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Physical Examination and Imaging of the Painful Athletic Hip

  • Yiğit Umur Cırdı
  • Selim Ergün
  • Mustafa Karahan
Chapter

Abstract

Hip and groin pain is a frequent complaint among competitive athletes. Effect of groin pain on athletic performance ranges from intermittent discomfort to severe and chronic career-threatening pain. Since it may be detected in wide variety of sport branches, physicians should be aware of numerous mechanisms of injuries. Management of groin pain remains challenging for clinicians because of its complex nature and broad range of underlying etiology. Therefore, excluding irrelevant causes of groin pain require meticulous effort for each individual. High recurrence rate and negative impact on athletic activity level of the groin pain should always be kept in mind and treatment algorithm must be started immediately to avoid undesired outcomes.

Keywords

Hip Groin Pubalgia Pain Athlete 

1.1 Introduction

Hip and groin pain is a frequent complaint among the competitive athletes. Even though it is commonly encountered in various branches of sports, there is increased prevalence of groin pain present in sports with sudden direction or momentum changes like pivoting, kicking, and over-limit rotation. The incidence of groin pain is relatively increased among football, rugby, and hockey players; however it may be seen in other sport branches with different levels of activity from amateurs to experts. Pain-related disability and undesired effect on athletic performance significantly increase the popularity and number of athletes seeking medical treatment.

Management of groin pain remains challenging for clinicians because of its complex nature and broad range of underlying etiologies (Table 1.1). Abnormal findings in asymptomatic athletes contribute to the complexity. Even with improved physical examination methods, advanced imaging techniques, and detailed muscle strength measurements, it is not always possible to make an accurate diagnosis, which remains a concern for athletes. It is shown that groin pain may have more than one underlying pathology; therefore athletes with groin pain should be evaluated comprehensively and systematically to narrow the differential diagnosis [1].
Table 1.1

Differential diagnosis of pain in groin and hip region

Intra-articular pathologies

Extra-articular pathologies

Other (non-musculoskeletal) pathologies

Red flags

Labral tears

Athletic pubalgia

Intra-abdominal reasons

Femur fracture

Femoroacetabular impingement

Strain/tendinitis

Aneurysm, inguinal or femoral hernia, diverticulosis, inflammatory bowel disease

Septic arthritis

Chondral damage

Snapping hip

Malignancies

Arthritis

Iliotibial band syndrome

Genitourinary reasons

Appendicitis

Loose bodies

Bursitis

Urinary tract İnfection, epididymitis, testicular torsion, endometriosis, nephrolithiasis, pelvic inflammatory disease

Pregnancy

Avascular necrosis

Lumbar spine pathology

Unexplained weight loss

Femoral neck stress fracture

Referred pain

Trauma

Synovitis

Peripheral nerve compression

Fever

Lig. teres rupture

Sacroiliitis

 

Hematuria

 

Myositis ossificans

  

Groin injuries account for 3–5% of all sports-related injuries [2, 3]. Incidence varies depending on the sports performed and level of competence. One large study pointed out that groin injury represents 12% of all injuries in professional football players [4, 5]. It has to be kept in mind that 50% of groin injuries result in a delay in returning to sport of more than a 1-week period, and reinjuries cause significantly longer delays than the index injury [6]. Considering the high recurrence rate and negative effect on activity level, complaints of the athletes should not be neglected, and appropriate diagnostic algorithm must be started immediately to prevent premature ending of their competitive careers [7, 8, 9].

Previously groin pain was taught to be generated mostly secondary to basic muscular strains and minor soft-tissue trauma. Increased understanding of the patho-anatomic features of the hip joint and surrounding anatomic structures with additional knowledge of how the hip joint reacts during sports has led to an evolution of the evaluation of groin pain in the athlete. As a result of the increased focus on the ongoing advancements and increased importance of groin pain evaluation in athletes, clinicians organized a meeting in 2014 to clarify the terminology and definitions for groin pain and categorized the underlying pathologies to create a consensus of simple explanations which are convenient for use in clinical practice and research. Search of the literature and common experience by these experts allowed evaluation of collective data, and below are some highlights for better comprehension:
  • Careful history taking and physical examination covering more than the musculoskeletal system alone with additional appropriate investigations or referrals are critical for identifying other possible causes.

  • Carefully taken history along with a clinical examination and assessment comprising palpation, stretching and resistance testing is critical in acute groin injuries.

  • Groin pain in athletes are divided into three main categories:
    • Adductor-related, iliopsoas-related, inguinal-related, and pubic-related groin (extra-articular) pain

    • Hip-related (intra-articular) groin pain

    • Other causes of groin pain in athletes

1.2 Pathoanatomy of the Groin

Hip joint is the largest joint in the body and able to produce multi-directional thrust during competition by complex muscular and neurologic interactions. Since the groin area is surrounded by many significant anatomical structures, the origin of the pain might be confusing. In addition, it should be kept in mind that the underlying cause of groin pain in athletes might be multifactorial. Anatomic features of tendons, ligaments, muscles, cartilage, and osseous structures should be understood well to establish an accurate diagnosis. Clinicians should be aware of the anatomic structures and related sources of pain which may radiate into groin area.

1.3 Clinical Assessment

1.3.1 Patient History

Successful evaluation of the patient begins with a detailed history-taking process. Since there are numerous underlying pathologies that may cause groin pain, it is important to obtain sufficient data to help narrowing the differential diagnosis and reach to the correct diagnosis. Medical information of the patient’s pain must include location, time of onset, characteristics of pain, relieving and exaggerating factors, age, sport branch, competitive level, and impact on performance. Duration of the pain should be questioned whether it is acute, subacute, or chronic. Considering many potential causes of groin pain, it is crucial to have a wide range of differential diagnoses before refining the diagnosis and planning the treatment strategy.

Obtained data will guide clinicians to discriminate the intra-articular, extra-articular or non-muscular pathologies. Each verbal clue should be interpreted wisely to eliminate irrelevant causes. Complaints should be processed by the clinician to reach the diagnosis and determine the origin. For instance, acute onset of groin pain accompanying with popping sound is likely to be musculotendinous in origin, whereas dull and long-lasting pain alleviated by activity corresponds an intra-articular origin [10]. Uninterrupted, low-scale pain with constant burning sensation might be interpreted as having a spinal pathology.

