Intrinsic risk factors for acute knee injuries among male football players: a prospective cohort study

This prospective cohort study was conducted to identify the risk factors for acute knee injuries among male football players. A total of 508 players representing 31 amateur teams were tested during the 2004 preseason for potential risk factors for knee injury through a questionnaire on previous injury, Knee Osteoarthritis Outcome Score (KOOS) and a clinical examination. Generalized estimating equations were used in univariate analyses to identify candidate risk factors, and factors with a P-value <0.10 were then examined in a multivariate model. During the football season, 61 acute knee injuries, affecting 57 legs (53 players), were registered. Univariate analyses revealed the KOOS subscores "Pain" and "Function in daily living" (OR for a 10-point difference in score: 1.26, 95% CI 1.03-1.55 and 1.35, 95% CI 0.98-1.85, respectively), any findings at clinical examination (OR: 2.62, 95% CI 1.03-6.68), flexion contraction in range of motion testing (OR: 0.96, 95% CI 0.93-1.00) and varus stress tests in full extension (OR: 8.50, 95% CI 1.85-39.0) and 30° flexion (OR: 5.69, 95% CI 1.73-18.8) as candidate factors. However, in a multivariate analysis, none of these factors were associated with an increased injury risk.     

Knee function among elite handball and football players 1‐6 years after anterior cruciate ligament injury

The aim of the study was to describe objective and self‐reported knee function for athletes who have returned to elite handball and football play after an ACL injury, comparing these to non‐injured players at the same level. A total of 414 handball and 444 football players completed baseline tests from 2007 through 2014, examining lower extremity strength, dynamic balance, knee laxity, and knee function (KOOS questionnaire). Measures were compared between injured and non‐injured legs and between injured legs and legs of controls. Eighty (9.3%) of the 858 players reported a previous ACL injury, 1‐6 years post‐injury (3.5±2.5 years), 49 handball (61.3%) and 31 football players (38.7%). We found no difference in strength or dynamic balance between previously ACL‐injured (N=80) and non‐injured players legs (N=1556). However, lower quadriceps (6.3%, 95% CI: 3.2‐9.2) and hamstrings muscle strength (6.1%, 95% CI: 3.3‐8.1) were observed in previously ACL‐injured legs compared to the non‐injured contralateral side (N=80). ACL‐injured knees displayed greater joint laxity than the contralateral knee (N=80, 17%, 95% CI: 8‐26) and healthy knees (N=1556, 23%, 95% CI: 14‐33). KOOS scores were significantly lower for injured knees compared to knees of non‐injured players. ACL‐injured players who have successfully returned to elite sport have comparable strength and balance measures as their non‐injured teammates. Subjective perception of knee function is strongly affected by injury history, with clinically relevant lower scores for the KOOS subscores Pain, Function, Sport, and Quality Of Life.     

Investigation of knee control as a lower extremity injury risk factor: A prospective study in youth football

This prospective study in youth football examined the relationship between frontal plane knee projection angle (FPKPA ) during the single‐leg squat and sustaining an acute lower extremity injury or acute non‐contact lower extremity injury. Secondly, side‐to‐side asymmetry in FPKPA and sex as injury risk factors were explored. In addition, we investigated the influence of age, sex, and leg dominance on the FPKPA . A total of 558 youth football players (U11 to U14) participated in the single‐leg squat test and prospective injury registration. FPKPA was not found as a risk factor for injuries at this age. There was no difference in the mean FPKPA between sexes. However, FPKPA was associated with age; oldest subjects displayed the smallest FPKPA . Among boys, the frontal plane knee control improved by age. Among girls, the relationship between age and FPKPA was not as clear, but the oldest girls displayed the smallest mean FPKPA in the study (12.2° ± 8.3°). The FPKPA was greater on the dominant kicking leg compared to the non‐dominant support leg (P  <  .001 for boys, P  =  .001 for girls). However, side‐to‐side asymmetry in FPKPA was not associated with future injuries. In conclusion, frontal plane knee control in the single‐leg squat was not associated with lower extremity injuries among young football players. As the single‐leg squat to 90° knee flexion was too demanding for many subjects, easier single‐leg squat test procedure or a different movement control test, such as a double‐legged squat, could be more suitable for the young football players.     

