Specific Aspects of Football in Recreational and Competitive Sport

FIFA world cup male

n = 543

[28]

FIFA world cup female

n = 220

[28]

FIFA U-17 male

n = 674

[28]

FIFA U-17

female

n = 223

[28]

UEFA

n = 4483

[12]

England

n = 6030

[23]

Spanish amateur

n = 243

[24]

US high school boys

100 schools

[42]

US high school girls

100 schools

[42]

Head and neck

2.2

7^a

Upper extremity

3.5

Trunk

Hip/groin

Thigh

Knee

Lower leg/TA

Ankle

Foot/toes

^aIncludes all spine injuries

The second most frequently injured area is the head and neck with surveillance at the FIFA world cups showing injuries in this area to be significantly more frequent in women than men [28]. However, this gender difference was not apparent at adolescent level [42].

The majority of injuries sustained in elite football players are due to acute trauma with approximately 10 % due to overuse [12, 15]. Lesions occur most frequently in connective tissues (sprains, strains, dislocations, and other joint injuries), vascular structures (hematomas, contusion, and lacerations), and bones. There is, in recent times, greater awareness of the need to identify and adequately treat concussion.

During World Football tournaments, contusions were the most frequent injury and accounted for approximately 50 % of injuries [28]. Whether this pattern is repeated at other levels is unclear as much of the literature only reports time loss injuries and therefore this would exclude many of these injuries. In amateur players in Spain, the incidence of contusions and hematoma is 23 % which, although it includes players who did not miss any training or matches, may still underreport the actual incidence as it is only recorded if medical attention was sought [24].

The incidence of fractures and dislocations is relatively low in elite football players and has been reported as between less than 1 and 6 % [3, 7]. Over a 15-year period in Japanese professional league players, 4.3 % of injuries were upper limb fracture/dislocations compared to 1.8 % in the lower limb [3]. In the UEFA study, 12 % of upper extremity injuries were shoulder dislocations, 25 % were upper limb fractures or bone stress injuries, and 5 % were AC joint dislocations [14]. Fifth metatarsal fractures accounted for 0.5 % of all injuries, and it has been estimated that a team can expect a fifth MT fracture every fifth season [15]. The overall rate of fracture in adolescents has not been reported, but in a study of American high school football players, it found that 31 % of injuries resulting in time loss of more than 3 weeks were due to fractures [42].

A study investigating all football-related fractures in one area of Scotland over one season estimated that the annual incidence of football-related fractures was 0.7 per 1000 of the general population but the incidence per number of population playing football is not known. Of the 367 football-related fractures identified, 68 % were in the upper limb and 32 % in the lower limb. The most common fractures were finger phalanx (20 %), distal radius (20 %), and ankle (13 %) [35].

Muscle injuries are believed to account for over 30 % of time loss injuries in professional football [4, 13], 18 % in high school players [42], and 11 % in the female and 7 % in the male U-17 World Cup [28]. The incidence in amateur players is reported as 17 %, but again this could be artificially lowered by players not seeking medical treatment [24]. Ninety-two percent of muscle injuries affected the lower extremity and two thirds were acute injuries [4, 13]. The most commonly acutely affected muscles are the hamstrings (37 %), adductors (23 %), quadriceps (19 %), and calf (13 %). Respectively these accounted for 12 %, 14 %, 4 %, and 4 % of all injuries sustained. However, overuse injuries with a gradual onset were significantly more likely to affect the hip/groin [12]. Ninety-six percent of Achilles tendon disorders were classified as gradual onset tendinopathies with an incidence of 0.16/1000 h compared to 0.01/1000 for an Achilles rupture [34]. This equates roughly to one Achilles tendinopathy per team per season and a rupture per team every 17 seasons.

Ligament strains and ruptures have been reported as between 17 and 25 % of all injuries in professional football players. Ankle sprains (7 %) and knee MCL (5 %) are among the commonest injuries sustained [12]. Ligament sprains have been shown to account for over 67 % of all ankle injuries, of which over 80 % were to the lateral ligament complex [39]. A professional squad is likely to suffer four or five ankle sprains each season. Thirty-nine percent of all injuries in the knee are ligament sprains and three quarters of these involve the MCL. Acromioclavicular joint sprains accounted for 13 % of all upper limb injuries [14]. In Spanish male amateur football, ligament sprains and ruptures accounted for 32 % of all injuries with nearly 22 % of all injuries being knee ligaments, which is markedly higher than the incidence found in professional sport [24].

The ACL and the lateral ligament had the highest incidence of injury. Female football player has in general a significant higher risk for ACL injuries than male player [41]. Several other risk factors for ACL injuries are described in the literature like young age, match play [40, 41], and previous knee injuries [20]. Furthermore, rapid changes in proprioception and the increase in physical impact on a footballer’s body result in higher injury rates [1, 33]. The participation of junior football players in professional senior football matches [16, 20] or implementation of a new professional league [31] results in short-term higher physical impact on player and can lead therefore to higher incidence of severe knee injuries. Therefore, injury prevention in professional football should be highlighted.

