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This quality study was carried out with seven semi-structured interviews and five of them were with elite women´s football coaches. What has been studied is how elite women’s football coaches are working with injury prevention training to their knees for the women’s football players. An anterior cruciate ligament injury in elite women’s football is both common and serious knee injury. This is a major problem area of ​​the anterior cruciate ligament injuries in women's football. In a squad of 20 women's football players occur an anterior cruciate ligament injury every two years. Injury prevention training is important to prepare the women's football players for the physical stresses that will arise during the season[1].  In this study includes, for example, theories of loss prevention training and risk factors for elite women’s football player to suffer an ACL injury. The interview guide has been focusing on the coach’s work and why they have chosen to use loss prevention training and how it can be planned and executed. This is to get information on how the elite women coaches working with the training to give the elite women football players the best position possible to prevent an ACL injury. The elite coaches have the help of physiotherapists, doctors and / or physiological coach with the loss prevention training must include for different exercises, and then determine the elite coaches themselves when it will be done during training week. In addition to interviews with the elite women coaches have also been interviewed by a physiotherapist and a doctor. This interview has been used to get information about the problem area with an ACL injury in elite women football. After that question I also touched on how and why the elite women’s football players should prevent this knee injury. The elite women’s football coaches all think the injury prevention training is important to use. This is to prepare women football players for the loads and stresses which will occur during the season. The loss prevention training is somewhat different in the five elite women´s football team that is part of my study. Any association uses a knee control program more than others, and cardio and strength training workouts vary in number. What unites them is that they all use a combination and the pulsation of the training. That is, they use both low and high intensity training and other training is a combination of different exercises and exercise. And they all have the injury prevention training scheduled throughout the season. [1] Martin Hagglund physiotherapist, interview February 8 2012, Markus Waldén orthopedic, interview  February 3 2012

Non-contact anterior cruciate ligament (ACL) injuries is a serius and traumatic injury to the knee that is common in female soccer players and often force the player to quit or lower the level of activity because of lost stability in the knee or from fear to suffer  a new injury. Female soccerplayers have a higher risk than their male counterparts to get an ACL rupture and especially adolescent females have a high risk. The most common causes to a non-contact ACL rupture is side-cutting manuvers and landing after jumping. Every other player with an ACL rupture develops osteoarthritis within 10-15 years from the time of injury Results: The higher risk for females to incur a ACL rupture is due to smaller intercondylar notch, they’re in the follicular or ovulatory phase of their menstrual cycle, increased knee laxity, dominance in the quadriceps muscles, flexion in hip and valgus movement in the knee. An effective preventionprogram is based on the risk factors individual players exhibit. Preventionprograms including plyometrics and at least one other component (strength, neuromuscular training, awarness or proprioceptiv training) at a regular basis have been most succesfull in reducing the risk for ACL injury for female soccer players. Discussion: Female soccer players may have neuromuscular, hormonal and anatomical differences that increase the risk of them achieving an ACL injury in a non-contact situation. Theese differences should be taken into account when designing a preventionprogram in order to succesfully reduce the risk for female soccer players to achieve an ACL injury. A preventionprogram should include plyometric training, proprioception, balance training and resistance training for hamstrings.

The anterior cruciate ligament (ACL) originates from posterior part of the medial side of the lateral condyle of femur to anterior intercondylar notch between a transverse meniscal ligament and medial side of medial meniscus of tibia. Once ACL is disrupted, pain, effusion and atrophy are commonly observable and cause functional disability. Because of the functional limitations, athletic participation is severely restricted. ACL injury is more prevalent in physically active females compared to their male counterparts in the sports of basketball and soccer in high school and collegiate levels. Several attributes of females are considered risk factors for the higher ACL injury incidences and include: anatomy, physiology and neuromuscular/biomechanics. Among them, neuromuscular/biomechanics is the only modifiable risk factor. Performing neuromuscular training may change muscular strength profiles, which may lead to reduction in ACL injury incidence in female athletes. However, this principle was not fully examined. Also, neuromuscular compliance may play a role in muscular strength development and ACL injury incidences. Thus, the purpose of this dissertation was to investigate the effects of neuromuscular training compliance on muscular strength development and ACL injury incidence. The influence of hip abductor, hamstrings and quadriceps strength was examined in this project. The results of these studies indicate neuromuscular training is an effective intervention to reduce ACL injury incidence in female athletes, and there is an inverse dose-response relationship between compliance of the neuromuscular training and number of ACL incidences in female athletes. The effect of compliance on muscular strength development was inconsistent. The results of these studies support that compliance of neuromuscular training is a key to reduce ACL injury incidences; however, more studies are need to conclude neuromuscular training compliance effects on muscular strength development in female athletes.

