Mechanisms of Hamstring Injury in Professional Soccer Players: Video Analysis and Magnetic Resonance Imaging Findings.

OBJECTIVE: To describe the injury mechanisms and magnetic resonance imaging (MRI) findings in acute hamstring injuries of male soccer players using a systematic video analysis. DESIGN: Descriptive case series study of consecutive acute hamstring injuries from September 2017 to January 2022. SETTING: Two specialized sports medicine hospitals. PARTICIPANTS: Professional male soccer players aged between 18 and 40 years, referred for injury assessment within 7 days after an acute hamstring injury, with an available video footage of the injury and positive finding on MRI. INDEPENDENT VARIABLES: Hamstring injury mechanisms (specific scoring based on standardized models) in relation to hamstring muscle injury MRI findings. MAIN OUTCOME MEASURES: Hamstring injury mechanism (playing situation, player/opponent behavior, movement, and biomechanical body positions) and MRI injury location. RESULTS: Fourteen videos of acute hamstring injuries in 13 professional male soccer players were analyzed. Three different injury mechanisms were seen: mixed-type (both sprint-related and stretch-related, 43%), stretch-type (36%), and sprint-type (21%). Most common actions during injury moments were change of direction (29%), kicking (29%), and running (21%). Most injuries occurred at high or very high horizontal speed (71%) and affected isolated proximal biceps femoris (BF) (36%). Most frequent body positions at defined injury moments were neutral trunk (43%), hip flexion 45-90 degrees (57%), and knee flexion <45 degrees (93%). Magnetic resonance imaging findings showed that 79% were isolated single-tendon injuries. CONCLUSIONS: According to a video analysis, most hamstring injuries in soccer occur during high-speed movements. Physicians should suspect proximal and isolated single-tendon-most often BF-hamstring injury, if represented injury mechanisms are seen during game play. In addition to sprinting and stretching, also mixed-type injury mechanisms occur.

Prevention of sudden death in adolescent athletes: Incremental diagnostic value and cost-effectiveness of diagnostic tests.

Introduction Pre-participation screening in athletes attempts to reduce the incidence of sudden death during sports by identifying susceptible individuals. The objective of this study was to evaluate the diagnostic capacity of the different pre-participation screening points in adolescent athletes and the cost effectiveness of the programme. Methods Athletes were studied between 12-18 years old. Pre-participation screening included the American Heart Association questionnaire, electrocardiogram, echocardiogram, and stress test. The cost of test was established by the Catalan public health system. Results Of 1650 athletes included, 57% were men and mean age was 15.09 ± 1.82 years. Positive findings were identified as follows: in American Heart Association questionnaire 5.09% of subjects, in electrocardiogram 3.78%, in echocardiogram 4.96%, and in exercise test 1.75%. Six athletes (0.36%) were disqualified from participation and 10 (0.60%) were referred for interventional treatment. Diagnostic capacity was assessed by the area under the curve for detection of diseases that motivated disqualification for sport practice (American Heart Association questionnaire, 0.55; electrocardiogram, 0.72; echocardiogram, 0.88; stress test, 0.57). The cost for each athlete disqualified from the sport for a disease causing sudden death was €45,578. Conclusion The electrocardiogram and echocardiogram were the most useful studies to detect athletes susceptible to sudden death, and the stress test best diagnosed arrhythmias with specific treatment. In our country, pre-participatory screening was cost effective to detect athletes who might experience sudden death in sports.

