Calcaneal (traction) apophysitis or Sever disease is a common overuse injury of the calcaneal tuberosity in the immature skeleton. The calcaneal apophysis is the attachment site of the Achilles tendon. The apophyseal physis is unfused in children and adolescents and therefore forms a weak link to the bone. Repetitive and chronic forces placed on the apophysis by the tendon result in an accumulation of microscopic avulsions along the apophyseal physis with subsequent inflammation at the attachment site (Davis 2010a).

Calcaneal traction apophysitis is mostly seen in the 9–12 year age group (Chang et al. 2013; Hoang and Mortazavi 2012). Calcaneal apophysitis is usually a clinical diagnosis. Conventional radiography might be useful to rule out other causes of heel pain or to show fragmentation and sclerosis of the apophysis, which is indicative of Sever disease. However, neither conventional radiography nor MRI are helpful in the initial evaluation of suspected apophysitis of the calcaneus, as imaging abnormalities are also often observed in asymptomatic children. MRI is only valuable in the follow-up of this injury in patients not responding to conservative therapy, to exclude a calcaneal stress fracture (Chang et al. 2013).

Osteochondritis dissecans (OCD) of the talar dome, also referred to as osteochondral lesions of the talus, is a condition of the subchondral bone and overlying articular cartilage. OCD can result from a single trauma or repetitive microtrauma and is also associated with inversion injuries (Davis 2010a). These lesions usually occur at the medial or lateral aspects of the talar articular surface. The medial lesions typically affect the posterior third of the talar dome, causing a deep cup- or crater-like defect. Lateral lesions are more shallow and mostly occur at the middle third of the talar dome (Iyer and Thapa 2013).

Conventional radiographs may demonstrate a focal radiolucent area subjacent to the articular surface, which may contain a central fragment of bone (Chang et al. 2013). Although OCD of the talus can be diagnosed using conventional radiography, this is not helpful in the evaluation of stability of the lesion. Assessing the stability of the osteochondral fragment is essential as it influences management decisions.

MRI and CT are equally suitable for the detection or exclusion of OCD lesions (Verhagen et al. 2005). Both techniques have their own advantages. CT is valuable for preoperative planning, as it adequately depicts the true extent of the OCD lesion. Moreover this technique is widely available and has a short acquisition time. MRI has its value in assessing the integrity of the talar articular cartilage and to evaluate the stability of the osteochondral defect (Narvaez et al. 2003). The most reliable sign of an unstable OCD fragment is a high-signal line on T2-weighted images interposed between the talus and the fragment. Furthermore, defects to the cartilage greater than 5 mm, cysts underlying the lesion, and loose bodies can be detected (Iyer and Thapa 2013; Narvaez et al. 2003).

The most common injury to the lower extremity among gymnastic athletes is the ankle sprain (Caine and Nassar 2005). Inversion trauma generally occurs during dismounts and landing from great heights, resulting in lateral ligamentous injury. The ligaments often tear in a predictable sequence, affecting first the anterior talofibular ligament, then the calcaneofibular ligament, and finally the posterior talofibular ligament (Narvaez et al. 2003).

The majority of ankle ligament injuries are diagnosed clinically and no further examination is indicated. When confirmation of the diagnosis is essential or when osseous lesions such as osteochondral fractures are suspected, MRI is considered the modality of choice to evaluate the ankle ligaments (Narvaez et al. 2003). MRI protocols for assessment of the ankle structures include axial and coronal T1-weighted, proton density-weighted, and T2-weighted images. Morphologic changes and increased intraligamentous signal intensity within and around the ligaments on T2-weighted images are indicative of ligament tears. Additionally, secondary signs of acute ligament injury, such as bone bruises or extravasation of joint fluid into the adjacent soft tissues, can be detected (Narvaez et al. 2003).

Injuries of the medial ligament complex are less common and are often secondary to an inversion injury of the ankle. Posteromedial impingement is a cause of residual medial ankle pain subsequent to an inversion injury. During an inversion injury, the deep fibers of the deltoid ligament may become compressed between the medial wall of the talus and the medial malleolus (Giannini et al. 2013). This lesion can resolve without any symptoms. However, hypertrophic and fibrotic scar tissue may persist and can impinge between the medial talus and the malleolus (Cerezal et al. 2003). MRI demonstrates the lesion and hypertrophic soft tissues (Fig. 20.2). Additionally it may show evidence of subchondral bone bruising of both the medial talus and medial malleolus (Cerezal et al. 2003).

Traction apophysitis of the knee or Osgood-Schlatter disease is an overuse injury resulting from repetitive microtrauma to the insertion of the patellar tendon on the tibial tuberosity.

