Bone and Joint Infections (Osteomyelitis, Septic Arthritis) MCQs

Orthopedics · 57 free questions with answers & explanations.

1. A 6-year-old boy presents with high fever, severe pain over the distal femur, and refusal to move the knee for 3 days. ESR is 80 mm/hr, CRP is elevated, and X-ray shows only soft tissue swelling. The most likely causative organism is:
2. A 3-year-old child presents with fever, a hot swollen hip, and the leg held in flexion, abduction, and external rotation. Ultrasound shows a large joint effusion. ESR is 100 mm/hr. The single most important next step in management is:
3. In chronic osteomyelitis, the dead bone sequestrum is surrounded by which structure that represents the body's attempt to wall off infection?
4. A 25-year-old intravenous drug user presents with low-grade fever and pain in the lumbar spine. MRI shows destruction of two adjacent vertebral bodies with disc space narrowing and paraspinal soft tissue swelling. The most likely causative organism is:
5. A 6-year-old boy presents with fever, limb pain, and refusal to bear weight for 4 days. ESR 95 mm/hr, CRP 45 mg/L. X-ray is normal. MRI shows periosteal edema and subperiosteal collection at the proximal tibia metaphysis. In acute hematogenous osteomyelitis of childhood, what is the anatomical basis for metaphyseal predilection?
6. A 2-year-old child with fever and painful hip is evaluated. Joint fluid aspiration yields cloudy fluid with WBC 85,000 cells/μL (90% neutrophils). The Kocher criteria for septic arthritis of the hip — which combination carries >99% probability?
7. A 55-year-old diabetic presents with a draining sinus over the right tibia for 2 years. X-ray shows sclerotic bone with a central lucency. Biopsy shows lamellar bone surrounding necrotic bone (sequestrum). The dead segment of necrotic cortical bone that has separated from the living bone is called:
8. A 40-year-old IV drug user develops fever and wrist pain. Blood cultures grow Staphylococcus aureus. Joint aspiration shows WBC 120,000/μL. After initiating antibiotics and joint drainage, which antibiotic is recommended as first-line for methicillin-sensitive S. aureus (MSSA) septic arthritis?
9. In haematogenous osteomyelitis of long bones in children, which vascular anatomical feature predisposes the metaphysis to bacterial seeding?
10. A 3-year-old child presents with a 3-day history of fever, pain, and pseudoparalysis of the right hip. Hip X-ray shows lateral displacement of the femoral head. Serum WBC is 18,000/mm³, CRP 120 mg/L. According to Kocher criteria, the predicted probability of septic arthritis is:
11. Involucrum in chronic osteomyelitis is best described as:
12. A Brodie's abscess is characteristically found in the:
13. In Cierny-Mader classification of chronic osteomyelitis, a Stage III lesion in a Class B (compromised) host describes:
14. A 2-year-old child with septic arthritis of the hip is taken for emergency surgical drainage. During the procedure, the surgeon must understand that in this age group, the femoral head blood supply is most likely to be compromised because:
15. A 60-year-old diabetic man has a painless diabetic foot ulcer (Wagner Grade 3) with deep space infection and osteomyelitis of the 2nd metatarsal head on MRI. Initial empirical antibiotic therapy should cover which organism as the predominant pathogen?
16. Brodie's abscess is a specific form of chronic osteomyelitis characterized by:
17. A 9-year-old boy with sickle cell disease presents with fever and severe pain over the mid-diaphysis of the tibia for 5 days. WBC 16,000, ESR 80. MRI confirms acute osteomyelitis. Which organism is MOST likely responsible, and what is the recommended first-line antibiotic?
18. A 3-year-old child has acute haematogenous osteomyelitis of the proximal femur for 10 days without treatment. X-ray shows periosteal elevation and a lytic area in the metaphysis. The hip is held in flexion and external rotation. Which complication is MOST immediately threatening?
19. A diabetic 65-year-old man has a chronic infected non-healing wound over the first metatarsal head for 3 months. MRI shows bone marrow oedema and cortical erosion of the first metatarsal head consistent with chronic osteomyelitis. The Cierny-Mader classification for this lesion would be:
20. A 7-year-old child has fever, knee pain, and refusal to weight-bear. Kocher's criteria for differentiating septic arthritis from transient synovitis include four factors. Which combination of THREE criteria confers a predicted probability of septic arthritis of approximately 93%?
