The body's center of gravity is located within the pelvis anterior to the second sacral vertebra, and tremendous loads are transferred through this area in virtually every athletic activity . Groin pain is common for athletes, especially those who engage in kicking, rapid accelerations and decelerations, and sudden direction changes. Diagnosis and management requires an understanding of pelvic anatomy and mechanics, a careful history and physical examination, and judicious use of imaging studies. Despite this, groin pain may go undiagnosed in up to 30% of patients . Groin pain should be considered as a spectrum of pathology, with overlapping symptoms and a second or multiple diagnoses present in 27% to 90% of patients [3,4]. The most common athletic-related causes are adductor muscle strain, osteitis pubis, and sports hernia, but one must systematically consider other musculoskeletal and nonathletic causes (Table 1). The following briefly reviews the most common causes of groin pain in athletes.
Adductor strain or tendinopathy
Strains of the adductor muscle group (adductor longus, magnus, and brevis; gracilis; pectineus; and obturatorius externus) are the most common cause of acute groin pain in athletes. Their primary function is stabilization of the lower extremity and pelvis in the closed kinetic chain, as well as adduction of the thigh in the open kinetic chain and assisting in femoral flexion and rotation .
Strains are common with sudden eccentric loading . The adductor longus is most frequently affected, likely due to its lack of mechanical advantage . The musculotendinous junction and muscle belly have a robust blood supply and allow for aggressive rehabilitation compared with lesions at the tendinous insertion where a poorer blood supply dictates a slower recovery [1,2].
Prior injury is a significant risk factor for adductor strain, with 32% to 44% of injuries classified as recurrent [6,7]. A study of soccer players found that preseason hip abduction range of motion was decreased in players who were subsequently injured . More recent studies in hockey players have found no correlation between flexibility and injury, but have found a significant relationship to muscular weakness or imbalance and low levels of off-season sport-specific training [6,9]. Sub-sequent studies showed that off- or early season adductor strengthening reduced both the severity and frequency of adductor strains in hockey .
Athletes may recall an acute strain or may present with a chronic, overuse tendinopathy. They are tender to palpation over the involved muscle belly, tendon, or insertion, and have reproduction of pain with resisted adduction [5,11]. This latter finding is not specific and is commonly seen with other entities described later [11–14]. Radiographs can exclude fractures or avulsions . In acute injury, MRI will show increased muscle signal from hemorrhage, with a high correlation with patient symptoms . In chronic cases, MRI can also document traction periostitis or stress fracture , and gadolinium enhancement may demonstrate tenoperiosteal granulation tissue in chronic tendinopathies .
Acute adductor strains can be rehabilitated with a three-phase goal-oriented protocol consisting of acute and subacute phases aimed at preserving range of motion and preventing atrophy followed by sports-specific training to regain strength and endurance . Rehabilitation typically takes 4 to 8 weeks and the athlete may return to sport when they have achieved full painless range of motion and adductor strength is at least 70% of the contralateral side .
Chronic adductor muscle–related groin pain can be the result of a noninflammatory tendinopathy or an incompletely rehabilitated acute injury causing chronic recurrent strains. A thorough kinetic chain evaluation should look for biomechanical abnormalities predisposing for injury. Treatment protocols are similar to the subacute and sports-specific training for acute strains but require a protracted (8- to 12-week) time period. Iso-metric followed by isotonic and eccentric strength training in a closed kinetic chain mode is the primary goal, with stretching of little importance. Athletes with chronic pain using an active training program had significantly better outcomes compared with those using stretching, massage, and other physical modalities .
Tenotomy of the adductor longus tendon is the best described surgical procedure for chronic adductor muscle–related groin pain [19•], but should be considered only after failure of a 6-month physical therapy program and exclusion of other causes of groin pain . One series demonstrated improvements in all patients, but only 63% were able to return to their previous level of sport .
Osteitis pubis is a painful, self-limited condition characterized by pain over the symphysis pubis exacerbated by activities producing shearing of the pubis, such as rapid accelerations, cutting, pivoting, or kicking [21•]. The onset is usually gradual, although acute onset following a single traumatic incident has been reported . Athletes will complain of dull aching pain over the symphysis, occasionally radiating to the lower abdomen, proximal adductors, testicles, scrotum, and perineum [21•,22,23].
Rarely, there is an infectious etiology in which the pain has a more acute, atraumatic onset and is associated with systemic symptoms such as fever, chills, and night sweats. The clinician should be alert to these red flags and order appropriate laboratory studies, including leukocyte count and sedimentation rate [21•].
Physical findings include tenderness to palpation over the symphysis and pain on passive stretch and active contraction of the adductors. Shearing of the symphysis through pressure over the pubic rami may be painful. Sacroiliac joint dysfunction (SIJD) is a common associated finding. Osteitis pubis has been linked to reduced hip range of motion and weakness of the abductor and adductor muscles, so these factors should be evaluated and deficiencies treated [9,24].
