compared with adults (5.8% vs 1.6% [adults 20-29 years] and 1.9% [adults 30-39 years]; P < .0001). Among the pediatric cohort, boys (odds ratio [OR], 0.78; 95% CI, 0.63-0.96; P = .0204) and patients >14 years old (OR, 0.62; 95% CI, 0.45-0.86; P = .0035) had a decreased risk of overall reoperation; patients undergoing concurrent meniscal repair (OR, 1.84; 95% CI, 1.43-2.38; P < .0001) or meniscectomy (OR, 2.20; 95% CI, 1.72-2.82; P < .0001) had an increased risk of revision surgery. According to the risk algorithm, the highest probability for revision ACLR was in girls <15 years old with concomitant meniscal and medial collateral ligament injury (36% risk of revision).

Conclusion:

As compared with adults, pediatric patients had an increased likelihood of revision ACLR, contralateral ACLR, and meniscal reoperation within 5 years of an index ACLR. Families of pediatric patients—especially female patients, younger patients, and those with concomitant medial collateral ligament and meniscal injuries—should be counseled on such risks.

Differences in Knee Shape between ACL Injured and Non-Injured: A Matched Case-Control Study of 168 Patients

OBJECTIVE

Anterior cruciate ligament (ACL) injury prevention programs could be more effective if we could select patients at risk for sustaining an ACL rupture. The purpose of this study is to identify radiographic shape variants of the knee between patients with and patients without an ACL rupture.

METHODS

We compared the lateral and Rosenberg view X-rays of 168 prospectively followed patients with a ruptured ACL to a control group with intact ACLs, matched for gender, after knee trauma. We used statistical shape modeling software to examine knee shape and find differences in shape variants between both groups.

RESULTS

In the Rosenberg view X-rays, we found five shape variants to be significantly different between patients with an ACL rupture and patients with an intact ACL but with knee trauma. Overall, patients who had ruptured their ACL had smaller, flatter intercondylar notches, a lower lateral tibia plateau, a lower medial spike of the eminence, and a smaller tibial eminence compared to control patients.

CONCLUSION

Patients with an ACL rupture have smaller intercondylar notches and smaller tibial eminences in comparison to patients with an intact ACL after knee trauma.

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

BACKGROUND

There 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.

METHODS

A 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.

RESULTS

All 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.

CONCLUSION

Quadriceps 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.

Neuromuscular Training Improves Biomechanical Deficits at the Knee in Anterior Cruciate Ligament-Reconstructed Athletes

OBJECTIVE

Athletes who return to sport after anterior cruciate ligament reconstruction (ACLR) demonstrate persistent biomechanical and neuromuscular deficits of the knee. There is limited evidence on what effect a neuromuscular training (NMT) program has on knee biomechanics in a cohort of athletes with ACLR. Therefore, the primary aim of this study was to quantify the effect of an NMT program on knee biomechanics in a cohort of ACLR athletes. Second, the post-training knee biomechanics were compared between the cohort of ACLR and control athletes.

DESIGN

Cohort study.

SETTING

Controlled laboratory setting.

PARTICIPANTS

Eighteen athletes with ACLR and 10 control athletes.

INTERVENTIONS

Neuromuscular training.

MAIN OUTCOME MEASURES

Knee kinematics and kinetics during a double-limb jump-landing task.

RESULTS

There were no significant interactions (P > 0.05) observed for the athletes with ACLR. However, there was a significant main effect of biomechanics testing session (P < 0.05) for knee flexion angle and moments; athletes with ACLR demonstrated greater knee flexion angle and lower knee flexion moment during the post-training biomechanics testing session. Post-training comparison between the ACLR and control athletes demonstrated no significant interactions (P > 0.05) between the groups. There was a significant main effect of group (P < 0.05) for knee frontal angle, as athletes with ACLR landed with greater knee adduction than the control athletes.

CONCLUSIONS

Significant improvements in knee sagittal plane biomechanical measures were observed after the NMT program by the athletes with ACLR. In addition, post-training comparison of the ACLR and control groups demonstrates comparable knee biomechanics.

Predictive Value of the Magnetic Resonance Imaging-Based Coronal Lateral Collateral Ligament Sign on Adolescent Anterior Cruciate Ligament Reconstruction Graft Failure

BACKGROUND

The coronal lateral collateral ligament (LCL) sign is the presence of the full length of the LCL visualized on a single coronal magnetic resonance imaging (MRI) slice at the posterolateral corner of the knee. The coronal LCL sign has been shown to be associated with elevated measures of anterior tibial translation and internal rotation in the setting of anterior cruciate ligament (ACL) tear.

