Groin pain is reported to account for 2-5% of all sports injuries. In sports that involve excessive twisting and turning movements such as soccer, ice and field hockey, tennis, and Australian-rules football, groin injuries may rise to 5-7% of all injuries [1, 2]. In professional athletes, injuries account for chronic morbidity, and the associated persistent pain and stiffness frequently prevent competitive involvement. Such injuries lead to personal distress and have dramatic economic consequences for professional sporting organizations. Despite the prevalence and importance of groin injuries, the pattern and nature of injury to the symphysis pubis that account for groin pain in athletes remain unclear; hence, approaches to management are varied and poorly constructed, and the outcomes are unpredictable [3-6].

In clinical practice, the term “athletic pubalgia” is used to describe exertional pubic or groin pain [7], and although many causes of pubalgia are described ranging from a labral tear of the hip, sacroiliitis, and lower lumbar disk disease to pelvic soft-tissue derangement in females, most authors conclude that adductor dysfunction, osteitis pubis, and prehernia complex (also termed “sportsman's hernia,” “conjoint tendon tear,” “external oblique tear,” and “rectus abdominis sheath tears”) are the most common causes [8-11]. Whether these entities are mechanically related is currently unclear. The purposes of this study were to determine the prevalence of adductor dysfunction and of osteitis pubis in soccer players presenting with pubalgia and, on the basis of these observations, to determine whether one of the ailments appears to precede or predispose the development of the other.

The symphysis pubis has uniquely evolved to dissipate and cushion the impaction forces imposed on the pelvis during gait. In healthy individuals, gait results in the rapid weight transfer from one side of the pelvis to the other with the associated forces centered on and applied to the symphysis. For sports in which players twist, turn, and kick, the applied forces are magnified, thus resulting in severe biomechanical strain on the symphysis and its associated support structures. As a result, groin injury presenting as groin pain is one of the most common musculoskeletal injuries encountered in athletes participating in these sports [17-22].

The articular surfaces of the symphysis pubis are covered by hyaline articular cartilage on either side and are the margins of a central fibrocartilaginous disk that primarily functions to dissipate impaction forces. In adults, a physiologic fluid-filled cleft develops in the fibrocartilage. Anteriorly, the fibrocartilaginous disk and symphyseal joint are supported by an aponeurosis created by the tendons of the anterior abdominal wall, particularly rectus abdominis muscles, and, to a lesser extent, by the aponeurosis created by the gracilis and adductor longus tendons. The gracilis and adductor longus tendons merge from both the right and left legs to provide support anteriorly and, to a greater extent, inferiorly where they merge with the arcuate ligament [12] (Fig. 5A, 5B, 5C). Superiorly, the fibrocartilage and symphyseal joint are supported by the superior pubic ligament [12], but in the absence of supporting musculature superiorly and posteriorly, repeated impaction forces lead to gradual herniation of the fibrocartilaginous disk superiorly and posteriorly, as was identified in 82 of the 100 symptomatic patients in the study group. The same finding was identified in 73 of the control subjects without groin pain, which suggests that herniation of the fibrocartilaginous disk is an asymptomatic mechanical phenomenon. In this study, fibrocartilage herniation was associated with narrowing of the joint space in most cases and with parasymphysial osteophytes in a minority of cases. Whether fibrocartilage herniation precedes or predisposes an individual to developing osteitis pubis is unclear.

Similarly, reflecting the complex aponeurosis that merges anteriorly and inferiorly to the symphysis and combines with muscles of the anterior abdominal wall and of both thighs, injury to the symphysis often results in pain that radiates to the groin, inside aspect of the thigh, and lower abdomen [23].

Although groin pain may be secondary to many entities remote from the symphysis, including hip and sacroiliac derangement, in most cases, exertional groin pain or pubalgia results from injury to the symphysis pubis and its supporting structures. Although this study focused on adductor dysfunction and osteitis pubis, in many cases, pubalgia is attributed to sportsman's hernia. This entity is one in which inguinal ligament laxity leads to widening and tearing of support structures of the internal ring. Although this single abnormality has been popularized as sportsman's hernia, confusion has given rise to a number of descriptive terms for the same entity including prehernia complex, conjoint tendon tear, external oblique tear, and rectus abdominis sheath tear [24-27]. In this study, sportsman's hernia was excluded in each of the study subjects on the basis of clinical examination before referral for MRI. Although herniography has been used and can show internal ring laxity [28] and although, more recently, Albers et al. [9] have shown the utility of MRI in revealing both muscular signal changes and myofascial bulging in affected patients, clinical examination is still considered to be the gold standard for this diagnosis [15].