Imaging may be helpful. Plain radiographs show erosions, sclerosis or lysis, and widening of the pubic symphysis. MRI may show increased T2-weighted signal in the symphysis; however, this finding is also frequently found in asymptomatic athletes, so its significance is uncertain and diagnosis should not be based on MRI alone .
Given its self-limited nature, treatment is supportive and includes ice massage, physical therapy modalities, and nonsteroidal anti-inflammatory drugs, although there is little evidence to support their use. Athletes should work on core stability and hip abductor and adductor strengthening and SIJDs should be corrected. More aggressive treatment in refractory cases with prolotherapy, corticosteroid injection, curettage, and stabilization with endoscopic mesh insertion or fusion have all been reported, but no comparative controlled trials have been conducted [21•,26,27].
Sports hernia or athletic pubalgia
Sports hernias are a syndrome of activity-related pain associated with abnormalities of the posterior abdominal wall. The incidence of this condition is controversial. Some researchers believe that sports hernias are the most common cause of chronic groin pain in athletes, whereas others consider this condition to be quite rare [28–31].
Athletic pubalgia is considered a more appropriate term because an actual hernia is not found in these patients [32,33]. The anatomic lesion is a tear or defect in the tissues surrounding the external inguinal ring, variously attributed to the conjoined tendon, rectus abdominus insertion, external oblique aponeurosis, or the deep transversalis fascia. Theories exist as to the etiology, including overuse, increased shear forces exerted across the hemipelvis, muscular imbalances of the pelvis and lower abdominal musculature, loss of rotational stability of abdominal wall, or a congenital weakness of the inguinal wall [28–32,34•].
There is often an insidious onset of pain with a gradually worsening of symptoms. Other athletes are able to identify a specific inciting event, such as kicking or suddenly changing direction at high speed, often associated with a pulling or tearing sensation. Patients complain of diffuse, deep, activity-related groin pain. The pain may radiate to the adductors, perineum, rectus muscles, inguinal ligament, and occasionally the testicles . There is no pain at rest and several authors suggest that pain at rest excludes the diagnosis of athletic pubalgia [32,33].
Resisted adduction of the hip, resistance to both a half sit-up and a simultaneous hip flexion, and Valsalva maneuvers may increase the pain and are useful provocative tests. No true hernia is palpable with a sports hernia because only the deep fascia are involved . Patients will have tenderness around the external inguinal ring and the posterior wall of the inguinal canal, and with Valsalva the examiner will occasionally feel the defect in the posterior wall tighten around the examining finger . Despite the examination tests, sports hernias are difficult to distinguish from other local pathology, which may also coexist in chronic cases.
Several imaging techniques are employed in the workup of groin pain, including radiographs, isotope bone scan, MRI, and herniography. Unfortunately, the findings are often nonspecific and demonstrate considerable overlap, and none have proven useful in confirming the diagnosis [15,25,35].
Initial management is nonoperative because of the difficulty of making a firm diagnosis and the frequency of overlapping pathology. If the pain persists, the patient should seek surgical exploration and repair by a surgeon skilled in the treatment of sports hernias. Both open and laparoscopic approaches to herniorrhaphy have been reported, occasionally using mesh reinforcement of the posterior wall [29,36–38]. Adjunctive rectus abdominus repair and adductor tenotomy have also been recommended [29,33]. Rehabilitation is focused on strengthening of the transverse and oblique abdominals and hip musculature, followed by jogging, running, and sport-specific activities . High rates of return to sport have been reported, generally within 6 to 12 weeks [29,32,33,35,39].
Stress fractures of the hip and pelvis are important considerations in overuse hip and groin pain. Although stress fractures of the pubis or sacrum are painful, they are rarely associated with significant complications. They are diagnosed with plain radiographs, bone scans, or MRI, and require symptomatic treatment and rehabilitation.
Femoral neck stress fractures are a major concern because they can progress to complete fracture and sub-sequent complications, including displacement and avascular necrosis. The most worrisome are to the tension side (superior aspect) of the femoral neck because they are most prone to failure. The compression side (inferior aspect) of the femoral neck is much less likely to displace.
Pain may be referred in a diffuse area, including the anterior hip, groin, and proximal femur. The pain will become progressive with continued running, and night pain is common in more advanced cases. Stress fractures of the proximal femur can produce groin pain, but also pain radiating down the thigh. The “hop test” is highly sensitive for stress fracture with reproduction of the index pain on gentle one-legged hopping. This test should be used with caution and avoided in patients with significant limping and pain. Focal palpable tenderness is uncommon due to the thickness of the overlying musculature.
