Reported incidence rates for ankle sprains range from 15% to 45%. This study looked at self-reported ankle instability in regional European football players and found that age and injury repetition as well as exposure time and position on the field were associated with instability rates, suggesting the need for specific prevention strategies.
By A. Cruz, R. Oliveira, A.G. Silva
Football [known in America as soccer] is one of the most popular sports worldwide, with an increasing number of active players as well as spectators. Assuming that one athlete plays on average 100 hours of football per year (about 50 hours per player for a local team, up to 500 hours per player for a professional team), it is estimated that every player will incur at least one performance-limiting injury per year. In a 15-year epidemiological study, Agel et al  found that approximately 17% of game and practice injuries restricted participation for at least 10 days post-injury.
The injuries sustained in football most frequently occur to the lower extremity, with ankle and knee areas being the most affected. Studies have defined the ankle sprain as one of the most common sports injuries, with a value of 15% to 45% incidence over football season. Most ankle sprains are due to lateral or medial forces over the ankle or foot resulting in excessive inversion or eversion, respectively. Ankle sprains represent 75% of all ankle injuries and 85% to 90% occur in inversion. Functional treatment of an acute ankle inversion trauma leads to full recovery in the majority of the patients, but more than 40% of these patients suffer from recurrent sprains or giving away.
Ankle joint instability includes both mechanical and functional instability conjoined with a wider range of possible dysfunctions. Mechanical instability refers to objective measurements of ligament laxity, whereas functional instability is a subjectively reported phenomenon characterized by repetitive episodes of “giving away” or instability about the ankle during daily living and sports activities and/or the incidence of recurrent, symptomatic ankle sprains. Along with increased laxity, patients with chronic ankle instability are thought to have disturbed neuromuscular control of the ankle caused by damage to muscles, receptors, or nerves by the initial ankle inversion injury. Associated with ankle instability, there are impaired proprioception, neuromuscular and postural control, and strength deficits.
Also, individual personal factors, such as a history of musculoskeletal injury and level of self-efficacy, will affect perceptions and behaviors. How a patient responds to impairments influences his or her perception of the injury and behavior, including motor output, in the presence and aftermath of the injury.
Despite the lack of consensus, some risk factors for foot and ankle injuries are listed in the literature: anthropometric measures, lack of structured warmup training or inadequate training, previous injuries, dominant limb, and position in the field.
The prevalence and impact of ankle sprain on society and healthcare systems along with sports structures support the need for continued research related to the prevention, treatment, and rehabilitation of ankle sprains and their associated sequelae.
Most studies to date have focused on prevalence rates and risk factors in elite teams, but the continuous growth of smaller teams and the increasing number of participants justify the need for studies of this different context. While the level of competition is lower than national leagues, athletes from regional teams have poor environmental training conditions, less intense training or structured warm-up routines, and are likely to not have a specialized medical team in their club to support them in case of an injury when compared to elite teams. These factors can contribute to higher rates of chronic ankle instability. Therefore, the primary aim of this study was to determine prevalence rates of self-reported ankle instability in football players from professional senior regional divisions in 2 districts of Portugal’s central area. A secondary aim was to explore the association between extrinsic factors and ankle instability in these football players.
Participants: All clubs (n = 66) from Coimbra and Aveiro [both in Portugal] regional male senior football divisions (n = 66) during season 2016/17 were contacted by e-mail or telephone requesting permission to include their athletes in the present study. A total of 58 clubs answered positively. Then, all players from each of these 58 teams were invited to enter the study. Demographic and anthropometric data were recorded concerning age, height, weight, years of training, mean number of training hours, position in camp along with specific questions related to an ankle injury. These included: previous history of injury, reinjury, and feeling of giving-away. Also, athletes that reported to: 1) have had at least one sprain, and functional inability to load while walking using crutches; and 2) have had at least a repeated sprain (recurrence) after the first injury or subjective feeling of instability or “giving away” on the ankle, were then asked to fill in the Cumberland Ankle Instability Tool [CAIT; Portuguese version]. A score of 24 or less on the CAIT scale was indicative of functional ankle instability in line with the International Ankle Consortium guidelines. The CAIT is a simple, reliable, and valid questionnaire for discriminating and measuring the severity of functional ankle instability enabling more homogenous subject groups to be identified, objectively defined, and compared. [Exclusion] criteria were defined in line with the recommendation from the International Ankle Consortium.
