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There is a big risk that neuroreceptors located in the knee, responsible for our proprioceptive ability, are damaged after an anterior cruciate ligament (ACL) injury occurs. This may cause miscommunication between the neuroreceptors and motoric function in the brain. Due to the brains plasticity, it has been shown that brain activity patterns, presented as blood oxygen dependent level-signal (BOLD-signal), achieved from functional magnetic resonance imaging (fMRI) differs between healthy and injured individuals when performing certain tasks involving knee movement. As there is little consensus on how a proprioceptive test should be performed, a unique test were participants uses blindfold during a knee bending exercise was created at U Motion Lab, Umeå University. A Matlab based general user interface (GUI) was created for evaluation of the proprioceptive test. This GUI is communicating with the third party toolbox SPM12 and performs necessary preprocessing fMRI-image steps for statistical analysis and statistical parametric mapping of the BOLD-signal for both a healthy control- and ACL-injured group. The fMRIimages preprocessed by the GUI were generated by a 3 T GE scanner and the motion data was collected using an eight-camera 3D-motion analysis system. Time events for three different tasks was investigated. These were passive resting, memorizing and proprioceptive events. For both the control (5 participants)- and ACL (2 participants) group the main area of brain activation during the proprioceptive tests occurred in the frontal lobe. For the control group, brain activation was found in the cerebellum anterior lobe which is a possible origin for unconscious proprioception. For the ACL group activation was found in the inferior parietal lobule which involves visuomotor integration. Activation was also found in the inferior frontal gyrus which according to previous studies, may indicate risk-taking/”out of character” decisions. The results of this study indicates that the proprioceptive test seems to be a promising tool for evaluation of proprioceptive ability. However, more subjects need to be included to validate the result of this study.

No description available.

No description available.

No / Anterior cruciate ligament (ACL) injuries are a major problem among female athletes. Screening for the risk of ACL injuries tends to focus on landing tasks, which may be limited in sports where changing direction is the main action involved in noncontact ACL injuries such as soccer. To investigate whether there is a relationship between single-legged landing (SLL), cutting (90° cuts), and pivoting (180° turns) in terms of the characteristics of dynamic valgus. Study Design: Controlled laboratory study. Methods: Twenty female soccer players (mean ± SD: age, 21.0 ± 3.9 years; height, 1.65 ± 0.08 m; mass, 58.4 ± 6.4 kg) performed a minimum of 6 trials of SLL from a 0.3-m drop height and cutting and pivoting all on the right leg. Kinematics and kinetics were calculated from 3-dimensional motion analysis. Results: Strong correlations were found for peak knee abduction angles between tasks (R = 0.63-0.86, P < .01), whereas only moderate correlations between SLL and cutting (R = 0.46, P < .05), cutting and pivoting (R = 0.56, P < .05), and SLL and pivoting (R = 0.43, P > .05) were found between tasks for peak knee abduction moments. Conclusion: The results suggest that female athletes who exhibit poor SLL mechanics perform the same during various changing direction tasks. Clinical Relevance: The results support the use of existing screening tests that involve landing tasks to identify at-risk athletes for noncontact ACL injuries.

