The Use of Musculoskeletal Ultrasound for the Diagnosis of Groin and Hip Pain in Athletes

Abstract

Athletes are particularly predisposed to injuries in the groin and pelvic region. Men in particular are predisposed to injuries like hernias in the inguinal region. The increased demands and training load on today’s athletes combined with individual factors may create the environment for these injuries. Five areas categorize the pain present from different pathological entities in this region: adductor-related, iliopsoas-related, inguinal-related, pubic-related, and hip-related groin pain. It has been extremely difficult in the past to accurately diagnose what has been previously labeled sports hernia, sportsman’s groin, or inguinal disruption. Therefore, this article describes the methods and procedures used for diagnostic ultrasound (US) and differentiation between these entities from one practice based on the most current research in musculoskeletal US.

Introduction

One particular area athletes are predisposed to injury is the abdomen, groin, or pelvic region. The increased demands and training load on today’s athletes combined with individual factors may contribute to groin or pelvic injuries. Based on a recent consensus statement in Doha, there are five areas that categorize groin and hip pain in athletes: adductor-related, iliopsoas-related, inguinal-related, pubic-related, and hip-related groin pain (¹¹). Pain in one area may be caused by two or more of these pathologies, and many times, patients have been through a gauntlet of orthopedic and surgical specialists before seeing us. Therefore, correct diagnosis relies on the exclusion of other pathological entities that also could be causing pain. This article will explain the methods and procedures used in this clinic for differentiating between adductor-related, inguinal-related, pubic-related, iliopsoas-related, and hip-related groin pain using dynamic ultrasound (US) testing. The methods for our diagnostic US procedure are based on current research in musculoskeletal US techniques (^2,7,10).

We specialize in identifying inguinal-related groin pain in our examination (also known as sports hernia, sportsman’s groin, or more recently, inguinal disruption) (⁸) and will be a primary focus of this article. There is much controversy about the nomenclature of this injury because it is not a true hernia — it is generally accepted that it is a weakness of the posterior wall of the inguinal canal (^8,11). Because the posterior wall of the inguinal canal is continuous with the transversalis fascia, we have chosen to use the term transversalis fascia diastasis (TFD) and this falls under the umbrella term inguinal-related groin pain. Although “inguinal-related groin pain” is a useful term when generalizing the location of groin pain, we feel the term TFD is more specific and more accurately describes the defect we are dealing with. This injury can be located anywhere within Hesselbach’s triangle, the same location as a direct hernia. TFD symptoms are only present in a dynamic setting where the patient is increasing intra-abdominal pressure that reproduces the diastasis and creates pain, much like a direct hernia, although more equivocal due to the defect not being a full tear.

Many imaging studies have their strengths and weaknesses with respect to groin pain in athletes. Multidetector computed tomography (CT) scanning, x-rays, and magnetic resonance imaging (MRI) scans can be used for bony and soft tissue irregularities to visualize fracture, arthritic degeneration, tears, effusion, edema, and others, but CT requires radiation exposure and MRI sometimes uses an iodinated contrast dye (³). It is our opinion that clinicians should use the less invasive and cheaper US imaging test to first assess the athlete’s pain along with history and physical examination before ordering these other tests. US is perhaps most powerful when assessing TFD because of the dynamic imaging abilities. This injury often presents with other injuries; therefore, accurate TFD diagnosis requires differentiation between other hip and groin pathologies as well as a dynamic test for symptom recreation to accurately assess the patient. We will discuss the use of US imaging with respect to TFD and differentiation between TFD and other injuries in the groin and hip area.