Statistical Analysis: All statistical analyses were conducted using SPSS for Windows Version 15.0 (SPSS Inc., Chicago, IL, USA). A global analysis for sample profile was made using descriptive statistics and presented as means ± standard deviations (SD) for continuous variables and as absolute frequencies for ordinal and nominal variables. Chi-squared statistical tests were carried out to assess if the occurrence of serious sprains, repeated sprains and instability varied among playing positions as well as dominant limbs. A t-student test was applied to assess for between group differences in terms of age, height, weight, or weekly training hours as well as CAIT values. Potential associations between variables such as history of injury, reinjury and giving away episodes were explored using the Spearman Rho test. Spearman Rho r-values (r) were interpreted as weak (0.01 – 0.40), moderate (0.41 – 0.69), or strong (0.70 – 1.00). The significance value was established at P < 0.05.
A total of 1044 athletes from 58 clubs were invited to participate in the present study. Of these, 589 (56.4%) male football players accepted to participate: 68 goalkeepers, 197 defenders, 177 midfielders and 147 forwards and their mean (±standard deviation) age, height and weight was 24 ± 5 years old, 177 ± 6.3 cm and 77 ± 8 Kg, respectively .
Of the 589 athletes, 290 (49.2%) reported a history of previous sprain. Considering this group of 290 athletes, 170 (58.6%) reported having repeated the injury and 112 reported subjective feelings of “giving away”.
A total of 117 (40%) of the athletes that reported a history of injury scored less than 24 in the CAIT in at least one of the limbs, ie, had self-perceived instability. Among these 117 athletes, 48 (41%) presented bilateral instability, with the remaining presenting instability in the right (n = 42, 36%) or left lower limb (n = 27, 23%). Considering the total sample, it is important to notice that a proportion of 1 in every 5 players (19%) presents instability and, from these, 2 in every 5 players (41%) presented bilateral complaints.
Our results show that the position in camp is associated with the occurrence of serious ankle sprains (P = 0.009), as well as the presence of instability (P = 0.02) as presented in Table 1 . In the analysis of cell count versus expected count, we found defenders and forwards to have greater rates of injury and instability.
Most of our athletes chose “right” as the dominant member, for a total of 82%. Our study found no differences between rates in right or left-sided in the existence of injury, reinjury, or the presence of instability. However, considering giving away episodes, our study shows an association between the dominant limb and existence of giving-away episodes (P = 0.02, χ2 = 9.69) with a higher cell count in left dominance athletes, meaning left-sided players report higher rates of giving-away episodes.
Also concerning laterality and how it is related to the side of instability, a significant association was found (P = 0.02, χ2 = 14.52), indicating that instability, as measured with CAIT, was associated with dominant limb.
An important result of our study was defining the association between first injury and the recurrence, as well as first injury and subjective feelings of giving away and instability. We found a significant association between a first injury and a subsequent recurrence injury as well as with episodes of giving away and instability with Spearman Rho r-values (r) reflecting moderate (0.41 – 0.69) correlations [Table 2. is available in the online original version.]
Reinjury was also associated with giving away with a moderate correlation and giving away was strongly correlated with CAIT values.