Caracterización por Ultrasound Tissue Characterization de los tendones rotulianos de jugadores de baloncesto; comparación entre profesionales versus formativos y asintomáticos versus sintomáticos / Patellar tendon analysis by ultrasound tissue characterization; comparison between professional and amateur basketball players. Asymptomatic versus symptomatic

Introducción: La ecografía convencional permite identificar los cambios macroscópicos que se producen en el tendón patológico, sin embargo, estos cambios no se correlacionan bien con los síntomas o la respuesta al tratamiento. La Ultrasound Tissue Characterization (UTC) evalúa la estructura del tendón en 3 dimensiones y la clasifica en 4 eco-tipos. El objetivo de este estudio fue investigar la estructura del tendón rotuliano de jugadores de baloncesto utilizando la técnica de la UTC y estudiar las diferencias entre jugadores profesionales y formativos, comparando la pierna dominante con la pierna no dominante, y sintomáticos con asintomáticos. Material y métodos: Un total de 40 tendones rotulianos (20 jugadores de baloncesto) se incluyeron en el estudio. La estructura del tendón rotuliano (proximal, medial y distal) se cuantificó mediante UTC en el inicio de la pretemporada. La fiabilidad inter e intraobservador se estudió mediante el coeficiente de correlación intraclase (CCI). Resultados: La edad media de los 10 jugadores profesionales y la de los 10 jugadores formativos fue de 28,1 años (DE 4,5) y 17,6 (DE 1,13), respectivamente. El espesor del tendón rotuliano fue mayor en los jugadores profesionales (p < 0,05), en la pierna dominante (p < 0,05) y en los tendones sintomáticos (p < 0,05). No se encontraron diferencias significativas para los eco-tipos, excepto en el caso del eco-tipo II del tendón rotuliano derecho en la porción proximal entre los jugadores profesionales y los académicos (p = 0,05), y en los eco-tipo III y IV del tendón derecho en su porción proximal entre los jugadores sintomáticos y los asintomáticos (p < 0,05). Se encontró una buena-alta fiabilidad con estas técnicas (CCI = 0,80-0,99). Conclusiones: Se ha caracterizado el patrón ecográfico de los tendones rotulianos de jugadores de baloncesto utilizando UTC. El espesor del tendón rotuliano es mayor en los jugadores profesionales que en los jugadores académicos. También se ha observado mayor grosor de los tendones sintomáticos que de los asintomáticos. No hubo diferencias importantes en el patrón de UTC entre los jugadores profesionales y los académicos ni entre los sintomáticos y los asintomáticos (AU)

Introduction: Conventional ultrasound helps to identify the macroscopic changes produced in the injured tendon. However, these changes do not correlate well with the symptoms or the response to treatment. The ‘characterization of tissues by ultrasound’ (UTC) evaluates the structure of the tendon in 3 dimensions and classifies it into 4 echo-types. The aim of this study was to investigate the structure of the patellar tendon in basketball players using the UTC technique, and to study the differences between professional and amateur players by comparing the dominant leg with the non-dominant one, and the asymptomatic with the asymptomatic ones. Material and methods: The study included 40 patellar tendons (20 basketball players). The structure of the patellar tendon (proximal, medial, and distal) was quantified by means of UTC at the beginning of the pre-season. The within and between observer reliability was measured using the intraclass correlation coefficient (ICC). Results: The mean ages of the 10 professional players and 10 amateur players were 28.1 years (SD 4.5) and 17.6 years (SD 1.3), respectively. The thickness of the patellar tendon was greater in the professional players (P < .05), in the dominant leg (P < .05), and in symptomatic tendons (P < .05). There were no significant differences in the echo-types, except in the case of echotype II in the proximal portion of the right patellar tendon, between professional and amateur players (P = .05). Similarly, there was a difference in echo-type III and IV of the proximal portion of the right tendon between symptomatic and asymptomatic players (P < .05). A good, high reliability was found with these techniques (ICC = .80-.99). Conclusions: The ultrasound pattern of the patellar tendons of basketball players has been characterised using UTC. The thickness of the tendon is greater in professional players than in amateur players. It has also been observed that the symptomatic tendons are thicker than in asymptomatic ones. There were no significant differences in the UTC patterns between professional and amateur players, or between symptomatic and asymptomatic ones (AU)

Muscle Injuries in Sports: A New Evidence-Informed and Expert Consensus-Based Classification with Clinical Application.

