Bone and joint infections US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Bone and joint infections. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Bone and joint infections US Medical PG Question 1: A 3-year-old patient is brought to the emergency department by her mother due to inability to walk. The child has been limping recently and as of this morning, has refused to walk. Any attempts to make the child walk or bear weight result in crying. She was recently treated for impetigo and currently takes a vitamin D supplement. Physical exam is remarkable for an anxious appearing toddler with knee swelling, erythema, and limited range of motion due to pain. Her mother denies any recent trauma to the child's affected knee. Temperature is 103°F (39.4°C), pulse is 132/min, blood pressure is 90/50 mmHg, respirations are 18/min, and oxygen saturation is 99% on room air. Which of the following is the best initial step in management?
- A. MRI
- B. Ultrasound
- C. Synovial fluid analysis (Correct Answer)
- D. Broad spectrum antibiotics
- E. Radiograph
Bone and joint infections Explanation: ***Synovial fluid analysis***
- The patient's presentation with **fever**, **joint pain**, inability to bear weight, and **swelling/erythema** of the knee is highly suggestive of **septic arthritis**.
- **Arthrocentesis** and subsequent **synovial fluid analysis** (cell count with differential, Gram stain, culture) is the definitive diagnostic test to confirm septic arthritis and identify the causative organism.
*MRI*
- While MRI can visualize soft tissue and bone, it is generally reserved for cases where the diagnosis is unclear or to evaluate for complications such as **osteomyelitis** or abscess formation, after initial diagnostic steps.
- It is not the **initial diagnostic step** for suspected septic arthritis, which requires prompt identification of the pathogen to guide antibiotic therapy.
*Ultrasound*
- **Ultrasound** can identify joint effusion, but it cannot differentiate between septic arthritis and other causes of joint effusion.
- It may be used to guide arthrocentesis if the effusion is difficult to aspirate.
*Broad spectrum antibiotics*
- Although **broad-spectrum antibiotics** are indicated for **presumed septic arthritis**, they should be administered *after* obtaining fluid for culture.
- Starting antibiotics before collecting cultures can lead to **false-negative culture results**, hindering identification of the causative organism and appropriate antibiotic selection.
*Radiograph*
- **Radiographs** can rule out fracture or dislocation and may show signs of soft tissue swelling or effusion, but they are not sensitive enough to diagnose early septic arthritis.
- They also cannot differentiate septic arthritis from other inflammatory arthropathies or sterile effusions.
Bone and joint infections US Medical PG Question 2: A 22-year-old female with no past medical history presents to her primary care physician with a 3-day history of knee pain. She denies any recent injury or trauma. On physical examination her knee is warm, erythematous, and has diminished range of movement. The patient reports having multiple sexual partners over the last year and does not use protection regularly. Her blood pressure is 124/85 mmHg, heart rate is 76/min, and temperature is 38.3℃ (101.0℉). A joint aspiration is performed and a growth of gram-negative diplococci is noted on bacterial culture. What is the treatment of choice for this patient's condition?
- A. Vancomycin monotherapy
- B. Fluoroquinolones
- C. Nafcillin monotherapy and joint aspiration
- D. Oxacillin and ceftriaxone
- E. Ceftriaxone monotherapy and joint aspiration (Correct Answer)
Bone and joint infections Explanation: ***Ceftriaxone monotherapy and joint aspiration***
- The patient's presentation with **acute monoarthritis**, fever, and **gram-negative diplococci** on joint culture is highly suggestive of **gonococcal arthritis**. Intravenous ceftriaxone is the treatment of choice for disseminated gonococcal infection.
- While joint aspiration confirms the diagnosis and can relieve pressure, definitive treatment requires systemic antibiotics to clear the infection.
*Vancomycin monotherapy*
- **Vancomycin** is primarily effective against **gram-positive bacteria**, particularly MRSA, and would not adequately cover the gram-negative diplococci found in this case.
- Using vancomycin alone would leave the patient's gonococcal infection untreated, potentially leading to worsening of symptoms or complications.