In high school adolescent football players, incomplete ligament sprains were the most frequent injury and accounted for 27 % of injuries [42]. In competitions girls were found to sustain complete knee ligament ruptures requiring surgery at a rate of 26.4/1000 h compared to 1.98/1000 h in boys.

9.2 Physical and Psychological Aspects in Football

Many investigations into the incidence of football injuries have attempted to understand which factors influence injury rates. The aspects that affect injury rates include the mechanism and timing of injury as well as player factors.

Injuries can occur at many different times and in different circumstances. The injury rate in matches is higher than training across all levels of competition with between 57 % and 63 % of injuries occurring during matches [5, 12, 23, 24]. In adolescents match injuries were three times more common than training injuries [42]. Upper limb injuries are seven times more likely to occur in matches and have a match incidence of 0.83/1000 h compared to a training incidence of 0.12/1000 h [14]. Muscle injuries in professional football players are six times more likely in match play (8.7/1000 h versus 1.4/1000 h) [4, 13], although in adolescents they were found to be more common in training [42].

Many studies categorize injuries into contact and non-contact injuries. The incidence of contact injuries varies considerably and has been reported as 25 % in the male amateur game [24] compared to 80 % at world tournaments [28]. Seventy percent of MCL and PCL injuries, 57 % of LCL, 37 % of ACL [32] and 58 % of ankle injuries [39] are contact injuries, whereas over 90 % of muscle injuries are non-contact [13].

Of the contact injuries reported, many occur as a result of foul play. At world tournaments the medical staff judged 47 % of the contact injuries to be caused by illegal play [28], which was similar to the level found in the Japanese league [3]. However, UEFA relied on the referee’s judgment to determine if a foul had taken place and found that only 21 % of contact injuries have been caused this way [12]. Forty percent of ankle injuries were felt to be caused by fouls, but only 5.8 % of these were given red or yellow cards [39].

Several studies have investigated the timing of injuries, both within the games and in the longer term. There are increased injuries in training during the preseason period [23], and in particular Achilles tendon injuries are more common at this time [18]. Overall the injury frequency does not vary within each season, although there is believed to be a decreasing trend of injuries over several seasons [3, 28, 32, 39]. Several studies have found an increased frequency of injuries in the last 15 min of each half [3, 12, 23, 32]. Calf strains are most common in the last 15 min of the match [13], and there are significantly fewer ankle injuries in the first 15min of a match [39].

The rate of injuries can vary according to the position played. The prevalence of upper limb injuries in goalkeepers is between 10 and 25 % compared to 2–5 % in field players [14]. However, the overall injury rate for goalkeepers is 0.5-fold lower than that for field players and significantly lower for contact injuries and lower limb injuries [3].

It is believed that limb dominance can also affect the injury incidence rate with 50 % of injuries affecting their dominant side compared to 37 % in the non-dominant side [23]. 60 % of MCL injuries are in the dominant leg [32] as are 60 % of quadriceps injuries [13]. However, injuries to other muscle groups do not appear to be affected by leg dominance.

One factor that does increase injury rate is a previous injury. Overall injury recurrence rates have been reported as around 7–12 % [12, 23] in professional footballers but at less than 3 % in amateur players [24]. Upper limb injuries, knee MCL ligament injuries, and ankle sprains have been shown to have recurrence rates of 12 %, 11 %, and 10 %, respectively [14, 32, 39]. The recurrence rate for Achilles tendinopathy is 31 % if the recovery period is 10 days or less and 13 % if the recovery period is longer [18]. In the first year after concussion, there is a significant increased risk of sustaining a subsequent injury [34]. There is a well-recognized tendency to sustain injury soon after return to play after any recent injury not affecting the area of the new injury, presumably due to deconditioning, leading to the concept of a “second injury syndrome.” Clearly delaying return to play until full recovery helps prevent this issue.

Another patient factor that can affect injury rate is age. In amateur players those aged 30 or over suffered 0.2–0.4/ 1000 h more injuries than those under 30 [24]. Muscle ruptures were higher in the older group but ligament injuries were lower. Professional players with Achilles tendinopathy were significantly older and had an average age of 27 years [18]. Newcomers in their first season of professional football were significantly younger (18.8 versus 26 years) than existing players and had lower training injuries, but there was no difference in overall match injury rates [30]. However, the younger group experienced less muscle and tendon injuries and significantly higher bone stress injuries.

The psychological aspects of injury prevention in football relate mainly to the abandonment of fair play rules and adoption of reckless play. On occasion we have all seen a player who seems to ‘lose the plot’ and behaves recklessly especially when the play involves tackling or occasional “off the ball” violence. There is no published evidence that the authors are aware of that shows a relationship between resting (non-playing) mental state and injury – either being injured or causing injury. The increasing desire to “win at all costs” mentality is obviously not helpful with regard to injury from foul play. Of course there is a role of football in promoting mental well-being.