Physical Assessment

A discussion with the patient alludes to the pain intensity and location. This is used to guide the physical examination. In our experience, adductor-related groin pain and inguinal-related groin pain are often seen together and are common in high-level athletes especially in soccer, hockey, and football as these sports place high strains on the inguinal region, abdominal, and adductor musculature. We ask the patient to point to where most of the pain is and they will guide us to either the adductor origin or the inguinal region. If the pain is hard to place, a quick way to differentiate adductor-related groin pain from inguinal-related groin pain is the physical examination from Preskitt’s article (⁶). It is likely that this task may produce pain in the adductors and the inguinal region of the abdomen. The patient is instructed to lie supine on the examination table with knees bent and feet placed together flat on the table. The patient is instructed to relax and let the knees fall to the side. The clinician’s forearm is used as a bar between the knees. The clinician asks the patient to squeeze tight (reproducing adductor-related pain) or do a partial sit-up (reproducing inguinal-related pain) or combine the two to see if it is localized at the adductor region or just above at the inguinal region. Despite these maneuvers, sometimes the pain is still hard to pinpoint. This is where the dynamic US is helpful.

Patients also may present with muscle imbalances between hip adductor and abductor musculature. Adductor/abductor strength ratios are important to evaluate muscle imbalance as it has been shown to be a risk factor for injury (⁹). This can be assessed in multiple ways; we use a physical test to assess the abductor strength similar to the test described in ref. (⁹) without the handheld dynamometer, and a step-down test in high-level athletes to determine adductor/abductor and thigh balance and strength. The step-down test starts with the patient standing on a box approximately 8 inches high with one leg while the other leg is dangling off the side. The patient is instructed to lower oneself to the ground and touch the ground with the heel of the free leg (similar to a single leg squat only performed standing on a box). The patient is instructed to place their hands on their hips and slowly lower themselves while trying to keep the knee of the loaded leg from diving inward, the chest from dipping forward, and the iliac crests level. If they cannot perform the step-down test without doing one or all of these movements above, or they cannot touch their dangling heel to the ground, the patient may be considered to have muscle weakness or imbalance predisposing them to injuries of this sort. The step-down test is usually reserved for advanced athletes because of the exercise difficulty, and the authors do not recommend this test to be used for older individuals. This test is useful to evaluate an athlete’s strength and balance during a more difficult task that more accurately emulates high-level sport performance.

Static and Dynamic US

Patients are asked to change into athletic shorts or gown, or cover themselves with a towel before the examination to allow easier access to the surface anatomy appropriate for the examination. Likewise, a medical chaperone should always be present during the duration of the examination, and an explanation of the examination should always be given to the patient before beginning the examination.

We prefer a flat linear 5 to 15 MHz probe but will use a lower frequency curvilinear probe if we have to. A curvilinear probe may be useful for visualization of deeper structures and a wider field of view as well as the attenuation of subcutaneous tissue in larger individuals with excessive amounts of subcutaneous fat. However, most of our patients are thin and very fit individuals so the resolution of the probe is key to help identify any abnormalities. Therefore, the flat linear 5 to 15 MHz probe is the probe of choice because it allows us to better visualize the fibrillar pattern of the tendons with less distortion of the anatomy than the curvilinear probe.

Pelvic-Related Groin Pain

Pelvic instability is assessed with pubic symphysis evaluation. The patient is placed in a supine position and instructed to flex the knees with the feet on the table (a sit-up position), then the patient is asked to relax the hips and let the knees fall to the side. This opens up the joint and allows the clinician to visualize the pubic symphysis. The US probe is placed transversely over the pubic symphysis to visualize the joint and bony structures for bony irregularity, asymmetry, or fluid presence. We are looking for any diastasis, fluid, or joint swelling that would indicate an injury or infection. Sometimes, visualization of local blood flow using the Doppler setting on the US machine will elucidate hyperemia or neovasculature indicative of injury. This is sometimes found even in asymptomatic individuals, but this is not significant if there is no pain upon palpation or gentle pressure with the US probe. The patient is then asked to straighten the legs and perform alternating leg lifts approximately 6 inches off of the table. Visualizing the pubic symphysis in a dynamic test allows the clinician to see any joint movement or note if this activity reproduces the patient’s pain; normal patients have no movement in the pubic symphysis. If there is movement of the pubic symphysis and this reproduces pain, then they are positive for pelvic instability. If this test is negative, we move laterally and superiorly to the superior pubic ramus.