Muscle injuries are among the most common injuries in sport and continue to be a major concern because of training and competition time loss, challenging decision making regarding treatment and return to sport, and a relatively high recurrence rate. An adequate classification of muscle injury is essential for a full understanding of the injury and to optimize its management and return-to-play process. The ongoing failure to establish a classification system with broad acceptance has resulted from factors such as limited clinical applicability, and the inclusion of subjective findings and ambiguous terminology. The purpose of this article was to describe a classification system for muscle injuries with easy clinical application, adequate grouping of injuries with similar functional impairment, and potential prognostic value. This evidence-informed and expert consensus-based classification system for muscle injuries is based on a four-letter initialism system: MLG-R, respectively referring to the mechanism of injury (M), location of injury (L), grading of severity (G), and number of muscle re-injuries (R). The goal of the classification is to enhance communication between healthcare and sports-related professionals and facilitate rehabilitation and return-to-play decision making.

Efficacy of autologous platelet-rich plasma for the treatment of muscle rupture with haematoma: a multicentre, randomised, double-blind, placebo-controlled clinical trial.

BACKGROUND: The goals of the treatment of muscle injuries are to shorten the time of healing and to avoid relapses. The aim of this study was to assess the efficacy of autologous platelet-rich plasma (PRP) in the healing of muscle injuries. MATERIALS AND METHODS: A multicentre, randomised, double-blind, parallel, controlled clinical trial was conducted in 71 patients (81.8% males) aged 45.6 (SD=10.0) years with muscle tears in the legs and haematoma. The haematoma was evacuated in all patients. Thirty-three patients were randomised to a single dose of autologous PRP and 38 patients to simulation of PRP administration. The primary end-point was time to complete recovery of muscle injury. Secondary end-points were pain, relapses, ultrasound parameters, and adverse events. The total follow-up per patient was 12 months. RESULTS: Time to complete recovery after the treatment was 31.63 days (SD=15.38) in the PRP group, and 38.43 days (SD=18.58) in the control group (p=0.261). Pain decreased over time in both groups without statistical differences between them. Eight patients relapsed (seven in the control group, and one in the PRP group). There were no adverse effects related to the interventions. DISCUSSION: Autologous PRP did not significantly improve the time to healing compared to that in the control group.

Utilidad del ecocardiograma en la revisión preparticipativa de deportistas de competición / Usefulness of Echocardiography in Preparticipation Screening of Competitive Athletes

Introducción y objetivos A pesar del establecido valor diagnóstico del electrocardiograma en la revisión preparticipativa de sujetos deportistas, algunas alteraciones estructurales cardiacas podrían pasar inadvertidas, en especial en fases precoces de la enfermedad. El objetivo de este estudio es valorar la prevalencia de alteraciones estructurales cardiacas mediante el uso sistemático de la ecocardiografía en la revisión preparticipativa de deportistas de competición. Métodos Se estudió a los deportistas incluidos en un programa de competición o profesionales. Se realizó a todos los deportistas una revisión que incluyó historia familiar y personal, examen físico, electrocardiograma, prueba de esfuerzo y ecocardiograma Doppler. Resultados Se incluyó a 2.688 deportistas (el 67% varones; media de edad, 21 ± 10 años). La mayoría de los estudios ecocardiográficos (92,5%) fueron estrictamente normales y solo 203 (7,5%) tenían alteraciones; la más frecuente de ellas fue la hipertrofia ventricular izquierda, en 50 deportistas (1,8%). En 4 casos (0,14%) se indicó el cese de la práctica deportiva: 2 por miocardiopatía hipertrófica (el electrocardiograma mostraba alteraciones pero no cumplía criterios diagnósticos), 1 pectus excavatum con compresión del ventrículo derecho y 1 estenosis valvular pulmonar significativa; el resto de las alteraciones no implicaron el cese de la práctica deportiva y solo requirieron seguimiento periódico. Conclusiones: Algunas alteraciones estructurales cardiacas, aunque poco frecuentes, pueden pasar inadvertidas al examen físico y en el electrocardiograma; en cambio, son fácilmente reconocibles con un ecocardiograma. Estas observaciones indican introducir el ecocardiograma al menos en la primera valoración preparticipativa de deportistas de competición para mejorar la eficacia de los programas de prevención de la muerte súbita del deportista (AU)