Aggravating factors and specific activities must be documented carefully such as pivoting, twisting, and sprinting. These data provide valuable information about the origin of pain and should create a scenario in mind for mechanism of injury and possible damaged anatomic structures causing pain. Pain aggravated by hip flexion and terminal internal rotation would suggest there is high probability of labral pathology. The symptoms of an athlete complaining of snapping sensation with sudden onset of pain might be caused by intra-articular loose body.

Previous medical interventions must be noted including medications, manual therapies, arthroscopies, and surgical dislocations. Documentation of previous injections is crucial. Most athletes tend to skip information about injections. Questioning the type, localization, and purpose of the injection is valuable for evaluating the athletic status, as is whether there was any relief from the injection and the timing of the relief. Consequently, clinicians should create their own well-constructed step-by-step questioning to obtain data about underlying pathology and determine which imaging modalities will be required to make an accurate diagnosis depending on patient’s history.

The examination of the hip sometimes can be confusing and challenging. However, with a systematic approach, possible diagnoses can be narrowed down. Appropriate treatment protocol is essential for returning to prior activity level and hinge on the clues obtained during physical examination [11].

1.3.2 Physical Examination

Examination of athlete should be comprehensive and made systematically. Comprehensive examination of the athlete takes place in different positions like standing, seated, supine, lateral, and prone as outlined by Martin et al. [12] (Table 1.2). In the standing position, evaluation begins with inspection. Various vital pieces of information can be gathered by just inspecting the patient carefully. Skin disturbances, ecchymosis, swelling, asymmetry, stance (equal weight bearing), leg-length discrepancy, and other observable disturbances should be inspected. Assessment of posture is crucial and might be an indicator of underlying pathology. Knowledge of normal gait biomechanics and frequently encountered compensatory mechanics are essential for integrating this information into the clinical picture. For instance, dysfunction of gluteal muscles may lead to drop in contralateral side of pelvis (Trendelenburg). Arthritic hip or slipped femoral head or osteonecrosis of the femoral head may manifest themselves as a gait abnormality. Any sort of muscle wasting, probably caused by nerve entrapment and other anatomical variations need to be documented.
Table 1.2

Physical examination modalities and tests for patients with hip or groin pain in five different positions

Patient position

Standing

Seated

Supine

Lateral decubitis

Prone

Posture

Neurologic

Passive ROM, palpation, tenderness

Palpation of greater trochanter

Evaluation of hip extension

Spine for scoliosis, lordosis

Circulation

FABER (flexion, abduction, external rotation)

Palpation of ischial tuberosity and sacroiliac joint

Walking pattern

Lymphatics

Resisted adduction

Ober test

Shoulder asymmetry

Hip rotation

Thomas test

FADIR (flexion, adduction, internal rotation)

Ely’s test

Trendelenburg test

Off-loading 1 buttock

Impingement tests

Evaluation of hip extension

Ecchymosis

Slouching to reduce hip flexion

Stinchfield test

Craig’s test

Limb length discrepancy

 

Thigh thrust test

  

Limitations in range of movement (ROM) can also be assessed by questioning about limitations in daily life activities. Ascending and descending stairs require 30–44° of hip flexion, sitting on a chair requires 112° of flexion, and putting on socks requires 120° of flexion [13]. Athletes with femoroacetabular impingement or other intra-articular pathologies may have limited ROM while performing their daily activities.

In a seated position, movement capability and neurologic functions can be assessed. Hip internal and external rotation of the hip can be evaluated, while pelvis is stabilized in the seated position.

Comprehensive range of motion assessment test and provocative pain tests are mostly performed in supine position. Examination should start with general range of motion assessments to high sensitivity pathology-specific tests to narrow differential diagnosis depending on the clinical suspicion. Intensity of pain on a provocative test is noted, and these findings should navigate the clinician to the underlying pathology. Frequently used examination tests in supine position are listed below:
  1. 1.

    Resisted adduction test: Resisted adduction is tested with the patient in the supine position and the hips and knees brought into flexion. The test is positive if the patient experiences pain in the proximal aspect of the adductor muscles while trying to bring the legs together against the examiner’s resistance (Fig. 1.1). In an experimental induced groin pain study, the 0° adduction test (same test done with hips at 0° flexion, as a neutral position) showed the best positive likelihood ratio (sensitivity (SN), 93%; specificity (SP), 67%) to detect adductor longus-related groin pain [14].

     
  2. 2.

    Thomas test: While the patient is in supine position, he or she is instructed to flex both the knee and hip joint on one side and pull the leg to the chest. A flexion contracture would be indicated by passive flexion of the contralateral straight leg lifting off the exam table (Fig. 1.2a, b). Thomas test is a good screening test (SN 89%; SP 92%) to predict intra-articular pathology without indicating specific diagnosis (labral tear, loose bodies, chondral defect, and arthritic changes) [15, 16]. This test would also be positive in the setting of iliopsoas tightness or hip flexion contracture.

     
  3. 3.

    Anterior impingement test: Anterosuperior part of the labrum is more susceptible to injury because of its anatomic features mentioned previously. Anterior impingement test is described for diagnosing anterosuperior labral lesions and femoroacetabular impingement (FAI). The hip is dynamically flexed to 90°, adducted and internally rotated. Deep anterior groin pain replicating the patient’s symptoms means the test is positive (Fig. 1.3). Positive anterior impingement test indicates whether the labrum has a lesion (SN, %59; SP, 100%; positive predictive value, 100%). Although the sensitivity of the anterior impingement test does not appear sufficient to detect anterosuperior quadrant labral lesions in patients with hip pain, the high positive predictive value makes the test useful [17, 18].

     
  4. 4.

    Posterior impingement test: The patient is in supine position, and the unaffected hip is slightly flexed. Affected limb is extended, abducted, and externally rotated by the examiner. When the femoral head contacts the posterior acetabular cartilage and rim, pain at the back side (buttock) indicates posterior impingement, especially the labrum (Fig. 1.4).

     
  5. 5.