Male football players in regional teams reported a high prevalence of ankle sprains, reaching half of the total number of athletes in our sample, along with high rates of reinjury (58.6%). The number of reinjuries observed and the tendency for these injuries to be chronic may suggest that rehabilitation programs used at clubs may not be adequate. Equally relevant were the findings that half of the players with reinjury develop self-perceived ankle instability and the fact that 2 in every 5 players with instability present a bilateral problem. Such values should lead to some reflection from either technical teams or medical teams once they represent a significant loss of players’ availability as well as associated expenses and, more importantly, leave sequelae and chronic impairments with effects on athlete’s future sports performance and well-being.
Studies regarding injuries associated with different skill levels have produced contradictory results. Nielsen and Yde  found the injury rate during games was highest at the division level and lowest at the series level. Whereas during practice, the outcome was the reverse. Blaser and Aeschlimann  reported that the highest frequency of injury was seen in the lower leagues. The need for more studies targeting lower-level competition is evident to identify specific needs.
The context in competition level is usually related to different training equipment and different turf conditions, along with less time for practice. Teams from lower competition levels have fewer training periods during a week. In a study with top Swedish male football teams, the average number of training sessions/week recorded was 5.7 with an average weekly period of 7.5 to 10.5 hours. In our study, mean number of hours for exposure time during weekly training was 5.5, usually distributed in 3 training sessions. This difference is important and may be compelling of the need for more technical training leaving aside adequate warm-up or stretching periods when considering minor leagues as the ones we are studying.
Concerning risk factors, we found no association between anthropometric features and ankle injury, reinjury, or instability. Hägglund et al  found that none of the anthropometric variables [height, weight, BMI] were significantly associated with injury. Milgrom et al  reported that during basic training, male military recruits who were taller and heavier were at increased risk of suffering an ankle injury. Different sports with specific technical gestures and movements and different contexts disable the possibility of general conclusions. So further studies must be enrolled focusing on anthropometric measures to determine if it represents a risk factor to consider particularly in contact sports like football and associated with ankle injury.
Although most authors have stated that the field position played does not influence the injury rate, other studies have found that position played could determine a greater risk of injury. In a study concerning youth football, Price et al  found defenders and midfielders sustained higher rates of injuries, while Hawkins and Fuller  found the same risk associated with defenders only. We found defenders and forwards to have higher rates of injury and instability. The high injury incidence among defenders could well be attributed to the need for defenders to take greater risks and be more reactive to prevent attacking situations and goals being scored with higher intensity in contact, as well as heading and jumping associated. Advanced players usually sprint and tackle before kicking and are also subjects of contact from other team defenders. Higher velocity in attacking positions requiring a constant change of direction and acceleration and deceleration may lead to higher injury probability.
These studies refer to overall injuries, not specifically to ankle injury or instability, pointing the need to develop specific analysis focusing on different types of injuries.
Although the evolution of football tends to make players more available to change field positions, the fact is that defenders maintain their defending tasks, despite different coaching strategies. While more advanced players also maintain offensive strategies related either with physical performance forcing contact and tackling or velocity. Defining the field position as an extrinsic risk factor would be important to develop different prevention strategies amongst players, creating specific training protocols.
The literature is not clear whether limb dominance is a risk factor for suffering an ankle-ligament sprain or to develop signs of instability. Limb dominance has been implicated as a risk factor for lower extremity trauma because most athletes place a greater demand on their dominant limb, producing increased frequency and magnitude of moments about the ankle, particularly during high-demand activities that place the ankle at risk. Our study focused on the relation between laterality and chronic ankle instability and found a statistically significant portion of athletes showed signs of self-perceived instability in their dominant limbs according to CAIT results. It remains undeniable that athletes tend to develop a great number of automatic patterns with a dominant limb preference (kicking, landing from jumps, initiating a sprint) placing that limb under higher stress and demand. When one considers landing from jumps is a key among injury mechanisms, along with contact between players (which can occur during kicking), it is plausible that dominant limbs are subject to a higher risk of injury/reinjury. Also, we should expect athletes to be more aware of subjective feelings related to their limb of preference and even have greater memory of events associated with them. The laterality issue is, therefore, an aspect with which the athletes may present higher retrospective confidence. Also worthy of reflection is the high rate of bilateral instability which may lead to the need for a deeper analysis concerning the origin of the problem, once it may be related to central changes concerning motor control. Futures studies should analyze this question with a specific focus on these subjects. This result may be related to deficient training programs, placing the athletes at a higher risk of injury instead of focusing on prevention strategies. This conclusion must be supported by other and more specific studies related to training structure in these teams.