Introduction and objectives Despite the established diagnostic value of the electrocardiogram in preparticipation screening of athletes, some cardiac structural changes can be missed, particularly in early disease stages. The aim of this study was to evaluate the prevalence of cardiac structural changes via the systematic use of echocardiography in preparticipation screening of competitive athletes. Methods Professional athletes or participants in a competitive athletic program underwent a screening that included family and personal medical history, physical examination, electrocardiography, exercise testing, and Doppler echocardiography. Results A total of 2688 athletes (67% men; mean age [standard deviation], 21 [10] years) were included. Most of the echocardiographic evaluations (92.5%) were normal and only 203 (7.5%) showed changes; the most frequent change was left ventricular hypertrophy, seen in 50 athletes (1.8%). Cessation of athletic activity was indicated in 4 athletes (0.14%): 2 for hypertrophic cardiomyopathy (electrocardiography had shown changes that did not meet diagnostic criteria), 1 pectus excavatum with compression of the right ventricle, and 1 significant pulmonary valve stenosis; the rest of the changes did not entail cessation of athletic activity and only indicated periodic monitoring. Conclusions Although rare, some cardiac structural changes can be missed on physical examination and electrocardiography; in contrast, they are easily recognized with echocardiography. These findings suggest the use of echocardiography in at least the first preparticipation screening of competitive athletes to improve the effectiveness of programs aimed at preventing sudden death in athletes (AU)

Osteitis pubis: can early return to elite competition be contemplated?

BACKGROUND AND PURPOSE: In elite athletes, osteitis pubis is a common painful degenerative process of the pubic symphysis and surrounding soft tissues and tendons. We report the diagnostic pathway and the rehabilitation protocol of six elite athletes with osteitis pubis in three different sports, and compare protocol stages and time to return to competition. METHODS: 6 athletes (2 soccer, 2 basketball, 2 rugby players) were diagnosed with osteitis pubis stage III and IV according to Rodriguez classification using standard clinical and imaging criteria. After performing a baseline lumbo-pelvic assessment, the rehabilitation protocol described by Verrall was adapted to each individual athlete. RESULTS: The length of time for each stage of the protocol was as follows; Stage 1 (rest from sport) was 26 +/- 5 days, Stage 2 (to achieve pain free running), 18 +/- 5 days, Stage 3 (squad training) 63 +/- 7, Stage 4 (return to competition) 86 +/- 15. Soccer players took longer to return to competition than basketball and rugby players. No recurrences were reported at 2 year follow-up. CONCLUSION: The protocol presented ensures a safe return to elite athletes. The time from diagnosis to full recovery is longer in football players, and seems to increase with age.

Usefulness of echocardiography in preparticipation screening of competitive athletes.

INTRODUCTION AND OBJECTIVES: Despite the established diagnostic value of the electrocardiogram in preparticipation screening of athletes, some cardiac structural changes can be missed, particularly in early disease stages. The aim of this study was to evaluate the prevalence of cardiac structural changes via the systematic use of echocardiography in preparticipation screening of competitive athletes. METHODS: Professional athletes or participants in a competitive athletic program underwent a screening that included family and personal medical history, physical examination, electrocardiography, exercise testing, and Doppler echocardiography. RESULTS: A total of 2688 athletes (67% men; mean age [standard deviation], 21 [10] years) were included. Most of the echocardiographic evaluations (92.5%) were normal and only 203 (7.5%) showed changes; the most frequent change was left ventricular hypertrophy, seen in 50 athletes (1.8%). Cessation of athletic activity was indicated in 4 athletes (0.14%): 2 for hypertrophic cardiomyopathy (electrocardiography had shown changes that did not meet diagnostic criteria), 1 pectus excavatum with compression of the right ventricle, and 1 significant pulmonary valve stenosis; the rest of the changes did not entail cessation of athletic activity and only indicated periodic monitoring. CONCLUSIONS: Although rare, some cardiac structural changes can be missed on physical examination and electrocardiography; in contrast, they are easily recognized with echocardiography. These findings suggest the use of echocardiography in at least the first preparticipation screening of competitive athletes to improve the effectiveness of programs aimed at preventing sudden death in athletes.

