Movement strategies and dynamic knee control after anterior cruciate ligament injury : a three-dimensional biomechanical analysis

Background: Rupture of the anterior cruciate ligament (ACL) is common and mainly occurs in non-contact situations in sports, often due to momentarily poor movement control. Assessment of movement quality during sport-like tasks iscrucial to understand how to decrease the high risk of reinjury for ACL-injured persons, but also how to prevent primary injury. This thesis addresses movement quality after ACL injury and includes development and evaluation of a novel standardized rebound side hop test (SRSH) for reliability and agreement of landing mechanics, and compares these outcomes between asymptomatic persons with different athletic levels, and between different hop tests. Methods: This thesis involves five papers based on two separate data collections performed in a motion analysis laboratory. Paper I is a long-term follow up of ACL-injured persons treated with or without ACL reconstruction (ACLR) compared to asymptomatic persons (total N = 99, age 35-63), while papers II-V included ACLR persons, and asymptomatic elite athletes and non-athletes (total N = 79, age 17-34). A motion capture system synchronized with force plates and surface electromyography (EMG) registered trunk, hip and knee angles and moments and knee muscle activity during the hop for distance, vertical hop, and SRSH. Novel measures of dynamic knee robustness were also evaluated using finite helical axis inclination angles extracted from knee rotation intervals of 10˚. Results: On average 23 years after injury, ACL injured persons performed the vertical hop with diverse angles compared to controls and their non-injured leg.The younger groups of ACLR persons and controls generally displayed excellent reliability and agreement for SRSH landing mechanics. These outcomes differed between the groups, and between legs for ACLR persons, despite similar dynamic knee robustness and acceptable knee function outcomes. Curve analyses further displayed differences between athletes and non-athletes, mainly with greater hip moments for athletes, although with similar values for dynamic knee robustness. Finally, greater knee angles and moments considered strenuous for the ACL were evident during the first rebound landing in SRSH compared to the other landings. Conclusions: Persons who have suffered an ACL injury, regardless of whether treated with ACLR or not, appear to use task-coping strategies in preparation for and during landings to decrease knee joint loading, probably to preserve dynamic knee robustness. More attention should be given to the trunk and hip in clinics when evaluating movement quality after ACL injury to reduce the risk of future injuries due to movement compensation. High-level athletic training may also improve the ability to maintain dynamic knee robustness whilst performing a sport-like side-to-side task more efficiently through increased engagement of the hip. Finally, side hop landings should be assessed when evaluating and correcting for erroneous landing mechanics to improve knee landing control.Bakgrund: Främre korsbandsskada (ACL-skada) är en vanlig idrottsskada som huvudsakligen uppstår i situationer utan kontakt med annan spelare till följd aven tillfälligt dålig rörelsekontroll. Utvärdering av rörelsekvalitet under idrottsliknande tester behövs för att bättre förstå hur risken för ACL-skador och återskador kan minskas. Denna avhandling är inriktad på rörelsekvalitet efter ACL-skada och behandlar utveckling samt utvärdering av ett nytt standardiserat sidohopp (SRSH). Tillförlitlighet och överensstämmelse av ledvinklar och moment utvärderas och jämförs mellan personer med och utan ACL-skada, mellan personer med olika atletbakgrund, samt mellan olika hopptester. Metoder: Denna avhandling omfattar fem studier, vilka är baserade på två separata datasamlingar utförda i ett rörelsesanalyslaboratorium. Studie I är en långtidsuppföljning av personer med ACL-skada behandlade både med och utan ACL-rekonstruktion, vilka jämförs med knäfriska kontroller (totala N = 99, 35-63 år). Studie II-V inkluderade personer med ACL-rekonstruktion, knäfriska kontroller och elitatleter (totala N = 79, 17-34 år). Ett rörelseanalyssystem synkroniserat med kraftplattor och ytelektromyografi registrerade bål, höft och knävinklar och moment, samt lårmuskelaktivitet under enbenshopp (på längden, på höjden, samt SRSH). Även nya utfallsmått som utvärderar knäets robusthet under rörelse analyserades med helixvinklar från intervaller av knärörelse på 10˚. Resultat: I genomsnitt 23 år efter ACL-skada utförde båda grupperna ett enbenshopp på höjden med olika ledvinklar, både jämfört med kontroller samt deras oskadade ben. De yngre ACL-skadade personerna och kontrollerna visade generellt utmärkt tillförlitlighet och överensstämmelse av ledvinklar och moment under SRSH. Dessa utfallsmått skiljde sig mellan grupperna och mellan benen för ACL-skadade personer, trots att lika resultat av knäets robusthet samt acceptabla knäfunktionsresultat visades. Kurvanalyser visade även på skillnader mellan atleter och icke-atleter, främst med större höftmoment för atleter, trots lika resultat av knäets robusthet. Den första landningen i SRSH visade större knävinklar och moment som anses belasta ACL jämfört med övriga landningar. Slutsatser: Personer med ACL-skada, oavsett om de behandlats med ACLrekonstruktion eller ej, verkar tillämpa rörelsestrategier för att hantera landningar från enbenshopp genom att minska belastningen på knäleden, troligen för att bevara knäets robusthet. I klinik bör ett större fokus läggas på bål och höftrörelser vid utvärdering av rörelsekvaliteten efter ACL-skada. Detta för att minska risken för framtida skador på grund av rörelsekompensation. Vidare förbättrar idrottsträning på hög nivå troligen förmågan att upprätthålla knäets robusthet samtidigt som utförandet av sidohoppstester blir effektivare genom ett ökat engagemang av höften. Slutligen bör sidhoppslandningar användas vid utvärdering och korrigering av landningsmekanik för en förbättrad knäkontroll

