international journal of athletic therapy & training march 2012 5

Skeletal Development and Pathophysiology

The skeleton forms in the first weeks of fetal development and is initially composed entirely of cartilage. During subsequent fetal development, and continuing after birth and into childhood and adolescence, the soft car-tilage skeleton is transformed into a skeleton made of mineralized bone. This transforma-tion process is known as endochondral ossi-fication. The physis, or growth plate, is the site where endochondral ossification occurs. The cartilage cells of the physis produce an extracellular matrix that ossifies, thereby forming hard bone tissue. This process results in longitudinal bone growth that increases its length. Long bones have a physis at one or both ends. Many bones of the immature skeleton have apophyses, which are growth areas that have muscle attachments in close proximity. Bone growth at the apophyses fills out surface contours, but does not contribute to linear growth. Having open growth plates has many advantages, e.g., fracture healing and remodeling are accelerated in young patients; however, because apophyses and physes are composed of cartilage, they are susceptible to injury. Whereas adults are more likely to experience disruption of liga-ments, muscles, and tendons with overuse,

Verle Valentine, MD, Report EditorPHYSICIAN PERSPECTIVE

Apophysitis and Apophyseal Avulsion of the Pelvis

© 2012 Human Kinetics - IJATT 17(2), pp. 5-9

Rebecca L. Carl, MD • Children’s Memorial Hospital Chicago

The phrase “children are not little adults” is a popular adage among health professionals caring for children. This saying holds true for overuse injuries in young athletes. Children and adolescents, with their immature skel-etons, have different injury patterns than those exhibited by skeletally mature indi-viduals. Strains of muscles that span the hip

and attach to the pelvis are a common cause of hip pain in adult athletes, and these injuries can occur in younger patients as well. In young athletes, irritation of the acces-sory growth areas of the pelvis (i.e., pelvic apophysitis) and avul-sion fractures of the pelvic apophyses are

often mistakenly diagnosed as muscle strains or hip pointers. Most clinicians are familiar with Osgood-Schlatter disease, which is an irritation of the apophysis of the tibial tuber-osity. Conditions affecting the apophyses of the pelvis are less well known. Clinicians who care for pediatric, adolescent, and young adult athletes should be familiar with the pathophysiology of apophysitis and apophy-seal avulsion injuries.

Young athletes have distinctive patterns of injury.

Irritation and injury to the pelvic growth areas can cause hip pain.

Apophyseal injuries in young athletes are often mistakenly diagnosed as muscle injuries.

Key PointsKey Points

6 march 2012 international journal of athletic therapy & training

children are more likely to have injuries to the physes and apophyses. Apophysitis refers to irritation of the apophysis, due to repetitive microtrauma that can occur during participation in athletics. With repeated muscle contractions, the apophysis can become irri-tated and may widen. Apophyseal avulsion fractures generally result from sudden traction generated by a strong eccentric contraction of a muscle group attached adjacent to the affected apophysis.

Case #1

A 15-year-old male track athlete presents to the training room with acute onset of right hip pain. He had sudden onset of his pain while sprinting during practice. He recalls feeling a “pop” at the time of injury. He is able to bear weight. On physical exam, he is tender over the anterior superior iliac spine (ASIS). Hip range-of-motion is symmetric, except for slightly decreased extension on the right. He reports pain with passive hip extension and resisted hip flexion. The athletic trainer refers him for radiographs; these demonstrate the presence of an avulsion fracture of the ASIS (Figure 1).

iliac crest. Hip range of motion is full and symmetric. Subsequent radiographs demonstrate widening of the iliac crest apophysis on the left.

Anatomy

The apophyses of the hip and pelvis are located at the anterior superior iliac spine (ASIS), anterior inferior iliac spine (AIIS), ischial tuberosity (IT), pubic sym-physis, iliac crest, and greater and lesser trochanters. Knowledge of the bone structure of the hip and pelvis, and muscle origins and insertions, is critical for under-standing apophysitis. For example, the iliopsoas is the most powerful of the hip flexors, which inserts on the lesser trochanter. With acute, forceful hip flexion, as the patient in case #1 experienced, the contraction of the iliopsoas can cause avulsion of the lesser trochanter of the apophysis.

The internal and external abdominal oblique mus-cles insert onto the iliac crest. Repeated trunk rotation puts traction on the iliac crest, which can cause iliac apophysitis, as seen in case #2. Table 1 lists the sites of pelvic apophyses and associated muscles that attach in close proximity.

Epidemiology

The exact incidence of pelvic apophysitis is unknown. There are data available for other sites of apophysi-tis. For example, Kujala et al. surveyed nearly 200 individuals who had been active in athletics during childhood and adolescence and found that 21% had experienced symptoms of Osgood-Schlatter Disease (OSD).1 Prevalence of OSD was elevated among siblings of athletes with OSD and individuals with a history of Sever Disease (apophysitis of the calcaneus). These data suggest that individuals with apophysitis at one site are more vulnerable to apophysitis at other sites. Poor flexibility is a risk factor, particularly in a muscle attached near the affected apophysis. The individu-als with Sever Disease were more likely to have poor flexibility, which may be associated with increased susceptibility to apophysitis at other sites.