    Anterior instability/apprehension test: Repetitive microtrauma to the hip capsuloligamentous structures may also result in symptomatic microinstability. This results in increased movement of the femoral head relative to the acetabulum and eventual damage to the labrum, cartilage, and capsular structures [19]. Philippon et al. stated that 35% of patients undergoing revision hip arthroscopy required capsulorrhaphy, suggesting that undiagnosed hip microinstability may have contributed to the need for revision surgery [20]. Anterior instability test gives information about the congruency of hip joint. This test is similar to posterior impingement test with extension, abduction, and external rotation of the affected hip. A feeling of apprehension, subluxation or instability is positive for the test and may point structural instability. Test showed high sensitivity (80.6%), specificity (89.4%) and negative predictive value (77.8%) during evaluation of the microinstability following hip arthroscopy [21].

     
  6. 6.

    Posterior apprehension test: While the patient is in supine position, the examiner flexes the hip to 90°, adducts, internally rotates, and then applies a posterior force on the knee. Test is positive with posterior pain or sensation of instability (Fig. 1.5).

     
  7. 7.

    Stinchfield test: The patient performs a straight leg raise and resists downward pressure by the examiner. Groin pain means the test is positive and indicates an intra-articular etiology, as the psoas muscle puts pressure on the anterolateral labrum (SN, 59%; SP, 32%; positive likehood ratio (+LR), 0.87) [22, 23]. Pathology-specific testing should be chased depending on the targeted suspicious intra-articular pathology (Fig. 1.6). However this test may also be positive in the setting of hip flexor tendinitis.

     
  8. 8.

    The McCarthy hip extension test: While the patient is in supine position with the hips and knees flexed, the affected hip is taken from flexion into extension and rolling it in arcs of internal and external rotation. The test is positive if pain and/or a “click” is reproduced indicating an acetabular labral tear (Fig. 1.7a, b).

     
  9. 9.

    Internal snapping hip test: Bringing the hip from a flexed, abducted, and externally rotated position to an extended, adducted, and internally rotated position frequently reproduces the anterior clunk or snap (Fig. 1.8). This usually is the result of the iliopsoas snapping over the anterior structures of the hip.

     
Fig. 1.1

Resisted adduction test

Fig. 1.2

Thomas test; (a) negative Thomas test, (b) positive Thomas test

Fig. 1.3

Anterior impingement test

Fig. 1.4

Posterior impingement test

Fig. 1.5

Posterior apprehension test

Fig. 1.6

Stinchfield test

Fig. 1.7

The McCarthy hip extension test. (a) Start, (b) end

Fig. 1.8

Iliopsoas tendon snapping over the femoral head in internal snapping of the hip

Gluteal muscles, iliotibial band and trochanter-related pathologies are best examined in lateral position. Iliotibial band snapping (external snapping) and abductor muscle group examinations are performed while the athlete is lying on his/her side. Frequently used examination tests in lateral decubitus position are listed below:
  1. 1.

    Ober test: This test is useful for evaluating the iliotibial band, tensor fascia lata, and greater trochanteric bursa. The patient is placed in a lateral decubitus position, while the upper knee and hip are flexed to 90°. Initially, the examiner passively abducts and extends the upper leg until the thigh is in line with the trunk, followed by passive adduction. Leg maintained in relative abduction with patient having discomfort indicates that the test is positive. If excessive tightness of the iliotibial band is present, this may show inflexibility. Focal pain overlying the trochanter points toward a possible trochanteric bursitis (Fig. 1.9).

     
  2. 2.

    FADIR test: Flexion-adduction-internal rotation test is performed with the upper leg flexed to 60° and the lower leg maintained in full extension. The examiner passively moves the leg into full flexion first and then into adduction and internal rotation. “Shooting” pain elicited by direct impingement of the sciatic nerve by the tight piriformis muscle shows the test is positive (Fig. 1.10). The pooled data of this test showed 99% sensitivity and 0.15 -LR [24]. In a review study, the SN values for this test ranged from 59 to 100%, and the SP values ranged from 4 to 75% for various intra-articular pathologies, and it showed 99% sensitivity and 7% specificity for detection of intra-articular pathologies when compared with arthroscopic diagnosis [15, 25].

     
Fig. 1.9

Ober test. (a) Start, (b) end

Fig. 1.10

FADIR test

Prone position is useful for examining sacroiliac joint and posterior thigh muscles and assessing femoral anteversion. Tenderness on sacroiliac joint may be the indicative for rheumatologic diseases. Femoral anteversion is best examined while patient is lying on prone position and knees flexed to 90 degrees and greater trochanter placed horizontally to the ground plane. Angle between the axis and tibia corresponds to femoral anteversion angle. Examination should be done bilaterally to compare both sides. Ely’s test is also performed in prone position to assess tightness in the rectus femoris muscle. Frequently used examination tests in prone position are listed below:
  1. 1.

    Craig’s test: The patient lies prone on the exam table with the knee flexed to 90°. The examiner palpates the greater trochanter to keep it in its most lateral position by internally and externally rotating the hip (Fig. 1.11). The degree of femoral anteversion can be estimated using a goniometer with one arm perpendicular to the floor and the other the angle of the leg.

     
  2. 2.

    Ely’s test: The patient is instructed to lie in the prone position with both legs fully extended. The examiner then passively hyperflexes the knee, taking care to avoid rotation or extension of the hip joint, and observes the ipsilateral hip for vertical separation from the exam table (Fig. 1.12). Test is positive if buttocks are elevated for touching to the heel when knee is terminally flexed to compensate rectus femoris tightness.

     
Fig. 1.11

The Craig’s test

Fig. 1.12

Ely’s test

Physical examination tests to rule out pelvic girdle-related pain:
  1. 1.

    Thigh thrust test: The hip joint is flexed to 90° when patient is lying on supine position to stretch the posterior structures. By applying an axial pressure along the length of the femur, the femur is used as a lever to push to the ilium posteriorly. One hand is placed beneath the sacrum to fix its position, while the other hand is used to apply a downward force on the femur. Longitudinal load force is applied for up to 30 s and repeated 3–5 times. If applied force provokes pain at the back of the pelvic girdle, then the test is positive for SI joint pathology (Fig. 1.13).

     
  2. 2.