*Fluoroquinolones*
- While some fluoroquinolones have activity against *Neisseria gonorrhoeae*, **widespread resistance** to this class of antibiotics has emerged, making them an unreliable choice for empiric or first-line treatment of gonococcal infections.
- The CDC no longer recommends fluoroquinolones for gonococcal infections due to high rates of resistance.
*Nafcillin monotherapy and joint aspiration*
- **Nafcillin** is a narrow-spectrum penicillin effective primarily against **methicillin-sensitive *Staphylococcus aureus*** and other gram-positive organisms.
- It would not provide appropriate coverage for the **gram-negative diplococci** identified in this patient's joint fluid.
*Oxacillin and ceftriaxone*
- While **ceftriaxone** is appropriate, the addition of **oxacillin** (another anti-staphylococcal penicillin) would be unnecessary.
- Oxacillin is primarily used for gram-positive infections and would not add benefit against **gonococcal arthritis**, increasing the risk of adverse effects without improving efficacy.
Bone and joint infections US Medical PG Question 3: A 42-year-old woman comes to the emergency department because of worsening severe pain, swelling, and stiffness in her right knee for the past 2 days. She recently started running 2 miles, 3 times a week in an attempt to lose weight. She has type 2 diabetes mellitus and osteoporosis. Her mother has rheumatoid arthritis. She drinks one to two glasses of wine daily. She is sexually active with multiple partners and uses condoms inconsistently. Current medications include metformin and alendronate. She is 161 cm (5 ft 3 in) tall and weighs 74 kg (163 lb); BMI is 29 kg/m2. Her temperature is 38.3°C (100.9°F), pulse is 74/min, and blood pressure is 115/76 mm Hg. She appears to be in discomfort and has trouble putting weight on the affected knee. Physical examination shows a 2-cm, painless ulcer on the plantar surface of the right toe. The right knee is swollen and tender to palpation. Arthrocentesis of the right knee with synovial fluid analysis shows a cell count of 55,000 WBC/μL with 77% polymorphonuclear (PMN) cells. Which of the following is the most likely underlying cause of this patient's presenting condition?
- A. Autoimmune response to bacterial infection
- B. Hematogenous spread of infection (Correct Answer)
- C. Occult meniscal tear
- D. Intra-articular deposition of urate crystals
- E. Direct inoculation of infectious agent
Bone and joint infections Explanation: ***Hematogenous spread of infection***
- The patient has a **diabetic foot ulcer**, which serves as a portal of entry for bacteria, and **poor glycemic control** (implied by type 2 diabetes) increases susceptibility to infections.
- The **synovial fluid analysis** with a very high **WBC count (55,000 WBC/μL)** and **predominance of PMN cells (77%)**, along with fever and acute severe pain in a single joint, is highly suggestive of **septic arthritis**, which can occur via hematogenous spread from a distant infection site like the foot ulcer.
*Autoimmune response to bacterial infection*
- This describes **reactive arthritis**, which usually presents with sterile synovitis occurring days to weeks after an infection, commonly genitourinary or gastrointestinal.
- While the patient's sexual history could be a risk factor for such infections, the **high synovial fluid WBC count with PMN predominance** and fever point more directly to active bacterial infection within the joint rather than a sterile autoimmune reaction.
*Occult meniscal tear*
- A meniscal tear typically causes mechanical pain, locking, or clicking, and while it can lead to swelling, it rarely presents with **fever** and such a **high inflammatory synovial fluid profile**.
- The patient's recent running could contribute to a tear, but the systemic signs of infection and significant synovial inflammation make this diagnosis less likely.
*Intra-articular deposition of urate crystals*
- This describes **gout**, which presents with acute, severe joint pain and inflammation, and can be triggered by trauma or metabolic stress.
- While synovial fluid in gout can have elevated WBCs, it would typically show **negatively birefringent needle-shaped crystals**, which are not mentioned, and the high fever and the presence of a diabetic foot ulcer make septic arthritis a more probable diagnosis.
*Direct inoculation of infectious agent*
- Direct inoculation usually occurs due to **trauma, surgery, or injection** into the joint.
- There is no history of such events in this patient, making hematogenous spread from the existing diabetic foot ulcer a more plausible route for infection.