Knee function after more than 20 years post injury is rarely described and none of the few follow-up studies have evaluated functional performance tasks. This thesis investigated self-reported knee function, physical activity level, physical capacity and movement pattern in the long-term perspective (on average 23 years) in persons who had suffered a unilateral ACL injury, treated either with physiotherapy in combination with surgery (ACLR, n=33) or physiotherapy alone (ACLPT, n=37) and compared to age-and-gender matched controls (n=33).  This thesis shows that regardless of treatment, there are significant negative long-term consequences on self-reported knee function and physical activity more than 20 years after injury. In comparison to the controls, the ACL-groups (ACLR and ACLPT) had lower knee function as measured by the Lysholm score and the Knee injury and Osteoarthritis Outcome Score (KOOS). The persons with an ACL injury also had a lower knee-specific physical activity level (Tegner activity scale), while no differences were seen in general physical activity level (International Physical Activity Questionnaire, IPAQ) compared to healthy controls. Regarding physical capacity, both ACL groups showed inferior jump capacity in the injured leg compared to the non-injured leg. However, compared to controls the ACL-injured had a relatively good jump performance. Knee extension peak torque, concentric and eccentric, was also lower for the injured leg compared to the non-injured leg for both ACLR and ACLPT. In addition, the ACLPT group showed reduced eccentric knee flexion torque of the injured leg. The non-injured leg, on the other hand, showed almost equal jump capacity and strength as controls. Balance in single-limb stance (30s) was inferior in persons who had an ACL injury. This was true for both the injured and non-injured leg and regardless of treatment. Movement pattern during the one-leg hop was analysed by a set of kinematic variables consisting of knee angles (flexion, abduction, rotation) and Centre of Mass (CoM) placement in relation to the knee and ankle joints. Both ACLR and ACLPT displayed movement pattern asymmetries between injured and non-injured legs. In comparison to controls, the ACLR group had a similar movement pattern with the exception of larger external knee rotation at Initial contact and less maximum internal rotation during the Landing. ACLPT showed several differences compared to controls both regarding knee angles and CoM placement. The ACL-injured persons with no-or-low knee osteoarthritis (OA) had better knee function as reflected by higher scores on Lysholm and KOOS subscale ‘symptom’ compared to those with moderate-to-high OA. The degree of OA had no influence on reported physical activity level, jump capacity, peak torque or the kinematic variables.  In conclusion, this thesis indicates that persons with a unilateral ACL injury, regardless of treatment, have some negative long-term consequences e.g. self-reported knee function, knee-specific activity level, strength and balance deficits, when compared to age-and-gender matched controls. The results, however, also indicate that the ACL-injured can manage reasonably well in some jumps and general activity level but have an inferior performance in more knee-demanding tasks. The ACLR group had similar movement pattern with the exception of knee rotation, indicating that a reconstruction may restore the knee biomechanics to some extent. The ACLPT group on the other hand, seem to use compensatory movement strategies showing several differences compared to controls.