    FABER (flexion, abduction, external rotation) test: The patient lies supine, and the affected leg is placed in a flexed, abducted, and externally rotated position, as if creating the number 4, with the foot of the leg being tested resting on the contralateral knee (Fig. 1.14). From this position, the examiner places gentle downward pressure on the ipsilateral knee. Pain or a decreased range of motion indicates a positive FABER test which is commonly utilized as a provocative test to detect intra-articular, lumbar spine, or sacroiliac joint pathology. Diagnostic value of FABER test compared to MR arthrography (MRA) in labral tears showed 41% sensitivity and 100% specificity [25]. Another study also supports this evidence and states that the sensitivity values for this test ranged from 42 to 81%, while the specificity values ranged from 18 to 75% [15]. Therefore, clinical signs of a painful, restricted hip quadrant and a positive FABER test should suggest the need for MR arthrography.

     
Fig. 1.13

Thigh thrust test

Fig. 1.14

FABER test

1.4 Diagnostic Imaging

Injuries of the hip and groin may lead to significant disability if left untreated [6, 7, 26, 27]. Imaging is the key assistant for accurate diagnosis, but it should be always accompany a well-constructed physical examination and thorough history. Many factors influence the decision-making process as to which is the most suitable radio-diagnostic modality for accurate diagnosis. All different imaging modalities have distinctive superiority on different tissues. Therefore, the optimal modality depends on the clinical suspicion of the involved tissue.

Conventional radiography (CR) may provide great amount of data to assess osseous structures, but it might be inadequate to diagnose tendinous, ligamentous, and chondral pathologies. Consequently, different imaging modalities with their strengths should be taken in consideration to create most suitable combination of imaging for each individual.

There has been huge evolution in technology in radiographic imaging studies in the past 30 years. Clinicians are now able to get tremendous amount of knowledge from anatomic structures around the groin area. Additionally, the understanding of potential pathologies causing groin pain has increased. Working with a radiologist experienced in musculoskeletal imaging may provide a significant advantage. Informing the interpreting radiologist about the clinical findings and preliminary diagnosis is crucial and cannot be overemphasized [28].

1.4.1 Conventional Radiography

Despite the ongoing advancement in imaging studies, CR remains one of the most important examination tools for groin pain. Advantages of the CR include relative low cost, high specificity and wide availability. Detailed analysis of CR can inform clinicians about many underlying pathologies. Subtle manifestations of underlying pathologies should be well recognized for proper interpretation.

CR is still a fundamental approach to imaging of the hip joint. Preparation and positioning of the patient is important to obtain proper images to increase diagnostic accuracy. In order to evaluate a plain radiography, confirmation of appropriate position is required. In a standard anteroposterior (AP) view, the coccyx and symphysis pubis should be straight and aligned with the midline (over the pubic symphysis), both obturator foramina and iliac wings should be symmetrical and pelvic tilt and rotation should be avoided [28, 29]. In addition, the legs are rotated 15° internally to accommodate femoral anteversion instead of the neutral position as is a common mistake (Fig. 1.15) [30]. Note that the lesser trochanter is barely seen on the AP view if internal rotation is well adjusted [31]. Joint space narrowing and assessment of neck-shaft angle, coxa vara/valga, center-edge angle, overcoverage, and femoral sphericity can be observed with standard AP view. Other than the hip joint, assessment of the sacroiliac joint, symphysis pubis, sacral vertebrate, and surrounding soft tissue should be done.
Fig. 1.15

In a standard AP view, legs are rotated 15° internally (a) to accommodate femoral anteversion, while patient is in supine position (b)

Various radiographic findings may help to identify underlying pathology. On an AP view, assessment of teardrop provides information about the location of femoral head. A wide teardrop corresponds to shallow acetabulum, whereas a narrow teardrop or teardrop located medial to ilioischial line can indicate deeper acetabulum and related overcoverage.

Stress fracture should be considered in athletes with recently increased athletic performance duration or intensity. Repetitive exposure to excessive load in chronic fashion is mostly the cause [32, 33]. Radiographic findings include sclerosis and periosteal reaction. However, CR has low sensitivity for stress fractures. Therefore, if there is strong clinical suspicion, MRI should be ordered.

Assessment of acetabular version is relatively difficult on CR as it can vary considerably by tilt or rotation of the pelvis and imaging techniques [34]. In a normally anteverted acetabulum, posterior and anterior walls reach each other at the lateral (superior) edge; thus lines representing anterior and posterior walls do not intersect each other (Fig. 1.16a). If there is posterior overcoverage of the femoral head secondary to a retroverted acetabulum, the line representing the posterior wall will likely to intersect with the line representing the anterior wall of the acetabulum (Fig. 1.16b). In this situation, a crossover sign is present and may indicate pincer-type impingement. In addition, a prominent ischial spine on a true AP view also indicates femoral retroversion.
Fig. 1.16

Crossover sign; (a) normal anteversion, (b) retroverted acetabulum

Slipped capital femoral epiphysis (SCFE) is a significant pathology in young athletes. The involved epiphysis tends to displace medially and inferiorly (in fact the femoral neck actually is displaced laterally and superiorly). On an AP view, a line drawn at the lateral edge of the femoral neck (Klein’s line) should contact femoral epiphysis. If intersection fails, displacement of the femoral epiphysis is likely present.

Avascular necrosis (AVN) is an osseous cell death causing disintegration of the normal weight-bearing structure of the femoral head. Even it might be asymptomatic at the beginning, progression to subchondral collapse is likely if left untreated. Imperfect sphericity of the femoral head and coexisting arthritic findings may indicate avascular necrosis of the femoral head (AVN). If clinical suspicion is present, MRI must be ordered to better illustrate the ongoing pathology.