Movement strategies and dynamic knee control after anterior cruciate ligament injury : a three-dimensional biomechanical analysis

Background: Rupture of the anterior cruciate ligament (ACL) is common and mainly occurs in non-contact situations in sports, often due to momentarily poor movement control. Assessment of movement quality during sport-like tasks iscrucial to understand how to decrease the high risk of reinjury for ACL-injured persons, but also how to prevent primary injury. This thesis addresses movement quality after ACL injury and includes development and evaluation of a novel standardized rebound side hop test (SRSH) for reliability and agreement of landing mechanics, and compares these outcomes between asymptomatic persons with different athletic levels, and between different hop tests. Methods: This thesis involves five papers based on two separate data collections performed in a motion analysis laboratory. Paper I is a long-term follow up of ACL-injured persons treated with or without ACL reconstruction (ACLR) compared to asymptomatic persons (total N = 99, age 35-63), while papers II-V included ACLR persons, and asymptomatic elite athletes and non-athletes (total N = 79, age 17-34). A motion capture system synchronized with force plates and surface electromyography (EMG) registered trunk, hip and knee angles and moments and knee muscle activity during the hop for distance, vertical hop, and SRSH. Novel measures of dynamic knee robustness were also evaluated using finite helical axis inclination angles extracted from knee rotation intervals of 10˚. Results: On average 23 years after injury, ACL injured persons performed the vertical hop with diverse angles compared to controls and their non-injured leg.The younger groups of ACLR persons and controls generally displayed excellent reliability and agreement for SRSH landing mechanics. These outcomes differed between the groups, and between legs for ACLR persons, despite similar dynamic knee robustness and acceptable knee function outcomes. Curve analyses further displayed differences between athletes and non-athletes, mainly with greater hip moments for athletes, although with similar values for dynamic knee robustness. Finally, greater knee angles and moments considered strenuous for the ACL were evident during the first rebound landing in SRSH compared to the other landings. Conclusions: Persons who have suffered an ACL injury, regardless of whether treated with ACLR or not, appear to use task-coping strategies in preparation for and during landings to decrease knee joint loading, probably to preserve dynamic knee robustness. More attention should be given to the trunk and hip in clinics when evaluating movement quality after ACL injury to reduce the risk of future injuries due to movement compensation. High-level athletic training may also improve the ability to maintain dynamic knee robustness whilst performing a sport-like side-to-side task more efficiently through increased engagement of the hip. Finally, side hop landings should be assessed when evaluating and correcting for erroneous landing mechanics to improve knee landing