Bone and joint infections US Medical PG Question 4: A 32-year-old man comes into your office because of pain in his right knee, left elbow, and left wrist. It started about a week ago but has particularly localized to his wrist. The patient states that he has 2 sexual partners. He states he has also had some white discharge from his penis with pruritis and pain during urination. His temperature is 97.6°F (36.4°C), blood pressure is 124/84 mmHg, pulse is 80/min, respirations are 12/min, and oxygen saturation is 98% on room air. Physical exam reveals pain upon palpation of the patient's left wrist which also appears erythematous and swollen. What is the best next step in management for this patient?
- A. Ibuprofen and observation
- B. MRI
- C. Arthrocentesis (Correct Answer)
- D. Azithromycin, ceftriaxone, and vancomycin
- E. Methotrexate
Bone and joint infections Explanation: ***Arthrocentesis***
- The patient presents with **migratory polyarthralgia** and then **monoarthritis**, along with symptoms of urethritis and risk factors for sexually transmitted infections (multiple sexual partners). This clinical picture is highly suggestive of **disseminated gonococcal infection (DGI)**, which can cause **septic arthritis**.
- **Arthrocentesis** (joint aspiration) is crucial to obtain joint fluid for analysis (cell count with differential, Gram stain, culture) to confirm the diagnosis of septic arthritis and identify the causative organism, guiding appropriate antibiotic therapy.
*Ibuprofen and observation*
- This approach is insufficient because the patient's symptoms are highly concerning for **septic arthritis**, a medical emergency that requires prompt diagnosis and treatment.
- Delaying definitive diagnosis and treatment of septic arthritis can lead to rapid **joint destruction** and permanent disability.
*MRI*
- An MRI can provide detailed images of the joint structures and surrounding tissues, which is useful in some cases of arthritis.
- However, for suspected septic arthritis, **joint fluid analysis via arthrocentesis** is the gold standard for definitive diagnosis, as it identifies the pathogen and confirms infection. MRI should not delay this critical diagnostic step.
*Azithromycin, ceftriaxone, and vancomycin*
- While this combination might broadly cover common pathogens, starting empiric antibiotics without **first confirming the diagnosis and identifying the organism** through arthrocentesis is not the best first step.
- Vancomycin is for MRSA, and while disseminated gonococcal infection is suspected, **antibiotic sensitivity** is crucial for effective treatment; a Gram stain and culture from joint fluid are needed.
*Methotrexate*
- Methotrexate is a **disease-modifying antirheumatic drug (DMARD)** typically used for chronic inflammatory conditions like rheumatoid arthritis or psoriatic arthritis.
- It is **not indicated for acute septic arthritis**, which requires immediate antibiotics and joint drainage, and its immunosuppressive effects could worsen an active infection.
Bone and joint infections US Medical PG Question 5: A 15-year-old boy presents to the emergency department for evaluation of an ‘infected leg’. The patient states that his right shin is red, swollen, hot, and very painful. The body temperature is 39.5°C (103.2°F). The patient states there is no history of trauma but states he has a history of poorly managed sickle cell anemia. A magnetic resonance imaging (MRI) scan is performed and confirms a diagnosis of osteomyelitis. Which of the following is the most likely causative agent?
- A. S. aureus
- B. S. pyogenes
- C. N. gonorrhoeae
- D. Salmonella species (Correct Answer)
- E. H. influenzae
Bone and joint infections Explanation: ***Salmonella species***
- **Salmonella** is the **most common cause of osteomyelitis in patients with sickle cell anemia**, accounting for a majority of cases in this population.
- Patients with sickle cell disease have **functional asplenia** (autosplenectomy), leading to impaired clearance of encapsulated organisms and increased susceptibility to Salmonella bacteremia.
- **Bone infarctions** in sickle cell disease create an avascular nidus that is prone to bacterial seeding, particularly by Salmonella species.
- The clinical presentation of fever, localized bone pain, and MRI confirmation of osteomyelitis in a patient with poorly managed sickle cell anemia is classic for Salmonella osteomyelitis.
*S. aureus*
- *S. aureus* is the most common cause of **osteomyelitis in the general population**, accounting for up to 80% of cases overall.