There are various types of lateral radiographs available. Each has specific advantages and limitations in terms of diagnostic accuracy. Cross-table lateral view, frog leg and lateral Dunn view provide information for calculating alpha angle and assessment of femoral neck sphericity. Frog leg view is performed with the patient in supine position with hip flexion, abduction and external rotation. It is suitable for general diagnostic purposes. Cross-table lateral view is performed with the patient in supine position and unaffected hip elevated to 90° flexion and affected lower extremity 20° internally rotated. The cross-table lateral view is performed to assess femoral head-neck junction step-off and may provide a better estimate of the femoral version. Dunn lateral views are obtained with the patient in supine position, while symptomatic hip flexed at 90° or 45° and slightly abducted (20°) to evaluate anterolateral head-neck junction. Dunn lateral view has greater sensitivity for calculation of alpha angle than other views [35]. The false profile view of Lequesne is a weight-bearing oblique view that does demonstrate the anterior wall of the acetabulum and an anterolateral view of the femoral head, making it useful for the evaluation of dysplasia (undercoverage anteriorly) and CAM lesions and to evaluate the AIIS. All lateral views are used for detection of asphericity of the femoral head and to demonstrate abnormal alpha angle corresponding to pathologic cam-type impingement. While each of these aforementioned lateral views are lateral views of the femoral head, only the cross-table lateral is a lateral view of the acetabulum. The alpha angle is calculated as the angle between a line drawn from the center of the femoral head through the central axis of the femoral neck and a second line drawn from the center of the femoral head to the point anteriorly where the radius of the femoral head first exceeds the radius of the more centrally located portion of the femoral head. An absolute cutoff value for pathologic alpha angle is still controversial. It is still questionable whether it discriminates symptomatic and asymptomatic impingement. Generally, values greater than 55–60° strongly suggest that cam impingement is likely, and further MRI or CT scan may be required to confirm the diagnosis [36, 37].

1.4.2 Computed Tomography

Computed tomography (CT) is a valuable tool for evaluation of static osseous pathologies in athletes with hip pain. As mentioned before, CR does not provide exact value of acetabular version and predicted values are highly dependent on the technique and position of the beam. Femoral version is also relatively calculated which represents the spatial position of the femoral head relative to the epicondylar axis of distal femur. Therefore, radiologic findings in CR are advisory, but reliable measurement of the femoral version is made by CT.

CT offers excellent delineation of cortical bone and is the ideal diagnostic tool for evaluation of fracture or blunt trauma. Even though it offers valuable information in suspected fractures, it has very limited value in the assessment of soft tissue-related differential diagnosis of sports injuries.

CT scan with three-dimensional (3D) reconstruction is an invaluable tool for visualizing the femoroacetabular relationship. Exact localization of overcoverage areas, morphologic abnormalities, and dimensions of the deformity can be easily evaluated by CT scans. Morphologic assessment of cam-type impingement is crucial for the selection of the suitable surgical approach. For instance, cam-type impingement that expands posteriorly through the retinacular vessels means that it is risky to reach the resection site arthroscopically without risking damage to the vasculature. Preoperative 3D reconstruction of CT scans provides the insight about the localization and size of the resection area prior to surgery to restore the sphericity of the femoral head. Moreover, localization of the pincer-type FAI and visualization of possible intra-articular loose bodies can be detected accurately. It is recommended to include the whole pelvis during the scan to measure the *alpha angle, center-edge angle, and femoral version precisely [38].

Dynamic animation of the impingement during movement is now possible with individual software. Relevant anatomic sites causing impingement during motion of the hip joint can be visualized by 3D construction and provide valuable preoperative information by pointing out the anatomic localization to be corrected. With dynamic software animation, expected improvements in range of motion can be simulated prior to surgery. Yet, authors expect to see this simulation as an intraoperative navigation tool in future [39].

1.4.3 Ultrasound

Considering the wide spectrum of differential diagnosis of groin pain in athletes, ultrasound imaging offers a rapid and cost-effective evaluation, and it can serve as a guide for percutaneous intervention. Ultrasound is especially useful for evaluating dynamic pathologies, such as snapping hip syndrome and hernias. The observer is able to demonstrate pathology simultaneously by simulating the precipitating movement [40]. It is also useful for monitoring the condition of the muscles and showing injury-related findings, such as edema along the fibers and discontinuity of tendons or ligaments. However, some deep muscle groups around the hip girdle are less accessible to ultrasound evaluation. Labral pathologies are also visualized by ultrasound, but only anterior part of the labrum is reachable. In a recent study on labral tears, ultrasound showed significantly high sensitivity (94%) when compared with MR arthrography (MRA) and clinical impingement tests [18].

Ultrasound-guided injection is a valuable replacement for fluoroscopy-guided injections since it is radiation-free. In addition, young athletes displayed higher satisfaction rates and less pain with ultrasound-guided intra-articular hip injections than fluoroscopy guided following the intervention [41].

1.4.4 Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) of the hip is an invaluable tool for diagnosis of sports-related hip and groin injuries in the setting of other imaging studies. With its sensitive soft-tissue contrast and multiplanar capabilities and ability to distinguish musculotendinous, osseous, cartilaginous, and labral pathologies, MRI is unique in the noninvasive diagnosis of both intra-articular and extra-articular pathologies. Although expensive and time consuming, MRI provides many diagnostic benefits by assessing different tissues and related pathologies simultaneously. Groin pain in athletes may be due to many different reasons, and generally more than one pathology may cause the symptoms. Therefore, a global examination of the hip and groin area in a competitive athlete is essential to evaluate concurrent abnormalities.

MRI is superior to other imaging modalities in the evaluation of the acetabular labrum, articular cartilage and surrounding soft tissues such as bursae and tendons [42]. Considering the wide range of differential diagnoses, a comprehensive evaluation of both intra- and extra-articular pathologies should be performed at the same time to determine the underlying pathology. MRI imaging of the hip and pelvis can provide a prompt and specific diagnosis, which allows for early diagnosis and return to previous activity level [43].

Due to the complex anatomy and mostly complicating source of the groin pain, clinicians should always inform the radiologist of the suspected diagnosis and physical examination findings. Keeping good communication with your radiologists would provide huge advantage in obtaining an accurate diagnosis. From the radiologist’s point of view, it has to be kept in mind that proper examination is done with appropriate equipment; therefore a well-done MRI greatly increases the diagnostic accuracy [28].

In a recent review, it has been shown that over 80% of athletic groin pain requiring surgery is attributable to five pathologies: FAI, athletic pubalgia, and adductor-related, inguinal-related, and labral-related pathologies [44]. MRI is the most valuable tool for evaluation of the chondrolabral complex in the athlete’s hip, where the information obtained is crucial to devise a treatment plan or to help make a decision for surgical intervention.