HYPOTHESIS

The coronal LCL sign (with greater anterior translation, internal rotation, and posterior slope of the tibia) will indicate a greater risk for graft failure after ACL reconstructive surgery.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Retrospective review was performed of adolescent patients with ACL reconstruction: a cohort without graft failure and a cohort with graft failure. MRI was utilized to measure tibial translation and femorotibial rotation and to identify the coronal LCL sign. The posterior tibial slope was measured on lateral radiographs. Patient-reported outcomes were collected.

RESULTS

We identified 114 patients with no graft failure and 39 patients with graft failure who met all criteria, with a mean follow-up time of 3.5 years (range, 2-9.4 years). Anterior tibial translation was associated with anterolateral complex injury (P < .001) but not graft failure (P = .06). Internal tibial rotation was associated with anterolateral complex injury (P < .001) and graft failure (P = .042). Posterior tibial slope was associated with graft failure (P = .044). The coronal LCL sign was associated with anterolateral complex injury (P < .001) and graft failure (P = .013), with an odds ratio of 4.3 for graft failure (95% CI, 1.6-11.6; P = .003). Subjective patient-reported outcomes and return to previous level of sport were not associated with failure. Comparison of MRI before and after ACL reconstruction in the graft failure cohort demonstrated a reduced value in internal rotation (P = .003) but no change in coronal LCL sign (P = .922).

CONCLUSION

Our study demonstrates that tibial internal rotation and posterior slope are independent predictors of ACL graft failure in adolescents. Although the value of internal rotation could be improved with ACL reconstruction, the presence of the coronal LCL sign persisted over time and was predictive of graft rupture (without the need to make measurements or memorize values of significant risk). Together, these factors indicate that greater initial knee deformity after initial ACL tear predicts greater risk for future graft failure.

Joint movement variability during landing in patients with anterior cruciate ligament reconstruction

BACKGROUND

Rapid knee valgus and knee internal rotation motions in the initial phase of landing are the known mechanisms for anterior cruciate ligament injury, and many studies have been investigated on knee joint peak angle during landing. However, the variability in joint movement during landing has not been fully investigated. This study aimed to compare the coefficient of variation of lower extremity range of motion in patients with anterior cruciate ligament reconstruction and healthy subjects during landing.

METHODS

In this cross-sectional study, 54 patients with anterior cruciate ligament reconstruction and 44 healthy subjects were enrolled. All participants underwent six trials of single-leg hop landing for maximum safe horizontal distance. The kinematic variables were the coefficient of variation during two discrete (0.05 after initial contact and maximum knee flexion) time points for selected three-dimensional hip and knee joint range of motion. Comparisons were performed between the two groups.

RESULTS

Compared with healthy subjects, patients with anterior cruciate ligament reconstruction had greater the coefficient of variation in hip internal/external rotation range of motion (patients with anterior cruciate ligament reconstruction had 41.9%, healthy subjects had 25.5%; P=0.0018; effect size: 0.32) and knee internal/external rotation range of motion (patients with anterior cruciate ligament reconstruction had 68.4%; healthy subjects had 48.1%; P=0.0014; effect size: 0.32) for periods that spanned 0.05 s from the initial contact.

CONCLUSIONS

Patients with anterior cruciate ligament reconstruction could be disadvantageous in ability to control and adapt hip and knee joint rotations when controlling landings.

Risk Factors for Contra-Lateral Secondary Anterior Cruciate Ligament Injury: A Systematic Review with Meta-Analysis

Background

The risk of sustaining a contra-lateral anterior cruciate ligament (C-ACL) injury after primary unilateral ACL injury is high. C-ACL injury often contributes to a further decline in function and quality of life, including failure to return to sport. There is, however, very limited knowledge about which risk factors that contribute to C-ACL injury.

Objective

To systematically review instrinsic risk factors for sustaining a C-ACL injury.

Methods

A systematic review with meta-analysis was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Four databases (MEDLINE, CINAHL, EMBASE, Sport Discus) were searched from inception to January 2020. Inclusion criteria were prospective or retrospective studies investigating any intrinsic risk factor for future C-ACL injury. Meta-analysis was performed and expressed as odds ratios (OR) if two or more articles assessed the same risk factor.