- While *S. aureus* can also cause osteomyelitis in sickle cell patients, it is **less common than Salmonella** in this specific population.
- Always consider *S. aureus* in osteomyelitis, but the sickle cell history makes Salmonella more likely.
*S. pyogenes*
- *S. pyogenes* (Group A Streptococcus) typically causes skin and soft tissue infections like **cellulitis**, **erysipelas**, and **necrotizing fasciitis**.
- While it can cause osteomyelitis, it is far less common than both *Salmonella* and *S. aureus* in this patient population.
*N. gonorrhoeae*
- *N. gonorrhoeae* can cause disseminated gonococcal infection, which may include **septic arthritis** and tenosynovitis, but osteomyelitis is rare.
- Gonococcal infection is usually associated with sexual activity and typically presents with symptoms of urethritis, cervicitis, or pelvic inflammatory disease, not isolated osteomyelitis.
*H. influenzae*
- Infections with *H. influenzae* type b were previously common in unvaccinated children but are now rare due to widespread **Hib vaccination**.
- While it can cause osteomyelitis, it is typically seen in younger children (under 5 years) and is not the most likely causative agent in this 15-year-old with sickle cell anemia.
Bone and joint infections US Medical PG Question 6: A 7-year-old boy is brought to the emergency department because of a 3-day history of generalized fatigue, myalgia, and fever. He has sickle cell disease. His current medications include hydroxyurea and folic acid. He appears ill. His temperature is 39.2°C (102.6°F), pulse is 103/min, and respirations are 28/min. Examination shows pale conjunctivae. The lungs are clear to auscultation. The abdomen is soft and nontender. Neurologic examination shows no focal findings, His hemoglobin concentration is 10.3 g/dL and leukocyte count is 14,100/mm3. Intravenous fluid is administered and blood cultures are obtained. Which of the following is the most appropriate next step in treatment?
- A. Clindamycin
- B. Prednisone
- C. Vancomycin
- D. Ceftriaxone (Correct Answer)
- E. Levofloxacin
Bone and joint infections Explanation: ***Ceftriaxone***
- This patient presents with **fever** and **sickle cell disease**, placing him at high risk for bacterial infections, especially from **encapsulated organisms** like *Streptococcus pneumoniae* and *Haemophilus influenzae*. **Ceftriaxone** is a broad-spectrum third-generation cephalosporin that provides excellent coverage against these common pathogens.
- Due to the high risk of **sepsis** and rapid progression of infection in sickle cell patients, empiric, prompt administration of **intravenous antibiotics** is crucial, even before culture results are available.
*Clindamycin*
- **Clindamycin** is primarily effective against **anaerobic bacteria** and some gram-positive organisms, including methicillin-sensitive *Staphylococcus aureus* (MSSA).
- It does not provide adequate coverage against the most common and life-threatening pathogens in febrile sickle cell patients, such as encapsulated bacteria.
*Prednisone*
- **Prednisone** is a corticosteroid used for its **anti-inflammatory** and immunosuppressive effects. It is not indicated for the initial management of fever and suspected bacterial infection.
- Administering corticosteroids in a patient with suspected infection without appropriate antibiotic coverage could worsen the infection.
*Vancomycin*
- **Vancomycin** is a powerful antibiotic primarily used to cover **multi-drug resistant gram-positive bacteria**, especially **MRSA** and drug-resistant *S. pneumoniae*.
- While it covers gram-positive organisms well, it does **not cover gram-negative bacteria** such as *H. influenzae* or *Salmonella* species, which are important pathogens in sickle cell patients. **Ceftriaxone** provides broader coverage including both gram-positive and gram-negative encapsulated organisms, making it the preferred empiric choice.
*Levofloxacin*
- **Levofloxacin** is a fluoroquinolone that provides broad-spectrum coverage, including against atypical organisms and some gram-negatives and gram-positives.
- However, **fluoroquinolones** are generally avoided in children due to potential adverse effects on cartilage development, and it is not the first-line empiric choice for severe bacterial infections in this age group, especially when **cephalosporins** are highly effective and safer.