Athletes are vulnerable to apophyseal injuries during the time that these growth areas are active. The apophyses of the hip and pelvis generally appear between 13 and 15 years of age, and they close in the early to mid-twenties. The lesser trochanter apophysis

Figure 1 avulsion of the anterior superior iliac spine (large white arrow). other sites where apophysitis can occur are indicated with arrows as follows: iliac crest (gray arrow), ischium (small white arrow), and anterior inferior iliac spine (black arrow).

Case #2

A 16-year-old female soccer player presents to the training room with a two-week history of left hip pain. She reports that her pain had an insidious onset; she believes it started while doing soccer kicking drills. She indicates the lateral aspect of the hip as the location of her pain. On physical exam, she is tender along the

international journal of athletic therapy & training march 2012 7

is active earlier, usually appearing between 9 and 13 years of age and closing by 17.2

Rossi and Dragoni3 reviewed the records of over 1200 athletes between the ages of 11 and 35 who had radiographs performed for assessment of hip pain. They found pelvic apophysis avulsion fractures in 16% of these athletes. The average age of the patients with avulsion fractures was 13 (range of 11 to 17), and 68.5% of affected patients were male. Additionally, there were 25 adult patients (ranging in age from 22 to 35) with radiographic evidence of “old” avulsion injuries. Athletes who participated in soccer and gymnastics were most likely to be affected. The ischial tuberosity was the most commonly affected site, followed by the ASIS and the AIIS.3 In another study of 27 patients with apophyseal avulsion fractures, the ASIS was the most commonly affected site.4

Clinical History and Physical ExaminationApophysitis

Apophysitis results from repetitive muscle tension at its attachment site. Patients tend to report an insidious onset of pain. On physical exam, tenderness is elicited by palpation over the apophysis. Pain is often elicited by passive stretch and resisted manual muscle testing, which puts traction on the irritated apophysis. Range of motion is generally unaffected, or minimally reduced.

Apophyseal Avulsion

Patients with apophyseal avulsion commonly describe acute onset of pain during an activity that involved forceful muscle contraction. Many recall having felt a “pop” at the time of injury. Athletes may demonstrate

an antalgic gait or difficulty ambulating following an avulsion injury. On physical exam, crepitus, swelling, and/or bruising may be apparent. Most patients exhibit significant tenderness in response to palpation of the affected apophysis. They often experience pain during passive stretching and difficulty in actively contract-ing the muscles attached near the affected apophysis. Range of motion is often limited by pain during the acute postinjury period.

Diagnostic Imaging

Apophysitis

Clinical history and examination provide the primary findings for the diagnosis of apophysitis. In some patients, radiographs demonstrate widening of the apophysis. When radiographs are obtained, they should include the contralateral pelvis and hip for comparison. Magnetic resonance imaging (MRI) is rarely warranted for patients with a clinical history that is strongly sug-gestive of apophysitis. When performed, MRI may show edema surrounding the affected growth area.5

Apophyseal Avulsion

Following an acute injury, radiographs will clearly demonstrate an avulsion fracture.6 With chronic injury, the affected areas may look bulkier than normal, due to new bone formation. The periosteal reaction and new bone formation associated with healing of such an injury may create an appearance that can be con-fused with a malignant neoplasm (Figure 2). Computed tomography (CT) may be a helpful to ensure the correct diagnosis in such cases.7-9

Table 1. Apophyses of the Pelvis and Their Muscle Attachments

Bone Landmark Muscle Muscle FunctionAnterior superior iliac spine Sartorius (O) Hip, knee flexion, external hip location

Anterior inferior iliac spine Rectus Femoris (O) Hip flexion, knee extension

Ischial Tuberosity Hamstrings (O) Hip extension, knee flexion

Iliac Crest Abdominal Muscles (I) Trunk rotation

Greater Trochanter Gluteus medius, Gluteus minimus (I) Hip abduction

Lesser Trochanter Iliopsoas (I) Hip flexion

Pubic ramus Adductor longus, brevis, magnus, pectineus, and gracilis (O)

Hip adduction

O-originates, I-inserts

8 march 2012 international journal of athletic therapy & training

Differential Diagnosis

For symptoms of apophysis over the anterior pelvis, hip, and proximal thigh, including the ASIS, AIIS, pubic ramus, and lesser trochanter, the differential diagnosis includes adductor muscle strain, tendinopathy, snap-ping hip syndrome, labral tear, and femoroacetabular impingement. Stress fracture, or stress reaction, of the pubic ramus, acetabulum, or femoral neck can also cause pain in this region. Slipped Capital Femoral Epiphysis (SCFE) can be responsible for groin pain in preadolescent and adolescent patients, which must be ruled out in such patients.

