– Written by Marcelo Bordalo, Brazil, Eduardo Yamashiro, Maryam Rashed Alnaimi, and Javier Arnaiz, Qatar

Imaging is an important arsenal in football medicine for guiding diagnosis, monitoring and treatment of sports injuries. An accurate diagnosis is required to design appropriate treatment and to determine prognosis in football players¹. Imaging modalities are also utilized to guide interventional procedures in the treatment of several injuries. 

Imaging methods have been around for a while, but they constantly undergo technical advances, which improve lesion characterization and accuracy. The three pillars for an adequate diagnosis in high level football medicine are experience of the musculoskeletal radiologist, applicable techniques and up-to-date equipment.

Football injuries can be acute or chronic from repetitive stress (overuse). In the professional level, ultrasound (US) and magnetic resonance imaging (MRI) are the methods of choice. Table 1 shows the major indications and disadvantages for the several imaging modalities.

Return to play decision is fundamental to the practice of football and must balance a fast return to play with complete healing, recovery, and re-injury risk. Recent studies on medical imaging focus on prognostic radiologic features to support this challenging multifactorial decision^2-4.

Lower extremity injuries are more common in football. In this chapter, we will review imaging aspects of the most frequent and important injuries in football players.

GROIN PAIN

Groin pain is a common problem in football players (10-14% of all injuries)^5,6. The term groin pain in athletes is defined by four clinical conditions: (1) adductor, (2) pubic, (3) inguinal, and (4) iliopsoas-related groin pain (Figure 1), according to the “Doha agreement meeting on terminology and definitions in groin pain in athletes”⁷. Hip joint injuries and other conditions (sacroiliitis, nerve entrapment and intra-abdominal abnormalities) can also cause groin pain and must be referred and managed. Diagnosis is based on clinical history and examination. Imaging will help in the diagnosis and classification of which condition (s) the injury applies.

Adductor-related is the most common cause of groin pain is football players^8,9. A combination of rectus abdominis and adductor longus strains are predominantly found. The injury can extend to the rectus-adductor aponeurosis at the symphysis pubis. US is the first-line image modality and MR gives a more detailed analysis. These methods can demonstrate adductor tendon abnormalities such as inflammation or ruptures (Figures 2, 3, 4). Cortical irregularities and calcifications are common in asymptomatic athletes (Figure 5). 

There is a close anatomic relationship between adductor tendons and the pubic symphysis. On imaging, pubic-related groin pain condition is seen on MRI as pubic bone edema, which may also occur along with other groin pain conditions⁹. It is important to state that subtle pubic bone edema on MRI is also frequently seen in asymptomatic athletes. However, as the athletes become more symptomatic, bone edema increases and other features are present, such as fluid within the pubic symphysis joint and periarticular edema (Figure 6). Chronic features (pubic spurs and cortical irregularities) are commonly present in athletes with a past history of groin pain (Figure 7). It is accepted that the pubic-related groin pain entity is on a spectrum of stress changes from asymptomatic athletes to degenerative changes in chronic cases.

In the iliopsoas-related groin pain, MRI and US can demonstrate iliopsoas tendinopathy and bursitis (Figure 8). 

US is the best imaging modality to evaluate inguinal-related groin pain. Although rare in athletes, dynamic US is highly accurate to diagnose inguinal and femoral herniation (Figure 9). Inguinal wall motion is present in many symptomatic and asymptomatic athletes, making clinical correlation mandatory. MRI is usually normal in the evaluation of the inguinal region.

MUSCLE INJURIES

Technical advances in US technology provided some advantages in the evaluation of muscle injuries, compared to MRI: relatively cheap and widely available, comparable spatial resolution, allows portability, dynamic evaluation, serial evaluation to follow healing and real-time guidance for muscle injections. However, MRI is considered the reference imaging method to assess muscle injuries in athletes due to excellent contrast, high resolution, and the ability to evaluate soft tissue. Also, MRI provides better evaluation of deep muscle compartments and demonstrates scar tissue formation at the site of injury. 

US features of muscle injuries are loss of fascicular pattern with fiber disruption, hypoechoic and/or hyperechoic focal areas within the muscle and focal or complete fiber discontinuity. Usually, fiber discontinuity occurs at the myofascial junction or around the musculotendinous junction, however it can occur at any location within the muscle (Figure 10). MRI most classic feature of muscle injury is diffuse ill-defined high signal intensity change (called “edema”) on fluid-sensitive sequences. When edema is found around the musculotendinous junction, we may have the classic “feathery” appearance (Figure 11). Fiber discontinuity is seen as a focal area of well-defined high signal intensity (Figure 12). Muscle injuries may also occur far from the musculotendinous junction and at the peripheral myofascial junction¹⁰ (Figure 13).