Bone and joint infections US Medical PG Question 7: An 11-year-old boy presents to the emergency department with sudden pain. The patient's parents state the child suddenly felt pain in his hands an hour ago. He has not eaten anything new lately. He did play football earlier this morning and admits to being tackled forcefully multiple times. The child is doing well in school and is proud that he has a new girlfriend. The child has a past medical history of obesity and is not currently on any medications. His temperature is 100°F (37.8°C), blood pressure is 120/68 mmHg, pulse is 100/min, respirations are 11/min, and oxygen saturation is 98% on room air. Cardiopulmonary exam is within normal limits. On physical exam of the patient's extremities, there was painful and symmetrical swelling of his hands and feet but no rashes were present. The patient is started on analgesics. Which of the following is the most likely cause of this patient's presentation?
- A. Viral infection
- B. Osteomyelitis
- C. Sexually transmitted infection
- D. Benign edema secondary to trauma
- E. Altered red blood cell morphology (Correct Answer)
Bone and joint infections Explanation: ***Altered red blood cell morphology***
- The sudden onset of **painful, symmetrical swelling of hands and feet** (dactylitis) in an 11-year-old African American boy, especially in the context of physical stress (football), is highly suggestive of a **vaso-occlusive crisis** in **sickle cell disease**.
- **Sickle cell disease** involves genetically altered hemoglobin leading to **sickling of red blood cells**, which obstructs small blood vessels and causes pain and inflammation in extremities.
*Viral infection*
- While viral infections can cause musculoskeletal pain, they typically do not present with such **acute, symmetrical, and painful swelling** confined primarily to the hands and feet.
- The absence of other common viral symptoms like widespread rash, upper respiratory symptoms, or severe fatigue makes this less likely.
*Osteomyelitis*
- **Osteomyelitis** usually presents with localized, severe bone pain and often has a focal area of tenderness or swelling, rather than **symmetrical swelling of hands and feet**.
- It is typically associated with **fever** and elevated inflammatory markers, but the widespread nature of the pain makes a single focus of infection less probable.
*Sexually transmitted infection*
- An 11-year-old boy, despite having a girlfriend, is **unlikely to have an STI** as the cause of sudden, painful hand and foot swelling.
- While some STIs can cause reactive arthritis, the presentation here is not typical of such conditions (e.g., usually affecting larger joints).
*Benign edema secondary to trauma*
- While trauma could cause swelling, the **symmetrical and sudden onset of pain and swelling in both hands and feet** makes isolated benign edema from trauma less likely.
- Furthermore, trauma-induced edema is generally localized to the site of injury and not typically diffuse across multiple extremities simultaneously without significant, widespread injury.
Bone and joint infections US Medical PG Question 8: An 8-year-old boy presents to his pediatrician accompanied by his father with a complaint of chronic cough. For the past 2 months he has been coughing up yellow, foul-smelling sputum. He has been treated at a local urgent care center for multiple episodes of otitis media, sinusitis, and bronchitis since 2 years of age. His family history is unremarkable. At the pediatrician's office, his temperature is 99.2°F (37.3°C), blood pressure is 110/84 mmHg, pulse is 95/min, and respirations are 20/min. Inspection shows a young boy who coughs occasionally during examination. Pulmonary exam demonstrates diffuse wheezing and crackles bilaterally. Mild clubbing is present on the fingers. The father has brought an electrocardiogram (ECG) from the patient’s last urgent care visit that shows pronounced right axis deviation. Which of the following is the most likely etiology of this patient’s condition?
- A. Failure of neural crest cell migration
- B. Maldevelopment of pharyngeal pouches
- C. Transient bronchoconstriction
- D. Defective maturation of B-lymphocytes
- E. Decreased motility of cilia (Correct Answer)
Bone and joint infections Explanation: ***Decreased motility of cilia***
- The recurrent respiratory infections (**otitis media, sinusitis, bronchitis**), chronic productive cough with **foul-smelling sputum**, and **bronchiectasis** (implied by chronic cough, wheezing, crackles) are highly suggestive of **primary ciliary dyskinesia (PCD)**.