21. In Cierny-Mader classification of adult osteomyelitis, a Stage III lesion is characterised by which anatomical distribution and host status, and what surgical implication does it carry?
22. In chronic osteomyelitis, an involucrum refers to which structural feature, and what role does it play in dictating surgical management?
23. A 6-year-old develops acute hematogenous osteomyelitis of the proximal femur. The physis is INTRACAPSULAR. This anatomical feature means that epiphyseal infection and secondary septic arthritis:
24. Brodie's abscess is a clinical variant of chronic osteomyelitis. Which radiological feature is PATHOGNOMONIC of Brodie's abscess?
25. In septic arthritis of the hip in adults, which organism is the MOST common causative agent in a sexually active 25-year-old?
26. In Cierny–Mader classification of osteomyelitis, a Stage III (localised) infection differs from Stage IV (diffuse) because:
27. A 4-year-old child presents with fever, refusal to walk, and pseudoparesis of the hip. ESR 80 mm/hr, CRP 45 mg/L, WBC 14,000/mm³, and ultrasound shows joint effusion. Kocher criteria score is 3 out of 4. What is the predicted probability of septic arthritis and what is the appropriate management?
28. In chronic haematogenous osteomyelitis, a Brodie's abscess is characterised by which radiological and pathological feature?
29. A 60-year-old diabetic undergoes total knee replacement. Three months later he develops wound breakdown, sinus tract, and pain. ESR 90, CRP 35, synovial WBC 55,000/mm³. Periprosthetic joint infection (PJI) is confirmed. What is the primary treatment for this chronic PJI with implant loosening?
30. A 5-year-old child presents with acute fever, refusal to weight bear, and swelling around the right knee for 3 days. Joint aspiration yields 18,000 WBCs/µL with 92% PMNs, glucose <40 mg/dL, and Gram stain negative. Crystal examination is negative. What is the most appropriate next step?
31. Cierny-Mader classification of osteomyelitis is based on anatomic type and physiological host class. A 45-year-old diabetic (uncontrolled, HbA1c 11%), smoker with peripheral neuropathy presents with chronic tibial osteomyelitis involving only the superficial cortex (medullary cavity intact). What is his Cierny-Mader stage and host class?
32. In Cierny-Mader classification for chronic osteomyelitis, a medullary osteomyelitis (Stage 1) with a compromised host due to diabetes and peripheral vascular disease is classified as:
33. In septic arthritis of the hip in a neonate, the mechanism of joint destruction that necessitates urgent joint drainage is:
34. A 45-year-old diabetic man develops chronic osteomyelitis of the tibia following an open fracture. Sequestrum formation is noted on CT. The Cierny-Mader staging system classifies this as a Type III (localised) lesion. Which feature distinguishes Type III from Type IV (diffuse) osteomyelitis in this system?
35. In acute haematogenous osteomyelitis of childhood, which is the most common metaphyseal site affected and why?
36. A 3-year-old child presents with septic arthritis of the hip. Which is the most important reason to perform emergency surgical drainage rather than needle aspiration alone?
37. A 6-year-old boy presents with fever, acute painful swelling, and inability to move his right knee for 3 days. Joint aspiration yields 80,000 WBCs/µL with 94% PMNs, glucose <40 mg/dL, and culture grows Staphylococcus aureus. The most critical early complication if treatment is delayed is:
38. In Cierny-Mader classification of chronic osteomyelitis, Stage III (localised) is characterised by:
39. A 60-year-old diabetic with peripheral vascular disease develops chronic osteomyelitis of the calcaneum with a discharging sinus. Bone biopsy and culture grow methicillin-resistant Staphylococcus aureus (MRSA). The antibiotic of choice for MRSA osteomyelitis requiring prolonged oral therapy after initial IV treatment is:
40. The Cierny-Mader classification of osteomyelitis is based on two criteria. Which pair correctly defines this classification system?