Musculotendinous Pathology

Adductor-related Groin Pain

An adductor tear or tendinopathy is especially common in athletes and should be a primary concern for the clinician when assessing a patient with groin pain. Moving the US from the pubic symphysis laterally and below the pubic tubercle allows the hip adductors to be evaluated. Static US examination identifies the gracilis medially closer to the symphysis; moving laterally, the adductor longus and brevis tendons lie superficial to the deeper adductor magnus. US allows the clinician to look for hypoechoic regions or dark spots suggesting tendinopathy in these musculotendinous structures. Cortical irregularities and Doppler blood flow also are helpful. The pectineus muscle is visualized more laterally and superficially. This is an easily identifiable muscle as it lies medial and posterior to the femoral artery and vein. It is an important landmark for femoral hernia diagnosis and will be discussed more in the Hernias section. If there is no evidence of hypoechoic regions on the US for these sites or the other adductor muscles, the clinician can move to the next region (Fig. 1).

Figure 1: Hypoechoic region of the adductor longus shown by an arrow. This hypoechoic region or “dark spot” is indicative of a tendinopathy. RA, rectus abdominis; PR, pubic ramus; SC, spermatic cord; AL, adductor longus. Note the orientation of the probe and placement in the body diagram in the bottom right.

Rectus Abdominis

After the adductor musculature is evaluated for tendinopathy, the US probe is moved back above the pubic ramus so the rectus abdominis can be evaluated. Tendinopathy is indicated as a hypoechoic region on the US at the tendon insertion site of the rectus abdominis. It is important to note the continuum of fibers from the adductor longus to the rectus abdominis tendon since any break in this usually is a source of pain and can precede the development of a direct hernia or TFD.

If the US is negative for hypoechoic regions suggesting tendinopathy at the rectus abdominis insertion, the patient will then be checked for hernias and TFD.

Hernias

Hernia evaluations require the patient to repeatedly perform Valsalva maneuvers, which can be tiring and painful if there is a hernia present. The clinician should keep this in mind and allow rest between each Valsalva if needed. The maneuver should provide sufficient intra-abdominal pressures to see any herniation or diastasis on the US. This is critical for visualizing the hernias as sometimes they can be inconspicuous and go unnoticed with lesser intra-abdominal pressures. The patient is instructed to blow on the back of their hand as if they were blowing up a balloon. This avoids confusion and gives the patient a good concept of the Valsalva maneuver while also reducing test ambiguity. Likewise, the patient can hold this with sufficient pressure for longer time periods as needed.

Femoral Triangle

The US probe is moved laterally and inferiorly following the pubic ramus to the femoral triangle. The femoral triangle is an area where the neurovascular bundle travels from the abdominal cavity into the thigh. This fossa between the abdomen and the thigh is a weak point, which is susceptible to hernias. The femoral nerve, artery, and vein that travel through the femoral triangle can be visualized on the US usually without the Doppler setting (the pneumonic NAVEL is used to remember nerve, artery, vein, empty space, and lymphatic). The structure of the femoral nerve is most lateral in the neurovascular bundle. If the acetabulum and femoral head are visible, the probe is moved back medially to find the femoral triangle. The pectineus muscle is noted deep and medial to the femoral triangle and should be examined for tendinopathies as well, although this is rare in our experience. For femoral hernias, the patient is asked to perform a Valsalva maneuver while the probe is over the empty space. If a femoral hernia is present, a bulge will be visible during the Valsalva maneuver medial to the femoral vein and traveling out toward the US probe. If the patient is negative for a femoral hernia, we move the probe superior and medially to evaluate for sports and direct hernias.