Results

44 moderate-to-high quality studies were eventually included in this review, whereof 35 studies were eligible for meta-analysis, including up to 59 000 individuals. We identified seven factors independently increasing the odds of sustaining a C-ACL injury (in order of highest to lowest OR): (1) returning to a high activity level (OR 3.26, 95% CI 2.10–5.06); (2) Body Mass Index < 25 (OR 2.73, 95% CI 1.73–4.36); (3) age ≤ 18 years (OR 2.42, 95% CI 1.51–3.88); (4) family history of ACL injury (OR 2.07, 95% CI 1.54–2.80); (5) primary ACL reconstruction performed ≤ 3 months post injury (OR 1.65, 95% CI: 1.32–2.06); (6) female sex (OR 1.35, 95% CI 1.14–1.61); and (7) concomitant meniscal injury (OR 1.21, 95% CI 1.03–1.42). The following two factors were associated with decreased odds of a subsequent C-ACL injury: 1) decreased intercondylar notch width/width of the distal femur ratio (OR 0.43, 95% CI 0.25–0.69) and 2) concomitant cartilage injury (OR 0.83, 95% CI 0.69–1.00). There were no associations between the odds of sustaining a C-ACL injury and smoking status, pre-injury activity level, playing soccer compared to other sports or timing of return to sport. No studies of neuromuscular function in relation to risk of C-ACL injury were eligible for meta-analysis according to our criteria.

Conclusion

This review provides evidence that demographic factors such as female sex, young age (≤ 18 years) and family history of ACL injury, as well as early reconstruction and returning to a high activity level increase the risk of C-ACL injury. Given the lack of studies related to neuromuscular factors that may be modifiable by training, future studies are warranted that investigate the possible role of factors such as dynamic knee stability and alignment, muscle activation and/or strength and proprioception as well as sport-specific training prior to return-to-sport for C-ACL injuries.

PROSPERO: CRD42020140129.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40279-020-01424-3.

Effect of Graft Rupture Prevention Training on Young Athletes After Anterior Cruciate Ligament Reconstruction: An 8-Year Prospective Intervention Study

Background:

There is a lack of research on the effects of a postoperative rehabilitation program on anterior cruciate ligament (ACL) graft rupture.

Hypothesis:

We hypothesized that a hip-focused rehabilitation protocol with graft rupture education and avoidance training (HIP-GREAT program) would demonstrate lower ACL graft rupture rates compared with a traditional physical therapy (PT) program.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

This study consisted of young athletes who had undergone ACL reconstruction at a single institution. Postoperatively, 136 participants (mean age, 16.9 ± 2.4 years) were enrolled in a traditional PT protocol between 2006 and 2010, and 153 participants (mean age, 17.0 ± 2.3 years) were enrolled in the HIP-GREAT protocol between 2011 and 2015. Follow-up rates were 31% (42/136) and 27% (41/153) in the traditional PT and HIP-GREAT groups, respectively, at 3 years postoperatively. The hazard ratio was calculated, and absolute risk reduction (ARR) and number-needed-to-treat (NNT) analyses were performed to compare the 2 protocols.

Results:

ACL graft rupture occurred in 10 patients (7.4%) in the traditional PT group and 5 patients (3.3%) in the HIP-GREAT group. This difference was not statistically significant (hazard ratio, 0.39; 95% CI, 0.14 to 1.16; P = .09). The ARR was 0.041 (95% CI, –0.011 to 0.093), and the NNT was 24.5.

Conclusion:

This study did not demonstrate a statistically significant reduction of ACL graft rupture in patients in the HIP-GREAT group. However, high ARR values and low NNT values were found, which suggests the possible effectiveness of the HIP-GREAT protocol to reduce ACL graft ruptures in young athletes.