There are several imaging classification systems for muscle injuries (table 2)^11-14. The classic 1-3 classification system lacks diagnostic accuracy and provides limited prognostic information. The grade 1 injury is defined as edematous pattern without muscle disruption on MRI. US can be negative or show ill-defined areas of increased echogenicity. Grade 2 is defined as an area of focal fiber disruption and grade 3, complete disruption of the musculotendinous unit with fluid (hematoma) filling the gap created by the tear¹⁰ (Figures 14 and 15). However, the presence of intramuscular hematoma can also occur in muscle contusions and grade 2 tears.  Dynamic evaluation of muscle tears on US is useful to evaluate the presence of fiber disruption. The Munich consensus on classification of muscle injuries included grades according to the cause of the injury¹³. Another recent classification system is based on extent and location of injury (myofascial junction, intramuscular and tendinous)¹⁴. Adequate staging of the muscle injury is crucial, avoiding underestimation of the injury and consequent recurrent muscle tear because of a premature return-to-play.

Hamstring musculotendinous tears are the most common injuries in football, representing 10-37% of all injuries^6,15. The hamstring complex is in the posterior compartment of the thigh and includes the semimembranosus, semitendinosus, and biceps femoris muscles. In football, the most injured muscle is the biceps femoris and over half of the cases involve more than one hamstring muscle. Most frequently, the proximal and distal musculotendinous junctions are injured^6,16 (Figure 16). Apophysitis and avulsion of the ischial tuberosity (the site of origin for the hamstring and hip adductor tendons) is seen most frequently in skeletally-immature players¹⁷ (Figure 17).

Some imaging findings are associated with a longer rehabilitation time: the presence of injury at MRI, injury of the proximal or intramuscular tendon at the deep musculotendinous junction and greater longitudinal length of the muscle injury^1,4,16(Figure 16). A negative-MRI is associated with a favorable recovery prognosis¹¹. However, based on the current literature, MR and US findings alone do not provide accurate information for prediction of time to return-to-play after a muscle injury¹⁸.

The rectus femoris is the most frequently injured muscle of the quadriceps complex. Injuries are located at the origin of the direct and indirect heads, proximal musculotendinous junction, deep musculotendinous junction of the indirect head and distal musculotendinous junction close to the knee joint¹⁹. More common injuries are located in the deep musculotendinous junction of the indirect head and are related to a longer return-to-play time^20,21. The “bull’s-eye” pattern is the most frequently observed finding in MRI^20,22 (Figure 18). A specific kind of lesion, the degloving injury, is seen in 9% of rectus femoris tears whereas the inner bipennate intramuscular portion of the indirect musculotendinous complex is separated from the surrounding superficial unipennate portion of the rectus femoris²³ (Figure 19). Acute avulsion fractures and chronic traction apophysitis of the origin of the direct head at the anterior inferior iliac spine are more common in skeletally-immature players^17,24 (Figure 20).

KNEE INJURIES

Knee is frequently injured in football (18% of all injuries)^5,6. The knee joint is exposed to elevated risk of injury, either acute trauma or chronic overuse injuries and is subject to stress from indirect and direct forces. Usually knee injuries have a worse effect on return-to-play and accelerate development of knee osteoarthritis²⁵.

Anterior cruciate ligament (ACL) tears are prevalent in children and women and MRI is the modality of choice for its evaluation. The pivot-shift is the most common noncontact mechanism involved in ACL injury, creating the typical osseous contusions of the anterior lateral femoral condyle and posterior aspect of the lateral tibial plateau (Figure 21). On acute phase, ACL injuries typically produce hemarthrosis, focal ligament discontinuity or diffuse thickening and edema. Also, abnormal ligament fiber orientation is seen (Figure 22). Secondary MRI signs are anterior translation of the lateral femoral condyle, uncovering of the posterior horn of the lateral meniscus and PCL buckling²⁶.