Både biomekaniska och neuromuskulära faktorer hos kvinnliga fotbollsspelare har visat sig påverka risken att drabbas av främre korsbandsskador. Obalanserad muskelaktivering kring knäleden har visat sig påverka ledstabiliteten. Syftet med studien var därför att undersöka sambandet mellan muskelaktiveringen i vastus medialis och vastus lateralis i relation till valgusvinkel hos fotbollsspelande kvinnor vid ett drop-landingtest. Studien gjordes i samarbete med det finska företaget Fibrux OY, som har utvecklat en bärbar sEMG-apparatur. I studien deltog 15 kvinnliga fotbollsspelare som under en drop-landing bar sEMG-elektroder på vastus medialis och vastus lateralis samtidigt som rörelsen filmades framifrån för att möjliggöra 2D analys av valgusvinkel. Resultaten visar en tendens till samband mellan muskelaktiveringsgrad och valgusvinkel (r=0,51) (p>0,05) samt ett svagt samband mellan muskelaktiveringsordning och valgusvinkel (r=0,32) (p>0,05). Det svaga sambandet gör att det inte går att utesluta att det är andra muskler kring knäleden som har större inverkan på ledstabiliteten. Framtida forskning bör utföras på en större population och rikta sig på prospektiv epidemiologisk forskning eftersom det är den enda studiedesignen som avslöjar vilka variabler som kan associeras med risken att drabbas av en knäskada. / Both biomechanical and neuromuscular factors affect the risk of suffering an ACL rupture among female soccer players. Unbalanced muscle activation around the knee has been found to affect the joint stability. The aim of this study was therefor to investigate the muscle activation in vastus medialis and vastus lateralis in relation to dynamic valgus among female soccer players. The study was conducted in cooperation with the Finnish company Fibrux OY, who has developed a portable sEMG testing equipment. The participants consisted of 15 female soccer players who were tested with sEMG electrodes on vastus medialis and vastus lateralis during a drop-landingtest that was filmed to enable 2D analysis of valgus angle. The results show a tendency to correlation between the activation ratio and valgus(r=0,51) (p>0,05), and between activation delay in vastus medialis and valgus (r=0,32) (p>0,05). But both correlations lack significance. The results could be explained by that there might be other muscles around the knee at that affects the joint stability even more than vastus lateralis and medialis do. Future studies should be conducted with larger sample size and focus on prospective epidemiological research because that is the only study design that reveals what variables can be associated with the risk of suffering a knee injury.

Purpose: Young adolescent females are at the highest risk of sustaining an ACL injury, which may alter their movement and muscle activation patterns yet there is a lack sex- and age- specific guidelines for ACL injury management. The purpose of this study was to (1) evaluate the effects of limb dominance in a healthy uninjured population to serve as a baseline for the ACL-deficient cohort and (2) provide evidence of the neuromuscular patterns and biomechanical loading of uninjured and ACL-deficient knee joints in a female paediatric population. Methods: Eighteen active female adolescents with ACL rupture (ACLd) and 21 uninjured female adolescent controls matched for limb dominance (CON) participated in this study. Participants completed bilateral squats and drop vertical jumps (DVJ) while lower limb electromyography, kinetics and kinematics data were collected. Muscle synergies were extracted using a concatenated non-negative matrix factorization (CNMF) framework and compared between limbs, (CON dominant vs CON non-dominant and CON vs ACLd) across tasks and between limbs within tasks using intraclass correlation coefficients and statistical paramedic mapping. Results: ACLd participants took significantly longer to perform the squat relative to their uninjured peers. No significant differences were found for hip, knee and ankle peak joint flexion angles and moments between populations for the squat. Squat and DVJ muscle synergies were equivalent for dominant and non-dominant uninjured control limbs. ACL injured (ACL deficient and contralateral limbs) exhibited greater variability in DVJ synergy vectors than for the squat task. When comparing across tasks, scaling coefficients were consistently higher for the DVJ for all populations. Conclusion: Differences in lower limb kinematics, muscle activity and muscle activation patterns between dominant and non-dominant limbs indicate that limb symmetry, a clinical tool commonly used to assess rehabilitation and return to play may not provide relevant results. DVJ scaling factors were larger than those of the squat for all groups, likely due to the increased demand of that task. ACLd and CON participants completed squats and DVJ with similar lower limb joint angle patterns and muscle activity. ACL injured groups had fewer consistent vectors across tasks demonstrating greater variability in muscle activation patterns. This increased variability may be due to the ACL injury however, as injured participants were not studied pre- injury it cannot be confirmed.