41. A 35-year-old intravenous drug user presents with lower back pain, fever, and elevated CRP. MRI shows high T2 signal in the L3-L4 disc with endplate erosion and a pre-vertebral soft tissue collection. The most likely organism and the drug of choice pending culture are:
42. A 5-year-old boy presents with fever, refusal to bear weight, and right hip held in flexion-abduction-external rotation. Ultrasound demonstrates joint effusion; hip aspiration yields 95,000 WBC/mm³. The Kocher criteria for septic arthritis of the hip include four variables. If all four criteria are present, the predicted probability of septic arthritis is:
43. A 7-year-old boy presents with a 3-day history of fever, right knee pain, and refusal to weight-bear. MRI demonstrates subperiosteal abscess with periosteal elevation. Blood culture grows Staphylococcus aureus sensitive to flucloxacillin. According to Nade's classification and the Cierny-Mader staging system (paediatric context), which histological type of osteomyelitis best describes this presentation?
44. In an adult with chronic osteomyelitis, the radiograph shows a cavity within sclerotic bone containing a dense bony fragment surrounded by pus. This radiological finding is referred to as:
45. Cierny-Mader staging of chronic osteomyelitis classifies the infection by both anatomical type and host physiological status. A patient with type III (localised — full-thickness cortical sequestrum with stable cortex) chronic osteomyelitis in a Class C host (prohibitive surgical risk or minimal disability) should be managed by:
46. In a neonate with septic arthritis of the hip, the most common causative organism and the clinical feature that distinguishes neonatal septic arthritis from Perthes disease on ultrasound is:
47. A 55-year-old diabetic man with chronic osteomyelitis of the tibia undergoes debridement. The dead bone (sequestrum) is removed along with surrounding sclerotic bone. A large bone defect of 6 cm is created. Bone transport using a circular fixator (Ilizarov) is planned. This procedure is also known as:
48. A 9-year-old boy presents with 5 days of fever, severe pain, and localised tenderness over the distal femoral metaphysis. ESR is 80 mm/hr, CRP elevated. X-ray is normal. MRI shows periosteal oedema and subperiosteal fluid. What is the most appropriate initial management?
49. A 16-year-old boy has a 6-week history of dull aching pain in the distal femur, worse at night and relieved by aspirin. X-ray shows a small, well-demarcated radiolucent nidus (less than 1 cm) surrounded by dense reactive sclerosis in the cortex. What is the most likely diagnosis?
50. A 14-year-old presents with a 3-month history of bone pain around the knee. X-ray shows a destructive lesion in the distal femoral metaphysis with periosteal elevation forming a Codman's triangle and a 'sunburst' spiculation pattern. Serum alkaline phosphatase is markedly elevated. The most likely diagnosis is:
51. A 30-year-old woman has a painless, eccentric lytic lesion in the epiphysis of the distal femur extending to the subchondral bone. There is a 'soap bubble' appearance on X-ray. Biopsy shows multinucleated giant cells on a mononuclear stromal background. Which of the following best describes the appropriate management of a Campanacci grade III lesion?
52. A 65-year-old man with known prostate cancer presents with severe back pain and an X-ray showing a sclerotic lesion in the L3 vertebral body. Bone scan shows multiple hot spots in the spine and pelvis. Which statement about metastatic bone disease is correct?
53. Cierny-Mader classification of chronic osteomyelitis has two components: anatomical type and physiological class. A host classified as Class B-L in the Cierny-Mader system indicates:
54. A 5-year-old child presents with acute septic arthritis of the hip. Which laboratory threshold most accurately differentiates septic arthritis from transient synovitis in the Kocher criteria?
55. A 7-year-old child presents with fever, limp, and refusal to weight bear. WBC is 18,000/mm3, ESR 65 mm/hr, CRP 85 mg/L. Hip ultrasound shows a joint effusion. The single most important investigation to differentiate septic arthritis from transient synovitis is:
56. In chronic osteomyelitis with a sequestrum and involucrum, which term describes the natural opening through the involucrum that allows discharge of pus and sequestrum to the surface?
57. Gonococcal septic arthritis in a sexually active 24-year-old female is best distinguished from non-gonococcal septic arthritis by which clinical pattern?