There are several newly developed techniques available to provide quantitative information about the quality of the cartilage tissue [45]. T2 mapping and gadolinium-enhanced techniques are the popular imaging techniques. With T2 mapping, pathologic injury to the chondral tissue can be accurately determined even though morphologically it appears normal (Fig. 1.17). Moreover, it detects anatomic localization of the injury with great accuracy as well as facilitating preoperative evaluation and long-term cartilage monitoring without requiring invasive contrast injection [46, 47]. Ellermann et al. compared the injury localization results of T2 mapping with direct visualization via arthroscopy and pointed out that there is a 91% true positive rate under the threshold specified [48].
Fig. 1.17

14-year-old FAI patient. (a) Sagittal cut of the T2 mapping MR image indicates loss of cartilage tissue which represented by red and orange colors. Anterior (arrow) and posteroinferior (arrowheads) localization of the defect is highly considered to be pincer-type impingement due to protrusio acetabuli. (b) Sagittal fat-saturated MR image of the same patient. Arrows and arrowheads mark the thinned articular cartilage layer. (Reprinted by the permission of Springer-Verlag, Radiologic analysis of femoral acetabular impingement: from radiography to MRI, Dwek, J.R., Monazzam, S. & Chung, C.B. Pediatr Radiol (2013) 43(Suppl 1): 61.  https://doi.org/10.1007/s00247-012-2588-7)

Gadolinium-enhanced MRI of cartilage (dGEMRIC) is a modality that relies on penetrance of negatively charged gadolinium into the injured cartilage tissue where lack of negatively charged glycosaminoglycans (GAGs) repels the contrast agent. Thus, it can show early cartilage injury before it becomes evident grossly. All acquired information collected by different imaging studies may assist the surgeon in decision-making and preoperative assessment for building treatment plan [49]. Bittersohl et al. observed lower gadolinium intake in FAI patients in comparison with asymptomatic volunteers [50]. Consequently, biochemically sensitive MR imaging is expected to bridge the gap in between asymptomatic FAI morphology and symptomatic pathology [51].

Most commonly seen pathologies causing groin and hip pain in athletes and their radiologic findings are listed below.

1.4.4.1 Extra-articular Hip Impingement

Ischiofemoral Impingement

Extra-articular hip impingement refers to a variety of increasingly recognized hip disorders causing pain and limited function in young, non-arthritic patients. Specific disorders include psoas impingement (PI), subspine impingement (SSI), ischiofemoral impingement [52] (IFI), and greater trochanteric/pelvic impingement (GTPI).

Ischiofemoral impingement is caused by impingement of soft tissues (especially the quadratus femoris muscle) in between proximal femur and the ischium (Fig. 1.18). It is more common in elderly and rarely seen in athletes.
Fig. 1.18

MRI of the pelvis, axial cut, and T2-weighted image without contrast. White arrows represent the restricted ischiofemoral space between femur and ischium. (Reprinted by permission From Springer-Verlag Berlin, Ischiofemoral impingement syndrome: a case report redefining this condition, Hotait, M., Makki, A. & Sawaya, R. Neurosurg Rev. (2016) 39: 707.  https://doi.org/10.1007/s10143-016-0766-z)

Subspine Impingement

Subspine impingement is a more commonly seen pathology in athletes, mostly soccer and tennis players. SSI is caused by soft-tissue impingement between anterior inferior iliac spine (AIIS) and the femoral head-neck junction during hip flexion. Usually avulsion fracture of the AIIS and caudally healed avulsed fragment is the cause.

1.4.4.2 Stress Fracture

Stress fractures are described as accelerated bony remodeling in response to repetitive submaximal trauma. Incidence of the stress fracture is increasing with weight-bearing activities and higher competitive level. In a typical sports medicine practice, bone stress injury accounts for 10–20% of cases [32, 33, 53]. Some authors state that in reality, the prevalence may actually be higher as a result of underdiagnosis [54]. Acetabulum and femur are the common sites for stress fracture in athletes, and mostly they are seen in endurance athletes. Athlete with a history of anterior hip or groin pain that is worsened with activity and insidious in onset often related to a change in type or intensity of workouts is highly suggestive for stress fracture.

Periosteal new bone formation can be seen in CR a few weeks after the fracture begins. MRI or bone scintigraphy is recommended if there is high clinical suspicion with a normal CR [55]. Bone marrow edema seen in fluid-sensitive MRI scans is the early finding of stress fracture. It is manifested as a hypointense line on T1- and T2-weighted images (Fig. 1.19). Bone marrow edema will diminish with healing.
Fig. 1.19

30-year-old male weightlifter with a sudden onset of bilateral groin pain. MRI shows hypointense line in right femoral neck in T1 (a)- and T2 (b)-weighted images. Bone marrow edema is seen bilaterally in T2-weighted images

1.4.4.3 Labral Pathologies

Acetabular labral tear is recognized as a source of groin pain in athletes and can be observed in a variety of sports such as football, basketball, hockey, ballet, golf and tennis. Acute labral tears can be misdiagnosed as a muscle strain and cause delay in appropriate treatment. Labral tears may be associated with significantly decreased athletic performance and prolonged periods of missed play [56]. Evidence suggests that labral tears are associated with corresponding osteochondral lesions of the femoral head and may lead to early degenerative joint changes [57].

MR arthrography is the best imaging modality for evaluation of labral pathologies. Evaluation should also include chondral, capsular, and ligamentous pathologies. Although MR arthrography is a powerful tool for diagnostic accuracy, it is still not superior to arthroscopic evaluation. By the way, diagnosis of the labral tear might require confirmation via arthroscopy [58].