control.Bakgrund: Främre korsbandsskada (ACL-skada) är en vanlig idrottsskada som huvudsakligen uppstår i situationer utan kontakt med annan spelare till följd aven tillfälligt dålig rörelsekontroll. Utvärdering av rörelsekvalitet under idrottsliknande tester behövs för att bättre förstå hur risken för ACL-skador och återskador kan minskas. Denna avhandling är inriktad på rörelsekvalitet efter ACL-skada och behandlar utveckling samt utvärdering av ett nytt standardiserat sidohopp (SRSH). Tillförlitlighet och överensstämmelse av ledvinklar och moment utvärderas och jämförs mellan personer med och utan ACL-skada, mellan personer med olika atletbakgrund, samt mellan olika hopptester. Metoder: Denna avhandling omfattar fem studier, vilka är baserade på två separata datasamlingar utförda i ett rörelsesanalyslaboratorium. Studie I är en långtidsuppföljning av personer med ACL-skada behandlade både med och utan ACL-rekonstruktion, vilka jämförs med knäfriska kontroller (totala N = 99, 35-63 år). Studie II-V inkluderade personer med ACL-rekonstruktion, knäfriska kontroller och elitatleter (totala N = 79, 17-34 år). Ett rörelseanalyssystem synkroniserat med kraftplattor och ytelektromyografi registrerade bål, höft och knävinklar och moment, samt lårmuskelaktivitet under enbenshopp (på längden, på höjden, samt SRSH). Även nya utfallsmått som utvärderar knäets robusthet under rörelse analyserades med helixvinklar från intervaller av knärörelse på 10˚. Resultat: I genomsnitt 23 år efter ACL-skada utförde båda grupperna ett enbenshopp på höjden med olika ledvinklar, både jämfört med kontroller samt deras oskadade ben. De yngre ACL-skadade personerna och kontrollerna visade generellt utmärkt tillförlitlighet och överensstämmelse av ledvinklar och moment under SRSH. Dessa utfallsmått skiljde sig mellan grupperna och mellan benen för ACL-skadade personer, trots att lika resultat av knäets robusthet samt acceptabla knäfunktionsresultat visades. Kurvanalyser visade även på skillnader mellan atleter och icke-atleter, främst med större höftmoment för atleter, trots lika resultat av knäets robusthet. Den första landningen i SRSH visade större knävinklar och moment som anses belasta ACL jämfört med övriga landningar. Slutsatser: Personer med ACL-skada, oavsett om de behandlats med ACLrekonstruktion eller ej, verkar tillämpa rörelsestrategier för att hantera landningar från enbenshopp genom att minska belastningen på knäleden, troligen för att bevara knäets robusthet. I klinik bör ett större fokus läggas på bål och höftrörelser vid utvärdering av rörelsekvaliteten efter ACL-skada. Detta för att minska risken för framtida skador på grund av rörelsekompensation. Vidare förbättrar idrottsträning på hög nivå troligen förmågan att upprätthålla knäets robusthet samtidigt som utförandet av sidohoppstester blir effektivare genom ett ökat engagemang av höften. Slutligen bör sidhoppslandningar användas vid utvärdering och korrigering av landningsmekanik för en förbättrad knäkontroll

ACL-reconstructed and ACL-deficient individuals show differentiated trunk, hip, and knee kinematics during vertical hops more than 20 years post-injury