9.3 Basic Aspects and Methodology of Prevention Conception in Football

9.3.1 Sport-Specific Adaptations on the Musculoskeletal and Myofascial System

Different sports and athletic disciplines – and specially ball team sports and football – are characterized by a multitude of highly specific, stereotypical patterns of movement. When the movements are performed at sufficient magnitudes for a long period of time, these sport-specific motor stimuli evoke specific responses in which certain biological structures undergo adaptations that enable the athlete to adequately “process” the loads. These changes affect bones, ligaments, and musculoskeletal and myofascial structures and are characterized in all sports by an asymmetrical distribution of loads between the right and left sides of the athlete’s body, especially in football with normally dominant kicking and standing leg.

Generally the adaptations heighten the quality of the sport-specific movement patterns and thus have a positive effect on the athlete’s performance in that particular sport. On the other hand, many of these adaptations cause changes in muscular loads and can sometimes lead to the overuse or unphysiologic loading of certain musculoskeletal structures. These loads may exceed the stress tolerance of the structures, resulting in muscular injury.

An awareness of sport-specific changes in the musculoskeletal system will make it easier for the members of the sports medicine staff, especially the physical therapists and rehabilitation trainers, to evaluate the structural and functional consequences of muscle injuries and formulate appropriate, complex treatment strategies. The following discussions are intended to alert coaches, team doctors, and therapists to the existence and importance of sport-specific adaptations and have a direct impact to the needs and the conception to prevention strategies.

9.3.2 Football-Specific Changes and Adaptations of the Musculoskeletal System

Taking football as an example of a sport with side-specific or asymmetrical stress patterns, we shall look at corresponding adaptation patterns that should be noted in the evaluation of injuries. The stereotypical loads that act on certain biological structures may vary greatly in football, both quantitatively and qualitatively, and reflect a long-term adaptation of the musculoskeletal system to a recurring stress pattern. Players with a symmetrical kicking technique tend to be the exception in this regard. Also, the play requirements and stereotypical movement patterns vary from one playing position to the next. This difference is particularly marked between the goalkeeper and field players but also exists among different playing positions on the field.

Sport-specific musculoskeletal adaptations are found in active football players as well as in players who retired from the sport years earlier. This is particularly important in physical therapy settings (provided by a doctor, therapist, or trainer) where it is important to consider whether the adaptive changes should be prophylactically “treated” and reversed, or at least limited, with the goal of preventing future degenerative problems. There is no generally valid recommended course of action, and management decisions should be made on a case-by-case basis depending on the extent of the changes and on individual physical factors.

9.3.3 Changes Caused by Contact of the Kicking Leg with the Ball

From a mechanical standpoint, the football player who kicks a ball is accelerating an approximately 350-g mass of a specified size and volume in a designated direction. This can be accomplished by various modes of ball contact, which impose corresponding mechanical loads on the striking area – the forehead for a header, the instep for a side-foot pass or shot, or the dorsum of the foot for shot “off the laces.” The weight of the football, the air pressure in the ball, the contact time, and the speed change at ball contact are all mechanical variables that determine the nature of the mechanical loads acting on the muscles, bones, and joints. Changing any one of these variables will alter the mechanical stress configuration, producing positive or negative effects on musculoskeletal structures. Variation in these factors has hugely improved with modern ball manufacturing techniques.

Besides the magnitude of the mechanical stresses associated with ball contact, the number of repetitive stereotypical loads caused by ball contact within the physiologic range will also trigger degenerative and overload changes in the musculoskeletal system. When the foot strikes a football, the impact exerts a force of short duration (ball contact time of 11–15 ms, depending on ball pressure) that is opposite to the arched construction of the foot, giving rise to intra-articular shear forces. The mechanical reaction forces generated by the ball mass have a magnitude that is well within physiologic limits and generally do not exceed the stress tolerance of the biological structures. But when a large number of contacts are repeated over a long period of time, which may be measured in years, they create stimuli that act as repetitive microtrauma and will eventually evoke changes in the musculoskeletal system.

Naturally, the body tries to prepare for the sudden, brief tensile stresses caused by ball contact by strengthening the attachment sites of the talonavicular ligament. As the Sharpey fibers become stronger and more numerous, they create a mass effect that appears as a talar beak and/or tibial peak on X-ray films. This feature decreases the range of foot extension at the ankle joint. Moreover, kicking balls with a faulty, biologically unfavorable technique will quickly increase the tensile stresses on the talonavicular ligament to unphysiologically high levels that may exceed stress tolerance, resulting in an acute injury. Poor footwear can further exacerbate this adverse change in the stability of the affected joint. While the soles of football shoes are designed to prevent excessive arch stresses in the extended foot (plantar flexion at the ankle joint), a poor kicking technique can still produce the adverse effects (Fig. 9.1). Striking the ball with the toe of the shoe as opposed to the laces has the effect of lengthening the lever arm of the ball-strike force and will multiply the torque and tensile stress acting on the talonavicular ligament, depending on the relationship of the extended lever arm to the lever-arm length of the talonavicular ligament. Under realistic conditions, the tensile stresses generated by executing a corner kick (initial ball speed of 50–80 km/h) are estimated at approximately 1200 N. This load is within physiologic limits and does not exceed the stress tolerance of the ligament. But a poor kicking posture will increase the tensile stress on the talonavicular ligament to as much as 3000 N, which approaches the stress limit and poses a risk of acute injury.