Bakgrund: Främre korsbandsskador (ACL-skador) är allvarliga och vanligt förkommande inom idrott, speciellt hos ungdomar i åldrarna 14-19 år. En förhöjd risk för ACL-skador har påvisats för individer aktiva inom fotboll och handboll, vilka är mycket populära sporter världen över. Inom dessa sporter har även kvinnor påvisats ha två till åtta gånger högre risk att drabbas än män. Syfte: Syftet var att undersöka om det fanns någon skillnad i knästabilitet vid en hopp-landningsrörelse mellan tjejer och killar i åldrarna 16-19 år, aktiva inom fotboll och handboll samt att undersöka om det fanns någon skillnad mellan fotbollsspelarna och handbollsspelarna, oavsett kön. Metod: Ett drop jump-test utfördes av 20 ungdomar, aktiva inom fotboll och handboll, medelålder ±SD 17,0 ± 0,9 år. Testerna filmades i frontal- och sagittalplanet och analyserades sedan med hjälp av Landning Error Scoring System (LESS). Post hoc-analyser genomfördes för att kontrollera skillnader i 1) graden av valgusställning i knäleden mellan tjejerna och killarna och 2) graden av knäflexion mellan fotbolls- och handbollsspelarna i landningsmomentet. Ett oberoende student’s t-test användes till de statistiska analyserna och signifikansnivån sattes till p ≤ 0,05. Resultat: Det fanns ingen signifikant skillnad i LESS-poäng mellan tjejerna och killarna (p = 0,694). Fotbollsspelarna hade signifikant lägre LESS-poäng än handbollsspelarna (p = 0,002). Andelen tjejer som uppvisade valgusställning i knäleden under testutförandet var högre än hos killarna. Fotbollsspelarna uppvisade enligt LESS tillräcklig knäflexion i landningsmomentet i högre utsträckning än handbollsspelarna under testutförandet. Slutsats: Ingen signifikant skillnad i knästabilitet och hopp-landningsteknik fanns mellan tjejerna och killarna. Fotbollsspelarna hade signifikant bättre knästabilitet och hopp-landningsteknik än handbollsspelarna. Tjejerna hade en större grad av valgusställning i knäleden vid testutförandet än killarna och handbollsspelarna uppvisade inte lika stor knäflexion som fotbollsspelarna vid testutförandet. Mer forskning krävs inom området för att resultaten ska kunna generaliseras. / Background: Anterior cruciate ligament injuries (ACL-injuries) are serious and common in sports, especially in adolescents between the ages of 14 and 19. An increased risk for ACL-injury has been shown in individuals active in soccer and team handball, which both are popular sports worldwide. Within these sports, women have been proven to have two to eight times greater risk for ACL-injury than men. Aim: The aim was to investigate whether there was any difference in knee stability during a jump-landing movement between girls and boys aged 16-19 years, active in soccer and team handball and also to investigate whether there was any difference between the soccer players and team handball players, regardless of gender. Method: A drop jump test was performed by 20 adolescents, active in soccer and team handball, mean ± SD age 17.0 ± 0.9 years old. The tests were recorded in the frontal and sagittal plane and were then analyzed using the Landing Error Scoring System (LESS). Post hoc analyzes were used to examine differences in 1) the degree of knee valgus alignment between the girls and the boys and 2) the degree of knee flexion between the soccer- and the team handball players in the landing movement. An independent student’s t-test was used in the statistical analysis and the level of significance was set at p ≤ 0.05. Results: There was no significant difference in LESS-score between the girls and the boys (p = 0.694). The soccer players had significantly lower LESS-score (p = 0.002). A higher frequency of the girls displayed a knee valgus alignment during the test compared to the boys. The soccer players displayed according to LESS adequate knee flexion to greater extent than the team handball players did during the test. Conclusion: No significant difference in knee stability and jump-landing technique was found between the girls and the boys. The soccer players displayed significantly better knee stability and jump-landing technique than the team handball players. The girls displayed a greater degree of knee valgus during the test than the boys did and the team handball players displayed a smaller degree of knee flexion then the soccer players did. More research is required within the area to be able to generalize the results.