Meniscal tears in football players are usually secondary to acute trauma, isolated or associated with ACL or chondral injuries. They are most common at the posterior horn of the medial meniscus; however, in young patients with acute injuries, lateral meniscal tears are common. MRI is highly accurate for the diagnosis of a meniscal tear, which is classified according to its direction and location: longitudinal, vertical, horizontal and radial tears²⁷ (Figure 21). A meniscal ramp lesion is located at the meniscocapsular junction of the posterior horn of the medial meniscus and is strongly associated with ACL tears²⁸ (Figure 23). Identification of displaced meniscal tears on MRI is important in patient management and preoperative planning (Figure 24).

Medial collateral ligament (MCL) injury is the second more common type of injury in football, after hamstring injuries, although injury rates have decreased in the last decade. MCL injury is more commonly caused by contact than non-contact situations²⁹. MRI is the imaging modality of choice to demonstrate the three types of injuries: Grade 1: peri-ligamentous edema; Grade 2: thickened and edematous MCL and Grade 3: complete MCL tear (Figure 25). Although US is not frequently ordered to assess the MCL, US features for MCL tear have been described and dynamic maneuvers with valgus stress are useful for diagnosis of grade 3 tears³⁰.

Patellar tendinopathy is seen in skeletally mature football players, and describes a spectrum of disorders at the proximal insertion of the patellar tendon³¹. Diagnosis can be performed by ultrasound and MRI (Figure 26). 

Knee osteoarthritis is common in football players. However, studies show that this condition is less likely to cause functional disability³². The main predisposing factor for development of early osteoarthritis in football players is direct trauma with potential surgical consequences³³ (Figure 27).

ANKLE INJURIES

The ankle is commonly injured in football, corresponding to 14% of all injuries⁶. Acute injuries are common and related to inversion injury of the ankle. Imaging is performed in cases where clinical diagnosis and grading is difficult and when there is development of chronic sequelae³⁴. In the ankle, MRI has the advantage over US of providing a global assessment including osseous and chondral injuries. However, for confirmation of tendon and ligament disorders of the ankle, US is very useful.

Ligament injuries from inversion sprains are common, however ankle stability is maintained by muscle recruitment and scar tissue and treatment is mainly conservative. Lateral ligament injuries are more common than medial ligament and syndesmotic injuries (Figure 28).

Achilles tendon disorders are relatively common in football, however injuries have decreased in recent years because of understanding of injury biomechanics and consequent modification of training protocols. Both methods, US and MR, are indicated for assessment of the Achilles tendon (Figures 29 and 30). 

All types of ankle impingements syndromes are common in football players, especially 2-4 weeks after an acute injury. MR imaging is accurate for assessing soft tissue and osseous abnormalities involved in the impingement syndrome. US is more useful to correlate clinical symptoms with imaging findings.

IMAGE-GUIDED INTERVENTION

Image-guided therapeutic interventions provide minimally-invasive treatments and can be performed in the acute and chronic settings. Real-time imaging guidance of interventional procedures, such as articular joint and tendon injections is advantageous over blind techniques in terms of greater accuracy and effectivity (the needle is accurately placed and medication is injected in the right place), patient safety (lesser risks of complication due to reduced risk of inadvertent injury to adjacent structures), patient comfort (less postprocedural pain, faster recovery and shorter stay) and consequent increase in treatment cost-effectivity³⁵. Improvement of imaging modalities, new technologies and materials also made possible the development of new intervention techniques, such as viscosupplementation, platelet-rich plasma and stem cell therapies, that may become potential state-of-the-art treatments in the future³⁶ (Figures 31 and 32).

SUMMARY

Various injuries occur in football players, especially in the lower extremities. Imaging allows fast and accurate diagnosis for the athletes, facilitating treatment. Image-guided interventions are the mainstay of nonsurgical intervention in athletes and can be used to treat several injuries. 

Marcelo Bordalo M.D.

Radiologist

Hospital das Clinicas – University of São Paulo Medical School and Hospital Sirio Libanes

Sao Paulo, Brazil

Eduardo Yamashiro M.D. 

Radiologist

Aspetar Orthopaedic and Sports Medicine Hospital

Doha, Qatar

Maryam Rashed Alnaimi M.D. 

Radiologist 

Aspetar Orthopaedic and Sports Medicine Hospital

Doha, Qatar

Javier Arnaiz  M.D.

Radiologist

Aspetar Orthopaedic and Sports Medicine Hospital

Doha, Qatar)

Contact: dr.mbordalo@gmail.com

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