Motives for sports participation as predictions of self‐reported outcomes after anterior cruciate ligament injury of the knee

Aim of the study was to access how individual's motives for participation in sports impact on self‐reported outcomes 2 years after an anterior cruciate ligament injury. Based on a longitudinal cohort study, this secondary analysis present data from the Knee Anterior Cruciate Ligament, Nonsurgical versus Surgical Treatment (KANON) study, a randomized controlled trial. At baseline, 121 patients recorded in an initial questionnaire that their motives for sports participation fell into four categories: achievement, health, social integration, or fun and well‐being. These four categories were used as variables in the analyses. All 121 subjects completed the 2‐year follow‐up. The largest improvement was seen in the Knee Injury and Osteoarthritis Outcome Score (KOOS) subscale sports and recreation function, with an effect size of 2.43. KOOS sports and recreation function was also the subscale score best predicted by the motives for sports participation. Baseline motives achievement and fun and well‐being predicted worse levels of pain and function 2 years after the injury, even after adjusting for age, gender, treatment and baseline scores. Psychological aspects, such as motives for participation in sport, can be factors in predicting of patient‐reported outcomes 2 years after injury. Evaluating motives for sports participation may help predict the outcome 2 years after ACL injury.     

Female soccer knee injury: Observed knowledge gaps in injury prevention among players/parents/coaches and current evidence (the KNOW study)

This study sought to determine if knowledge regarding the risk for knee injuries and the potential for their prevention is being translated to female adolescent soccer players (13–18 years), their parents, and coaches. Eligible participants in the 2007 indoor soccer season were surveyed to determine their knowledge of the risk for and the potential to prevent knee injuries, and their knowledge of effective prevention strategies, if they felt that injury prevention was possible. Team selection was stratified to be representative of both competitive and recreational level play and age group distributions within the selected soccer association. Of the study subjects, 773/1396 (55.4%) responded to the survey: 408 (53%) players, 292 (38%) parents, and 73 (9%) coaches. Most respondents (538 [71%]) were aware of the risk for knee injury. Coaches and parents were more likely than players to view knee injuries as preventable; however, appropriate prevention strategies were often not identified. Four hundred eighty‐four (63.8%) respondents reported that they had never received information on knee injuries. Substantial knowledge gaps regarding knee injury prevention and effective preventative strategies were identified. Given the predominance of knee injuries in female adolescent soccer players, there is an urgent need for knowledge translation of prevention strategies to decrease both incidence and long‐term consequences of knee injuries.     

Adoption and use of an injury prevention exercise program in female football: A qualitative study among coaches

This study focuses on an injury prevention exercise program (IPEP ), Knee Control, which has been shown to reduce the incidence of acute knee injury in female adolescent football players. The aim was to explore the factors influencing coaches’ adoption and use of Knee Control within female football in Sweden. This was a qualitative study involving interviews with 20 strategically selected coaches for female football teams, predominantly adolescent teams. The semi‐structured interview guide was influenced by the Health Belief Model, and an ecological perspective was adopted during the interviews. Interviews were analyzed with qualitative content analysis. The results illustrate the different influences that interact on adoption and use of Knee Control by coaches. The coaches described themselves as crucial for Knee Control adoption and use, but external facilitators and barriers such as resources for training, social support from other coaches, clubs and football associations and player buy‐in were also described as important. Knee Control characteristics, such as how well the program fit the team, also influenced use of Knee Control. Many coaches modified the program to improve player buy‐in and Knee Control fit. Such modifications may risk compromising the preventive effect but may increase feasibility, that is the ease of using Knee Control, and thereby long‐term use. These findings may guide the design and delivery of future IPEP s, and improve use of Knee Control, for example, by expanding the program to fit different target groups and supporting coaches and players in the use of Knee Control.     