Periodization in Anterior Cruciate Ligament Rehabilitation: A Novel Framework

More than 250,000 anterior cruciate ligament (ACL) injuries occur each year in the USA, and approximately 65% of these injuries undergo reconstructive surgery. Appropriate rehabilitation after ACL reconstruction can yield predictably good outcomes, with return to previous levels of activity and high knee function. At present, periodization is used at all levels of sports training. Whether conceptualized and directed by coaches, or by athletes themselves, competitors structure their training in a cyclic fashion, enabling athletes to best realize their performance goals. In practical application, sport physical therapists use periodization: postoperative "protocols" serve as rudimentary forms of periodization, albeit implemented over shorter time frames than that typically employed in preparation for competition. An ACL injury should not be considered a "simple" musculoskeletal pathology with only local mechanical or motor dysfunctions. Together with the psychological trauma and reduction in physical capacity, there is a cascade of events, including neurological insult to the central nervous system and reduction in afferences to the sensorimotor system. Rehabilitation should consider all these issues, and periodization would allow to better define and to plan aims and objectives to return athletes to their sport. Technological resources including advanced neuroimaging methods, virtual reality for injury risk screening and return to sport assessment, and interactive artificial reality-based neuromuscular training methods offer new approaches and tools to address this important biomedical problem. The cost and availability of many of these technologies will continue to decrease, providing greater availability, scientific rigor, and ultimately, utility for cost-effective and data-driven assessments.

Quadriceps strength to body weight ratio is a significant indicator for initiating jogging after anterior cruciate ligament reconstruction

BACKGROUND

Quadriceps strength recovery after anterior cruciate ligament (ACL) reconstruction is an important criterion for progress in rehabilitation and return to sports. The purpose of this study was to determine whether quadriceps strength to body weight ratio (QS/BW) is a significant indicator for initiating jogging after ACL reconstruction.

METHODS

Isokinetic quadriceps strength at 60°/s was measured and a jogging trial was completed 3 months after ACL reconstruction with hamstring tendon autograft in 83 patients (36 male, 47 female; mean age, 26.6 ± 12.4 years). Based on the jogging trial results, patients were assigned to either a successful jogging group (mean velocity ≥ 9 km/h) or an unsuccessful jogging group (mean velocity < 9 km/h). The association between QS/BW and successful jogging after surgery was investigated by multivariate logistic regression analysis and the cut-off value was determined by receiver operating characteristic analysis.

RESULTS

Forty-four patients (53.0%) were assigned to the successful jogging group and 39 (47.0%) to the unsuccessful jogging group. QS/BW was independently associated with initiating jogging 3 months after surgery. The cut-off value of QS/BW for successful jogging was 1.45 Nm/kg (area under the curve = 0.94; sensitivity = 88.6%, specificity = 87.2%). All of the patients who initiated jogging with QS/BW of > 1.45 Nm/kg at 3 months returned to sports without recurrence or contralateral injury by 10 months after surgery.

CONCLUSIONS

QS/BW is a significant indicator for safely initiating jogging 3 months after ACL reconstruction. The cut-off value of QS/BW for initiating jogging was 1.45 Nm/kg.

CRITERION-BASED REHABILITATION PROGRAM WITH RETURN TO SPORT TESTING FOLLOWING ACL RECONSTRUCTION: A CASE SERIES

Background

Less than 50% of those sustaining an anterior cruciate ligament (ACL) injury return to their preinjury level of sports participation or participate in competitive sport at two to seven years post ACL reconstruction (ACLR). After ACLR, it has been reported that frequency of subsequent ACL tears has reached as high as 31%.

Purpose

The purpose of this case series was to evaluate return to sport and reinjury rates following the use of a criterion-based rehabilitation protocol with a final return to sport test that utilizes minimal equipment following ACL reconstruction.

Study Design

Case series.

Methods

Following ACL reconstruction, participants were included if they had a goal of returning to their pre-injury sport or level of activity, were between 16 and 50 years of age at the time of evaluation, had at least 25 physical therapy visits covered by insurance, and planned to complete physical therapy until clearance for return to sport.

Results

Forty-three participants met the inclusion criteria and enrolled in the study. Twenty-one participants completed the full course of rehabilitation including passing their return to sport test and nineteen participants completed the two-year follow-up. Data obtained at two years indicated that 84% were able to return to their preinjury level of sports competition. A smaller percentage (16%) were able to return to a reduced level of sport and only one participant reported a second ACL injury.

Conclusion

Participants that completed the full course of rehabilitation and passed return to sport testing had a larger percentage that were able to return to preinjury participation levels than currently reported in the literature. This case series did not exclude participants based on graft type, single vs double bundle procedure, ACL revision surgeries, nor concomitant procedures or injuries.

Level of Evidence

Level 4.