The labrum demonstrates low-intensity signals on both T1 and T2 images like organized collagen elsewhere in the body. Anterosuperior part of the labrum has lower compressive force durability and lower tensile modulus when compared with the other parts; therefore labral tears are likely to occur in this area. Increased intensity in the labrum in an asymptomatic athlete mostly signifies labral degeneration. However, significantly increased signal intensity with or without extravasation of the contrast agent inside the cartilage tissue is suggestive for a torn labrum (Fig. 1.20). MR arthrography shows high sensitivity and specificity for diagnosing labral injuries when compared with arthroscopy [59].
Fig. 1.20

43-year-old man with cam-type FAI. (a) Black and white arrowheads indicate complex labral tear in coronal T1-weighted MR arthrogram (MRA) image. (b) Articular cartilage layers became more distinguishable with traction. White arrows indicate the delamination tear of the acetabular cartilage, and black arrowhead indicates dislocation of intrasubstance labrum component of the complex labral tear. (Reprinted by the permission of Springer Berlin Heidelberg, Diagnostic performance of direct traction MR arthrography of the hip: detection of chondral and labral lesions with arthroscopic comparison. Schmaranzer F, Klauser A, Kogler M, Henninger B, Forstner T, Reichkendler M, Schmaranzer E. Eur Radiol. 2015 Jun;25(6):1721–30. https://doi.org/10.1007/s00330-014-3534-x)

There is a normal perilabral recess between the capsule and hip. This recess may not be seen in conventional MRI due to lack of capsular distension and might be confusing for evaluation. Moreover, small sub-labral sulcus in the posteroinferior site of the labrum may be seen and reported as a normal finding. It has also been shown that anterosuperior part of the labrum might be absent in older individuals; however identical findings in young and active athletes are highly suggestive for torn labrum [60]. Conclusively, normal variants and unique structure of the labrum should be known for accurate diagnosis.

1.4.4.4 Tendinous and Ligamentous Injuries

Among the athletes, myotendinous injuries are common and mostly are the result of a single traumatic event rather than overuse trauma. Gallo et al. concluded that return to sport rates following muscle strain and tendinosis are relatively high in professional athletes (90%) in asymptomatic athletes with incidental findings [61]. However, the contribution of the myotendinous injury to hip pain should be carefully evaluated, and the severity of the injury should be determined. In general, thickening and intratendinous signal enhancement is observed on T1-weighted images of injured tendons. Inflammatory response and surrounding edema can be detected around the affected tendon or fluid-filled defects inside the tendons in fluid-sensitive sequences like T2 and short tau (inversion time) inversion recovery (STIR) can be noted in partial tears [62]. Complete discontinuity of a tendon with accompanying tendon retraction denotes probable full-thickness tear.

Ligamentum Teres Injury
Tears of the ligamentum teres was first described by Gray and Villar in 1997 [63]. Ligamentum teres injury is a possible source of pain in an athlete. It may be identified in up to 51% of all arthroscopic interventions possibly because of increased awareness [64]. With increased understanding, the diagnosis of ligamentum teres pathologies has gained popularity. Arthroscopically, ligamentum teres ruptures are classified as complete, partial rupture or degeneration. The normal ligamentum teres is hypointense, homogenous and smooth in all MR sequences. Discontinuity of the normal appearance and lax positioning of the ligament instead of normal taut look refer to complete rupture. Partial tears and degeneration are shown to be similar to other ligamentous injuries with increased intraligamentous signal intensity (Fig. 1.21). MR imaging and MR arthrography both offer high sensitivity for the detection of complete ruptures; however, partial tears can be spotted more easily with MR arthrography [65]. On the other hand, some authors report that preoperative identification of ligamentum teres injuries is insufficient even with high-resolution MRI [66]. In another study, nine hips were diagnosed with LT tears based on preoperative MRI (seven of nine are according to MRA). Of these nine cases, LT tears were identified in only five at the time of arthroscopy; the remaining four were considered false positives when correlated with arthroscopy [64].
Fig. 1.21

65-year-old female with arthroscopically confirmed partial ligamentum teres tear. Coronal T2-weighted MRA images. (a) Black arrow shows undamaged part of the ligament. (b) White arrow points out the partially torn ligamentum teres. (c) Note the increased intraligamentous signal intensity which is the indicator of partial tear in axial proton density-weighted MR image with fat suppression (black arrowhead) and the partially intact ligamentum teres structure (black arrow). (Reprinted by the permission of Springer Berlin Heidelberg, Use of MR arthrography in detecting tears of the ligamentum teres with arthroscopic correlation, Chang, C.Y., Gill, C.M., Huang, A.J. et al. Skeletal Radiol (2015) 44: 361.  https://doi.org/10.1007/s00256-014-2082-4)

Hamstrings Injury

The hamstring tendon complex is formed by the biceps femoris, semitendinosus, and semimembranosus muscles. In professional football players, adductor injury is the most common type of injury and corresponds to 12% of all injuries with high (15%) reinjury rate [2, 67]. In addition, 10% of hamstring injuries are classified as severe (injury causing absence of over 28 days from training and playing) [2]. Therefore, such injuries are major concern for professional athletes representing large portion of time loss for return to sport.

As a normal tendinous structure, hamstring tendons are observed to be hypointense on T1 views. Modified Peetrons classification system is defined to evaluate severity of hamstring injuries [67, 68]. MRI evaluation as grade I (only edematous changes and ill-defined high-signal abnormality on T2-weighted sequences, “feathery” pattern), grade II (in addition to the edema, a partial tear is depicted, represented by a well-defined high-signal abnormality on PD-weighted and T2-weighted sequences), and grade III (complete tear) (Fig. 1.22). More than 50% of hamstring injuries occur in the biceps femoris muscle and mostly at the proximal muscle tendon junction [69, 70].
Fig. 1.22

MR image in a 23-year-old professional male football player with a sudden onset of posterior hip pain. T2-weighted coronal image shows longwise extending edema and hemorrhage (a); axial image (b) shows complete tear of the hamstring tendon (arrow) proximally close to its origin at ischial tuberosity

According to mechanism of injury, type I injuries are observed during high-speed running, and type II hamstring strains are mostly secondary to excessive lengthening of the hamstrings and mostly observed in sports such as dancing, slide tackling, and high kicking that combine hip flexion with knee extension [69]. Recovery from type II injuries has been shown to be prolonged when compared with type I injuries.

