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here is increasing attention in the literature to psychological consequences of anterior cruciate ligament injury, particularly those related to reinjury fear/anxiety. However, noticeable knowledge gaps exist, pertaining to how different fear-related constructs (eg, kinesiophobia, reinjury anxiety) are defined and consequently assessed. This editorial tackles some fundamental issues: first regarding the distinction between reinjury anxiety, which is assessed using questionnaires, and fear of reinjury, which is an acute response to injury-relevant scenarios. Next, the frequent focus of practitioners on pain as the major injury-instigated threat, which oversimplifies the complex injury experience and, in turn, the individual anxiety perceived by patients. A call to researchers and clinicians is issued to further consider the constructs they evaluate and related assessment tools. While fear is more challenging to assess and requires individual exposure to threatening situations, anxiety-relevant questionnaires should be carefully selected rather than using common ones that may not suit the population.

Bakgrund: Den höga förekomsten av främre korsbandsskador (ACL-skada) i sport tyder på en inblandning av både biomekaniska och neurokognitiva riskfaktorer. Idrottare utsätts ständigt för utmanande idrottsscenarier som ofta kännetecknas av komplexa rörelser i en miljö med många olika stimuli och även psykologisk press. Förlust av knäproprioception efter ligamentskadan och långvariga neuroplastiska förändringar utgör en utmaning för idrottare i sådana situationer efter återgång till idrott (RTS). Detta antas bidra till den höga frekvensen av sekundära skador, trots att man uppfyllt kriterierna för RTS. Psykologiska faktorer som t.ex. rädsla eller oro för sekundära skador antas också påverka central sensorimotorisk bearbetning och därför spela en roll i hur funktionella rörelser genereras och kontrolleras. Bedömning av rädsla för skada är dock en utmaning och baseras vanligen på suboptimala verktyg, särskilt när de används för elitidrottare. Nuvarande kliniska bedömningar utgår främst från grova utfallsmått samtidigt som man bortser från flerledskontroll och psykologiska aspekter på motorisk prestation. Denna avhandling fokuserar på betydelsen av proprioception och rädsla/oro för sekundär skada med avseende på funktionell rörelsekontroll efter ACL-skada som behandlats med rekonstruktion (ACLR) och rehabilitering.

Metoder: Avhandlingen består av fyra tvärsnittsstudier (delarbeten I-IV), som härrör från två datainsamlingar utförda i ett rörelseanalyslaboratorium. Delarbete I introducerar ett nytt test där man kliver över ett hinder med så litet avstånd som möjligt och utan information från nedre synfältet. Testet syftar till att funktionellt bedöma proprioception och sensorimotorisk kontroll. Individer med ACLR och rehabilitering jämfördes med två kontrollgrupper av icke-skadade individer; moderat aktiva personer (CTRL) samt elitidrottare (ATH). En kinematisk analys, med 3D motion capture, inkluderade rörelsenoggrannhet, variabilitet och symmetri i nedre extremiteterna. Delarbete II utvärderar knäproprioception hos samma individer med hjälp av ett viktbärande knäledspositionstest (JPS), och resultaten jämfördes med motsvarande resultat från hindertestet. Delarbete III undersöker om självrapporterad rädsla för ny skada tar sig uttryck i biomekaniken (kinematik och elektromyografi [EMG]) i ett standardiserat s.k. ”rebound side-hop”-test (SRSH). En ACLR-grupp delades in i två undergrupper: de med hög rädsla respektive de med låg rädsla baserat på en diskriminerande fråga, och dessa grupper jämfördes även med personer utan ACL-skada (CTRL). I delarbete IV som är en metodologisk studie introduceras ett testparadigm med kraftiga balansstörningar som syftar till att framkalla och mäta neurofysiologiskt svar på eventuell rörelserelaterad rädsla/oro. Metodstudien fokuserar på oskadade individer. Konditionerade hörselstimuli följdes ibland av en snabb förskjutning av den plattform som testdeltagaren stod på, och detta jämfördes med neutrala stimuli utan efterföljande förskjutning. Elektroencefalografi registrerades kontinuerligt och händelserelaterade potentialer undersöktes som potentiella biomarkörer för ökad uppmärksamhetsgrad möjligen förknippade med oro för rörelse/ny skada.