Injuries among male and female elite football players

All 12 female football clubs (228 players) and 11 of 14 male clubs (239 players) in the Swedish premier league were followed prospectively during the 2005 season. Individual exposure (playing time), injuries (time loss), and injury severity (days lost due to injury) were recorded by the team medical staffs. Injury incidence was higher for male players during both training (4.7 vs 3.8 injuries/1000 h, P=0.018) and match play (28.1 vs 16.1, P<0.001). However, no difference was found in the incidence of severe injury (absence >4 weeks) (0.7/1000 h in both groups). The thigh, especially the hamstrings, was the overall most commonly injured region in both sexes, while the hip/groin was more commonly injured in male players and the knee in female players. Knee ligament injuries accounted for 31% and 37% of the total time lost from football for male and female players, respectively. In conclusion, male elite players had a higher injury incidence than their female counterparts although no difference was observed in the incidence of moderate to severe injury. We recommend that preventive measures should be focused on hamstring and knee ligament injury in order to reduce the overall injury burden.     

Association between eccentric knee flexor strength and hamstring injury risk in 185 elite Gaelic football players

Hamstring strains are the most common time-loss injury in elite Gaelic football affecting over 20% of players per season. Thus, there is a need to identify factors contributing to the onset of hamstring injuries in order to inform injury risk management strategies. The current study investigated whether eccentric knee flexor strength and between-limb imbalances were associated with increased risk of sustaining a time-loss hamstring injury in elite Gaelic football players. A total of 185 elite male players (26.9 ± 2.7 years, 86.4 ± 6.2 kg, 183.4 ± 5.6) were prospectively followed for 12 weeks from the day of testing. Injury data were provided by the team medical staff. Twenty-eight players (16%) sustained a time-loss hamstring injury following testing. Players that did not sustain a hamstring injury had greater average between-limb asymmetries (uninjured = 9.1%, 95% CI 7.8-10.1; injured = 5.1%, 95% CI 3.7-6.7; P = .001). Eccentric knee flexor strength profiles were not associated with increased or decreased risk of sustaining a hamstring injury and did not alter the post-test probability of sustaining a hamstring injury across the investigation period. These findings do not support the use of eccentric knee flexor strength metrics in managing hamstring injury risk in elite male Gaelic football players.     

Anterior cruciate ligament injury after more than 20 years: I. Physical activity level and knee function

Little is known about physical activity level and knee function including jump capacity and fear of movement/reinjury more than 20 years after injury of the anterior cruciate ligament (ACL). Seventy persons with unilateral ACL injury participated (23 ± 2 years post‐injury): 33 treated with physiotherapy in combination with surgical reconstruction (ACL_R), and 37 treated with physiotherapy alone (ACL_PT). These were compared with 33 age‐ and gender‐matched controls. Assessment included knee‐specific and general physical activity level [Tegner activity scale, International Physical Activity Questionnaire (IPAQ)], knee function [Lysholm score, Knee injury and Osteoarthritis Outcome Score (KOOS)], jump capacity (one‐leg hop, vertical jump, side hops), and fear of movement/reinjury [Tampa Scale for Kinesiophobia (TSK)]. Outcomes were related to degree of osteoarthritis (OA). ACL‐injured had lower Lysholm, KOOS, and Tegner scores than controls (P < 0.001), while IPAQ score was similar. ACL‐injured demonstrated inferior jump capacity in injured compared with noninjured leg (6–25%, P < 0.001–P = 0.010 in the different jumps), while noninjured leg had equal jump capacity as controls. ACL groups scored 33 ± 7 and 32 ± 7 of 68 on TSK. Lower scores on Lysholm and KOOS symptom were seen for persons with moderate‐to‐high OA than for no‐or‐low OA, while there were no differences for physical activity and jump capacity. Regardless of treatment, there are still negative knee‐related effects of ACL injury more than 20 years later.     

High risk of new knee injury in elite footballers with previous anterior cruciate ligament injury

Background

Anterior cruciate ligament (ACL) injury is a severe event for a footballer, but it is unclear if the knee injury rate is higher on returning to football after ACL injury.

Objective

To study the risk of knee injury in elite footballers with a history of ACL injury compared with those without.

Method

The Swedish male professional league (310 players) was studied during 2001. Players with a history of ACL injury at the study start were identified. Exposure to football and all time loss injuries during the season were recorded prospectively.

Results

Twenty four players (8%) had a history of 28 ACL injuries in 27 knees (one rerupture). These players had a higher incidence of new knee injury of any type than the players without ACL injury (mean (SD) 4.2 (3.7) v 1.0 (0.7) injuries per 1000 hours, p  =  0.02). The risk of suffering a knee overuse injury was significantly higher regardless of whether the player (relative risk 4.8, 95% confidence interval 2.0 to 11.2) or the knee (relative risk 7.9, 95% confidence interval 3.4 to 18.5) was used as the unit of analysis. No interactive effects of age or any other anthropometric data were seen.