- **Clubbing** and **right axis deviation** (suggesting right ventricular hypertrophy from pulmonary hypertension) are complications of chronic lung disease such as severe bronchiectasis, which is characteristic of PCD.
*Failure of neural crest cell migration*
- This is associated with conditions like **DiGeorge syndrome** or **Hirschsprung disease**, which present with different clinical features (e.g., cardiac defects, hypocalcemia, intestinal obstruction).
- It does not directly explain the recurrent respiratory tract infections and bronchiectasis seen in this patient.
*Maldevelopment of pharyngeal pouches*
- Similar to neural crest cell defects, issues with pharyngeal pouch development (e.g., **DiGeorge syndrome**) affect the immune system and cardiac structures.
- While it can lead to recurrent infections, it typically involves **T-cell deficiencies** and specific cardiac anomalies, rather than chronic suppurative respiratory disease and bronchiectasis as the primary presentation.
*Transient bronchoconstriction*
- This describes conditions like **asthma**, which causes reversible airway narrowing and wheezing.
- However, asthma does not explain the chronic **foul-smelling sputum**, **clubbing**, persistent recurrent infections like otitis media and sinusitis, or the development of bronchiectasis.
*Defective maturation of B-lymphocytes*
- This leads to **immunodeficiencies** primarily affecting **antibody production**, such as **X-linked agammaglobulinemia**.
- While patients would experience recurrent bacterial infections, the specific pattern of chronic sinusitis, otitis, and bronchiectasis with **foul-smelling sputum** (suggesting chronic bacterial colonization and impaired clearance) points more towards a structural or ciliary defect than a purely humoral immune deficiency.
Bone and joint infections US Medical PG Question 9: A 3-year-old girl is brought to the emergency room because of a 5-day history of high fever and fatigue. During this time she has been crying more than usual and eating less. Her mother says that the child has also complained about pain in her arms and legs for the past 3 days. She was born at term and has been otherwise healthy. She appears ill. Her temperature is 39.5°C (103.1°F), pulse is 128/min, and blood pressure is 96/52 mm Hg. The lungs are clear to auscultation. A grade 3/6 systolic murmur is heard at the apex. There is mild tenderness to palpation of the left upper quadrant with no guarding or rebound. The spleen is palpated 3 cm below the left costal margin. There is no redness or swelling of the joints. Laboratory studies show:
Hemoglobin 11.8 g/dL
Leukocyte count 16,300/mm3
Platelet count 220,000/mm3
Erythrocyte sedimentation rate 50 mm/h
Serum
Glucose 96 mg/dL
Creatinine 1.7 mg/dL
Total bilirubin 0.4 mg/dL
AST 18 U/L
ALT 20 U/L
Urine
Protein 2+
RBC casts rare
RBC 10/hpf
WBC 1–2/hpf
Which of the following is the most appropriate next step in management?
- A. Obtain a transesophageal echocardiography
- B. Administer intravenous vancomycin
- C. Obtain a renal biopsy
- D. Measure rheumatoid factors
- E. Obtain 3 sets of blood cultures (Correct Answer)
Bone and joint infections Explanation: ***Obtain 3 sets of blood cultures***
- The patient presents with **fever, new murmur**, and **splenomegaly**, in addition to elevated ESR and proteinuria. These findings are highly suggestive of **infective endocarditis**, which requires urgent diagnosis via blood cultures.
- Blood cultures are essential to identify the causative organism for targeted antibiotic therapy and confirm the diagnosis of endocarditis.
*Obtain a transesophageal echocardiography*
- While echocardiography is crucial for diagnosing endocarditis, **blood cultures should be obtained first** to identify the pathogen before initiating empiric antibiotics.
- Transesophageal echocardiography (TEE) provides superior visualization of vegetations compared to transthoracic echo (TTE) but is usually performed after positive blood cultures or if TTE is inconclusive.
*Administer intravenous vancomycin*
- Administering antibiotics prior to obtaining blood cultures can **sterilize the blood**, making it difficult to identify the causative organism and select effective definitive treatment.
- Empiric antibiotic therapy, such as vancomycin, is typically initiated after blood cultures are drawn, especially if the patient is severely ill and infective endocarditis is highly suspected.