PURPOSE: Little is known regarding movement strategies in the long term following injury of the anterior cruciate ligament (ACL), and even less about comparisons of reconstructed and deficient knees in relation to healthy controls. The present purpose was to compare trunk, hip, and knee kinematics during a one-leg vertical hop (VH) ~20 years post-ACL injury between persons treated with surgery and physiotherapy (ACLR), solely physiotherapy (ACLPT), and controls (CTRL). Between-leg kinematic differences within groups were also investigated. METHODS: Sixty-six persons who suffered unilateral ACL injury on average 23 ± 2 years ago (32 ACLR, 34 ACLPT) and 33 controls performed the VH. Peak trunk, hip, and knee angles during Take-off and Landing phases recorded with a 3D motion capture system were analysed with multivariate statistics. RESULTS: Significant group effects during both Take-off and Landing were found, with ACLPT differing from CTRL in Take-off with a combination of less knee flexion and knee internal rotation, and from both ACLR and CTRL in Landing with less hip and knee flexion, knee internal rotation, and greater hip adduction. ACLR also presented different kinematics to ACLPT and CTRL in Take-off with a combination of greater trunk flexion, hip flexion, hip internal rotation, and less knee abduction, and in Landing with greater trunk flexion and hip internal rotation. Further, different kinematics and hop height were found between legs within groups in both Take-off and Landing for both ACL groups, but not for CTRL. CONCLUSION: Different kinematics for the injured leg for both ACL groups compared to CTRL and between treatment groups, as well as between legs within treatment groups, indicate long-term consequences of injury. Compensatory mechanisms for knee protection seem to prevail over time irrespective of initial treatment, possibly increasing the risk of re-injury and triggering the development of osteoarthritis. Detailed investigation of movement strategies during the VH provides important information and a more comprehensive evaluation of knee function than merely hop height. More attention should also be given to the trunk and hip in clinics when evaluating movement strategies after ACL injury. LEVEL OF EVIDENCE: Prospective cohort study, Level II

Fear of reinjury following anterior cruciate ligament reconstruction is manifested in muscle activation patterns of single-leg side-hop landings

OBJECTIVE: The purpose of this study was to determine whether fear of re-injury is manifested in joint kinematics and muscle activation patterns during landings of a standardized rebound side-hop (SRSH), or in patient-reported outcome measures (PROMs), among individuals with anterior cruciate ligament reconstruction (ACLR). METHODS: In this cross-sectional observational study, 38 individuals within 2 years post-ACLR were grouped into HIGH-FEAR (n = 21, median 11.2 months post-surgery) or LOW-FEAR (n = 17, median 10.1 months post-surgery) based on a discriminating question (Q9; Tampa Scale of Kinesiophobia-17). These individuals and 39 asymptomatic controls performed the SRSH. Three-dimensional motion recordings were used to calculate trunk, hip, and knee joint angles at initial contact and range of respective joint motion during landing. Surface electromyography registered mean amplitudes and co-contraction indexes for thigh muscles during pre-activation (50 ms) and landing phases. PROMs of knee function, knee health, and physical activity were also analyzed. RESULTS: The HIGH-FEAR and LOW-FEAR classification was corroborated by distinct Tampa Scale of Kinesiophobia-17 total and subscale scores and revealed distinguishable muscle activation patterns. HIGH-FEAR demonstrated higher biceps femoris electromyography amplitude and higher anterior-posterior co-contraction index during landing than both LOW-FEAR and controls. However, there were no fear-related differences for kinematics or PROMs. Instead, both ACLR subgroups showed different kinematics at initial contact to controls; HIGH-FEAR with more trunk, hip, and knee flexion, and LOW-FEAR with more hip and knee flexion. CONCLUSION: Individuals with ACLR who had high fear of re-injury seem to have adopted a protective strategy with higher muscular activation patterns, presumably to stabilize the knee joint, compared with individuals with low fear of re-injury and controls. SRSH landing kinematics or knee-related PROMs may not be as sensitive to fear of re-injury. IMPACT: Fear of reinjury following anterior cruciate ligament injury should be evaluated as an independent psychological outcome throughout rehabilitation after ACLR for improved return to sport transition. LAY SUMMARY: If you have an anterior cruciate ligament injury treated with reconstructive surgery, you might have a high fear of reinjury, and that can change how you activate the muscles around your knee. Your physical therapist can do a simple screening test in addition to functional tests to help reduce your fear and improve your treatment outcomes