Effect of Sand on Knee Load During a Single-Leg Jump Task: Implications for Injury Prevention and Rehabilitation Programs

Richardson, MC, Murphy, S, Macpherson, T, English, B, Spears, I, and Chesterton, P. Effect of sand on knee load during a single-leg jump task: implications for injury prevention and rehabilitation programs. J Strength Cond Res 34(11): 3164-3172, 2020-The purpose of the study was to determine potential differences in landing strategies and subsequent joint loads at the knee (knee abduction moment [KAM], anterior-posterior [AP] tibial translation, and total knee shear force) when jumping onto sand and firm ground from both a level surface and a 30-cm height. Firm ground would act as the control for the study. Seventeen subjects (age: 23.6 ± 3.7 years; body mass: 67.7 ± 10.3 kg; height: 168.5 ± 7.4 cm) performed 3 single-leg jumps on their dominant leg for each of the 4 conditions tested (ground level, sand level, ground height, and sand height). A repeated-measures design investigated the effect of sand on KAM, AP tibial translation, and total knee shear force. Data were analyzed using magnitude-based inferences and presented as percentage change with 90% confidence limits. Results indicated that sand had a clear beneficial effect on KAM, which was possibly moderate during a drop jump (30 cm) and possibly small from a level jump. Sand also had a possibly moderate beneficial effect on AP tibial translation from a level jump. The effect of sand on total knee shear force was unclear. These results suggest that sand may provide a safer alternative to firm ground when performing jump tasks commonly used in anterior cruciate ligament and patellofemoral joint injury prevention and rehabilitation programs. Sand may also allow for an accelerated rehabilitation program because jumping activities could potentially be implemented more safely at an earlier stage in the process.

Timing of Muscle Activation Is Altered During Single-Leg Landing Tasks After Anterior Cruciate Ligament Reconstruction at the Time of Return to Sport

OBJECTIVES

It is well known that alterations in landing mechanics persist for years after anterior cruciate ligament reconstruction (ACL-R). Nevertheless, existing literature is controversial in reporting successful or unsuccessful recovery of prelanding muscle activation timing after ACL-R. The study aimed at comparing myoelectric and kinematic patterns during landing tasks between ACL-R and healthy subjects.

DESIGN

Cross-sectional study.

SETTING

Institutional research laboratory.

PATIENTS AND INTERVENTION

Fifteen male athletes after ACL-R using patellar tendon and 11 using hamstrings autograft at the time of return to sport were recruited. Fifteen healthy athletes served as control group. Participants performed 4 different single-leg landing tasks arriving onto a force plate.

MAIN OUTCOME MEASURES

Electromyographic (EMG) activity of knee extensors and flexors, normalized vertical ground reaction force (vGRF), and knee angular displacement were recorded.

RESULTS

In all the tasks, preimpact EMG duration was longer in ACL-R (112 ± 28 ms in the knee extensors; 200 ± 34 ms in the knee flexors) compared with healthy participants (74 ± 19 ms in the knee extensors; 153 ± 29 ms in the knee flexors; P < 0.05). Initial contact (IC) and maximum postimpact knee angle were lower in ACL-R (9 ± 7 degrees at IC; 39 ± 12 degrees at maximum flexion) compared with healthy participants (17 ± 9 degrees at IC; 52 ± 15 degrees at maximum flexion; P < 0.05). Normalized vGRF was higher in ACL-R compared with healthy participants (3.4 ± 0.5 and 2.7 ± 0.6; P < 0.05).

CONCLUSIONS

At the time of return to sport, ACL-R subjects showed altered motor control strategies of single-leg landings. These alterations may lead to uncoordinated movement, hence increasing the risk of reinjury.

Altered Neuromuscular Activity of the Lower-Extremities During Landing Tasks in Patients With Anterior Cruciate Ligament Reconstruction: A Systematic Review of Electromyographic Studies

CONTEXT

Altered lower-limb biomechanics have been observed during landing task in patients with anterior cruciate ligament reconstruction (ACLR), which increases the risk of secondary anterior cruciate ligament injury. However, the alteration in neuromuscular activity of the lower-extremity during landing task is not clear.

OBJECTIVE

To compare the muscle activity pattern assessed by electromyography between the involved limb of patients with ACLR and the contralateral limb or control limb of matched healthy subjects during landing task.

EVIDENCE ACQUISITION

Database of PubMed, Ovid, Scopus, and Web of Science from the inception of the databases until July 2019, using a combination of keywords and their variations: (anterior cruciate ligament OR ACL) AND (electromyography OR EMG) AND (landing OR land). Studies that assessed lower-extremity muscle activity patterns during landing task in patients with ACLR and compared them either with the contralateral side or healthy controls were included.