Ischial tuberosity apophysitis or apophseal avulsion may present similar symptoms to those associated with hamstring strain, tendinopathy, or myofascial pain. Referred pain from the lumbar spine can mimic symptoms of apophysitis affecting the ischial tuberos-ity, lesser trochanter, or greater trochanter. Symptoms associated with iliac crest apophysitis can be confused with those of a strain of an abdominal muscle or irrita-tion of the proximal portion of the iliotibial band. The differential diagnosis for greater trochanter avulsion or apophysitis includes greater trochanteric bursitis and lateral snapping hip syndrome.

For any patient who presents with symptoms asso-ciated with pelvic apophyseal irritation or avulsion, clinicians must consider the existence of systemic conditions, such as inflammatory arthritis, malignancy, or infection as potential causes of pain. Intraabdominal abnormalities (e.g., appendicitis) and lumbar spine

conditions (e.g., radiculopathy) may cause pain that is referred to the hip and pelvis.

TreatmentApophysitis

Treatment includes cryotherapy and rest from activity. Athletes can begin gentle stretching when daily activi-ties become pain free, with subsequent progression to strengthening exercises. Activity progression should be gradual, with explosive, plyometric movements involving muscles attached to a site near the affected apophysis added last. Livel et al10 recently reported the use of bone stimulator treatment to accelerate healing in two patients with iliac crest apophysitis.

Apophysis Avulsion

Avulsion of a pelvic apophysis generally heals with con-servative therapy, including activity restriction and pro-tected weight bearing when the patient has difficulty with ambulation. If pain free after two to four weeks of rest, the patient can progress to gentle stretching and light resistance exercises. Athletes are generally able to return to light sport-specific drills at six weeks after injury and capable of return to full participation at two months after injury if asymptomatic. Clinicians should consider referral for surgical fixation of the avulsed fragment if separated from its normal position by more than 2.5 cm. Most apophysis avulsion injuries heal with conservative treatment, but surgery may be indicated for nonunion or excessive bone formation at the injury site.11 Rossi and Dragoni3 reported that only three out of 198 patients required surgery.

Conclusions Sports medicine clinicians should suspect pelvic apophysitis and apophyseal avulsion fracture in an adolescent or young adult athlete who presents gluteal or hip pain. Individuals with skeletal maturity tend to experience injury to the musculotendinous junction, because it is the weakest portion of the muscle-tendon-bone unit. Individuals with incomplete skeletal growth are more likely to experience injury to the cartilaginous apophysis. Generally, this type of injury heals with con-servative therapy, and athletes are eventually capable of returning to the preinjury level of performance.

Figure 2 the right ischium has a hazy, bubbly appearance consistent with periosteal reaction secondary to apophyseal injury (white arrow). the appearance of this lesion can be confused with that of a malignant neoplasm.

international journal of athletic therapy & training march 2012 9

References 1. Kujala UM, Kvist M, Heinonen O. Osgood-Schlatter’s disease in ado-

lescent athletes. Retrospective study of incidence and duration. Am J Sports Med. Jul-Aug 1985;13(4):236-241.

2. Moeller JL. Pelvic and hip apophyseal avulsion injuries in young ath-letes. Curr Sports Med Rep. Apr 2003;2(2):110-115.

3. Rossi F, Dragoni S. Acute avulsion fractures of the pelvis in adolescent competitive athletes: prevalence, location and sports distribution of 203 cases collected. Skeletal Radiol. Mar 2001;30(3):127-131.

4. Metzmaker JN, Pappas AM. Avulsion fractures of the pelvis. Am J Sports Med. Sep-Oct 1985;13(5):349-358.

5. Sanders TG, Zlatkin MB. Avulsion injuries of the pelvis. Semin Muscu-loskelet Radiol. Mar 2008;12(1):42-53.

6. Fernbach SK, Wilkinson RH. Avulsion injuries of the pelvis and proxi-mal femur. AJR Am J Roentgenol. Sept 1981;137(3):581-584.

7. Bahk WJ, Brien EW, Luck JV, Jr., Mirra JM. Avulsion of the ischial tuber-osity simulating neoplasm: a report of 2 cases. Acta Orthop Scand. Apr 2000;71(2):211-214.

8. Stevens MA, El-Khoury GY, Kathol MH, Brandser EA, Chow S. Imaging features of avulsion injuries. Radiographics. May-Jun 1999;19(3):655-672.

9. Yamamoto T, Akisue T, Nakatani T, et al. Apophysitis of the ischial tuberosity mimicking a neoplasm on magnetic resonance imaging. Skeletal Radiol. Dec 2004;33(12):737-740.

10. Kivel CG, d’Hemecourt CA, Micheli LJ. Treatment of iliac crest apophy-sitis in the young athlete with bone stimulation: report of 2 cases. Clin J Sport Med. Mar 2011;21(2):144-147.

11. McKinney BI, Nelson C, Carrion W. Apophyseal avulsion fractures of the hip and pelvis. Orthopedics. Jan 2009;32(1):42.

Rebecca Carl is an attending physician in Pediatric Sports Medicine at Children’s Memorial Hospital in Chicago. She is also an assistant professor of Pediatrics at Northwestern University Feinberg School of Medicine.

Frequency: Bimonthly (January, March, May, July, September, November)ISSN (print): 2157-7277 ISSN (online): 2157-7285

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