Resultat: Kinematisk asymmetri observerades för ACLR-gruppen under hindertestet, både för enskilda leder och för flerledsrörelse- och hastighetskurvor. Dessutom var variabiliteten i det efterföljande benets bana för högre hinder lägre för ACLR jämfört med båda kontrollgrupperna. Den mindre fysiskt aktiva CTRL-gruppen visade både lägre noggrannhet under klivet över hindret (större hinderavstånd) och JPS-fel jämfört med både ACLR och ATH. Måttliga positiva korrelationer observerades mellan absoluta fel i knä JPS-testet och hinderavståndet i det funktionella testet endast för det skadade benet i ACLR-gruppen. Individer med ACLR och hög rädsla, visade högre biceps femoris EMG amplitud samt högre anterior-posterior co-kontraktion index under landning vid sidohoppet. Sido-hoppsprestanda kunde också särskiljas för ACLR (oavsett rädsla) med större höft- och knäböjning, medan individer med hög rädsla också hade mer bålböjning. I balansstörningstestet återspeglades möjlig rörelserädsla vid EEG-mätningarna som en hög-amplitud betingad negativ variation (CNV) våg som svar på konditionerade jämfört med neutrala stimuli. CNV-vågen observerades över alla elektrodplaceringar men var mest framträdande över frontala och centrala kortikala områden.

Slutsatser: Även efter rehabilitering uppvisade individer med ACLR en avvikande sensorimotorisk funktion, kännetecknad av mindre rörelsevariabilitet och större asymmetri i flera leder när proprioceptionen utmanades (dvs. när nedre synfältet var blockerat). Knäledspositionskänslan verkade dock inte vara nedsatt bland dessa individer, utan större fel associerades snarare till lägre grad av fysisk aktivitet än till ACLR-historik. Korrelationer till JPS-fel, som endast ses för ACLR-benet, kan tyda på en tendens att fokusera uppmärksamheten mer internt när man korsar ett hinder (vanligtvis en extern fokusuppgift), även om detta bör undersökas ytterligare. Högre grad av självrapporterad rädsla för ny skada uttrycktes i biomekaniken under sidohoppen, med till synes styvare landningar och en neuromuskulär strategi för att skydda knäleden. Detta har potentiella konsekvenser för påskyndande av leddegeneration samt minskad motorisk anpassningsförmåga, vilket kan innebära en risk för ny skada. Slutligen framkallade testparadigmet med balansstörningen en slags hot-associerad ökad uppmärksamhetsgrad i form av en CNV-våg, hittills bara testat på oskadade individer. CNV-vågen bör ytterligare utforskas som en potentiell biomarkör för oro för ny skada. Framtida forskning bör implementera detta paradigm på individer med olika nivåer av självrapporterad rörelserelaterad rädsla/oro, i strävan efter ett mer holistiskt tillvägagångssätt i rehabilitering efter ACLR där psykologiska aspekter tydligt vägs in.

Background: Non-contact injuries are highly prevalent among young athletes and occur particularly in situations that require fast decision making and divided attention. Administering relevant neurocognitive tests could help identify deficiencies in these cognitive abilities and thus potentially mitigate injury risk. However, processes such as selective attention and response inhibition might depend to some extent on the athlete’s maturation stage. We aimed to examine the effect of maturation on selective visual attention and response inhibition among adolescent volleyball players.

Methods: In this cross-sectional study, 52 female adolescents (age 12.3 ± 2.1 years) performed an Eriksen Flankers task. Participants were divided into subgroups based on their estimated adult stature, using the Khamis & Roche method: Pre-pubertal (PRE; n = 13, age: 9.9 ± 1.3), early-puberty (EPUB; n = 7, age: 10.5 ± 0.6), mid-puberty (MPUB; n = 8, age: 12.6 ± 0.8) and late puberty (LPUB; n = 24, age: 14.1 ± 0.9). Analyses of covariance (ANCOVA) were performed on congruent and incongruent reaction times (RT), with corresponding success rates (% correct responses) as covariate. Flanker interference effect was tested using ANOVA. Correlations were further examined between the dependent variables and participants’ chronological age.

Results: There was a significant group effect, with PRE demonstrating longer RT compared with LPUB (P < 0.001) for both congruent and incongruent RT. Moderate negative correlations were observed between age and RT (Rp= -0.695, Rp= -0.614 for congruent and incongruent RT, respectively) and low positive correlations between age and incongruent success rate (Rs= 0.318). Low to moderate correlations were also observed within the LPUB group for RT (Rp= -0.431–-0.532) and success rate (negative Rs= -574 for congruent and positive Rs= 0.417 for incongruent). There were no group differences nor age associations with interference effect.

