Archive Of Standardized Exam Questions: Septic Arthritis


This page is dedicated to organizing various examples of standardized exam questions whose answer is septic arthritis. While this may seem a odd practice, it is useful to see multiple examples of how septic arthritis will be characterized on standardized exams (namely the boards and the shelf exams). This page is not meant to be used as a tradition question bank (as all of the answers will be the same), however seeing the classic “test” characterization for a disease is quite valuable.


Question # 1

A 5 year old girl is brought to the clinic one day after she develops a fever and has increasingly severe left knee pain/swelling. Her parents explain she was unable to sleep last night due to the severity of the pain. She is unable to bear weight on her left leg in the clinic, and appears visibly uncomfortable. Her temperature is 102.0°F, pulse is 115min, respirations are 26/min, and her blood pressure is 100/55 mm Hg. A physical exam reveals a swollen, red, warm, and tender left knee. The patient constantly keep the knee bent during the exam. She refuses to move the knee and resists passive movement of the knee. The rest of the physical exam is non contributory. What is the likely diagnosis?

Explanation: fever + swollen/tender knee = septic arthritis

Question # 2

A 7 year old boy is brought to the clinic because he is refusing to walk. All day today he has insisted that his mother carry him around everywhere, and he cries when anyone tries to move his left leg. About 8 days ago he was diagnosed with cellulitis. He completed a 7 day antibiotic course yesterday. HIs temperature is 102.2°F, blood pressure is 100/60 mm Hg, push si 120/min, and respirations are 19/min. A musculoskeletal exam demonstrates that the patient will scream when his left hip moved at all. He keeps this hip externally rotated. The rest of his physical exam is unremarkable. His joint is aspirated and labs are ordered:

Complete blood count:

  • Leukocytes: 30,000/µl
  • Neutrophils: 90%
  • Lymphocytes: 6%
  • Bands: 4%

Erythroid sedimentation rate: 55 mm/h

Synovial fluid analysis: 

  • Color: yellow
  • Clarity: turbid
  • Leukocytes: 120,000/µl
    • Neutrophils: 93%
  • Gram stain: negative
  • Culture: pending

Blood cultures have also been collected and are pending. What is the likely diagnosis in this pate?

Question # 3

A 6 year old boy is brought to the clinic because he is not feeling well. He has had a fever and left knee pain. About 2 weeks ago the child was diagnosed with bacterial pharyngitis, and he was given antibiotics to treat his illness. Two days ago is when he developed a fever and became fatigued. As of today he has been complaining of his left knee “hurting” and has been reluctant to walk on his own. His mother confirms that there has been no trauma to the child’s knee. The child’s temperature is 102.8°F, blood pressure is 100/50 mm Hg, pulse is 110/min, and respirations are 16/min. A physical exam reveals a left knee that is swollen and tender to palpation. The child appears to have significant pain with active range of motion and weight bearing. Laboratory results are collected and are shown below:

Complete blood count: 

  • Leukocytes: 15,100/µL
  • Hemoglobin: 12.2g/dL
  • Platelets: 280,000/µL

Immunological studies:

  • CRP: 65 mg/L
  • ESR: 45 mm/h

An X-ry shows left knee fusion as well as overlying soft tissue swelling. What diagnosis should be strongly considered in this patient?

Question # 4

A 24 year old woman comes to the hospital because she has had a fever and right knee pain of the past 2 days. She denies having a cough, abodminla pain, or any dysuria. Her past medical history is unremarkable. The patient’s temperature is 102.5°F, pulse is 115/min, respirations are 15/min, and blood pressure is 115/70 mm Hg. A physical exam reveals a free raised erythematous papules present on both aplms. The right knee is warm to the touch, erythemtaotus, and tender. There appears to be a moderate sized effusion. Passive flexion of the knee is limited due to pain. Analysis of joint fluid aspirated from the right knee shows a leukocyte count of 40,000/mm3 (85% segmented neutrophils and 15% lymphocytes). A Gram stain of this joint fluid and microscopic examination for crystals are negative. What diagnosis explains this clinical picture?

Explanation: absence of anything on gram stain does not RULE OUT septic arthritis in this setting.

Question # 5

A 25-year-old woman comes to the clinic because she has been experiencing pain in her joints for the past 9 days. She first had pain in her left elbow, and then her left shoulder, and now has pain, redness, and swelling in her right knee that began 3 days ago. Her previous elbow and shoulder pain has resolved as of now. She denies any history of trauma. She is sexually active, and she and her partner use condoms for contraception inconsistently. Examination of the patient’s right knee shows reveals a warm, tender, swollen, and erythematous joint. Range of motion of the knee is limited to 15 degrees of flexion. The rest of the physical exam is non-contributory. Aspiration of the joint fluid yields a cloudy fluid with a leukocyte count of 19,200/mm³ (95% segmented neutrophils). A gram stain will likely confirm what diagnosis?

Explanation: migratory arthralgias + inconsistent condom usage + increased leukocytes in joint tap = septic arthritis (likely caused by gonorrhea)


Page Updated: 11.18.2016