Introducing a novel test with unanticipated medial/lateral diagonal hops that reliably captures hip and knee kinematics in healthy women

Despite a vast literature on one-leg hops and cutting maneuvers assessing knee control pre/post-injury of the anterior cruciate ligament (ACL), comprehensive and reliable tests performed under unpredictable conditions are lacking. This study aimed to: (1) assess the feasibility of an innovative, knee-challenging, one-leg double-hop test consisting of a forward hop followed by a diagonal hop (45°) performed medially (UMDH) or laterally (ULDH) in an unanticipated manner; and (2) determine within- and between-session reliability for 3-dimensional hip and knee kinematics and kinetics of these tests. Twenty-two healthy women (22.3 ± 3.3 years) performed three successful UMDH and ULDH, twice 1–4 weeks apart. Hop success rate was 69–84%. Peak hip and knee angles demonstrated moderate to excellent within-session reliability (intraclass correlation coefficient [ICC] 95% confidence interval [CI]: 0.67–0.99, standard error of measurement [SEM] ≤  3°) and poor to excellent between-session reliability (ICC CI: 0.22–0.94, SEM ≤ 3°) for UMDH and ULDH. The smallest real difference (SRD) was low (≤ 5°) for nearly all peak angles. Peak hip and knee moments demonstrated poor to excellent reliability (ICC CI: 0–0.97) and, in general, moments were more reliable within-session (SEM ≤ 0.14 N.m/kg.m, both directions) than between-session (SRD ≤ 0.43 N.m/kg.m). Our novel test was feasible and, in most but not all cases, provided reliable angle estimates (within-session > between-session, both directions) albeit less reliable moments (within-session > between-session, both directions). The relatively large hip and knee movements in the frontal and transverse planes during the unanticipated hops suggest substantial challenge of dynamic knee control. Thus, the test seems appropriate for evaluating knee function during ACL injury rehabilitation

A novel standardised side hop test reliably evaluates landing mechanics for anterior cruciate ligament reconstructed persons and controls

We propose a novel one-leg standardised rebound side-hop test (SRSH) specifically designed for detailed analysis of landing mechanics. Anterior cruciate ligament reconstructed persons (ACLR, n = 30) and healthy-knee controls (CTRL, n = 30) were tested for within-session and test-retest (CTRL only, n = 25) reliability and agreement. Trunk, hip and knee angles and moments in sagittal, frontal, and transversal planes during landing, including time to stabilisation (TTS), were evaluated using intra-class correlations (ICCs), average within-person standard deviations (SW) and minimal differences. Excellent within-session reliability were found for angles in both groups (most ICCs > 0.90, SW ≤ 5°), and excellent to good for moments (most ICCs > 0.80, SW ≤ 0.34 Nm/kg). Only knee internal rotation moment showed poor reliability (ICC < 0.4). Test-retest results were excellent to fair for all angles and moments (ICCs 0.47–0.91, SW < 5° and ≤ 0.25 Nm/kg), except for peak trunk lateral bending angle and knee internal rotation moment. TTS showed excellent to fair within-session reliability but poor test-retest results. These results, with a few exceptions, suggest promising potential of evaluating landing mechanics during the SRSH for ACLR and CTRL, and emphasise the importance of joint-specific movement control variables in standardised tasks

Spatiotemporal lower-limb asymmetries during stair descent in athletes following anterior cruciate ligament reconstruction