Many authors investigated the correlation between return-to-play time and severity of the hamstring injury on MRI. Schneider-Kolsky stated that only moderate and severe hamstring injuries are possible predictors of long rehabilitation period [71]. In another study, no association between time necessary to return back to sport and extent of edema-like changes on MRI in athletes with grade I hamstring injuries was found, probably because grade I injuries may show large variations of size and extent of edematous changes [72]. The British Athletics Muscle Injury Classification System was proposed in 2004 by evaluating not only extent of the injury but also the localization [73]. This classification system was developed to provide reliable information on player readiness to return back to play.

Proximal Rectus Femoris Injury
As a powerful knee extensor and hip flexor, the rectus femoris muscle is most frequently injured by excessive stretching [74]. The rectus femoris is located at anterior compartment of thigh as the most superficial muscle of the quadriceps muscles complex. Rupture occurs during the acceleration phase of running, jumping, and kicking or during contraction against resistance [75]. The myotendinous junction is the most common location of the tear; however imaging should include both origin and insertion of the tendinous parts to evaluate the extent of the edema. The rectus femoris has two tendinous origins, the direct or straight head, which arises from the AIIS, and the indirect or reflected head, which arises from the superior acetabular ridge and the posterolateral aspect of the hip joint capsule. The two heads join and form a conjoined tendon. Proximal rectus femoris strains mostly occur at the junction of the conjoint tendon with the muscle belly. Fluid collection and gap between the fibers might be observed in severe injuries (Fig. 1.23) [76].
Fig. 1.23

A 25-year-old woman with sudden onset of hip pain that occurred while sprinting. T2-weighted MR images with fat saturation in (ad) axial cuts show fluid collection around the direct (white arrows) and indirect (red arrows) heads of rectus femoris which is observed in severe injuries. (e) Coronal plane shows complete rupture (white arrow) of the rectus femoris. (Reprinted by the permission of Springer Berlin Heidelberg, Imaging of rectus femoris proximal tendinopathies, Pesquer, L., Poussange, N., Sonnery-Cottet, B. et al. Skeletal Radiol (2016) 45: 889.  https://doi.org/10.1007/s00256-016-2345-3)

Athletic Pubalgia

Athletic pubalgia is an umbrella term which accounts for pain originated from pubic symphysis area and radiates into groin region such as rectus abdominis insertion, hip adductor tendons, and symphysis pubis joint. The term was formerly used as “sports hernia,” as well as “Gilmore’s groin,” “hockey gut,” “slap shot gut,” and “core muscle injury.”

The pubic symphysis is formed by two bones and a hyaline cartilage disc in between them [62]. There are numerous ligaments and tendons attaching to the pubic complex to provide stability. Evaluation of the underlying pathology is only possible by understanding the dynamic relations of associated ligaments and tendons. For this reason, use of the term “osteitis pubis” in athletes simply describes an empiric sign or a radiologic finding rather than an actual diagnosis [77]. Athletic pubalgia accounts for around 4% of groin injuries in professional soccer players [2]. A wide aponeurotic plate provides numerous connecting points for tendons and ligaments. In case of injury, partial avulsion of the plate or related damage should be evaluated carefully.

Tears or surrounding edema of the aponeurosis and attached muscles can be observed in fluid-sensitive MRI images (STIR-T2) [78]. Separation of the aponeurotic plate forms a cleft shape containing fluid inside and named as the secondary cleft sign. Pathology can be demonstrated by performing a symphysography. Filling of the cleft following contrast injection can be visualized (Fig. 1.24). However, visualization of secondary cleft sign on MRI has only moderate sensitivity (57%) and specificity (60%) for diagnosing aponeurotic injury [62, 79].
Fig. 1.24

Patient with left thigh pain; (a) symphysography shows the accumulation of contrast medium into the cleft at inferior pubic ramus. (b) Coronal T1 MR image in the same patient confirms left-sided secondary cleft sign. (Reprinted by the permission Springer-Verlag, “Superior cleft sign” as a marker of rectus abdominus/adductor longus tear in patients with suspected sportsman’s hernia, Murphy, G., Foran, P., Murphy, D. et al. Skeletal Radiol (2013) 42: 819.  https://doi.org/10.1007/s00256-013-1573-z)

Tendon avulsion and related retraction of the tendon should be carefully assessed. Bone marrow edema inside pubic bones can be observed as hyperintense signals which are present in almost 50% of athletes with athletic pubalgia and can be a significant clue for recognizing the pathology [79]. Reduced tendon diameter and observable muscle atrophy compared with the contralateral side are mostly seen in tendinopathies and often associated with aponeurotic injuries.

Chronic changes of pubic complex secondary to injury should be well recognized by the physician for both follow-up measurements and performance evaluation. Osteophyte formation, osseous asymmetries, and sclerosis accompanying with or without aponeurotic plate damage might possibly be observed in athletes with osteitis pubis. Osteitis pubis is a painful overuse stress injury of pubic symphysis and parasymphyseal bone due to chronic overloading stress [80]. Usually there is no precipitating event and begins insidiously. Because of the frequency of concomitant pelvic pathologies, a variety of clinical tests may be positive on clinical exam, but tenderness to palpation over the symphysis, positive resisted adduction test, and the hop test are most sensitive to osteitis pubis [81]. Osteitis pubis is most commonly presented as a hyperintense T2 signal within the symphysis and parasymphyseal bone [80, 82].

1.5 Conclusion

Hip and groin pain in athletes is becoming more common, likely due to increased understanding of differing pathologies about the hip and groin but also possibly due to early sports specialization. As the area is deep and has complex and overlapping anatomy, evaluation of the hip and groin may be difficult. A careful history and physical examination are critical to the evaluation of the athlete with hip and/or groin pain. An understanding of the pathophysiology of these injuries is also helpful. Properly performed conventional radiographs are essential in the evaluation of these athletes. Appropriate imaging, such as MRI, MRA, CT, and ultrasound, can be essential in the evaluation, diagnosis, and then planning of management of these patients.

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Copyright information

© ISAKOS 2019

Authors and Affiliations

  • Yiğit Umur Cırdı
    • 1
  • Selim Ergün
    • 2
  • Mustafa Karahan
    • 2
  1. 1.Erciyes University School of Medicine, Department of Orthopedic SurgeryKayseriTurkey
  2. 2.Acıbadem Mehmet Ali Aydınlar University School of Medicine, Department of Orthopedic SurgeryIstanbulTurkey

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