Plain radiographs are frequently normal in the early stages but may show sclerosis, periosteal reaction, or a cortical break. Although an abnormal radiograph may be diagnostic for a femoral neck stress fracture, a normal radiograph does not rule out the problem. MRI shows bone marrow edema and cortical disruption if present. It is the most sensitive imaging modality and is considered the gold standard by most clinicians. Bone scans are also diagnostic, and single-photon emission CT can be used to localize the site of the fracture to the compression or tension side of the femoral neck. Bone scan is also helpful if metastatic disease is a consideration or if you are unsure of the exact site in the femur and are concerned that the fracture might be in the proximal femur out of the field of view of the MRI.
The management of femoral stress fractures is contro-versial. Treatment options have included complete bed rest, crutches and non–weight bearing, or modified rest with avoidance of offending activities . MRI-positive fractures without cortical disruption can be treated with activity modification to eliminate impact activity but allow pain-free activities of daily living. Compression-side fractures with an incomplete cortical defect on radiographs or MRI can be treated similarly, but may require crutches until they are symptom free in daily activity. Tension-side fractures should probably be treated more aggressively, and many authors recommend open reduction, internal fixation , although some studies have shown no displacement of either tension or compression side fractures with nonoperative treatment . If nonoperative treatment is selected, it is essential that the patient understands the significance and potential complications of their injury and will be compliant with the activity restriction. Surgical fixation is used in cases of displaced and complete nondisplaced fractures [42–44].
A high index of suspicion for this injury is essential to avoid missing the diagnosis. Any running or impact sport athlete with poorly defined hip and groin pain, a positive hop test, and the absence of palpable tenderness should be considered to have a stress fracture until proven otherwise.
Sacroiliac joint dysfunction
SIJD is a common, poorly understood, and frequently overlooked condition. Although it is more commonly a cause of back pain, it can refer pain to the groin in 14% of patients . In addition to its role in referring pain to the groin, SIJD can produce pelvic instability and predispose other hip and pelvic structures to injury through functional overload. SIJD is also a frequent predisposing factor to overuse injuries of distal structures . The most common dysfunctions occur with rotational subluxation of the innominate and sacral torsion, leading to a functional asymmetry in the pelvic ring.
Examination is directed at the identification of functional asymmetries of the pelvic girdle and sacroiliac joint. These are manifest by asymmetric positioning of the levels of the anterior and posterior superior iliac spines in the frontal plane. In addition to rotation of the innominates, the sacrum may be tilted. Additional clues are leg lengths, which are asymmetric and change when the patient goes from a supine position to a long sitting position in which the patient sits upright on the examination table with the hips flexed to 90° and the knees extended. An asymmetric range of hip motion suggests SIJD, with the hips having the same total range of motion, but one hip having more pronounced external rotation and the other more pronounced internal rotation. Hamstring flexibility will be affected by an SIJD, with the hamstring on the side of the anterior rotation having a reduced flexibility relative to the other. Although these are not diagnostic, they are certainly suggestive of this problem.
SIJD correction will often relieve the groin pain, but is also an important adjunct to normalize the forces and relieve the functional overload on other pelvic structures. Lee  and Brolinson et al.  provide more extensive discussions of this topic.
Extra-articular snapping hip syndromes
Lateral or anterior hip snapping with movement is common, although less than one third are painful and require treatment. The lateral form is most common and occurs when the iliotibial band, tensor fascia lata, or gluteus medius tendon slides over the greater trochanter, occasional causing a secondary bursitis [19•]. Symptoms are rarely felt in the groin and can typically be reproduced and palpated laterally. Treatment involves correction of bio-mechanical abnormalities including SIJD, and abductor and hip rotator strengthening.
Medial snapping hip syndrome results from the iliopsoas tendon catching on the anterior inferior iliac spine, lesser trochanter, or iliopectineal ridge. This occurs when the thigh goes from flexion to extension and the iliopsoas tendon moves from an anterolateral to posteromedial position [19•]. Mechanical trauma may lead to tendon degeneration or inflammation of the iliopsoas bursa. There is pain on deep palpation over the femoral triangle, and reproduced supine with a 15° straight leg raise when the iliopsoas is the only active hip flexor . The diagnosis is clinical, with MRI confirmation as needed . Treatment options begin with physical therapy similar to adductor-related groin pain. Guided bursal corticosteroid injection [50•] or fractional surgical lengthening  may be required in refractory cases.
Intra-articular hip disorders
The intra-articular form of snapping hip syndrome is mechanical in nature and usually involves symptomatic acetabular labral tears. Labral tears have been documented in athletes with chronic groin pain , but the natural history and the clinical significance of this finding have yet to be determined.