Could single nucleotide polymorphisms influence on the efficacy of platelet-rich plasma in the treatment of sport injuries?

Platelet-rich plasma (PRP) is a new powerful biological tool in sports medicine, when used to treat tendon, ligament and muscle injuries. PRP is a fraction of autologous whole blood containing an increased number of platelets and a wide variety of cytokines that can improve and accelerate the healing of various tissues. An analysis of the literature shows promising pre-clinical results for PRP treatment, but there is a lack of solid clinical proof to support its use in sports medicine, and in fact, clinical findings on individual responses to PRP treatment are contradictory. These contradictions may be due to interindividual differences in the presence of single nucleotide polymorphisms (SNPs) in genes related to PRPs and/or their receptors. These SNPs can determine a greater or lesser response to this treatment and consequently a shorter or longer recovery time. We have focused our attention in the study of genes related to PRP with the aim to develope a genetic profile that will identify the individuals and injuries most likely to benefit from PRP treatment.

Epidemiología lesional del balonmano de elite: estudio retrospectivo en equipos profesional y formativo de un mismo club / Epidemiology of injuries in elite handball: Retrospective study in professional and academy handball team

Objetivo: Evaluar la incidencia y el patrón lesional en el balonmano de elite. Método: Estudio retrospectivo y transversal de 496 jugadores, de 29 equipos (divididos por categorías según edad y nivel), durante 5 temporadas (2007-2012), de un club del sur de Europa. El equipo médico evaluó las lesiones y el tiempo de exposición por equipos. Se siguieron los criterios epidemiológicos según consenso UEFA y codificación OSICS-10. Resultados: Se registraron 557 lesiones con 117.723 h de exposición totales. La incidencia lesional media de los equipos fue: 4,9 lesiones/1.000 h de exposición. Para el equipo Senior A (Profesional) fue de 4,3 (DE 1,8); Senior B, 3,4 (DE 1,6); Juvenil, 5,6 (DE 1,4); Cadete A, 5,5 (DE 2,5); Cadete B, 5,7 (DE 3,2), e Infantil, 4,9 (DE 1,9). No hubo diferencias estadísticamente significativas entre ellos, aunque los seniors tuvieron la mayor cantidad de horas de exposición (p < 0,001).Las localizaciones más frecuentes fueron tobillo (18,1%), rodilla (15,3%), muslo (12,9%) y región lumbar (10,6%). Las estructuras afectadas con más frecuencia fueron la lesión ligamentosa (27,3%) y la lesión «muscular por mecanismo indirecto» (20,5%). Esta última más en el Senior A, y la lesión ligamentosa en las categorías inferiores, aunque no se registraron diferencias significativas entre categorías. Conclusión: El patrón y la incidencia lesional en el balonmano de elite es uniforme entre los equipos de diferentes categorías, con pequeñas diferencias que deberán tenerse en cuenta para optimizar los programas de prevención en cada categoría del balonmano formativo de elite