Direct Hernias and TFD

The direct hernia is a disruption or tear of the transversalis fascia where a bulge can be seen or felt by the clinician in Hesselbach’s triangle. This diagnosis is often unequivocal on US and can be seen as the abdominal contents protruding through the defect. TFD, on the other hand, is stretching or ballooning of transversalis fascia that occurs in Hesselbach’s triangle instead of a complete tear and therefore a bulge may not be seen or felt upon palpation. Explicitly stated, a direct hernia and TFD occur in the same location within Hesselbach’s triangle and both protrude with increased intra-abdominal pressures, but the direct hernia is a tear in the transversalis fascia that the abdominal contents can penetrate through, whereas the TFD is not a tear but a weakness that balloons outward without completely tearing. One could think of a direct hernia analogous to a herniated disc and a TFD analogous to a bulging disc. For a detailed description and diagram of the anatomy of this region, see ref. (^2,4). TFD is better visualized under dynamic US because the pain is typically present only during strenuous activity, which significantly increases intra-abdominal pressure. The direct hernia or TFD is not seen on US unless the patient performs a Valsalva maneuver.

To evaluate for TFD and direct hernias, we move the probe above the pubic ramus to visualize the abdominal wall. The symptoms occur in Hesselbach’s triangle that consists of the inguinal ligament inferiorly, the lateral border of the rectus abdominis medially, and inferior epigastric artery laterally. These are the most important landmarks for localizing and identifying TFD. If the clinician cannot visualize the inferior epigastric artery, the probe can be moved superiorly toward the umbilicus where the inferior epigastric artery travels. Once the artery is visualized, the clinician can follow it inferiorly to the branching site off the external iliac artery. Another important landmark in men is the spermatic cord above the inguinal ligament. The spermatic cord can be seen as an oval (oval in a transverse view) hyperechoic region that runs along the inguinal ligament and is superficial to the inferior epigastric artery. The round ligament in women also can be found this way but is quite difficult to see when the clinician is just starting to learn the techniques. All of these structures are important for identifying a direct hernia or TFD with US.

The clinician identifies the borders of Hesselbach’s triangle as described above. Once the probe is in the correct position and these anatomical structures are visualized, the patient performs a Valsalva maneuver. The rectus abdominis will enlarge with the Valsalva maneuver, but in normal healthy patients, one should not see any diastasis of the abdominal contents or any movement of the inferior epigastric artery and spermatic cord. However, if the patient does have TFD, the clinician can see the diastasis of the abdominal contents as it pushes between the rectus abdominis and the inferior epigastric artery. This pushes the artery and spermatic cord (in men) superficially and laterally as the abdominal contents are causing the diastasis. In the poorly conditioned individual, the diastasis can tent or move the rectus abdominis medially. The bladder also can move in the diastasis with the Valsalva maneuver. However, we have found in the well-trained athlete that the ballooning of the fascia with movement of the cord laterally is the defining characteristic of TFD on dynamic US.

Indirect Inguinal Hernia

An indirect inguinal hernia is common in men because of the intrinsic factors of the male anatomy. The testes are provided with blood supply and innervation from the spermatic cord, which includes the neurovascular bundle that runs with the ductus deferens through the abdomen to the testes. The spermatic cord must run through the abdominal wall to enter the scrotum. There are two foramina of the inguinal canal that allow passage of the spermatic cord from the abdomen to the scrotum: an internal and an external inguinal ring. An indirect inguinal hernia is a dilation of the internal inguinal ring so either fat mass or abdominal contents can travel through the inguinal canal sometimes all the way down into the scrotum. Inguinal hernia indications include complaints of pain in the abdomen, groin, and scrotum (for men) with Valsalva maneuvers such as coughing, sneezing, or lifting. This has been traditionally diagnosed by palpating the external inguinal ring and having the patient cough or bear down (¹). The clinician is trying to feel for abdominal contents traveling through the inguinal canal and out the external inguinal ring. The findings with this physical examination are sometimes equivocal because the abdominal contents may not travel all the way down the inguinal canal to the external inguinal ring. Therefore, the clinician may not be able to feel the hernia upon palpation of the external inguinal ring, but the indirect inguinal hernia can be seen on a diagnostic US examination regardless of how far it travels down the inguinal canal when the probe is placed properly (⁴).