Background: Joint stability has been experimentally and clinically linked to mechanisms of knee injury and joint degeneration. The only dynamic, and perhaps most important, regulators of knee joint stability are contributions from muscular contractions. In participants with unstable knees, such as anterior cruciate ligament (ACL) injured, a range of neuromuscular adaptations has been observed including quadriceps weakness and increased co-activation of adjacent musculature. This co-activation is seen as a compensation strategy to increase joint stability. In fact, despite increased co-activation, instability persists and it remains unknown whether observed adaptations are the result of injury induced quadriceps weakness or the mechanical instability itself. Furthermore, there exists conflicting evidence on how and which of the neuromuscular adaptations actually improve and/or reduce knee joint stability. Purpose: The overall aim of this thesis is therefore to elucidate the role of injury and muscle weakness on muscular contributions to knee joint stability by addressing two main objectives: (1) to further our understanding of individual muscle contribution to internal knee joint moments; and (2) to investigate neuromuscular adaptations, and their effects on knee joint moments, caused by either ACL injury and experimental voluntary quadriceps inhibition (induced by pain). Methods: The relationship between individual muscle activation and internal net joint moments was quantified using partial least squares regression models. To limit the biomechanical contributions to force production, surface electromyography (EMG) and kinetic data was elicited during a weight-bearing isometric force matching task. A cross-sectional study design determined differences in individual EMG-moment relationships between ACL deficient and healthy controls (CON) groups. A crossover placebo controlled study design determined these differences in healthy participants with and without induced quadriceps muscle pain. Injections of hypertonic saline (5.8%) to the vastus medialis induced muscle pain. Isotonic saline (0.9%) acted as control. Effect of muscle pain on muscle synergies recruited for the force matching task, lunging and squatting tasks was also evaluated. Synergies were extracted using a concatenated non-negative matrix factorization framework. Results/Discussion: In CON, significant relationships of the rectus femoris and tensor fascia latae to knee extension and hip flexion; hamstrings to hip extension and knee flexion; and gastrocnemius and hamstrings to knee rotation were identified. Vastii activation was independent of moment generation, suggesting mono-articular vastii activate to produce compressive forces, essentially bracing the knee, so that bi-articular muscles crossing the hip can generate moments for the purpose of sagittal plane movement. Hip ab/adductor muscles modulate frontal plane moments, while hamstrings and gastrocnemius support the knee against externally applied rotational moments. Compared to CON, ACL had 1) stronger relationships between rectus femoris and knee extension, semitendinosus and knee flexion, and gastrocnemius and knee flexion moments; and 2) weaker relationships between biceps femoris and knee flexion, gastrocnemius and external knee rotation, and gluteus medius and hip abduction moments. Since the knee injury mechanism, is associated with shallow knee flexion angles, valgus alignment and rotation, adaptations after ACL injury are suggested to improve sagittal plane stability, but reduce frontal and rotational plane stability. During muscle pain, EMG-moment relationships of 1) semitendinosus and knee flexor moments were stronger compared to no pain, while 2) rectus femoris and tensor fascia latae to knee extension moments and 3) semitendinosus and lateral gastrocnemius to knee internal rotation moments were reduced. Results support the theory that adaptations to quadriceps pain reduces knee extensor demand to protect the joint and prevent further pain; however, changes in non-painful muscles reduce rotational plane stability. Individual muscle synergies were identified for each moment type: flexion and extension moments were respectively accompanied by dominant hamstring and quadriceps muscle synergies while co-activation was observed in muscle synergies associated with abduction and rotational moments. Effect of muscle pain was not evident on muscle synergies recruited for the force matching task. This may be due to low loading demands and/or a subject-specific redistribution of muscle activation. Similarly, muscle pain did not affect synergy composition in lunging and squatting tasks. Rather, activation of the extensor dominant muscle synergy and knee joint dynamics were reduced, supporting the notion that adaptive response to pain is to reduce the load and risk of further pain and/or injury. Conclusion: This thesis evaluated the interrelationship between muscle activation and internal joint moments and the effect of ACL injury and muscle pain on this relationship. Findings indicate muscle activation is not always dependent on its anatomical orientation as previous works suggest, but rather on its role in maintaining knee joint stability especially in the frontal and transverse loading planes. In tasks that are dominated by sagittal plane loads, hamstring and quadriceps will differentially activate. However, when the knee is required to resist externally applied rotational and abduction loads, strategies of global co-activation were identified. Contributions from muscles crossing the knee for supporting against knee adduction loads were not apparent. Alternatively hip abductors were deemed more important regulators of knee abduction loads. Both muscle pain and ACL groups demonstrated changes in muscle activation that reduced rotational stability. Since frontal plane EMG-moment changes were not present during muscle pain, reduced relationships between hip muscles and abduction moments may be chronic adaptions by ACL that facilitate instability. Findings provide valuable insight into the roles muscles play in maintaining knee joint stability. Rehabilitative/ preventative exercise interventions should focus on neuromuscular training during tasks that elicit rotational and frontal loads (i.e. side cuts, pivoting maneuvers) as well as maintaining hamstring balance, hip abductor and plantarflexor muscle strength in populations with knee pathologies and quadriceps muscle weakness.

No description available.

More than 350,000 anterior cruciate ligament (ACL) injuries occur every year in the United States. A torn ACL is typically replaced with an allograft or autograft tendon (patellar, quadriceps or hamstring), with the choice of tissue generally dictated by surgeon preference. Despite the number of ACL reconstructions performed every year, the process of ligamentization, transformation of a tendon graft to a healthy functional ligament, is poorly understood. Previous research studies have relied on mechanical, biochemical and histological studies. However, these methods are destructive. Clinically, magnetic resonance imaging (MRI) is the most common method of graft evaluation, but it lacks adequate resolution and molecular specificity. There is a need for objective methodology to study the ligament repair process that would ideally be non- or minimally invasive. Development of such a method could lead to a better understanding of the effects of therapeutic interventions and rehabilitation protocols in animal models of ligamentization, and ultimately, in clinical studies. Fourier transform infrared (FT-IR) spectroscopy is a technique sensitive to molecular structure and composition in tissues. FT-IR fiber optic probes combined with arthroscopy could prove to be an important tool where minimally invasive tissue assessment is required, such as assessment of graft composition during the ligamentization process. Spectroscopic methods have been used to differentiate normal and diseased connective tissues, but have not been applied to investigate ligamentization, or to investigate differences in tendons and ligaments. In the proposed studies, we hypothesize that infrared spectroscopy can provide molecular information about the compositional differences between tendons and ligaments, which can serve as a foundation to non-destructively monitor the tissue transformation that occurs during ligamentization. / Bioengineering