Objective: To evaluate the injury incidence and pattern of injuries in elite handball by different ages. Method: A retrospective, cross sectional study, was conducted over 5 seasons (2007-2012), analyzing a total of 496 players, 29 teams (from different categories separated by age and performance level) of the same club in southern Europe. The same medical team has assessed the injuries and exposure time by teams. Epidemiological criteria according to UEFA and consensus OSICS-10 diagnostic coding were followed. Results: A total of 57 injuries were recorded during 117,723 hours of total exposure. There was a mean team injury incidence of 4.9 injuries/1000 hours of total exposure. For the Senior A (Professional Senior) it was was 4.3 (SD 1.8), Senior B (Amateur 18-28 years) 3.4 (SD 1.6), Youth (U-18 year) 5.6 (SD 1.4), Cadete A (U-16 year) 5.5 (SD 2.5), Cadete B (U-15 year) 5.7 (SD 3.2) and Infantil (U-14 year) 4.9 (SD 1.9). There were no statistically significant differences between categories, although seniors teams had more hours of exposure compared to other teams (P < 0.001). The most frequently affected sites were ankle (18.1%), knee (15.3%), thigh (12.9%) and lumbar region (10.6%). The most common type of injury to all teams was the sprain (27.3%) and non-traumatic muscle injury (20.5%). Muscle injuries were more common at Senior A (Professional) level, but in lower level teams it was the sprain, although there is no significant differences between them. Conclusion: The pattern and incidence of injury in elite handball is uniform between teams from different categories at the same club; with a few differences between each other that you should take this into account to optimize a preventions programs in each category of elite handball training

Epidemiology of injuries in elite taekwondo athletes: two Olympic periods cross-sectional retrospective study.

OBJECTIVE: Taekwondo injuries differ according to the characteristics of the athletes and the competition. This analytical cross-sectional retrospective cohort study aimed to describe reported taekwondo injuries and to determine the prevalence, characteristics and possible risk factors for injuries sustained by athletes of the Spanish national team. In addition, we compared each identified risk factor-age, weight category, annual quarter, injury timing and competition difficulty level-with its relation to injury location and type. SETTINGS: Injury occurrences in taekwondo athletes of the Spanish national team during two Olympic periods at the High Performance Centre in Barcelona were analysed. PARTICIPANTS: 48 taekwondo athletes (22 male, 26 female; age range 15-31 years) were studied; 1678 injury episodes occurred. Inclusion criteria were: (1) having trained with the national taekwondo group for a minimum of one sports season; (2) being a member of the Spanish national team. RESULTS: Independently of sex or Olympic period, the anatomical sites with most injury episodes were knee (21.3%), foot (17.0%), ankle (12.2%), thigh (11.4%) and lower leg (8.8%). Contusions (29.3%) and cartilage (17.6%) and joint (15.7%) injuries were the prevalent types of injury. Chronological age, weight category and annual quarter can be considered risk factors for sustaining injuries in male and female elite taekwondists according to their location and type (p≤0.001). CONCLUSIONS: This study provides epidemiological information that will help to inform future injury surveillance studies and the development of prevention strategies and recommendations to reduce the number of injuries in taekwondo competition.

Compression garments to prevent delayed onset muscle soreness in soccer players.

The purpose of this study was to evaluate the use of a compression garment as DOMS prevention. This was accomplished by provoking a DOMS in 15 athletes, running on a treadmill at 73% of their maximal aerobic velocity, during 40 minutes with a 10% negative slope; wearing the compression garments on one thigh, protected thigh (PT), and not in the contralateral thigh, control thigh (CT). A clinical and MRI diagnosis of DOMS was performed. Biopsies in both vastus lateralis were done, and the amount and severity of the DOMS was estimated by measuring intracellular albumin, and lymphocytes CD3+ and neutrophils intra/interfibrilar infiltrates, 48h after the induced damaging exercise. There was less total injury in the PT than in the CT, a 26.7% average. These data indicate that this compression garment is an effective method to reduce the histological injury in DOMS.

Importancia de la epidemiología en medicina del deporte / The importance of epidemiological research in sports medicine

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Revision, uptake and coding issues related to the open access Orchard Sports Injury Classification System (OSICS) versions 8, 9 and 10.1.

