A 17-year-old girl comes to the office due to knee pain. She first noticed a dull, achy pain in her left knee a week ago after soccer practice. Despite icing her knee regularly, the patient has been unable to participate this week due to pain when running and jumping. She does not recall trauma to the knee and has otherwise been healthy. Vital signs are normal. Examination shows a well-appearing adolescent with a moderate effusion of the left knee and a limp. There is mild tenderness to palpation and limited knee extension. Which of the following additional pieces of information is most likely to help identify the underlying diagnosis?

Question

A 17-year-old girl comes to the office due to knee pain.  She first noticed a dull, achy pain in her left knee a week ago after soccer practice.  Despite icing her knee regularly, the patient has been unable to participate this week due to pain when running and jumping.  She does not recall trauma to the knee and has otherwise been healthy.  Vital signs are normal.  Examination shows a well-appearing adolescent with a moderate effusion of the left knee and a limp.  There is mild tenderness to palpation and limited knee extension.  Which of the following additional pieces of information is most likely to help identify the underlying diagnosis?

Quizplus · Accepted Answer

Explanation: Limp and knee pain are relatively common and may arise from a wide range of pathologies affecting the spine, hip, thigh, knee, and patella. However, the presence of a monoarticular knee joint effusion indicates the disorder is within the knee joint itself and somewhat narrows the differential diagnosis. Common etiologies include: Traumatic injury - Ligament or meniscal tears often cause knee joint effusions, but patients almost always recall recent joint trauma. Bacterial joint infection - Most cases are marked by significant systemic symptoms (eg, fever, malaise, tachycardia) and severe joint pain, erythema, and warmth. Inherited blood disorders - Both sickle cell anemia (vasoocclusive crisis) and hemophilia (hemarthrosis) can present with knee swelling. However, both conditions typically cause severe (not mild) knee pain, and hemophilia typically occurs in male patients (X-linked) and presents in childhood (Choice B). Thoroughly reviewing the patient's history can often elicit less common causes of monoarticular knee effusion. Inquiring about the presence of a recent rash is important for diagnosis because a rash frequently precedes or accompanies several causes of monoarticular arthritis, including late Lyme disease (spreading, annular rash), juvenile arthritis (evanescent, macular, salmon-colored rash), and serum sickness (pruritic rash). Late Lyme disease frequently presents with mild, monoarticular knee joint arthritis and few other symptoms (as in this case), whereas juvenile arthritis and serum sickness often cause high fever and polyarthritis. (Choice A) Diets rich in meat, seafood, and alcohol increase the risk of developing gout, a common cause of monarticular arthritis. However, patients with gouty arthritis typically have excessive pain and evidence of inflammation (eg, erythema, warmth). (Choice C) Streptococcus pneumoniae and Haemophilus influenzae can both cause septic bacterial arthritis; however, bacterial joint infections are usually marked by high fever, malaise, and severe joint tenderness. (Choice D) New medications (eg, cefaclor, seizure medications) can occasionally trigger a serum sickness-like reaction, which frequently presents with a polyarticular arthritis, high fever, and rash. Educational objective: A monoarticular effusion of the knee in an adolescent is most often caused by trauma, bacterial infection, or inherited blood disorder. Less common causes include late Lyme disease, juvenile arthritis, and serum sickness, all of which are typically accompanied by a preceding/ongoing rash. References: Diagnosis and treatment of Lyme arthritis. (http://www.ncbi.nlm.nih.gov/pubmed/25999223)

A 17-Year-Old Girl Comes to the Office Due to Knee