*Obtain a renal biopsy*
- The patient has elevated creatinine and proteinuria with RBC casts, suggesting **glomerulonephritis**, which can be a complication of infective endocarditis or other systemic diseases.
- However, a renal biopsy is an invasive procedure and generally not the initial step in management for a sick child with suspected endocarditis, as the primary concern is the cardiac infection.
*Measure rheumatoid factors*
- Rheumatoid factors are associated with **rheumatoid arthritis** and other autoimmune conditions, which do not fully explain the constellation of symptoms (fever, new murmur, splenomegaly, elevated ESR, renal involvement) seen in this patient.
- While some autoimmune conditions can cause similar symptoms, the acute presentation with fever and a new murmur points more strongly towards an infectious etiology like endocarditis.
Bone and joint infections US Medical PG Question 10: A 60-year-old man comes to the clinic with the complaint of knee pain for the past few weeks. The pain is located in the left knee, associated with morning stiffness for about an hour, and improves with activities throughout the day. He also has a history of diabetes mellitus, hypertension, peptic ulcer disease, and ischemic heart disease. He underwent angioplasty last year for a STEMI. The patient takes metformin, aspirin, clopidogrel, atorvastatin, ramipril, omeprazole, and bisoprolol. He used to smoke one pack of cigarettes a day for the last 45 years but stopped smoking for the past one year following his heart attack. He drinks alcohol socially. His father has Alzheimer’s disease and is in adult home care, and his mother died of breast cancer when she was 55. His temperature is 37.6°C (99.8°F), blood pressure is 132/65 mm Hg, pulse is 90/min, respirations are 14/min, and BMI is 22 kg/m2. On examination, his left knee is swollen, warm, tender to touch, and has decreased range of movement due to pain. Cardiopulmonary and abdominal examinations are negative. Laboratory investigation is shown below:
Complete blood count:
Hemoglobin 11.5 g/dL
Leukocytes 14,000/mm3
Platelets 155,000/mm3
ESR 40 mm/hr
What is the best next step in the management of this patient?
- A. Ceftriaxone and azithromycin
- B. Ibuprofen
- C. Synovial fluid analysis (Correct Answer)
- D. Flucloxacillin
- E. X-ray left knee
Bone and joint infections Explanation: ***Synovial fluid analysis***
- The patient presents with **acute monoarticular arthritis** with signs of inflammation (swelling, warmth, tenderness, decreased range of motion, elevated ESR, leukocytosis), which necessitates **urgent synovial fluid analysis** to differentiate between inflammatory and septic arthritis.
- This procedure, including **cell count, Gram stain, and culture**, is crucial for timely diagnosis and management, especially given his multiple comorbidities.
*Ceftriaxone and azithromycin*
- This antibiotic combination is typically used for **community-acquired pneumonia** or **sexually transmitted infections**, which are not indicated by the current presentation.
- Empiric antibiotics without prior diagnostic fluid analysis are generally not recommended for suspected septic arthritis unless the patient is critically ill and the diagnosis is highly probable, as it can delay definitive diagnosis and appropriate treatment.
*Ibuprofen*
- **NSAIDs** like ibuprofen are contraindicated in this patient due to his history of **peptic ulcer disease** and recent **angioplasty while on dual antiplatelet therapy**, which significantly increases the risk of gastrointestinal bleeding and cardiovascular events.
- While NSAIDs can reduce inflammation, they would mask symptoms and potentially worsen an underlying infection without addressing the primary cause.
*Flucloxacillin*
- **Flucloxacillin** is an antibiotic primarily used for **staphylococcal infections**, but starting empiric antibiotics without **synovial fluid analysis** (Gram stain, culture) is inappropriate in this context.
- Identifying the specific pathogen is crucial for effective treatment; administering an antibiotic without confirmation could lead to inadequate coverage or antibiotic resistance.
*X-ray left knee*
- While an X-ray might show **joint effusions** or chronic changes, it is **not the best initial step** for acute inflammatory or septic arthritis because it cannot differentiate between these conditions.
- An X-ray is less urgent than synovial fluid analysis, which directly evaluates the joint fluid for signs of infection or inflammation.
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