The Orchard Sports Injury Classification System (OSICS) is one of the world's most commonly used systems for coding injury diagnoses in sports injury surveillance systems. Its major strengths are that it has wide usage, has codes specific to sports medicine and that it is free to use. Literature searches and stakeholder consultations were made to assess the uptake of OSICS and to develop new versions. OSICS was commonly used in the sports of football (soccer), Australian football, rugby union, cricket and tennis. It is referenced in international papers in three sports and used in four commercially available computerised injury management systems. Suggested injury categories for the major sports are presented. New versions OSICS 9 (three digit codes) and OSICS 10.1 (four digit codes) are presented. OSICS is a potentially helpful component of a comprehensive sports injury surveillance system, but many other components are required. Choices made in developing these components should ideally be agreed upon by groups of researchers in consensus statements.

Piomiositis no traumática recurrente en un jugador de fútbol profesional / No disponible

La piomiositis representa una importante infección del músculo esquelético causada principalmente por Staphylococcus aureus. En este artículo se presenta el caso clínico de un futbolista de élite con antecedentes de foliculitis de repetición y portador crónico de S. aureus que presenta en un período de 6 meses dos episodios de piomiositis muscular no traumática que, tras las pruebas complementarias adecuadas, el cultivo del microorganismo y el tratamiento antibiótico correcto, se resolvieron sin complicación alguna(AU)

Pyomyositis is an important infection of skeletal muscle frequently caused by Staphylococcus aureus. This article presents a case of an elite soccer player with a recurrent history of folliculitis and chronic carrier of S. aureus that in a 6 months period presents two episodes of non-traumatic pyomyositis. After suitable complementary tests, culture of the microorganism and the correct antibiotic treatment, abscesses resolved without any complication(AU)

El sistema de clasificación y codificación OSICS-10 traducido del inglés / The Orchard Sports Injury Classification System (OSICS) Version 10

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A Hypothesis: Could Portable Natural Grass be a Risk Factor for Knee Injuries?

Previous study has shown a likely link between increased shoe- surface traction and risk of knee Anterior Cruciate Ligament (ACL) injury. Portable natural grass systems are being used more often in sport, but no study to date has investigated their relative safety. By their nature, they must have high resistance to falling apart and therefore newly laid systems may be at risk of creating excessive shoe-surface traction. This study describes two clusters of knee injuries (particularly non-contact ACL injuries), each occurring to players of one professional football team at single venue, using portable grass, in a short space of time. The first series included two ACL injuries, one posterolateral complex disruption and one lateral ligament tear occurring in two rugby league games on a portable bermudagrass surface in Brisbane, Australia. The second series included four non-contact ACL injuries over a period of ten weeks in professional soccer games on a portable Kentucky bluegrass/perennial ryegrass surface in Barcelona, Spain. Possible intrinsic risk factors are discussed but there was no common risk shared by the players. Although no measures of traction were made at the Brisbane venue, average rotational traction was measured towards the end of the injury cluster at Camp Nou, Barcelona, to be 48 Nm. Chance undoubtedly had a part to play in these clusters, but the only obvious common risk factor was play on a portable natural grass surface soon after it was laid. Further study is required to determine whether portable natural grass systems may exhibit high shoe-surface traction soon after being laid and whether this could be a risk factor for knee injury. Key pointsExcessive shoe-surface traction is a hypothesised risk factor for knee ligament injuries, including anterior cruciate ligament injuries.Portable natural grass systems (by their nature in order to prevent grass rolls or squares from falling apart) will tend to exhibit high resistance to tearing when first laid. This may lead to excessive shoe-surface traction.This dual case series describes two clusters of non-contact knee ligament injuries which occurred in circumstances of newly laid portable turf.Further research is warranted to undercover any link between non-contact knee ligament injuries and ground surfaces conditions.