The results of this study suggest that isolated adductor dysfunction with a microtear at its attachment is a more frequent cause of pubalgia in soccer players than isolated osteitis pubis. Indeed, our findings show that when osteitis pubis does occur, it is usually in association with a microtear at the pubic attachment of the adductor longus. Although somewhat speculative, the described patterns of disease at the symphysis suggest that an adductor microtear is frequently a primary event, followed by the development of osteitis presumably secondary to the induced muscular instability, laxity, and secondary impaction of surfaces at the symphysis. Similarly, sportsman's hernia or laxity and inflammation at the internal ring orifice, the third recognized cause of groin pain, may develop as a result of attempts to compensate for imbalance at the symphysis incurred by an adductor microtear. The fact that groin pain is frequently due to soft-tissue derangement, an adductor microtear, or a sportsman's hernia accounts for normal findings on radiographs and bone scans that are traditionally seen in these patients and further increases the requirement for MRI in this population.

It is worth noting that, similar to the findings of an MRI study of Australian-rules football players, bone edema and inflammation at the symphysis were present in only the symptomatic study group; thus, when those findings are absent, an imager should have a high level of confidence in excluding disease. Similarly, we found that the cleft created by a microtear at the adductor enthesis was also present in only the symptomatic group, as was shown in another study [29].

Why a microtear at the adductor attachment occurs so frequently in soccer players is unclear. Although it is possible that overuse of the adductor longus muscle with associated increased contractility and power in the muscle belly cannot be accommodated by the small enthetic adductor attachment, it is likely that a microtear is the consequence of tendon stretching and applied traction to the enthesis due to twisting and turning [12, 14] or, more likely, is secondary to both. The initial tear appears to occur at the tendon attachment to the inferior border of the symphyseal fibrocartilage and to extend gradually to the true bone enthesis. The extension of the physiologic cleft within the fibrocartilage created by such a tear allows interposition of fluid between the tendon and pubic bone and appears to restrict healing. Repeated activity leads to progression of the tear, inflammation, pain, and imbalance at the symphysis and subsequently to osteitis pubis. This cycle can be dramatically halted by autotenotomy where superimposed macrotrauma leads to complete detachment of the adductor longus tendon from bone with resolution of symptoms within weeks. In most, the detached tendon ultimately lengthens but heals with extensive scar formation preserving some function but limiting the imposed traction effect.

Management of groin injuries requires rest regardless of the cause. Sportsman's hernia diagnosed on the basis of clinical discomfort elicited by scrotal digital invagination [11, 25] was excluded in all the patients in this study. When confirmed by clinical findings, laxity of the internal ring is treated surgically by suture repair termed “Gilmore groin repair.” Whether such a procedure facilitates recovery of osteitis pubis is unclear; the symptoms improve in many either due to renewed groin stability or as a result of enforced rest after surgery [30-33]. Gilmore's groin repair—that is, tightening the internal ring—has no impact on the adductor attachment. When an adductor microtear is identified, symptom resolution may follow guided steroid injection to the symphyseal cleft, which communicates to the site of the tear [16]. Physiotherapy, focusing on the development of core stability, has been shown to reduce symptom recurrence [34]. In refractory cases, mimicking the effects of autotenotomy, surgical tenotomy is undertaken, with division of the adductor tendon from the pubic attachment. After undergoing postprocedural physiotherapy, individuals generally return to participating in sports within 3 months of the procedure [35].

There are a number of limitations to this study. First, the control population in this study included a mixed group of athletes, rowers and soccer players, in contrast to the study population who were all soccer players. Although this difference is a potential limitation, no difference in the imaging appearances at the symphysis were recorded between the two sporting groups. Second, although previous authors have advocated and shown the utility of gadolinium enhancement in characterizing groin ailments [13], gadolinium administration was considered unnecessary in this study because the secondary cleft sign was used as a marker of adductor dysfunction [12]. Finally, we acknowledge that one cannot make a true prediction about the pathogenesis of groin pain, as was attempted in this study, without conducting a longitudinal study. Therefore, we acknowledge that assumptions based on a single observation in time drawn from data in this study, although indicating a possible trend, are somewhat speculative.

In summary, MRI more frequently shows an adductor microtear as a cause of groin pain in soccer players than osteitis pubis. MRI reliably allows differentiation of these two entities and should therefore be performed in all patients with pubalgia to allow accurate diagnosis. The identification of a secondary cleft sign or bone edema at the symphysis should increase the index of suspicion that groin pain symptoms relate to an injury at the symphysis pubis. Although speculative, the results of this study suggest that in soccer players adductor dysfunction and microtear often precede the development of osteitis pubis.

Address correspondence to P. M. Cunningham.

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