Conclusions: Our findings indicate that information processing and selective visual attention are superior at late maturation compared with early maturation among female adolescents. The same cannot be said for response inhibition, which did not differ between maturation groups. Similar tendencies were observed with regards to chronological age, but not entirely explained by it. Maturation level, rather than chronological age, should guide practitioners during sport participation and injury prevention programs for young athletes, whose neurocognitive abilities are not yet fully developed, placing them at risk for non-contact injuries.

Sensorimotor deficits, particularly proprioceptive, are often reported following rupture of the anterior cruciate ligament (ACL). High secondary injury rates and long-term negative consequences suggest that these deficits are not properly identified using current assessment methods. We explored a novel obstacle clearance test to evaluate sensorimotor control in individuals following ACL reconstruction (ACLR) and rehabilitation. Thirty-seven post-ACLR individuals, 23 nonathletic asymptomatic controls (CTRL), and 18 elite athletes stepped over a hurdle-shaped obstacle, downward vision occluded, aiming for minimal clearance. Kinematic outcomes (3D motion capture) for the leading and trailing legs, for two unpredictably presented obstacle heights, were categorized into Accuracy: vertical foot clearance and minimal distance from the obstacle; Variability: end-point and hip/knee trajectory; and Symmetry: trunk/hip/knee crossing angles, hip–knee–ankle movement, and velocity curves. Accuracy was worse for CTRL compared with both other groups. ACLR had less leading and trailing vertical foot clearance with their injured compared with their noninjured leg. ACLR and athletes had less crossing knee flexion in their injured/nondominant legs compared with their contralateral leg, both leading and trailing. ACLR showed greater trunk flexion when crossing with their injured leg, both leading and trailing. For the leading leg, ACLR showed greater asymmetry for the hip–knee–ankle velocity curve compared with elite athletes. Trailing leg trajectory variability was lower for ACLR compared with CTRL and athletes for higher obstacles. Clinical significance: Sensorimotor deficits in individuals post-ACLR were reflected by greater asymmetry and less variable (more stereotypical) trajectories rather than limb positioning ability. This consideration should be addressed in clinical evaluations.

Objectives: To evaluate knee joint position sense (JPS) among individuals with anterior cruciate ligament reconstruction (ACLR), cleared for return to sport, and investigate whether JPS errors are associated with outcomes of a functional obstacle clearance test (OC; downward vision occluded).

Design: Cross-sectional.

Setting: Controlled laboratory.

Participants: Thirty-four individuals following ACLR, 23 non-athletic asymptomatic controls (CTRL), 18 athletes (ATH).

Main outcome measures: absolute error (AE) and variable error (VE) for weight-bearing knee JPS (target angles: 40°, 65°); minimal distances of the lower extremity from the obstacle (at any time and vertical clearance; two obstacle heights).

Results: Larger AE (P = 0.023) and VE (P = 0.010) were observed for CTRL compared with ACLR. CTRL also had larger OC distances for the trailing leg compared with ATH (P ≤ 0.046) and greater variability compared to both other groups (P ≤ 0.033). Moderate positive correlations (Rs ≥ 0.408, P ≤ 0.029) were observed between AE for the 40° angle and low-obstacle distances, for the injured ACLR leg.

Conclusions: Knee JPS was worse in less-active individuals rather than following ACLR. Functional assessments like our OC test should complement isolated JPS tests, as they emphasize whole-body coordination and thus constitute more relevant estimations of proprioception.

Objective: Evaluate active knee joint position sense (JPS) throughout rehabilitation after anterior cruciate ligament reconstruction (ACLR).

Design: Longitudinal.

Setting: Motion laboratory.

Participants: Twenty-two individuals post-ACLR and 22 activity-matched non-injured controls performed weight-bearing and non-weight-bearing knee JPS tests. The ACLR participants performed at three functional timepoints: T1, able to perform single-leg sit-to-stand; T2, able to hop maximally; T3, cleared for return to sports. Controls performed on one occasion.

Main outcome measures: Constant, absolute, variable errors (CE, AE, VE) and interlimb symmetry estimates (100% signifying perfect symmetry), for 40° and 65° knee flexion target angles.