EVIDENCE SYNTHESIS

Of the 21 studies, 16 studies reported altered muscle activity pattern during landing tasks when compared with either the healthy controls or the contralateral side. For the specific muscle activity patterns, the majority of the studies showed no significant difference in reactive muscle activity, and comparisons across studies revealed a possible trend toward the early onset of quadriceps and hamstring activity and increased cocontraction of the involved limb. There are inconsistent findings regarding the alteration in muscle timing and preparatory muscle activity.

CONCLUSIONS

Patients with ACLR displayed an altered muscle activity pattern during landing tasks, even though they were considered to be capable for sport return. Nevertheless, a firm conclusion could not be drawn due to great heterogeneity in the subject selection and study methods.

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.

INVESTIGATION OF PRIMARY AND SECOND ANTERIOR CRUCIATE LIGAMENT TEARS USING A GEOGRAPHIC DATABASE

BACKGROUND

The incidence of anterior cruciate ligament (ACL) injuries has been estimated at 1 in 3500 individuals in the literature. Second ACL tears represent 7-14% of all ACL tears. The location of ACL tears has been noted to be primarily proximal.

PURPOSE

The purpose of this study was to corroborate previous data as well as to add novel data to the literature regarding the location of ACL tears, risk factors associated with second ACL tears, and correlation between hearing a "pop" at the time of injury and concomitant injuries.

STUDY DESIGN

Epidemiologic Review.

METHODS

A geographic database containing the medical records of individuals in a rural county in Midwest, USA was utilized to identify ACL injuries that occurred in the county from 2011 to 2016. A total of 743 ACL injuries were identified, which were reviewed and stratified by primary and second tears, sex, race, age, activity level, number of "pops" heard at time of injury, side of injury, location of tear, graft type used in reconstruction, location of fixation, and concomitant injuries.

FINDINGS

ACL tear location was noted to be primarily midsubstance (44.1%) or proximal (34.1%). The majority of individuals (56.3%) who reported hearing "multiple pops" at the time of injury sustained multiple types of concomitant injuries. The incidence of second ACL tears was 16.8% of total ACL injuries. Second ACL tears were associated with multiple factors, including tear type (p < 0.015) and tear location (p < 0.022). When comparing primary versus second ACL tears, no significant difference in concomitant injuries was noted.

CONCLUSIONS

The majority of ACL tears (78.2%) occur in the midsubstance or proximal fibers. Hearing multiple "pops" at the time of injury may be associated with more concomitant injuries. The incidence of second ACL tears in this population was comparable to previous studies. Second ACL injuries differed statistically from primary injuries in association with tear type and location.

LEVEL OF EVIDENCE

2C.

Ski boot canting adjustments affect kinematic, kinetic, and postural control measures associated with fall and injury risk

OBJECTIVES

The aim of this study was to investigate if and to what extent small lateral wedges inserted under the ski boot, known as canting, could impact knee kinematics/kinetics, balance, and neuromuscular activity in recreational alpine skiers in the laboratory setting.

DESIGN

Experimental, crossover study with repeated-measures analysis METHODS: Thirty-eight recreational skiers completed a single-leg postural balance test while wearing standardized ski boots in their unmodified state (control), and with medial and lateral canting wedges applied. Kinematics, kinetics, postural control measures, and neuromuscular activity of the lower extremity were assessed using optical motion capture, instrumented force plates, and electromyography.

RESULTS

Canting modifications had significant impact on lower extremity kinematics and kinetics: canting wedges on the medial side of the foot significantly decreased knee valgus moments, hip internal rotation, and hip adduction. Medial canting also improved some postural control measures associated with balance quality, and reduced activation levels of the Vastus Lateralis, Biceps Femoris, and Tibialis Anterior.

CONCLUSIONS

In the laboratory setting, canting appears to be an appropriate option for improving balance in alpine skiers. Medial canting can alter skier kinematics and kinetics in ways which are consistent with mechanisms of ACL injury. Canting may also result in reduced neuromuscular effort. These changes in movement have potential to prevent lower limb injuries in alpine skiers. The findings of this study motivate future research to predict individual responses to canting treatment in a study setting more closely resembling the sports environment.

