Apophysitis

Anatomy

An apophysis is a bony protuberance near a physis, or growth plate, and serves as the insertion site of major tendons and ligaments. A physis, consisting of cartilage and new bone, is where bones actively grow during development, and as a bone matures, the physis will fuse and become all bone. However, while the physis is still open, it is weaker than all the surrounding tissues, including the formed bone, ligaments, tendons, and muscles, so when stress is applied to an apophysis, it generally is the part that is injured, resulting in apophysitis. In most cases, the tension from a repetitively firing tendon is what causes the apophysitis.

Epidemiology

The increase in organized sports participation has resulted in a similar increase in injuries among pediatric athletes. Increased specialization at a young age, year-round training, and increased intensity of training at an early age also contribute to overuse injuries in general and to apophysitis in particular.

Causes

Most cases of apophysitis have a number of causes. These causes can be divided into two broad categories: intrinsic and extrinsic. Intrinsic factors are issues related to the patient's body. Examples include biomechanical abnormalities such as pes planus (flat foot), pes cavus (high arches), excessive pronation, limb length differences, or abnormal rotation of the thigh (femoral anteversion). Muscular imbalances can be another intrinsic factor. If one muscle is significantly stronger than its antagonist muscle (e.g., the quadriceps and hamstring muscles), then abnormal stresses can occur at a joint, resulting in injury. This often occurs when an athlete focuses too much on one muscle group. Another common cause is inflexibility. Children who are going through their adolescent growth spurt are at risk for this because bones tend to grow faster than muscles, resulting in inflexibility. The growth spurt also happens to be the time when many types of apophysitis are at highest risk. Muscular weakness, poor conditioning, or inadequate muscular endurance can also cause apophysitis.

Extrinsic factors are issues related to the patient's interaction with the environment. Shoes are a common extrinsic factor. It is important for athletes to use shoes that are designed for their sport, appropriate for the competition and practice surface, and correct for their foot type. It is also important to replace shoes regularly; it is generally recommended to replace running shoes every 300 to 500 miles (mi; 1 mi = 1.6 kilometers) and other shoes every season. Training errors are also another common extrinsic factor. Many athletes increase their training intensity too fast, resulting in an overuse injury. Other training errors include improper techniques, such as improper throwing or weight lifting, training on too hard or too soft a surface, or using equipment that is not suited to one's size, age, or ability.

Symptoms and Signs

Most cases of apophysitis have a gradual onset of pain. Pain initially tends to be worse after activity and improves with warming up, but as the pain worsens, it will be present during activity and, [Page 89]eventually, become constant. Specific activities tend to worsen the pain, depending on which type of apophysitis the patient has. There may be swelling, or bony protuberances may become more prominent. Examination will show point tenderness at the site of the apophysitis, and resisted strength testing of the affected tendon may be painful. The natural history of most of these entities is to resolve without sequelae once the physis fuses.

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