Results: For the weight-bearing 40° condition, CE and AE of the ACLR knee significantly increased from T1 to T2 (P = 0.010) and T1 to T3 (P = 0.002). Consequently, interlimb asymmetry for AE significantly increased from T1 (AEsym% = 101.2% ± 55.4%) to T3 (AEsym% = 139.7% ± 54.8%). Compared to controls, AE for the ACLR knee was significantly smaller at T1 (P = 0.016). No other significant differences were observed.

Conclusions: Smaller JPS errors at early rehabilitation while weight-bearing may have been due to heightened quadriceps activation and increased γ motor neuron sensitivity, compensating for deficient ACL mechanoreceptors. In contrast, non-weight-bearing testing did not reveal changes over time. Clinicians are advised to consider these distinctions when assessing proprioception at different rehabilitation stages.

Background: Psychophysiological consequences often persist following musculoskeletal trauma and can result in vastly decreased quality of life. Re-injury anxiety is particularly common among individuals following anterior cruciate ligament (ACL) injury. Existing assessments of re-injury anxiety are, however, restricted to subjective suboptimal questionnaires, which may result in under-reporting and thus poorer injury management. We propose a novel approach to objectively quantify arousal response to movement-related anxiety. A new experimental paradigm was implemented to induce and record a conditioned electrophysiological response to a sudden perturbation, experienced to be potentially injurious.

Objective: To explore the feasibility of detecting anxiety-associated electrocortical response and to evaluate its discriminative ability between asymptomatic individuals and those who had experienced an ACL injury.

Methods: Physically-active asymptomatic persons and individuals post-ACL reconstruction stood blindfolded on a perturbation platform capable of generating high-acceleration translations (1.5 m/s2). Auditory stimuli were repeatedly presented in four-second intervals, as either low- or high-frequency tones. Half of the high-frequency tones were followed 1.5 seconds later by a destabilizing perturbation in one of eight randomized directions. The two tone conditions were thus termed ‘Neutral’ and ‘Anxiety’, as the high-frequency tone was intended to invoke an arousal response in anticipation of a potential perturbation. Event-related potentials (ERP) were computed for nine electrodes by averaging 100 Neutral and 100 Anxiety trials. Significant ERP components were identified using functional data analysis. Paired difference-waves’ amplitudes (Neutral - Anxiety) were compared between groups.

Results: ERP correlates of anxiety were detected for both groups in frontal and central midline locations, with an observable contingent negative variation (CNV) from 500 ms post-stimulus in Anxiety compared with Neutral trials. This ERP component is reflective of a threat-induced arousal response, associated with attention and expectancy of an anxiety-relevant event. Preliminary data indicate no group differences in CNV amplitudes.

Conclusions: Objective evaluation of an arousal response to movement-related anxiety was found to be feasible, resulting in a threat-induced CNV. Further investigation will elucidate the discriminative power of such an approach to differentiate between individuals with high and low re-injury anxiety, as well as potential associations with existing patient-reported outcome measures.

Psychological consequences often persist following musculoskeletal trauma and can result in vastly decreased quality of life. Re-injury anxiety is reported to hinder return to sports and can itself be a precursor for secondary injuries. Existing assessments of re-injury anxiety are restricted to subjective questionnaires, which may result in under-reporting and thus poorer injury management. In the current study, we introduced an experimental approach to objectively quantify movement-related anxiety using a threat-conditioning paradigm. We aimed to explore the feasibility of such an approach among non-injured persons.

Ten physically-active individuals stood blindfolded on a platform capable of generating high-acceleration translations in eight different directions. Consecutive auditory stimuli were presented (four-second intervals), as either high- (conditioned stimulus; CS⁺) or low- (neutral stimulus; CS^–) tones. Half of the CS⁺ trials were followed by a perturbation in a pseudo-random order. Event-related potentials were computed for nine electrodes by averaging 100 X CS^– and 100 X CS⁺ trials. Significant latencies for CS^– – CS⁺ comparisons were identified using interval-wise testing. Mean-amplitudes for significant intervals were used to detect a channel effect.

Large negative CS+ waveforms were observed from 302-627ms post-stimulus and continuing until the end of the trials, most prominently over frontal and central midline locations (p ≤ 0.025). This effect, inferred as a contingent negative variation wave (CNV), may be reflective of threat-induced arousal response.

Our test paradigm was found to be feasible, with a CNV suggested as a potential biomarker for re-injury anxiety. Further validation is needed, as well as exploring the discriminative power of such an approach between individuals with and without previous injury.