Femoroacetabular impingement is a recently described entity that deserves special mention as a cause of hip and groin pain and early hip osteoarthritis in young athletes [53,54,55•]. There are two main mechanisms causing impingement between the femoral head and the acetabulum. The cam-type involves an abnormally shaped, nonspherical femoral head with decreased offset at the anterolateral head-neck junction leading to impingement on the normal acetabulum and medial displacement of the labrum with flexion and internal rotation. The pincer-type is caused by impingement of the normally shaped femoral head on a retroverted or abnormally deep acetabulum. Both types occur on a spectrum and frequently coexist to some extent. Patients typically present with groin and hip pain that is reproduced by hip flexion, internal rotation, and adduction (the impingement test). Findings of acetabular retro-version and decreased head-neck offset on plain radiographs suggest the diagnosis and MRI arthrogram is used to stage labral and articular cartilage pathology. Management initially involves activity modification and pelvic stabilization. Open and arthroscopic options have been described as pain-relieving and motion-restoring procedures, but their long-term results are still unknown [55•].
Other intra-articular hip pathologies that may present as groin pain include osteoarthritis, avascular necrosis of the femoral head, transient osteoporosis of the hip, and ligamentum teres injury [19•]. Radiographs may be normal and MRI is usually required for the diagnosis. Fluoroscopically guided injection of local anesthetic is often helpful in identifying intra-articular pain generators.
Groin pain may be produced by nerve entrapment or trauma, or referred from a lumbar radiculopathy. The most common causes of peripheral nerve injury are constriction by fascial or muscle bands, and direct injury due to trauma or following surgical procedures. Nerve injury may lead to motor weakness and paresthesia or sensory loss in the distribution of the involved nerve. Electromyography and nerve conduction studies may be helpful in making the diagnosis and localizing the site of the nerve injury, and may assist in differentiating spinal from peripheral nerve injuries. MRI is useful in diagnosing nerve root compression. Diagnostic blocks will often confirm the diagnosis of peripheral nerve injury. Surgical exploration with decompression and/or neurolysis is the definitive treatment for most peripheral nerve entrapments. The review article by McCrory and Bell  is an excellent resource for more detailed information.
Although uncommon, radiculopathy of the L1–L3 levels can radiate pain to the hip, groin, and anterior thigh. These will not reproduce pain with straight leg raise, but will have a positive femoral nerve stretch test. Hip flexor weakness may be present.
The obturator nerve may become entrapped at the obturator foramen or by the adductor brevis. Entrapment produces pain and paresthesia in the distal, medial thigh and worsens following exercise. Weakness is rare, but may be more pronounced following exercise. Nerve stretch by having the patient externally rotate and then abduct the leg may provoke pain. There may be pain with active adduction and passive abduction .
The iliohypogastric nerve may be injured where it pierces the abdominal musculature about halfway between the highest point of the iliac crest and the anterior superior iliac spine (ASIS). It provides motor supply to the lower abdominal wall and sensory innervation to an area just superior to the pubis.
The ilioinguinal nerve travels around the pelvic brim then pierces the abdominal wall medial to the ASIS, then passes through the inguinal canal. Entrapment results in pain in the suprapubic region and around the inguinal ligament. Injury produces paresthesia in the medial thigh and lateral scrotum or labia. Tenderness will often be localized to an area one inch medial to the ASIS or the inguinal canal. It is often difficult to distinguish clinically from injury to the genitofemoral nerve, which must be considered in the differential diagnosis in patients who have undergone previous surgery .
The femoral nerve passes under the inguinal ligament lateral to the femoral artery. It can be injured with forced hyperextension of the hip, a strain with iliopsoas hematoma, or psoas bursitis. Injury will produce pain in the anteromedial thigh and quadriceps weakness. Surgical exploration has not proven very successful .
The lateral femoral cutaneous nerve enters the lateral thigh under the inguinal ligament anterior to the ASIS and pierces the tensor fascia lata. Injury produces burning pain and paresthesia in the anterolateral thigh. Sensation may be reduced in its distribution. Tinel's sign may be positive over the nerve. Most cases improve with time and symptomatic treatment. Surgery is rarely indicated .
Hip and groin pain is often multifactorial, with involvement of several anatomic structures. It can be diagnosed with careful attention to the history and physical examination. Imaging studies may be helpful, but findings are often nonspecific, and many pain-free athletes demonstrate MRI changes. Muscle and tendon injuries and osteitis pubis will often respond to appropriate treatment, although the time course may be prolonged. Surgery is frequently indicated for athletic pubalgia or sports hernia. It is critical to rule out a femoral neck stress fracture in running athletes with groin pain, no palpable tenderness, and a positive hop test. Failure to do so can result in significant complications. Intra-articular symptoms should suggest labral tears and femoroacetabular impingement. Nerve injuries can be problematic if not considered in the differential diagnosis, but can be diagnosed with electromyography and diagnostic blocks.
References and Recommended Reading
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