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Studiedesign: Kvantitativ experimentell studie Syfte: Det primära syftet var att undersöka hur knäledens kinematik påverkas av simultana kognitiva uppgifter under hopplandningar bland fotbollsaktiva kvinnor med och utan främre korsbandsskada. Det sekundära syftet var att, genom poweranalyser, beräkna gruppstorlekar och vilka variabler som bör analyseras i framtida studier. Metod: Sju kvinnor med och sex kvinnor utan korsbandsskada utförde tre olika hopptester med och utan maximalt upphopp. Test 1 utfördes utan tillägg av kognitiva uppgifter, test 2 involverade elementen reaktionstid och inhibitorisk kontroll, test 3 involverade elementen reaktionstid, inhibitorisk kontroll och arbetsminne. Knäledens kinematik i alla tre plan (maxvärden och rörelseomfång) och maximal hopphöjd i upphoppet jämfördes mellan grupperna och testerna. Upprepad mixad ANOVA med effekterna Test, Grupp, och interaktionen Test*Grupp genomfördes och dess effektstorlekar användes i poweranalyserna.  Resultat: Det skedde mindre rörelse i sagittalplan och mer rörelse i frontalplan hos korsbandsgruppen samt att knäledens kinematik skiljer sig åt mellan grupperna under mer kognitivt krävande situationer simultant med idrottsspecifik rörelse. Power-analyserna för interaktionseffekten Test*Grupp med upphopp visade att 9/10 variabler kräver <100 testpersoner för att få en signifikant statistisk skillnad med en power på 80%.  Motsvarande resultat för landning utan upphopp visade att 5/9 variabler kräver <100 testpersoner. Konklusion: Hopplandningar med olika antal simultana kognitiva uppgifter visade på skillnader i knäkinematik mellan individer med och utan tidigare korsbandsskada, mellan testerna oberoende grupptillhörighet samt mellan testerna beroende på grupptillhörighet. De variabler som visade signifikanta skillnader vid landning följt av maximalt upphopp var hopphöjd, Max knäadduktion, Min knäflexion, Max knäutåtrotation och ROM knäadduktion-abduktion. Vid endast landning var det maximal knäflexion och Max knäabduktion som hade signifikanta värden.

INTRODUCTION: The prevalence of ACL injuries is increasing in previous years. One of the most common studied kinematic risk factors related to ACL injuries is a resultant weak, leg axis alignment known as the dynamic knee valgus angle presented during a vertical drop jump [8, 14, 15]. Hewett et. al. concluded that a knee valgus angle was a primary predictor of the mechanism that leads to an ACL rupture [8]. By increasing the excessive knee valgus angle during a two-legged DVJ, an athlete is in turn increasing the possibility of a high knee valgus moment, which can increase the anterior tibial translation as well as the load on the ACL several-fold and the chances for an ACL tear [4]. METHODS: In our study, ten collegiate female participants, including ballet and non-ballet athletes performed two-legged DVJs for 6 different flexor and extensor muscles while digital recordings of knee valgus angle were captured at initial contact and push off with simultaneous collection of EMG data. RESULTS: Results displayed statistical significance for the average valgus angle to estimated GRF ratio for the non-dominant leg at push-off between the ballet and non-ballet athletes (0.8 ± 0.43 vs. 1.8 ± 0.33 degrees/N, p < 0.05). In addition, we also found that the hip extensor activity significantly increased for the non-ballet group and that the lateral thigh CCI noticeably increased for the non-dominant leg for the non-ballet group, which could be indicative of the noticeable difference in the biceps femoris muscle activation for the non-ballet group when comparing sports type. In addition, statistically significant interactions between sports type and leg type for vastus medialis and gluteus maximus were produced. Observed results also indicated that there was an increase in overall variability for the dominant leg of the non-ballet athletes amongst all studied muscles and for the non-dominant leg for the ballet group specifically studying the gluteus maximus muscle activity. DISCUSSION: Relatively, the non-ballet group could be at a higher risk for increase in femoral adduction, hip adduction, and tibial external rotation, and overall predict a larger knee valgus moment; therefore, the non-ballet group could potentially be at a higher risk for an ACL injury than the ballet group. In addition, there is potential in continued research of neuromuscular differences between ballet and non-ballet athletes to further investigate the vastus medialis and the gluteus maximus muscle activations as well as to investigate the knee valgus moment values.