Conclusion

The risk of new knee injury, especially overuse injury, was significantly increased on return to elite football after ACL injury regardless of whether the player or the knee was used as the unit of analysis.     

Health problems in former elite female football players: Prevalence and risk factors

The aim of this study was to assess the prevalence of health problems and associated risk factors in former elite female football players. A cross‐sectional research design was employed, using an online questionnaire on personal characteristics and health complaints during/after the career. One hundred fifty‐two (response rate: 62.0%) former first German league players answered the survey. Around 70% described their current health as good or very good. Over half (57.9%) reported knee problems during the last 4 weeks while exercising and a third (33.6%) during normal daily activities. The second most common location for complaints was the head (53.3%). Almost one quarter (23.7%) of players suffered from osteoarthritis (OA). Regression analysis showed that OA in knee/ankle and physical complaints (PC) in knee/ankle/head were significantly predicted by number and severity of previous injuries (P < 0.05). Further, increases in age, training volume, and level of play were associated with an increased likelihood of presenting with OA (P < 0.05), but not PC. In conclusion, a football career may lead to specific long‐term health problems in elite female players. Prevention strategies should focus on knee, ankle, and head injuries. Future studies are needed to clinically assess the prevalence rates of OA and possible neurocognitive changes.     

Text messaging as a new method for injury registration in sports: A methodological study in elite female football

Methodological differences in epidemiologic studies have led to significant discrepancies in injury incidences reported. The aim of this study was to evaluate text messaging as a new method for injury registration in elite female football players and to compare this method with routine medical staff registration. Twelve teams comprising 228 players prospectively recorded injuries and exposure through one competitive football season. Players reported individually by answering three text messages once a week. A designated member of the medical staff conducted concurrent registrations of injuries and exposure. Injuries and exposure were compared between medical staff registrations from nine teams and their 159 affiliated players. During the football season, a total of 232 time‐loss injuries were recorded. Of these, 62% were captured through individual registration only, 10% by the medical staff only, and 28% were reported through both methods. The incidence of training injuries was 3.7 per 1000 player hours when calculated from individual registration vs 2.2 from medical staff registration [rate ratio (RR): 1.7, 1.2–2.4]. For match injuries, the corresponding incidences were 18.6 vs 5.4 (RR: 3.4, 2.4–4.9), respectively. There was moderate agreement for severity classifications in injury cases reported by both methods (kappa correlation coefficient: 0.48, confidence interval: 0.30–0.66).     

Neuromuscular exercises prevent severe knee injury in adolescent team handball players

Purpose

Team handball is associated with a high risk of severe knee injury that needs to be reduced, particularly at the youth level. The purpose of this study was to show how an injury-prevention programme effectively reduces severe knee injury in adolescent team handball players.

Methods

Of 23 adolescent handball teams of both sexes, 13 were randomly allocated into the intervention group (168 players) and 10 into the control group (111 players). Players of the intervention group regularly participated in an injury-prevention programme for one season. Handball exposure and sustained injuries were documented for both groups on a monthly basis. The primary outcome parameter of the injury-prevention programme was the incidence of severe knee injury.

Results

Of the 279 included players, 68 (24%) sustained 82 injuries yielding an overall incidence of 1.85 injuries per 1000 h handball exposure (intervention group: 50 injuries/incidence: 1.90/1000 h; control group: 32 injuries/incidence: 1.78/1000 h). Knee injury was the second most frequent injury in adolescent team handball. The primary outcome parameter, severe knee injury occurred significantly more often in the control group [mean age (SD) 15.1 (1.0), injury incidence 0.33/1000 h] than in the intervention group [mean age (SD) 14.9 (0.9), injury incidence 0.04/1000 h]. The odds ratio was 0.11 (95% CI 0.01–0.90), p?=?0.019. Other injuries to the lower extremities showed no significant difference between the two groups.

Conclusions

Frequent neuromuscular exercises prevent severe knee injury in adolescent team handball players and should thus be included in the practical routine as well as in the education of team coaches.

