A 62-year-old woman comes to the emergency department due to a 2-day history of right knee pain and swelling. In the past, the patient has occasionally had knee pain brought on by physical activity, but the current episode is more severe and persistent. She has had difficulty bending the knee or bearing weight; NSAIDs have provided minimal relief. The patient's other medical conditions include hypertension, type 2 diabetes mellitus, chronic kidney disease, and diabetic foot ulcers. Temperature is 38.4 C (101.1 F), blood pressure is 142/84 mm Hg, and pulse is 104/min. On physical examination, the right knee is swollen, warm, and erythematous with limited active and passive range of motion. The left knee appears normal, but there is mild crepitus on movement. X-rays of the right knee reveal subcutaneous edema, joint effusion, and degenerative changes. Right knee arthrocentesis yields 5 mL of cloudy fluid with a leukocyte count of 55,000/mm³, of which 95% are polymorphonuclear cells. No bacteria or crystals are visualized. Cultures of the synovial fluid are sent, and empiric antibiotics are begun. Which of the following additional interventions are most appropriate in management of this patient?

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11ec25c8_d978_0148_bc81_238635328e23_MD0003_00 This patient's presentation of acute knee pain, fever, and synovitis (eg, erythema, warmth, swelling) is concerning for septic arthritis. This diagnosis is further supported by joint aspiration yielding cloudy synovial fluid with >50,000/mm³ leukocytes. Initial treatment of septic arthritis includes intravenous antibiotics and, as with other purulent infections in closed spaces (eg, abscess), adequate drainage of purulent material. For easily accessed joints (like the knee in this patient), needle aspiration may be performed. However, for deep joints (eg, hip) or when needle aspiration does not facilitate adequate drainage, arthroscopic irrigation or open surgical drainage may be needed. Regardless of drainage technique, serial procedures (eg, daily needle aspirations) are often required to completely clear the infection. (Choice A) Systemic lupus erythematosus (with a positive antinuclear antibody assay) can cause synovitis of the knee, but it is usually polyarticular and symmetric; the synovial fluid leukocyte count is relatively low, often in the noninflammatory range (eg, <2,000/mm³). Even though this patient's Gram stain is negative, the severe synovial leukocytosis and single joint involvement are more consistent with septic arthritis. (Choice B) For the first few days of treatment, splinting the infected joint to reduce motion may facilitate relief of pain. However, placement of a cast can limit clinical access to the joint and is not advised. (Choice C) MRI or CT scan can often be helpful for assessing effusions involving deep (eg, hip) or atypical joints in septic arthritis. However, for the knee, plain film x-ray is typically adequate. (Choice E) Systemic glucocorticoids (eg, prednisone) are sometimes used as an adjunctive measure for reducing joint damage in pediatric septic arthritis. However, they are not well studied in adults and are relatively contraindicated in this patient with comorbid diabetes. (Choice F) Arthroplasty is sometimes needed in chronic management (after resolution of infection) for patients with severe joint injury and impaired mobility. However, arthroplasty would not be considered for this patient with an active infection. Educational objective: Initial treatment of septic arthritis includes intravenous antibiotics and adequate drainage of purulent material via needle aspiration, arthroscopic irrigation, or open surgical drainage. Serial procedures are often required to completely clear the infection. References: Septic arthritis of native joints. (http://www.ncbi.nlm.nih.gov/pubmed/28366221)

A 62-Year-Old Woman Comes to the Emergency Department Due to a 2-Day