From barefoot hunter gathering to shod pavement pounding. Where to from here? A narrative review

Understanding the current prevalence and incidence of running injury from an evolutionary perspective has sparked great debate. Proponents of the evolutionary approach to understanding running injury suggest that humans ran using less injurious biomechanics prior to the invention of cushioned running shoes. Those who disagree with this view, point to the many runners, wearing cushioned running shoes, who do not get injured and suggest that the evolutionary approach is indulging in a 'natural fallacy'. This polarises the scientific debate into discrete categories such as 'shod' vs 'barefoot'. This review aims, first, to describe humans' innate impact moderating mechanisms which arise from our evolutionary legacy. Second, we discuss the impact of footwear on these mechanisms and the potential link to injury in some runners. Finally, we discuss the role of barefoot training in sports medicine and attempt to make some practical suggestions as to how it might be integrated in our modern urban environments.

Principles of Motor Learning to Support Neuroplasticity After ACL Injury: Implications for Optimizing Performance and Reducing Risk of Second ACL Injury

Athletes who wish to resume high-level activities after an injury to the anterior cruciate ligament (ACL) are often advised to undergo surgical reconstruction. Nevertheless, ACL reconstruction (ACLR) does not equate to normal function of the knee or reduced risk of subsequent injuries. In fact, recent evidence has shown that only around half of post-ACLR patients can expect to return to competitive level of sports. A rising concern is the high rate of second ACL injuries, particularly in young athletes, with up to 20% of those returning to sport in the first year from surgery experiencing a second ACL rupture. Aside from the increased risk of second injury, patients after ACLR have an increased risk of developing early onset of osteoarthritis. Given the recent findings, it is imperative that rehabilitation after ACLR is scrutinized so the second injury preventative strategies can be optimized. Unfortunately, current ACLR rehabilitation programs may not be optimally effective in addressing deficits related to the initial injury and the subsequent surgical intervention. Motor learning to (re-)acquire motor skills and neuroplastic capacities are not sufficiently incorporated during traditional rehabilitation, attesting to the high re-injury rates. The purpose of this article is to present novel clinically integrated motor learning principles to support neuroplasticity that can improve patient functional performance and reduce the risk of second ACL injury. The following key concepts to enhance rehabilitation and prepare the patient for re-integration to sports after an ACL injury that is as safe as possible are presented: (1) external focus of attention, (2) implicit learning, (3) differential learning, (4) self-controlled learning and contextual interference. The novel motor learning principles presented in this manuscript may optimize future rehabilitation programs to reduce second ACL injury risk and early development of osteoarthritis by targeting changes in neural networks.

Effect of Sand on Landing Knee Valgus During Single-Leg Land and Drop Jump Tasks: Possible Implications for ACL Injury Prevention and Rehabilitation

CONTEXT

Despite significant emphasis on anterior cruciate ligament injury prevention, injury rates continue to rise and reinjury is common. Interventions to reduce injury have included resistance, balance, and jump training elements. The use of sand-based jump training has been postulated as an effective treatment. However, evidence on landing mechanics is limited.

OBJECTIVE

To determine potential differences in landing strategies and subsequent landing knee valgus when performing single-leg landing (SLL) and drop jump (DJ) tasks onto sand and land, and to compare between both male and female populations.

DESIGN

A randomized repeated-measures crossover design.

SETTING

University laboratory.

PARTICIPANTS

Thirty-one participants (20 males and 11 females) from a university population.

INTERVENTIONS

All participants completed DJ and SLL tasks on both sand and land surfaces.

MAIN OUTCOME MEASURES

Two-dimensional frontal plane projection angle (FPPA) of knee valgus was measured in both the DJ and SLL tasks (right and left) for both sand and land conditions.

RESULTS

FPPA was lower (moderate to large effect) for SLL in sand compared with land in both legs (left: 4.3° [2.8°]; right: 4.1° [3.8°]) for females. However, effects were unclear (left: -0.7° [2.2°]) and trivial for males (right: -1.1° [1.9°]). FPPA differences for males and females performing DJ were unclear; thus, more data is required. Differences in FPPA (land vs sand) with respect to grouping (sex) for both SLL left (4.9° [3.0°]) and right (5.1° [4.0°]) were very likely higher (small)/possibly moderate for females compared with males.

CONCLUSIONS

The effects of sand on FPPA during DJ tasks in males and females are unclear, and further data is required. However, the moderate to large reductions in FPPA in females during SLL tasks suggest that sand may provide a safer alternative to firm ground for female athletes in anterior cruciate ligament injury prevention and rehabilitation programs, which involve a SLL component.