The apophyseal physis on the tibia is exposed to traction forces from the attached muscle. Repetitive and chronic submaximal forces at the site of attachment results in microscopic avulsion injury to the apophysis that exceeds the body’s capacity for healing. This overuse injury is referred to as traction apophysitis of the knee or Osgood-Schlatter disease.

It is most often seen in children 10–15 years of age who participate in sports involving jumping, running, and squatting (Chang et al. 2013; Stevens et al. 1999).

Conventional radiographs may reveal thickening and irregularity of the patellar tendon. Furthermore, fragmentation or irregularity of the tibial tubercle ossification center and soft tissue swelling can be seen (Chang et al. 2013). Ultrasound can be used to support clinical findings of traction apophysitis of the tibial tuberosity. The patellar tendon is often thickened and intratendinous calcifications can be detected. MRI features of Osgood-Schlatter disease include soft tissue swelling anterior to the tibial tuberosity, loss of the sharp inferior angle of the infrapatellar fat pad and surrounding soft tissues, thickening and edema of the inferior patellar tendon, and infrapatellar bursitis (Stevens et al. 1999).

Sinding-Larsen-Johansson disease is another traction apophysitis affecting the inferior pole of the patella, the proximal attachment site of the patellar tendon. As in Osgood-Schlatter disease, this injury results from chronic traction forces of the patellar tendon. Conventional radiography or MRI of Sinding-Larsen-Johansson disease demonstrates identical findings to Osgood-Schlatter disease, although they are seen at the lower pole of the patella (Davis 2010a).

Apophyseal avulsion fractures of the pelvis in adolescent competitive athletes occur most frequently in soccer and gymnastics. The apophyseal physis is the weakest site of the bone, especially in the pelvis as it tends to fuse later than many other epiphyseal centers (Vandervliet et al. 2007). The ischial tuberosity, the insertion site of the hamstring muscle group, is the most common site of injury in gymnasts. Injuries to other apophyseal locations such as the anterior superior iliac spine and the anterior inferior iliac spine are less common (Rossi and Dragoni 2001). The underlying biomechanics of avulsion injuries of the pelvis can again be divided into chronic and acute. Repetitive forces placed by the tendon on the unfused apophysis may result in an overuse injury referred to as traction apophysitis (Davis 2010a). Acute injuries to the ischial tuberosity in gymnasts are associated with sudden and excessive lengthening of the hamstring muscles during floor exercises (Rossi and Dragoni 2001).

Conventional radiography is the modality of choice in the imaging workup of suspected apophyseal injury. Clinical history and radiographic appearance may provide a definitive diagnosis. Acute avulsion injuries appear as a sharply marginated displaced fragment adjacent to its origin. However, the displacement of fragments can be subtle and requires attention to detail (Davis 2010a).

Traction apophysitis can demonstrate both irregularities or smooth margins of the bone or prominent bone formation. Additionally, areas of lysis and sclerosis can be seen secondary to healing of the repetitive microtrauma. These findings may be confused with more aggressive processes like neoplasm or infection (Stevens et al. 1999). Therefore understanding the underlying biomechanics of pelvic apophyseal injuries is essential and can help differentiate between these conditions. Additionally, CT or MRI may be helpful in the diagnostic process.

CT is also valuable in the follow-up of avulsion injuries as it is often the best imaging modality for bony structures (Chang et al. 2013). MRI characteristics of traction apophysitis in adolescent athletes include increased signal intensity on fluid-sensitive sequences (Fig. 20.3) and mild widening of the physis, often with adjacent bone marrow edema (Hodnett et al. 2009). Furthermore, avulsion injuries may demonstrate irregularity and bony protuberance at the site of avulsion with visibly displaced bone fragments. Non-displaced avulsion injuries are seen as sharply marginated pieces of bone adjacent to their donor site (Hodnett et al. 2009).

Gymnastic wrist injuries can be categorized into traumatic and overuse injuries. Acute traumatic wrist injuries commonly arise from a fall on the outstretched hand and include fractures of the radius, ulna, and carpal bones. This section will focus on gymnastic wrist injuries caused by repetitive stress, which is the most common mechanism of wrist injury in gymnasts and can lead to chronic wrist pain. The prevalence of chronic wrist pain ranges from 46 to 79 % (Mandelbaum et al. 1989; Caine et al. 1992). Chronic wrist pain in gymnasts can be caused by various disorders. These gymnastic overuse injuries of the wrist have been classified by Dobyns and Gabel into osseous and soft tissue injuries (Table 20.2) (Dobyns and Gabel 1990).