Purpose: This study evaluated motor control recovery at different times following anterior cruciate ligament reconstruction (ACLR) by investigating lower-limb spatiotemporal symmetry during stair descent performances. Methods: We used a cross-sectional design to compare asymptomatic athletes (Controls, n = 18) with a group of people with ACLR (n = 49) divided into three time-from-ACLR subgroups (Early: <6 months, n = 17; Mid: 6–18 months, n = 16; Late: ≥18 months, n = 16). We evaluated: “temporal symmetry” during the stance subphases (single-support, first and second double-support) and “spatial symmetry” for hip-knee-ankle intra-joint angular displacements during the stance phase using a dissimilarity index applied on superimposed 3D phase plots. Results: We found significant between-group differences in temporal variables (p ≤ 0.001). Compared to Controls, both Early and Mid (p ≤ 0.05) showed asymmetry in the first double-support time (longer for their injured vs. non-injured leg), while Early generally also showed longer durations in all other phases, regardless of stepping leg. No statistically significant differences were found for spatial intra-joint symmetry between groups. Conclusion: Temporal but not spatial asymmetry in stair descent is often present early after ACLR; it may remain for up to 18 months and may underlie subtle intra- and inter-joint compensations. Spatial asymmetry may need further exploration

A novel standardised side hop test reliably evaluates landing mechanics for anterior cruciate ligament reconstructed persons and controls

We propose a novel one-leg standardised rebound side-hop test (SRSH) specifically designed for detailed analysis of landing mechanics. Anterior cruciate ligament reconstructed persons (ACLR, n = 30) and healthy-knee controls (CTRL, n = 30) were tested for within-session and test-retest (CTRL only, n = 25) reliability and agreement. Trunk, hip and knee angles and moments in sagittal, frontal, and transversal planes during landing, including time to stabilisation (TTS), were evaluated using intra-class correlations (ICCs), average within-person standard deviations (SW) and minimal differences. Excellent within-session reliability were found for angles in both groups (most ICCs > 0.90, SW ≤ 5°), and excellent to good for moments (most ICCs > 0.80, SW ≤ 0.34 Nm/kg). Only knee internal rotation moment showed poor reliability (ICC < 0.4). Test-retest results were excellent to fair for all angles and moments (ICCs 0.47–0.91, SW < 5° and ≤ 0.25 Nm/kg), except for peak trunk lateral bending angle and knee internal rotation moment. TTS showed excellent to fair within-session reliability but poor test-retest results. These results, with a few exceptions, suggest promising potential of evaluating landing mechanics during the SRSH for ACLR and CTRL, and emphasise the importance of joint-specific movement control variables in standardised tasks

Test-retest reliability of entire time-series data from hip, knee and ankle kinematics and kinetics during one-leg hops for distance: Analyses using integrated pointwise indices

Motion capture systems enable in-depth interpretations of human movements based on data from three-dimensional joint angles and moments. Such analyses carry important bearings for evaluation of movement control during for instance hop landings among sports-active individuals from a performance perspective but also in rehabilitation. Recent statistical development allows analysis of entire time-series of angle and moment during hops using functional data analysis, but the reliability of such multifaceted data is not established. We used integrated pointwise indices (intra-class correlation, ICC; standard error of measurement, SEM) to establish the test–retest reliability of three-dimensional hip, knee and ankle angle and moment curves during landings of one-leg hop for distance (OLHD) in 23 asymptomatic individuals aged 18–28. We contrasted these findings to reliability of discrete variables extracted at specific events (initial contact, peak value). We extended the calculations of ICC and SEM to handle unbalanced situations (varying number of repetitions) to include all available data. Hip and knee angle curves proved reliable with stable ICC curves throughout the landing, with integrated ICCs ≥ 0.71 for all planes except for knee internal/external rotation (ICC = 0.57). Hip and knee moment curves and ankle angle and moments were less reliable and less stable, particularly in the first ~ 10–25% of the landing (integrated ICCs 0.44–0.57). Curve data were generally not in agreement with the results for discrete event data, thus advocating analysis of curve data which contains more information. To conclude, hip and knee angle curve data during OLHD landings can reliably be evaluated, while moment curves necessitate careful consideration