**6.3 Gluteal tendons**

*Tendons*

recovery (IR) images [23].

**6.2 Ultrasound examination technique**

MR sequences of the entire pelvis and unilateral symptomatic hip. Imaging sequences of the hip are performed with bilateral legs placed in 15° of internal rotation. Hip MRI generally includes the following imaging sequences: non-fat saturated T1WI, fat saturated T2WI, PD fat saturated images and inversion

Examination can be divided in the following approaches [24, 25]:

1. Anterior hip: Patient lies supine with hip in neutral position. Examination starts with the anterior synovial recess, for which the transducer is placed over the femoral head in the oblique longitudinal plane. Examination continues with identifying the anterior glenoid labrum, located cranially in this plane, and the iliofemoral ligament that lies superficially in relation to the labrum. Next, the transducer is placed at the interphase between the femoral head and the joint space to examine the iliopsoas muscle and tendon. The neurovascular bundle and the iliopectineal eminence are used as anatomical landmarks to identify these structures. Lateral to the neurovascular bundle, the iliopsoas muscle is visualized. The iliopsoas tendon lies deep within the bellies of the muscle and on top of the iliopectineal eminence.

The adjacent bursa is identified if there is a pathologic process present.

transversus abdominis and internal oblique muscles.

2.Medial hip: Patient remains in the supine position, now with abduction and external rotation of the hip and flexion of the knee. Examination starts in the long axis plane to scan over the insertion of the iliopsoas tendon at the lesser trochanter of the femur. Next, the adductor muscles are evaluated in the axial plane. The muscles of the medial hip compartment are divided in three layers. The adductor longus is located at the lateral aspect of the superficial muscular layer, while the gracilis is located at the medial aspect. The adductor brevis makes up the intermediate muscular layer and the adductor magnus makes up the deep muscular layer. Scan continues in the long axis plane with the transducer moved along the abductor muscles to identify the abductor longus tendon, using the pubic bone as reference landmark. The adductor longus tendon insertion is identified as a hypoechoic triangular structure. Lastly, the transducer is placed over the pubis in the transverse plane, from which oblique longitudinal plane is achieved to evaluate the tendon complex formed by the

3.Lateral hip: The patient is moved to the lateral decubitus position, lying on opposite hip of interest. With this examination, the following structures are evaluated: abductor muscles, gluteus medius, gluteus minimus, and tensor fascia lata. To begin, the transducer is placed over the greater trochanter. Scanning is performed in the transverse and longitudinal planes. The gluteus medius, seen as a curvilinear fibrillar band, lies superficial to the gluteus minimus. The tensor fascia lata serves as an anatomical landmark to identify the gluteus muscles, which is visualized as a superficial hyperechoic band in the coronal plane.

4.Posterior hip: Evaluated with the patient in the prone position. Important structures to evaluate include: the hamstring muscles and the sciatic nerve. Examination starts in the transverse plane with the transducer positioned at the ischial tuberosity to identify the hamstring tendon complex, where no distinction can be made between each individual tendon. The sciatic nerve is a lateral flattened structure with fascicular echotexture. As the transducer is

**26**

The gluteus medius and gluteus minimus tendons are part of the lateral compartment of the hip. The gluteus medius tendon inserts at the lateral and superoposterior facets of the greater trochanter of the femur, while the gluteus minimus tendon inserts at the anterior aspect of the greater trochanter. Ultrasound shows the gluteus medius tendon as a hyperechoic structure arising from a fan shaped hypoechoic structure that represents the gluteus medius muscle. The gluteus medius and minimus muscles are separated by an echogenic layer of fascia and adipose tissue [26].

The gluteus medius and minimus are the most commonly affected tendons of the hip abductor group that cause greater trochanteric pain syndrome [28]. Gluteus tendon abnormalities may be due to acute injury or chronic wear and tear of the hip joint. Therefore, it typically affects women in the middle and elderly age groups.