Musculoskeletal injuries are commonly associated with muscle atrophy as a function of immobilization or change of normal function. For example, injuries to the anterior cruciate ligament (ACL) which may involve ligament reconstruction, results in the "quadriceps avoidance" gait which leads to atrophy of the knee extensormuscles. In these situations it is not clear whether or not the atrophy is associated with loss of specific muscle fibre types with accompanying functional deficits. Such knowledge would be helpful in implementing exercise regimes designed to compensate for loss of particular fibre types. It is believed that isokinetic exercise performed at speeds below 180° per second strengthens type I muscle fibres, and type II fibres at fast speeds. However, there is no evidence to indicate the specific muscle fibre response to different rates of muscle contraction. Identification of muscle fibre type is most directly determined by biopsy technique but is too invasive for a routine measurement. Electromyography median frequency has been used as a non-invasive measure to infer muscle fibre composition in various studies. However, the reliability and accuracy of this technique has been questioned and improvement is necessary. This research was designed to provide a more accurate and reliable protocol for the determination of EMG median frequency which may be used, after validation against more direct biopsy techniques, as a routine method for inferring muscle fibre composition. The investigation also explored the muscular response as measured by EMG median frequency to varying speeds of muscle contraction, fatiguing exercise and atrophy following ACL reconstruction. The ultimate aim of this research was to improve the reliability of the determination of EMG median frequency to enhance its application as a predictor of muscle fibre composition. This provides information which may improve ACL rehabilitation programs designed to restore and prevent specific muscle fibre types loss that have not previously been targeted by current rehabilitation programs. This research was conducted in three studies. Study one determined the stability of the EMG median frequency bilaterally for the quadriceps and hamstrings muscles and identified the mode of contraction associated with the greatest reliability. The strength and EMG median frequency of the vastus lateralis, medial hamstrings and vastus medialis of 55 subjects was determined across 5 speeds from 0° to 240° per second using a Kin-Com isokinetic dynamometer and an EMG data acquisition system. Isometric contraction was found to have the least bilateral discrepancy (4.01% ±3.06) and between trials standard deviation (4.50) in the vastus lateralis, medial hamstrings and vastus medialis. Study two investigated the EMG median frequency changes in the vastus lateralis which occur immediately following different speeds of isokinetic exercise to the point of fatigue in normal subjects. Thirty-four subjects participated in the study, and performed a 90-second period of isokinetic exercise to activate the knee extensors at either 30° or 300° per second. EMG median frequency of the vastus lateralis was determined before, immediately after and 7 minutes after the fatiguing exercise. The percentage drop in EMG median frequency of the vastus medialis was gnificantly (p<0.05) greater after slow speed (27.9%) than fast speed (20.25%) exercise, while no significant difference was found for the percentage drop in extension torque. Full recovery was found 7 minutes after the fatiguing exercise. By reference to previous research showing a relationship between EMG median frequency and muscle fibre type, an increase in activation of type I muscle fibres with slow speed exercise and an increase in type II muscle fibres with fast speed exercise was observed. Study three identified the changes in EMG median frequency following ACL reconstruction and evaluated the bilateral differences in EMG median frequency of the knee muscles. The relationships between EMG median frequency and the measures of knee functional ability, knee muscle strength, age and time since surgery were also investigated. Twelve subjects who had undergone ACL reconstruction using a semitendinosus and gracilis graft 6 to 12 months earlier, participated in the study. EMG median frequency was determined from an 8-second isometric contraction and knee functional ability was assessed using the Cincinnati Rating Scale. Bilateral EMG median frequency shifts were inconsistent among subjects. On the basis of previous research which indicated a relationship between EMG median frequency and fibre type, no consistent pattern of muscular fibre type atrophy subsequent to ACL reconstruction occurred within 6 to 12 months (ranged from -43 to 57 Hz). Additionally, no significant correlations were found between the EMG median frequency and the knee functional score and knee extension and flexion torques, age, time since operation and the bilateral differences in EMG median frequency. The results of this investigation will serve to improve the reliability of EMG median frequency across a range of conditions in which it has been evaluated. Further research is needed to confirm the relationship between EMG median frequency and direct observations of muscle fibre composition to improve the predictive value of this measure. Following this validation it will be possible to evaluate the bilateral EMG median frequency shift to infer the type of muscle fibre atrophy, and use this measure in determining the efficacy of specific rehabilitation programs. In conclusion * An 8-second isometric contraction is recommended for determining EMG median frequency. * EMG median frequency of a muscle decreases significantly more after slow fatiguing exercise than after fast speed fatiguing exercise. * There was no generalised bilateral EMG median frequency shift found in a group of subjects 6 to 12 months following semitendinosus and gracilis graft ACL reconstruction. * The results of this study will serve to improve the reliability of procedures used to determine EMG median frequency under a range of different contractile conditions. The EMG median frequency changes in response to these conditions require further validations with muscle biopsy in future.