Overuse injuries are becoming more common in young athletes because of early sport specialization, year-round sports participation, participation in multiple sports in the same season, and increased training demands.1 Apophysitis is an overuse injury unique to the skeletally immature athlete and comprises a significant proportion of musculoskeletal complaints in this population.
The apophysis is a secondary ossification center that serves as the attachment site for a muscle-tendon unit.1-3 In the growing athlete, the apophysis is the biomechanically weak point of the muscle-tendon-bone attachment and is subject to injury from repetitive stress or an acute avulsion injury.1,4
Multiple factors may contribute to the development of apophysitis. First, during a time of rapid growth, such as the pubertal growth spurt, bone growth exceeds the ability of the muscle-tendon unit to stretch sufficiently to maintain its previous level of flexibility, causing increased tension at the attachment site.1,3,5 In the young athlete, training and competition increase force generation of the attached muscle and amplify traction forces at the apophysis.3,4 Underlying biomechanical factors such as foot pronation or genu valgum may exacerbate abnormal forces at the apophysis.1 The end result of these processes is inflammation and microtrauma of the apophysis.
In general, apophysitis presents with gradual onset of pain without a specific history of injury; however, it also may present as persistent and/or worsening symptoms after a single traumatic event.3 Athletes generally localize their pain to the apophysis.
Apophysitis typically develops from repetitive submaximal loading at the apophysis, but a forceful eccentric (lengthening) muscle contraction may cause an acute avulsion fracture at the apophysis, with immediate disability.4-7
The diagnosis of apophysitis can be made solely on the basis of classic history and physical exam findings. Radiographs are not necessary for diagnosis but may help rule out other conditions such as infection or tumor, especially with an atypical history, or when concerning historical factors such as night pain, fever, weight loss, or pain persisting after skeletal maturity are present.1 If radiographs are not obtained initially but the athlete has persistent symptoms or is not responding to therapy, then x-rays or advanced imaging such as magnetic resonance imaging (MRI) should be considered.
Unfortunately, evidence-based reports of treatment for apophysitis are lacking in the literature, but treatment protocols generally follow the same principles. First, one must provide rest from activities that cause pain and protect the apophysis from further injury. Providers must keep in mind that an open growth plate is still vulnerable to injury, and, although rare, inadequate protection of the apophysis during a time of increased stress can result in an avulsion fracture. Activity may be modified to allow continued participation, but certain athletes require complete rest depending on their level of pain and disability. A general rule is that sports participation is allowed as long as limping is not present during normal walking or during or after activity. A rehabilitation program in the form of a home exercise program, formal physical therapy, or rehab with an athletic trainer is used to correct underlying flexibility and strength deficits.1
This article will discuss apophysitis of the hip/pelvis, knee, and foot (Figure 1), focusing on presentation, physical examination and x-ray findings, contributing biomechanical factors, differential diagnosis, management, and potential complications.
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