Perhaps the most frequently studied risk factor for lateral ankle-ligament sprains is a previous sprain of this complex. This is based on the fact that disruption of a ligament may compromise an important biomechanical stabilizer creating partial deafferentation of the ankle. Our study found statistical significance in the relation between the existence of a primary injury to the ankle and reinjury, as well as with self-perceived instability. The literature is divided about whether a previous sprain influences the risk for a future sprain. One of the original prospective risk factor studies is the work of Ekstrand and Gillquist  where an increased risk for lateral ankle-ligament injury in athletes who had suffered a prior ankle-ligament sprain was reported. Subsequent studies of soccer and basketball athletes and military recruits undergoing basic training found that they were at increased risk for lateral ankle ligament injury after suffering a prior ankle injury. However, other studies of athletes participating in similar sports have revealed no increased risk for lateral ankle ligament injury after suffering a prior ankle injury.
According to our findings, after first injury, athletes are more predisposed to the repetition of the same injury, and also a significant relation was found between the repetition of the sprain and further sensation of giving away and instability, enhancing the existence of a chain of events toward a chronic ankle instability. In Hertel’s new model for instability published in 2019, the author states that repeated episodes of giving away and recurrent ankle sprains are likely to produce further secondary tissue damage, thus resulting in additional pathomechanical impairment.
One explanation for the divergent findings may be that the condition of the joint after injury not only depends on the index injury and the associated damage to the ligaments, muscles, and deafferentation of the joint, but also on what type of rehabilitation was administered, whether the player complied with the rehabilitation program, and the quality of recovery that was achieved. Future studies should focus on this point or, at least, include it as an evaluation item.
The natural progression of acute ankle sprains is for players to report gradual improvement as the initial symptoms of pain, swelling, and loss of function subside in the weeks after injury.
However, lack of compliance with treatment associated with team’s pressure to an early return to practice and competition may be responsible for the existence of incomplete rehabilitation.
On the other hand, our study confirms the existing theory that reinjury leads to constant feeling of giving away and instability, which some authors consider to be a cycle conducive to injury repetition and chronic instability.
[Limitations to the study can be found in the authors’ original publication; see page 32 for location.]
The discussion about factors that may represent a possible risk factor for injury in sports is as important as the training strategies or results.
When one considers ankle injury, the inclusion of strategies to avoid injury repetition that leads to chronic ankle instability seems urgent, despite the lack of local supportive studies. Factors like age, quality in training protocols, position played, limb dominance should be taken into account as factors to consider while preventing chronic ankle instability.
In a moment when prevention is the key to effective clinical work in sports, more individualized clinical/physical work should be planned to answer more specific framing for different athletes.
More studies should be developed to establish definite significant relations between different factors and injuries to prevent the absence of players along with the development of chronic symptoms.
Cruz is with the School of Health Sciences at the University of Aveiro in Aveiro, Portugal, and the Laboratory of Neuromuscular Function at the University of Lison, Portugal.
Oliveira is on the Faculty of Human Motricity in the Neuromuscular Research Lab at the University of Lisbon, Portugal.
AG Silva is a researcher at CINTESIS – the Center for Health Technology and Services Research, at the University of Aveiro in Aveiro, Portugal.
This article, under the same title and the same authors, originally appeared the Open Journal of Orthopedics 2020;10;77-92. Minor edits have been made and references have been removed for brevity. Use is per the Creative Commons Distribution 4.0 International License. To read the full article, go to https://doi.org/10.4236/ojo.2020.104010