Groin injuries often happen during forceful action such as kicking, sprinting, and sudden change of direction, and other sporting movements where the muscle is being highly activated and/or stretched during forceful contraction [8, 9].

In elite soccer it has been reported that the majority of injuries (90 %) in the hip and groin region recover within 4 weeks [3]. However, if the initial injury is not treated appropriately in the first place or if an athlete is returned to sport too quickly these injuries might develop into a more long-standing or chronic state [3]. This type of injury can take months to recover from. What started out as minor acute strain can develop into a long-standing problem, where important and decisive sporting movements such as maximum kicking, acceleration, deceleration, and change of direction becomes so problematic and painful that the athletes performance is significantly impaired [1, 10]. Also, secondary injuries can develop as other muscle groups are recruited and are at risk of overuse. It has been shown in a number of studies that more than one entity can be identified as a cause of the groin pain in up to one-third of athletes with long-standing groin injury [1, 2].

Age, previous injury, and low levels of off-season sports-specific activities are significant risk factors for sustaining a groin injury [2, 11–14]. In Australian Rules football (AFL), young players who reported a previous hip or groin injury at the draft medical assessment demonstrated a rate of hip/groin injury in the Australian Football League (AFL) >6 times higher than players without a pre-AFL hip or groin injury history [15]. Other factors such as decreased hip adduction strength and [14, 16] decreased hip flexibility [12, 17, 18] have been suggested to be predictive of sustaining a groin injury; however, contradictive findings in this area exist [11, 14, 19].

In male soccer a prospective study of the elite teams in UEFA during seven seasons found a total of 628 hip/groin injuries accounting for 12–16 % of all injuries per season. The total injury incidence was 1.1/1,000 h (3.5/1,000 match hours and 0.6/1,000 training hours). This means that a male professional soccer team will suffer an average of seven groin injuries per season, with more than half of them leading to at least 1 week injury time. Of the 18 different diagnostic entities that were registered, adductor-related (n = 399) and iliopsoas-related (n = 52) groin injuries were the most common [3]. The mean absence per injury was 15 days and 15 % of the injuries were re-injuries. Groin injuries are less common among female soccer players [7].

In line with the UEFA study a prospective study following 998 Danish male sub-elite soccer players registering all groin injuries found that the most common entities were also adductor-related groin injuries followed by iliopsoas-related and abdominal-related injuries [2]. The incidence at the sub-elite level was lower (0.40 injuries/1,000 h) [2]. In studies with a comparative cohort from the Nordic countries the injury incidence ranged from 0.6 to 0.8/1,000 h, suggesting that players at the sub-elite level may suffer from fewer groin injuries than the elite [2, 12]. Severe injuries (injury time >28 days) accounted for 33 % of all groin injuries. In line with the finding in ice hockey by Emery and Meeuwisse [11] that abdominal groin problems add to injury time, it was found that having an adductor-related groin injury doubles the injury time compared to injuries with no adductor and no abdominal pain. If it is combined with an abdominal-related injury, the injury time is more than quadrupled compared to injuries with no adductor and no abdominal pain [2].

The groin injuries in soccer are mostly overuse injuries. In the UEFA study 27 % were traumatic injuries and the sub-elite study found 39 % traumatic injuries [2, 3]. Very interestingly, in only one of five situations was contact with another player involved in the injury mechanism, implying that the majority (80 %) of the traumatic injuries are probably happening as the result of kicking, sprinting, or sudden changes of direction, movements where the groin-related muscles are involved at high speed, often with a forceful eccentric element [2]. Hip and groin injuries account for one-third of the injuries in goalkeepers in soccer [22]. Adductor strains are the most common subtype with a mean lay off time 2.5 times longer than for hamstring strains. The incidence of hip and groin injuries was higher in goalkeepers than in field players [22].

Groin injuries are also frequent in ice hockey. A retrospective epidemiological study found 617 groin/abdominal injuries in the National Hockey League (NHL) during six seasons [20]. The majority of injuries reported were adductor groin muscle strains; however, abdominal groin injuries had a significantly longer time loss (10.6 sessions) compared to other groin injuries (6.6 sessions) [11].

In a recent database study including injury surveillance data of NHL players from the years 2006 to 2010, a total of 890 hip or groin injuries were identified in a cohort of 1,441 players participating in at least one game [23]. The differential diagnosis of the groin injuries are not reported but 94 intra-articular hip injures in 49 athletes (10.6 %) were reported [23].

In the National Football League (NFL, American football) the most common injuries related to the groin over a 10-year period were rectus femoris strain, adductor strain, fracture/dislocation of the hip joint, and labral tears of the hip joint. However, no clear definitions of how the injuries were diagnosed were reported. No injuries related to the abdominal muscles were reported [24].

