Case Presentation: A 66 yo man with a past medical history of CAD, b/l knee osteoarthritis, CKD, CVA, T2DM, HTN, and HLD presented to the ED complaining of back pain and left knee pain. In the ED, patient was responsive and fully alert. Labs were significant for hyperkalemia of 6.0, anemia of 9.1. He was given insulin, dextrose, and lokelma. He became lethargic and difficult to arouse with increased work of breathing. EKG had sinus tachycardia with HR of 130 bpm. Viral panel negative and CXR showed pneumonitis and b/l pleural effusions. B/l lower extremity doppler was negative for DVT. Lactic acid was 3. He was given IV fluids. CTAPE was not done due to CKD. Patient was started on heparin gtt with a plan to later obtain V/Q scan. Patient then became agitated, continuing to complain of knee and back pain. He was given a dose of 10 mg of diazepam. Shortly after, he had generalized tremors and became unresponsive with loss of gag reflex. He was intubated. Non-contrast Brain CT had no acute abnormalities. CTAP had non-specific findings. Patient was admitted to the ICU. He continued to grimace even while intubated when his knees were bent on exam. On knee exam, there was no warmth or erythema but there was swelling. Of note, patient did have a recent history of b/l steroidal knee injection at an outside hospital for knee osteoarthritis. He has had multiple knee injections in the past. B/l knee joints were aspirated which drew cloudy, purulent fluid. Empiric antibiotics were started with ceftriaxone and vancomycin. Blood and aspirate cultures were positive for strep pneumoniae. Patient remained minimally responsive and thus unable to extubate. Lumbar puncture was done which showed 10,000 WBCs and 97% neutrophils in the CSF. Glucose was 2 and protein was 873. CSF cultures also grew Strep pneumoniae. Patient was transitioned to 4,000,000 units of penicillin G IV every 4 hours. Gradually his mentation did improve and he was extubated. He underwent multiple b/l knee irrigation and debridements. He was then transitioned to IV ceftriaxone for a total of 6 weeks with gradual return close to baseline.
Discussion: B/l knee Septic arthritis is a rare phenomenon of joint inflammation secondary to an infectious etiology, most often bacterial. It is an orthopedic emergency. Septic arthritis post joint injection, also known as iatrogenic septic arthritis (ISA), is an uncommon complication. In one 17-year retrospective study in an academic hospital, ISA occurred mostly after corticosteroid injection and often involved knees. Staphy aureus was most often isolated. The authors observed that the risk of infection increased in patients with a history of multiple injections and poor health/immunological conditions [1]. It can be seen in the case presented here, this patient did receive multiple prior knee injections and he had multiple comorbid conditions, consistent with the findings of the study.
Conclusions: Septic arthritis should be a major diagnosis on the differential when a patient is coming in for severe or worsening knee pain. This patient also had history of knee injections in the past which were another key to finding his diagnosis and managing appropriately even though the knee exam was slightly misleading. In this case, after appropriately treating for septic arthritis, patient remained minimally responsive. Further investigation should be made in these circumstances to find the underlying cause of such decreased responsiveness as bacteremia and septic arthritis of the knees with appropriate treatment should not solely cause prolonged unresponsiveness.