A 6-year-old girl is brought to the clinic for evaluation of knee pain. The patient first had soreness in her right knee 4 days ago, after her first gymnastics class. Her mother gave her acetaminophen and massaged her knee, but this did not help. The patient also developed a limp over the past 2 days. She has no chronic medical conditions and does not take daily medications. Height is at the 50th percentile and weight is at the 75th percentile. Temperature is 37.9 C (100.2 F). When walking, she limits weight-bearing on her right side. When supine, the right hip is held flexed with the knee pointed laterally. There is limited internal rotation and extension of the right hip. The right knee has full range of motion and there is no tenderness on palpation around the knee. Laboratory evaluation shows leukocyte count of 11,500/mm³ and C-reactive protein of 8 mg/L (normal:

Question

A 6-year-old girl is brought to the clinic for evaluation of knee pain. The patient first had soreness in her right knee 4 days ago, after her first gymnastics class. Her mother gave her acetaminophen and massaged her knee, but this did not help. The patient also developed a limp over the past 2 days. She has no chronic medical conditions and does not take daily medications. Height is at the 50th percentile and weight is at the 75th percentile. Temperature is 37.9 C (100.2 F). When walking, she limits weight-bearing on her right side. When supine, the right hip is held flexed with the knee pointed laterally. There is limited internal rotation and extension of the right hip. The right knee has full range of motion and there is no tenderness on palpation around the knee. Laboratory evaluation shows leukocyte count of 11,500/mm³ and C-reactive protein of 8 mg/L (normal: <10). Ultrasound of the hips shows small, bilateral effusions. Which of the following is the most likely diagnosis in this patient?

Quizplus · Accepted Answer

11ec25c8_d61e_4ed4_bc81_bda44314e660_MD0003_00 This child with knee pain has limited hip mobility and bilateral hip effusions, consistent with transient synovitis (TS). TS is a common, self-limiting, inflammatory hip condition that occurs in children age 3-8. The etiology is unclear but often involves postviral or, less commonly, posttraumatic (eg, gymnastics class) joint inflammation. In some cases, no preceding trigger is identified. Presentation includes a well-appearing child with acute hip pain or referred knee pain. Knee examination is normal (as in this case), and patients often hold the hip flexed, abducted, and externally rotated to relieve pressure in the joint space. Limping is common, although patients can usually bear weight on the affected leg. Fever is typically absent (or low-grade), and laboratory evaluation (eg, C-reactive protein, white blood cell count) is usually normal. Ultrasound reveals small unilateral or bilateral effusions (even when symptoms are confined to one hip). Treatment of TS is conservative (eg, nonsteroidal anti-inflammatory medications), and symptoms generally resolve within days to weeks. (Choice A) Juvenile idiopathic arthritis presents with chronic joint pain and inflammation and may be associated with rash and fever. The hips are rarely involved, and elevated inflammatory markers are expected. (Choice B) Osgood-Schlatter disease, or osteochondritis of the tibial tubercle, presents in active adolescents with chronic anterior knee pain that is worse with running and jumping. Tenderness over the tibial tubercle is a characteristic finding not seen on this patient's examination. Osgood-Schlatter disease (Choice C) Septic arthritis typically presents in ill-appearing, febrile children with acute joint pain and inflammation. Patients classically refuse to bear weight on the affected extremity, unlike in this case. In addition, leukocytosis and elevated inflammatory markers are typical, and ultrasound reveals a unilateral (not bilateral) effusion. (Choice D) Slipped capital femoral epiphysis occurs when the femoral diaphysis is displaced anteriorly along the growth plate relative to the femoral head. Typical presentation involves an obese adolescent with chronic hip (or referred knee) pain, limp, and limited internal rotation of the hip. Ultrasound may detect the slippage but would not show effusions, as seen in this patient. Slipped capital femoral epiphysis Educational objective: Transient synovitis is a self-limiting, inflammatory hip condition most common in children age 3-8. Presentation may include limp (with ability to bear weight), hip pain, or pain referred to the knee. Most patients are afebrile with normal laboratory studies (eg, white blood cell count, C-reactive protein) and small, bilateral hip effusions. References: Differentiating transient synovitis of the hip from more urgent conditions. (http://www.ncbi.nlm.nih.gov/pubmed/27294495)

A 6-Year-Old Girl Is Brought to the Clinic for Evaluation