     

Risk factors for acute knee injury in female youth football

Purpose

To prospectively evaluate risk factors for acute time-loss knee injury, in particular ACL injury, in female youth football players.

Methods

Risk factors were studied in 4556 players aged 12–17 years from a randomised controlled trial during the 2009 season. Covariates were both intrinsic (body mass index, age, relative age effect, onset of menarche, previous acute knee injury or ACL injury, current knee complaints, and familial disposition of ACL injury) and extrinsic (no. of training sessions/week, no. of matches/week, match exposure ratio, match play with other teams, and artificial turf exposure). Hazard ratios (HRs) and 95 % confidence intervals (CIs) were calculated from individual variable and multiple Cox regression analyses.

Results

Ninety-six acute knee injuries were recorded, 21 of them ACL injuries. Multiple Cox regression showed a fourfold higher ACL injury rate for players with familial disposition of ACL injury (HR 3.57; 95 % CI 1.48–8.62). Significant predictor variables for acute knee injury were age >14 years (HR 1.97; 95 % CI 1.30–2.97), knee complaints at the start of the season (HR 1.98; 95 % CI 1.30–3.02), and familial disposition of ACL injury (HR 1.96; 95 % CI 1.22–3.16). No differences in injury rates were seen when playing on artificial turf compared with natural grass.

Conclusion

Female youth football players with a familial disposition of ACL injury had an increased risk of ACL injury and acute knee injury. Older players and those with knee complaints at pre-season were more at risk of acute knee injury. Although the predictive values were low, these factors could be used in athlete screening to target preventive interventions.

Level of evidence

II.

     

Previous injury as a risk factor for injury in elite football: a prospective study over two consecutive seasons

Background

Previous injury is often proposed to be a risk factor for football injury, but most studies rely on players reporting their own medical history and are thus potentially subject to recall bias. Little is known about the natural variation in injury pattern between seasons.

Objectives

To study whether prospectively recorded injuries during one season are associated with injuries sustained during the following season, and to compare injury risk and injury pattern between consecutive seasons.

Methods

The medical staffs of 12 elite Swedish male football teams prospectively recorded individual exposure and time loss injuries over two full consecutive seasons (2001 and 2002). A multivariate model was used to determine the relation between previous injury, anthropometric data, and the risk of injury.

Results

The training and match injury incidences were similar between seasons (5.1 v 5.3 injuries/1000 training hours and 25.9 v 22.7/1000 match hours), but analysis of injury severity and injury patterns showed variations between seasons. Players who were injured in the 2001 season were at greater risk of any injury in the following season compared with non‐injured players (hazard ratio 2.7; 95% confidence interval 1.7 to 4.3, p<0.0001). Players with a previous hamstring injury, groin injury, and knee joint trauma were two to three times more likely to suffer an identical injury in the following season, whereas no such relation was found for ankle sprain. Age was not associated with an increased injury risk.

Conclusions

This study confirmed previous results showing that previous injury is an important risk factor for football injury. Overall injury incidences were similar between consecutive seasons, indicating that an injury surveillance study covering one full season can provide a reasonable overview of the injury problem among elite football players in a specific environment. However, a prolonged study period is recommended for analyses of specific injury patterns.     

Prophylactic knee bracing in college football

American football can be harmful to knees. In an attempt to reduce the number and severity of knee injuries, the intercollegiate football team at the University of Arizona (Pacific Ten Conference) has been using protective braces since 1981. Objective evaluation of the effectiveness of this program is the purpose of this study. All linemen, offensive and defensive, as well as linebackers and tight ends were considered to be the players at greatest risk and were required to use the braces. The brace used was the Anderson Knee Stabler. Each player at each practice session or game was counted as one exposure. During the 4 years of brace use, there were 28,191 exposures, while the control group numbered 29,293 exposures. The data were analyzed from the perspectives of days lost from practice or games, player's position, the type and severity of injury, and the rate of injury per 100 players per season. Players at risk showed no trend to change in injury rate. Of the players at risk, the type and severity of injury in nonbraced and in braced groups were similar. A significant finding in players at risk was a two-fold increase in knee ligament injury rate per 100 players when compared to rates for an entire team. The number of season-ending injuries remained unchanged. Practice time missed for third-degree medial ligament, and for medial meniscus injuries, was significantly lower in the braced group, but this was due to improved treatment techniques initiated in 1981. Seven NCAA rule changes, directed at reducing knee injuries, have been introduced since 1981.(ABSTRACT TRUNCATED AT 250 WORDS)     

