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Emergency and Acute Medicine - Toxic Synovitis
Toxic synovitis is a nonspecific, self-limiting inflammation of the synovium associated with an effusion, most commonly affecting the hip joint in children. It is the most frequent cause of acute hip pain and limping in children between 3 and 10 years of age, particularly in those aged 3 to 6 years. Boys are affected more commonly than girls, and the right hip is more frequently involved than the left. Although it can involve other joints, the hip is by far the most typical site.
The exact cause of toxic synovitis is unknown, but it is often preceded by a viral illness, particularly an upper respiratory infection, in about half of cases. This association suggests a possible postinfectious or inflammatory response rather than a direct infection of the joint.
Children typically present with an acute onset of unilateral hip pain, which may radiate to the anteromedial thigh or even the knee. Pain is usually worse with weight bearing, leading to a limp or refusal to walk. There is often a low-grade fever, generally below 38.5°C, and the child appears nontoxic. On examination, there is decreased range of motion of the affected hip due to pain, and the hip is commonly held in a position of flexion and external rotation to maximize comfort. High fever or a toxic appearance should raise concern for more serious conditions such as septic arthritis.
Evaluation is primarily aimed at excluding more serious diagnoses. Plain radiographs of the hip are usually normal but may help identify alternative causes of pain or show joint effusion. Laboratory tests such as white blood cell count, C-reactive protein, and erythrocyte sedimentation rate may be normal or mildly elevated, but they are not specific. If these inflammatory markers are normal and the child is able to bear weight, toxic synovitis is more likely. Ultrasound can be useful to detect joint effusion and guide aspiration if needed. Advanced imaging such as MRI or bone scan is reserved for unclear or recurrent cases or when conditions such as Legg–Calvé–Perthes disease or osteomyelitis are suspected. Joint aspiration is generally unnecessary unless septic arthritis is strongly suspected.
Management is conservative, as the condition is self-limiting. Treatment includes rest, positioning the hip for comfort (usually flexion and external rotation), and administration of nonsteroidal anti-inflammatory drugs. Heat may be applied for additional comfort. Antibiotics and steroids are not indicated. Some clinicians recommend limiting weight bearing for several days after symptom improvement to reduce the risk of recurrence.
Disposition depends on severity. Most patients can be discharged once more serious conditions are excluded, provided there is reliable follow-up. Hospitalization may be required in cases of severe pain or significant joint effusion requiring close observation and analgesia. Follow-up with a pediatric orthopedic specialist within one to two weeks is recommended, and repeat imaging at around six months is advised to exclude the development of Legg–Calvé–Perthes disease.
Toxic synovitis is largely a clinical diagnosis based on history and physical examination, with key features being low-grade fever and the ability to bear weight. Nearly all children recover completely within two weeks without long-term complications. However, a small proportion may experience recurrence, and approximately 2 to 10 percent may later develop Legg–Calvé–Perthes disease, making close follow-up essential.
Toxic synovitis is a nonspecific, self-limiting inflammation of the synovium associated with an effusion, most commonly affecting the hip joint in children. It is the most frequent cause of acute hip pain and limping in children between 3 and 10 years of age, particularly in those aged 3 to 6 years. Boys are affected more commonly than girls, and the right hip is more frequently involved than the left. Although it can involve other joints, the hip is by far the most typical site.
The exact cause of toxic synovitis is unknown, but it is often preceded by a viral illness, particularly an upper respiratory infection, in about half of cases. This association suggests a possible postinfectious or inflammatory response rather than a direct infection of the joint.
Children typically present with an acute onset of unilateral hip pain, which may radiate to the anteromedial thigh or even the knee. Pain is usually worse with weight bearing, leading to a limp or refusal to walk. There is often a low-grade fever, generally below 38.5°C, and the child appears nontoxic. On examination, there is decreased range of motion of the affected hip due to pain, and the hip is commonly held in a position of flexion and external rotation to maximize comfort. High fever or a toxic appearance should raise concern for more serious conditions such as septic arthritis.
Evaluation is primarily aimed at excluding more serious diagnoses. Plain radiographs of the hip are usually normal but may help identify alternative causes of pain or show joint effusion. Laboratory tests such as white blood cell count, C-reactive protein, and erythrocyte sedimentation rate may be normal or mildly elevated, but they are not specific. If these inflammatory markers are normal and the child is able to bear weight, toxic synovitis is more likely. Ultrasound can be useful to detect joint effusion and guide aspiration if needed. Advanced imaging such as MRI or bone scan is reserved for unclear or recurrent cases or when conditions such as Legg–Calvé–Perthes disease or osteomyelitis are suspected. Joint aspiration is generally unnecessary unless septic arthritis is strongly suspected.
Management is conservative, as the condition is self-limiting. Treatment includes rest, positioning the hip for comfort (usually flexion and external rotation), and administration of nonsteroidal anti-inflammatory drugs. Heat may be applied for additional comfort. Antibiotics and steroids are not indicated. Some clinicians recommend limiting weight bearing for several days after symptom improvement to reduce the risk of recurrence.
Disposition depends on severity. Most patients can be discharged once more serious conditions are excluded, provided there is reliable follow-up. Hospitalization may be required in cases of severe pain or significant joint effusion requiring close observation and analgesia. Follow-up with a pediatric orthopedic specialist within one to two weeks is recommended, and repeat imaging at around six months is advised to exclude the development of Legg–Calvé–Perthes disease.
Toxic synovitis is largely a clinical diagnosis based on history and physical examination, with key features being low-grade fever and the ability to bear weight. Nearly all children recover completely within two weeks without long-term complications. However, a small proportion may experience recurrence, and approximately 2 to 10 percent may later develop Legg–Calvé–Perthes disease, making close follow-up essential.
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