MRI is the gold standard imaging modality for the identification of gluteus tendon tears (**Figure 6**). Axial and coronal T2W fat saturated images of the hip and coronal T1WI of the pelvis are recommended when abductor tendon pathology is suspected [29]. MRI diagnostic criteria for tendon tears include discontinuity of the tendon, elongation of the gluteus medius 2 cm or greater and T2 hyperintensities superior to the level of the greater trochanter of the femur [27]. Additional MR findings, although nonspecific, may include atrophy of the adipose tissue, changes of the adjacent bone structures and fluid collection within the bursa.

### **Figure 6.**

*T2 fat saturated axial image shows a full thickness tear of the gluteus medius tendon as a fluid-filled defect along the greater trochanter.*

### **6.4 Iliopsoas tendon**

The psoas major and iliacus muscles form the iliopsoas tendon complex. The psoas major originates at the transverse processes of L1-L5 vertebrae; while the iliacus muscle has various origins, including the superior two thirds of the iliac fossa, the anterior sacroiliac ligaments, and the anterior sacral ala. This tendon complex inserts at the lesser trochanter of the femur.

The iliopsoas tendon has an echogenic sonographic imaging appearance, with anterior extension in relation to the anterior-superior acetabular labrum [28]. On MRI sequences, the iliopsoas tendon complex is characteristically identified as two parallel homogeneously hypointense structures, separated by a hyperintense region that represents adipose tissue of the fascia [28].

Snapping iliopsoas tendon is characterized by an audible or palpable painful snap with movement of the hip. Repetitive movements of the hip serve as predisposition to develop a snapping tendon, such as those performed by young athletes in different sports, with ballet dancers being the most commonly affected [30]. Iliopsoas tendon as the source of a snapping hip is classified as an internal cause of the broader term snapping hip syndrome. It may get trapped during movement due to a prominent iliopectineal eminence, an insertion site osseous projection or the anterior inferior aspect of the iliac spine [30].

Dynamic evaluation of the hip joint with US and MRI allows the identification of the source of snapping iliopsoas tendon. Sonographic evaluation is performed with a high-frequency transducer (linear 5–12 MHz) placed in the transverse oblique plane, above the hip joint and parallel to the pubis [28]. The patient is in the supine position, with initial static evaluation performed following the iliopsoas tendon until reaching its insertion at the lesser trochanter. Dynamic evaluation is performed while the ipsilateral leg is moved from the "frog leg" position (extension, adduction, and internal rotation) to the neutral position (flexion, abduction, and external rotation). The position of the iliopsoas tendon can be traced along the anterior compartment of the hip as the leg is moved from the aforementioned positions and snapping occurs. Regarding MRI examination for this particular pathology, fast GRE sequence allows dynamic evaluation of the iliopsoas tendon during movement [28]; change from "frog leg" to neutral position is also performed during this MRI sequence.

### **6.5 Hamstring tendons**

The hamstring tendon complex is located at the posterior compartment of the hip, formed by three muscles groups: biceps femoris, semimembranosus and semitendinosus. The biceps femoris is composed of a short and a long head. Origin of the short head is at the lateral linea aspera of the posterior femur, the lateral supracondylar line and the intermuscular septum [31]. The long head shares origin with the semitendinosus tendon at the inferomedial facet of the ischial tuberosity to form a conjoint tendon. Distal biceps femoris tendon inserts at the lateral fibular head and lateral condyle of proximal tibia, while the semitendinosus inserts at the anteromedial aspect of the tibia, sharing insertion with the gracilis and sartorius muscles to form the pes anserinus tendons [32]. The semimembranosus tendon originates at the superolateral ischial tuberosity and has several insertion sites through tendinous arms [31]. The anterior, direct, and inferior arms insert at the medial condyle of the tibia. The capsular arm inserts at the posterior oblique ligament. There is also insertion into the posterior joint capsule and arcuate ligament through the oblique popliteal ligament.

**29**

*Imaging of Tendons*

**7. Ankle**

**7.1 MRI protocol**

T2WI and IR sagittal images [34].