No association between rate of torque development and onset of muscle activity with increased risk of hamstring injury in elite football

Hamstring injuries remain a significant burden in sports that involve high‐speed running. In elite male football, hamstring injury has repeatedly been identified as the most common non‐contact injury, representing 12% of all injuries. As the incidence remains high, investigations are aimed at better understanding how to improve prevention efforts. Intrinsic risk factors such as strength have been investigated extensively in a cohort of professional football players; however, other intrinsic measures of neuromuscular function have not been studied in this cohort. This study aims to investigate the association between timing of hamstring muscle activity onset and the rate of torque development during the early phase of isokinetic strength testing with risk of hamstring injury in professional football players in a prospective cohort study. All teams (n = 18) eligible to compete in the premier football league in Qatar underwent a comprehensive strength assessment during their annual periodic health evaluation at Aspetar Orthopaedic and Sports Medicine Hospital in Doha, Qatar. Variables included rate of torque development and timing of muscle activity onset. A total of 367 unique players (60.6% of all QSL players) competed for 514 player seasons (103 players competed both seasons) and sustained 65 hamstring injuries. There was no difference in the onset of muscle activity between the biceps femoris and medial hamstrings comparing the injured to uninjured players. For both onset of muscle activity and rate of torque development, there were no significant differences between any of the variables (P  > .05), with small effect sizes detected across all the different variables (d < 0.3). Rate of torque development and onset of muscle activity were not associated with a risk of future hamstring injury. The use of these measures as part of a periodic health evaluation to identify risk of hamstring injury is unsupported.     

Intrinsic and extrinsic risk factors for anterior cruciate ligament injury in Australian footballers

The aim of this study was to examine the interaction between intrinsic (player-related) and extrinsic (environment-related) variables as risk factors for anterior cruciate ligament injury in Australian football. Between 1992 and 1999, 100,820 player-match exposures were analyzed for risk of anterior cruciate ligament injury using logistic regression analysis. There were 63 surgically proven noncontact anterior cruciate ligament injuries. The strongest risk factors were a player history of anterior cruciate ligament reconstruction either in the previous 12 months (relative risk [RR], 11.33; 95% confidence interval [CI], 4.02 to 31.91) or before the previous 12 months (RR, 4.44; 95% CI, 2.46 to 8.01). Weather conditions that were associated with dry field conditions--high water evaporation in the month before the match (RR, 2.55; 95% CI, 1.44 to 4.52) and low rainfall in the year before the match (RR, 2.87; 95% CI, 1.30 to 6.32)--were also significantly associated with these injuries. The increased risk of injury in the first 12 months after reconstruction was associated with the reconstructed knee, whereas after 12 months there was an even distribution of new injuries to the reconstructed knee and contralateral knee. A history of anterior cruciate ligament reconstruction is a risk factor for further injury. Weather conditions of high evaporation and low rainfall before matches are associated with noncontact anterior cruciate ligament injury.     

Risk factors for injury in high school football players

BACKGROUND: Many studies have reported the frequency and types of injuries in high school football players. However, few have assessed the relationship between player characteristics and risk of injury. PURPOSE: To describe the epidemiologic characteristics of and risk factors for injury in high school football players and to determine whether players' characteristics could be used to predict subsequent injury. STUDY DESIGN: Prospective cohort study. METHODS: This study was part of a 2-year prospective investigation (1998 to 1999) of risk factors for injury in 717 (343 in the 1998 season and 374 in the 1999 season) high school football players in the Oklahoma City, Oklahoma, School District. Player characteristics (playing experience, position, injury history) and physical parameters (body mass index, weight, height, grip strength) were measured at the beginning of each season. Logistic regression analysis was used to determine whether any of the baseline variables were associated with the odds of subsequent injury. RESULTS: The physical characteristics of players, such as body mass index and strength, were not associated with risk of injury. More playing experience and a history of injury in the previous season were significantly related to increased risk. Linemen were at the highest risk of injury, particularly knee injuries and season-ending injuries. CONCLUSIONS: Future research should focus on decreasing the risk of injury to linemen.