US evaluation of the indirect inguinal hernia starts by examining the inguinal ligament and spermatic cord. Move the US probe from the direct hernia site following the spermatic cord laterally until the internal inguinal ring is visualized just lateral to the origin of the inferior epigastric artery. The patient is instructed to perform a Valsalva maneuver again while the probe is over the internal inguinal ring. This should be done in both long and short axes. In a normal patient, the internal inguinal ring should not change size and there should be no evidence of protrusion from the abdominal contents. The clinician should look for the internal inguinal ring dilating and abdominal contents coming up and over the inferior epigastric artery and protruding toward the US probe into the inguinal canal. This defines an indirect inguinal hernia (Fig. 2 and 3).

Figure 2: US image of the sports hernia site at rest (without a Valsalva maneuver). RA, rectus abdominis; A, external iliac artery; V, external iliac vein; SC, spermatic cord; TF, transversalis fascia. The arrow indicates the edge of TF and the area where the diastasis occurs.

Figure 3: US image of the sports hernia site with the patient performing a Valsalva maneuver. RA, rectus abdominis; A, external iliac artery; V, external iliac vein; SC, spermatic cord. The arrow indicates diastasis of the transversalis fascia shown protruding into the diastasis causing deformation of the spermatic cord. This is the defining characteristic of a sports hernia.

Hip Pathology

During a normal US examination, we will assess the iliopsoas-related groin pain and related musculature superficial to the hip joint first as several pathologies including snapping hip syndrome, iliopsoas bursitis, and tendinitis can occur. First, move the US probe laterally following the inguinal canal over to the patient’s anterior superior iliac spine where the sartorius muscle originates scanning for hypoechoic regions. Continuing inferiorly to the anterior inferior iliac spine, the rectus femoris is seen and evaluated for hypoechoic regions. Next, the probe is moved medially and inferiorly to visualize the iliopsoas muscle and tendon. These are evaluated for hypoechoic regions or edema indicating tendinopathy. The iliopsoas bursa deep to the tendon may be seen with edema and excess fluid indicating bursitis. Other US images and probe orientation for the iliopsoas examination and muscles around the hip are described in better detail elsewhere (⁵).

Next, the hip joint is evaluated. If the depth setting on the US machine is not set deep enough from examining the superficial musculature, it is adjusted so the acetabulum, labrum, and femoral head are visualized. The joint is evaluated for bony irregularities, joint space narrowing, swelling, edema, and acute injuries such as labral tears. Bony abnormalities on the acetabulum, head, or neck of the femur can cause labral tears or femoral acetabular impingement syndrome and soft tissue damage. The clinician is looking for any of these bony irregularities or abnormal joint spacing, and swelling on the US. Although US imaging is good to see some of the superficial bony and cartilaginous hip structures, it may not do as well with the deeper structures. As such, hip US examination should not replace x-ray or contrast MRI for the diagnosis of hip pathology as the latter two imaging techniques each have their own benefits for hip pathologies. Merely, US is used to gain further insight into possible injuries, probable cause for ordering other imaging studies, and to rule out soft tissue pathologies.

Conclusion

This article discusses some areas of interest and basic imaging tests for the evaluation of groin pain with dynamic US. Identifying inguinal-related groin pain (direct hernia or TFD) has been extremely challenging in the past, but with this US technique, clinicians have the ability to perform dynamic tests while imaging the site of pathology thereby reducing the diagnostic error rate. It is important to note that the US examination may not follow the exact sequence of anatomical locations. We may spend more time in one area depending on what the history and physical examination tells us. This is part of the use of the US examination. If warranted, the clinician can move the probe around as they see fit, but the authors urge the beginner musculoskeletal ultrasonographer to stick to this sequence developed by Van Holsbeeck (¹⁰) so as not to miss concomitant pathology.

While US use is necessary for diagnosis of TFD and is useful in other pelvic and hip pathologies, it is a skill that takes time to develop. Orientation and landmark identification are the keys to success. Diagnostic US is becoming increasingly popular as its multitude of uses is being elucidated. The use is apparent with TFD and can be an extremely useful tool for musculoskeletal diagnostics in the hands of a skilled clinician.