A retrospective study focusing on injuries to kickers in the NFL over a 20-year period (1988–2007) utilizing the injury surveillance database found a total of 488 injuries in kickers. Of those, 19 % were groin injuries with the adductor-related strains being by far the most common, especially for those located to the pelvis. However, no clear definitions of how the injuries were diagnosed were reported. No injuries related to the abdominal muscles were reported [25]. A study focusing on one NFL team from 1998 to 2007 registered all injuries sustained during the teams training camps; 696 different players participated in the camps, with approximately 90 players in camp each year. In total 728 injuries were registered and 10 % were groin injuries including groin, hip flexor, and abdominal strain. The abdominal strains accounted for ten injuries during the 10-year period. However, no clear definitions of how the injuries were diagnosed were reported [24].

Soccer is one of the most popular sports in the world, and it is estimated that more than 500 million people play some kind of football worldwide, which means that groin injuries are frequently encountered in countries where football is a popular sport.

While the incidence of groin injuries seem to vary between 10 and 20 %, the problem is not sufficiently described by incidence alone, as many players will report having groin pain, even though this will not keep them from training and playing. This means that these “injuries” will not be included in the registration of injuries because these registrations are usually based upon injuries causing absence from training and match play—also known as time-loss injuries. Recent studies focusing on all injuries including injuries without time loss have shown that the prevalence of pain in the hip and groin in male football has been documented to be up to 70 %, which means that two out of three male players will have problems in this region during the soccer season [26, 27]. Focus on hip and groin pain and function, will, therefore, be important information to obtain in the future, instead of solely focusing on time-loss injuries. The Copenhagen Hip And Groin Outcome Score (HAGOS) is a measure of pain and function in athletes, and reference values have already been obtained in soccer players, so that decreased hip and groin function can be determined [28, 29].

The taxonomy regarding groin injuries is still somewhat confusing and regional differences exist depending on the current focus [6]. Very few well-established diagnosis regarding groin injuries in athletes exist. In recent years the clinical entity approach has been found very useful [3, 30–36]. In this approach a standardized clinical examination with reproducible examination techniques is used [1]. The main goal of the examination is to locate the anatomical structures causing the pain. This is done with palpation, functional testing, and stretching. Combining the results of these tests the clinical entities can be defined. The most commonly affected structures are the adductors, iliopsoas, abdominal muscles, and hip joint.

Adductor–related groin pain is characterized by pain medially in the groin often located around the insertion of the adductor longus at the pubic bone, and may radiate distally along the adductor group. The clinical signs of the diagnostic entity “adductor-related groin pain” are defined as: (1) tenderness at the origin of the adductor longus and/or the gracilis at the inferior pubic ramus and (2) groin pain on resisted adduction [1, 5]. A decline in adductor muscle strength and groin pain on full passive abduction is also frequent signs. Ultrasonography and MRIs can often show pathologies at the enthesis.

It is not reported how many of these injuries become long-standing or chronic. Interestingly, it has been reported that if an elite player sustain a re-injury in their groin, the recovery period for the re-injury is almost twice as long compared to the index injury [3], emphasizing the importance of getting the injury sorted properly the first time. In adductor-related injuries in elite male soccer the re-injury rate has been reported to be 15 %, which must be considered high [3]. Injuries classified as enthesopathies are not commonly reported in elite soccer, but these injuries can take very long time to recover from [3].

A number of case reports about total adductor longus ruptures have been published; fortunately, this does not seem to be a common injury [37–40]. In the NFL, the mean time for return to play in players treated conservatively for an acute adductor longus rupture was 6.1 ± 3.1 weeks (range, 3–12 weeks) [40]. However, recent case studies on both operative and conservative treatment seem to suggest that strength is not normalized before 8–10 weeks, and that strength recovery may vary considerable from rupture to rupture [37, 38].

Iliopsoas–related groin pain is characterized by pain in the anterior part of the proximal thigh, more laterally than adductor-related groin pain, and is, therefore, a differential diagnosis for hip joint problems. The clinical signs of the diagnostic entity “iliopsoas-related groin pain” are defined as: (1) tenderness when palpating the muscle through the lower abdominal wall and (2) pain on passive stretching of the muscle during the Thomas test [1, 5]. Additionally, the iliopsoas muscle can be tight and tenderness is frequently found when palpating the muscle just distal to the inguinal ligament. Resisted isometric testing of the muscle with 90° of hip flexion often results in muscle weakness and pain. Ultrasonography can often show pathologies in the area of the distal part of the muscle or the tendon as thickening of the tendon, small calcifications of the tendon, or tissue disruption suggestive of specific injury to the muscle–tendon complex.

Injuries to the iliopsoas seem to be the second most common injury related to the groin region; however, it is much less frequent than adductor-related injuries [2, 3, 25]. Iliopsoas-related injury is also a common problem in runners and dancers. In elite male soccer it has been reported that for every seven to eight adductor-related injuries occurring, one psoas-related injury also occurs [3]. The iliopsoas also tends to become sensitized in patients with other kinds of hip and groin injuries. Iliopsoas-related groin pain, therefore, often seems to coexist with intra-articular hip problems, but is also seen coexisting with adductor-related groin problems. Whether this clinical entity always represents an injury in itself, or just a protective response, with increased tenderness and pain during palpation and stretching is unknown.