**7.2 Ultrasound examination technique**

*DOI: http://dx.doi.org/10.5772/intechopen.84521*

On MRI sequences at the level of the ischial tuberosity, the hamstring tendons are identified as well-defined round areas of low signal intensity, where the conjoint

The hamstrings are the most commonly injured muscle group in athletes, with tendon avulsion as the most severe injury diagnosed with medical imaging, requiring prompt surgical management. Avulsion injuries are defined as complete tear of the tendon from its osseous insertion site and typically affect the hamstrings proximally, particularly the conjoint tendon. This type of injury can include pulling of a bone piece by the torn tendon, which most commonly occurs in children due to presence of growth plates. MRI is the gold standard for examination of suspected hamstring tendon avulsion. Evaluation approach involves identifying the affected tendon and determining whether a partial or full thickness tear occurred. In the case of full thickness tears, distal tendon retraction, degree of underlying tendinopathy, and proximity of the tear to the sciatic nerve must be included in the evaluation approach [32].

The ankle tendons are visualized as low signal intensity structures in all MR sequences. The T1WI sequences are used to evaluate the anatomy and the T2W sequences are used to assess abnormal increase in fluid, usually related to tendon pathology [33]. Axial images are used to evaluate morphologic features of the tendons and synovial sheath distention, longitudinal splits, fluid within the tendon sheath, and adjacent soft tissue abnormalities, if any. For evaluating the Achilles tendon, sagittal images prove most useful. Sagittal images also assess the proximal-to-distal extent of tendon pathologies. Oblique coronal or short axis images at the level of the mid- and forefoot are best for assessment of the tendons distal to the ankle [33, 34]. When the normal tendons form an angle of approximately 55° with the main magnetic vector, it produces increased signal intensity within the tendons. This phenomenon is called the magic angle, more commonly in sequences with echo times less than 20 msec (T1WI, PD or GRE). This effect is particularly common with ankle tendons because of their curvatures around the ankle joint [33, 34]. For general purposes, an ankle MRI should include at least the following: axial T1WI or PD sequences and fat-suppressed T2WI, coronal T1WI or fat-suppressed

1.Peroneal tendon: Evaluated with the patient in the supine position with the knee semi-flexed and the ankle in internal rotation. For evaluation of the plantar aspect of the peroneus longus tendon, the patient should be in the prone position [35]. Both peroneal tendons are examined with linear transducers in their short and long planes. The transducer is placed behind the lateral malleolus over the tendons to examine their short-axis first. The transducer should be tilted along the way, to maintain the perpendicular position of the US beam. The tendons should be evaluated upwards for approximately

2.Posterior tibial tendon: Evaluated with the patient in a seated position with internal rotation of the plantar surface of the foot. If this position cannot be

5 cm and downwards into the inframalleolar region [34, 36, 37].

tendon is posteromedial to the semimembranosus tendon [31].

### *Imaging of Tendons DOI: http://dx.doi.org/10.5772/intechopen.84521*

On MRI sequences at the level of the ischial tuberosity, the hamstring tendons are identified as well-defined round areas of low signal intensity, where the conjoint tendon is posteromedial to the semimembranosus tendon [31].

The hamstrings are the most commonly injured muscle group in athletes, with tendon avulsion as the most severe injury diagnosed with medical imaging, requiring prompt surgical management. Avulsion injuries are defined as complete tear of the tendon from its osseous insertion site and typically affect the hamstrings proximally, particularly the conjoint tendon. This type of injury can include pulling of a bone piece by the torn tendon, which most commonly occurs in children due to presence of growth plates. MRI is the gold standard for examination of suspected hamstring tendon avulsion. Evaluation approach involves identifying the affected tendon and determining whether a partial or full thickness tear occurred. In the case of full thickness tears, distal tendon retraction, degree of underlying tendinopathy, and proximity of the tear to the sciatic nerve must be included in the evaluation approach [32].
